{"Bibliographic":{"Title":"San Fernando, California, earthquake of February 9, 1971. Volume 3. Geological and geophysical Studies","Authors":"","Publication date":"1971","Publisher":""},"Administrative":{"Date created":"08-16-2023","Language":"English","Rights":"CC 0","Size":"0001135690"},"Pages":["San Fernando, California,\nEarthquake of February 9, 1971\nU.S. DEPARTMENT OF COMMERCE\nNational Oceanic and Atmospheric Administration\nDEPARTMENT COMMUNITY\nOF\n*\n*\nAvenue\nSTATES OF","QE\n535\n.559\nV. 3\nSan Fernando, California,\nEarthquake of February 9, 1971\nLEONARD M. MURPHY\nScientific Coordinator\nIn Three Volumes\nAND NOAA ATMOSPHERIC\nis\ncountry\nDEPARTMENT\nOF\nU.S. DEPARTMENT OF COMMERCE\nFrederick B. Dent, Secretary\nNATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION\nRobert M. White, Administrator\nENVIRONMENTAL RESEARCH LABORATORIES\nWilmot N. Hess, Director\nWASHINGTON, D.C.\n1973","Volume I\nEFFECTS ON BUILDING STRUCTURES\nPart A. Introduction and Buildings\nPart B. Buildings continued; Soils and Foundations\nVolume II\nUTILITIES, TRANSPORTATION, AND\nSOCIOLOGICAL ASPECTS\nVolume III\nGEOLOGICAL AND GEOPHYSICAL STUDIES\nPortions of these volumes were prepared under a\ncooperative agreement by the National Oceanic\nand Atmospheric Administration and the Earth-\nquake Engineering Research Institute.\nEditors\nNEIL A. BENFER\nEnvironmental Science Information Center\nEnvironmental Data Service, NOAA Washington, D.C.\nJERRY L. COFFMAN\nNational Geophysical and Solar-Terrestrial Data Center\nEnvironmental Data Service, NOAA Boulder, Colo.\nJOHN R. BERNICK\nPublications Services\nEnvironmental Research Laboratories\nNOAA Boulder, Colo.\nAssociate Editor\nLOLA T. DEES\nUDC 550.349.4:62: 69 (794) \"1971.02.09\"\n550.34\nSeismology\n.349\nEarthquake effects\n.4\nEarthquake damage\nEngineering and construction\n62\n69\nBuilding\n(794)\nCalifornia\n\"1971.02.09\"\nFebruary 9, 1971\nFor sale by the Superintendent of Documents,\nU.S. Government Printing Office\nWashington, D.C. 20402 Price $11.90\nStock Number 0317-0089","VOLUME III\nGeological and Geophysical Studies\nCLASSICAL SEISMOLOGY\nSURFACE AND SUBSURFACE GEOLOGY\nVERTICAL AND HORIZONTAL GEODESY\nSTRONG-MOTION SEISMOLOGY\nGEOMAGNETISM","","Editors' Preface\nVolume III of this three-volume set contains find-\nfessional experts in the fields of engineering seis-\nings of geological and geophysical investigations and\nmology, geology, and geophysics, and for public\nstudies that were conducted after the earthquake. It\nofficials charged with the administration of emer-\nincludes papers in classical seismology, surface and\ngency preparedness and safety programs.\nsubsurface geology, vertical and horizontal geodesy,\nThe National Oceanic and Atmospheric Admin-\nstrong-motion seismology, and geomagnetism. A map\nistration does not approve, recommend, or endorse\n(pocket insert) of the San Fernando and surrounding\nany proprietary product or proprietary material men-\narea shows the locations of many surface breaks and\ntioned in this publication. No reference shall be\neffects resulting from the earthquake. Volume I of\nmade to the National Oceanic and Atmospheric\nthe series describes the earthquake's effects on build-\nAdministration, or to this publication furnished by\ning structures and on soils and foundations. Volume\nthe National Oceanic and Atmospheric Administra-\nII treats utilities, transportation, and sociological\ntion, that would indicate or imply-directly or in-\naspects.\ndirectly-that the National Oceanic and Atmospheric\nAdministration approves or disapproves of the use\nDisclaimer\nof any proprietary product or proprietary material\nmentioned herein.\nThe reports contained in these volumes include\ndetailed findings in engineering seismology-particu-\nAcknowledgments\nlarly, objective evaluations of causes and effects in\nearthquake damage-and in the seismic and geologic\nPublication of this volume involved the efforts of\ncharacteristics of the physical environment. Although\nmany individuals. Those who mobilized and con-\nderived entirely from the analysis of factual data,\nducted the postearthquake field investigations and\nsome of the findings, in a very limited sense, might\nthose who contributed papers are acknowledged\nbe interpreted as damaging to individual segments of\nthroughout the volume. Christopher Rojahn, of\nbusiness and industry or as being subject to other\nNOAA's Seismological Field Survey, San Francisco,\ninterpretation.\nCalif.-who served as a NOAA liaison representative\nThe scientific papers reflect the interpretation and\nwith the Earthquake Engineering Research Institute\nopinions of their authors and do not necessarily\n-assisted in the compilation of manuscripts and\nrepresent the viewpoints of the National Oceanic\nillustrations. Among the many persons who assisted\nand Atmospheric Administration or the United States\nin the technical processes of publishing this vol-\nDepartment of Commerce. The United States-while\nume, the editors express their special appreciation\nproviding for the presentation of these papers in the\nto Lola T. Dees, Lila V. Paavola, and Gabriel J.\npublic interest and for their obvious informational\nBren for help in editing the volume; to Edward W.\nvalue-assumes no responsibility for any of the views\nKoehler, NOAA Publications Officer, and William E.\nexpressed therein. The National Oceanic and Atmos-\nKusterbeck for printing and production assistance at\npheric Administration's Environmental Research\nall stages; and to John L. Cooke of the U.S. Govern-\nLaboratories, in the interest of fulfilling its statutory\nment Printing Office for designing and guiding the\nfunctions, offers these volumes as a forum for pro-\npublication through the final stages of production.\nV","","Contents\nPage\nEditors' Preface\nV\nIntroduction: Leonard M. Murphy\n1\nClassical Seismology:\nHistorical Seismicity of San Fernando Earthquake Area: Charles F. Richter\n5\nSan Fernando Earthquake: Seismological Studies and Their Tectonic Implica-\ntions: Clarence R. Allen, Thomas C. Hanks, and James H. Whitcomb\n13\nFelt Area and Intensity of San Fernando Earthquake: Nina H. Scott\n23\nFocal Mechanism of San Fernando Earthquake: W. H. Dillinger\n49\nSeismograms, S-Wave Spectra, and Source Parameters for Aftershocks of San\nFernando Earthquake: Brian E. Tucker and James N. Brune\n69\nIncreased Seismic Shaking Above a Thrust Fault: Robert Nason\n123\nSurface and Subsurface Geology:\nMap of Surface Breaks Resulting From the San Fernando, California, Earth-\nquake of February 9, 1971: A. G. Barrows, J. E. Kahle, F. H. Weber, Jr., and\nR. B. Saul\n127\nEffects of San Fernando Earthquake as Related to Geology: R. F. Yerkes\n137\nSubsurface Geology of Portions of San Fernando Valley and Los Angeles Basin:\nJ. A. Johnson and C. M. Duke\n155\nSubsurface Investigation of Ground Rupturing During San Fernando Earth-\nquake: Edward G. Heath and F. Beach Leighton\n165\nTrench Exposures Across Surface Fault Ruptures Associated With San Fernando\nEarthquake: M. G. Bonilla\n173\nPlanetable Survey of Parking Lot Damaged by San Fernando Earthquake: James\nB. Pinkerton and Jane M. Buchanan\n183\nGround Displacement at San Fernando Valley Juvenile Hall During San Fer-\nnando Earthquake: Richard B. Fallgren and Jay L. Smith\n189\nGround Movements in Van Norman Lake Vicinity During San Fernando\nEarthquake: T. Leslie Youd\n197\nEarth Rupture and Structural Damage by San Fernando Earthquake in North\nSylmar Housing Development: Donald O. Asquith and F. Beach Leighton\n207\nGeology, Earthquake Damage, and Water Table Fluctuations-Metropolitan\nWater District Facilities, Sylmar Area: Metropolitan Water District of\nSouthern California\n213\nvii","viii Contents\nPage\nVertical and Horizontal Geodesy:\nLand Movement Studies Related to San Fernando Earthquake: Department of\n223\nCounty Engineer, County of Los Angeles\nHorizontal Crustal Movements Determined From Surveys After San Fernando\n243\nEarthquake: Buford K. Meade and Robert W. Miller\nVertical Crustal Movements Determined From Surveys Before and After San\n295\nFernando Earthquake: Nancy L. Morrison\nStrong-Motion Seismology:\nStrong-Motion Accelerograph Records: R. P. Maley and W. K. Cloud\n325\n349\nA Statistical Summary of Accelerograph Performance: R. P. Maley\n353\nSeismoscope Results: B. J. Morrill\n365\nStrong-Motion Accelerogram Processing: D. E. Hudson\nAnalysis of Pacoima Dam Accelerogram: M. D. Trifunac and D. E. Hudson\n375\nVelocity Response Envelope Spectrum as a Function of Time: Virgilio Perez\n393\nResponse of Pacoima Dam to Aftershocks of San Fernando Earthquake: W. V.\n403\nMickey, V. Perez, and W. K. Cloud\nGeomagnetism:\nRepeat Magnetic Field Survey of San Fernando Earthquake Epicentral Area:\n417\nJ. E. O'Donnell and H. E. Kaufmann\n423\nIndex","Introduction\nIn Volume III, studies of classical seismology, sur-\nface and subsurface geology, vertical and horizontal\ngeodesy, strong-motion seismology, and geomagnetism\nmake available a vast source of physical environ-\nmental data about the San Fernando earthquake.\nThese studies provide the scientific input for further\nevaluation of structural damage to buildings, dams,\ntowers, highways, bridges, and multipurpose facilities\nof utility companies as described in Volumes I and II.\nMany of these studies must be considered preliminary\nin their findings because of their early publication,\nwhich did not permit sufficient time to conduct\ndetailed analyses. It is anticipated that the results of\nmany additional investigations on the scientific\naspects of this earthquake will appear in future\npublications.\nIn a review of the seismicity of the San Fernando\narea, C. F. Richter describes the events that appear\nto be most significant with reference to past earth-\nquake activity and probable future earthquakes in\nthe affected area. Included in the descriptive list\nare 28 earthquakes dating from July 28, 1769,\nthrough July 16, 1965. He singles out the Pico\nCanyon earthquake of April 4, 1893, which had a\ncenter of disturbance that was somewhat farther west\nand a magnitude that was probably less, for com-\nparison with the San Fernando earthquake of 1971.\nThe hypocenter of the San Fernando main shock\n(34°24.7'N., 118°24.0'W., h=8.4 km), 55 aftershocks\nof magnitude 4.0 and greater through December 31,\n1971, and their tectonic implications are discussed by\nC. R. Allen, T. C. Hanks, and J. H. Whitcomb. Al-\nthough it is dangerous to attempt to draw conclusions\nabout possible migrations in aftershock activity with\ntime, it may be significant that all of the larger after-\nshocks that were located in the southwestern ex-\ntremity of the aftershock zone-near Chatsworth and\nLEONARD M. MURPHY\nGranada Hills-occurred relatively late in the after-\nDirector-Seismological Investigations Group\nshock period. The basic mechanism of the initial\nEarth Sciences Laboratories\nfaulting was that of a thrust fault which had a strike\nEnvironmental Research Laboratories, NOAA\n1","2\nSan Fernando Earthquake of 1971\nof about N.70°W., a dip of about 50° NE., and a\nCalifornia Division of Mines and Geology (and in-\nsignificant component of left-lateral slip in addition\ncluded in the pocket inside the back cover of this\nvolume), depicts the many surface effects of the\nto the thrust component.\nN. H. Scott reports Modified Mercalli intensities\nearthquake.\nranging from VIII-XI over an area of approximately\nIn describing the effects of this earthquake as re-\n190 square miles and a \"generally felt\" area of 80,000\nlated to the geology, R. F. Yerkes states that the\nsquare miles. The maximum intensity of XI is as-\npermanent deformation accompanying the faulting\nsigned to the Olive View Hospital in the northern\nincluded: an east-trending zone of tectonic ruptures\nSylmar area. Intensities of IX-X are indicated in the\nthat traverse the urbanized valley floor and that co-\nincide with evidence of prior faulting; uplift, tilting,\nSylmar-San Fernando area. The detailed summaries\nand southwestward shifting of an area of more than\nof the effects were compiled from 2,000 reports re-\n75 square miles of the southwesternmost San Gabriel\nceived through the earthquake questionnaire card\nMountains; and numerous slope failures. The San\ncanvass and many preliminary releases prepared\nshortly after the earthquake. This detailed compila-\nFernando fault is not known to have ruptured pre-\ntion of earthquake effects by Scott, the special studies\nviously during historic time and, although segments\nappearing in this volume, and those in Volumes I\nof the fault had been mapped, no evaluation of their\npotential activity had been attempted. Abundant\nand II, provide the most comprehensive catalog of\nevidence of geologically recent faulting along the\nsuch data for any United States earthquake since the\ngreat San Francisco earthquake of 1906.\nsame trend indicates the activity of the zone.\nW. H. Dillinger, studying both P- and S-wave data\nJ. A. Johnson and C. M. Duke describe the sub-\nfrom over 170 seismograph stations throughout the\nsurface geology of portions of the San Fernando\nworld, considers the focal mechanism of the main\nValley and Los Angeles Basin. A generalized geologic\nshock. His results give one plane with strike N.65°W.,\nmap shows the major rock types in the area and their\ndipping 55°NE., and a second plane with a strike\nrelationship to topographic and geologic features. In\nN.40°W., dipping 37.7°SE.\nthe subsurface investigation of ground rupturing dur-\nIn a study of 167 aftershocks 1/2 to 41/2),\ning this earthquake, E. G. Heath and F. B. Leighton\nB. E. Tucker and J. N. Brune report that the char-\nexamined 14 trenches ranging from 6 to 14 feet in\nacteristics of the S-wave spectra apparently represent\ndepth. They give detailed information for each\nseismic source properties, giving seismic moments of\ntrench and related tectonic events along the Tujunga\n1018 to 1022 dyne-cm, source dimensions of 50 to\nand Sylmar segments of the San Fernando fault. The\n500 m, and stress drops of 1 to 300 bars. An apparent\nsubsurface trenching demonstrates that faults can be\nupper value in stress drop (more than an order of\nobserved and mapped in test trenches, but commonly\nmagnitude greater than stress drops previously re-\ntwo or three trenches must be located along a sus-\nported for small earthquakes) may represent the\npected fault zone to establish with certainty the\nregional effective stress, while the range in stress\npresence or absence of faulting. Further information\ndrops may correspond to a range in fractional stress\nis presented by M. G. Bonilla based on detailed study\ndrops.\nof four trenches, seven other trenches examined in\nTwo possible mechanisms, the effects of uncon-\nreconnaissance, and trench data provided by others.\nfined elastic-strain release above a thrust fault and\nTrenches at a particular project site may not reveal\nmultiple reflection of seismic waves at the thrust\ndiagnostic relations despite use of the best judgment\nfault, are offered by R. Nason as explanations for\nin locating the trench. Realistic evaluation of the\nincreased shaking above an earthquake thrust fault.\nactivity of a fault usually requires consideration of\nDetailed field mapping of the geology and surface\ndata obtained well outside the confines of a particular\neffects of the earthquake by the California Division\nsite.\nof Mines and Geology are reported by A. G. Barrows,\nA planetable survey of a severely damaged paved\nJ. E. Kahle, F. H. Weber, Jr., and R. B. Saul. They\nparking lot is described by Pinkerton and J. M.\ndiscuss surface faulting, surface effects other than\nBuchanan. The survey, which made it possible to\nfaulting, the Granada Hills aftershock of March 31,\ncompare postearthquake maps of the parking area\n1971, and findings from a series of backhoe trenches\nwith preearthquake maps, was part of preliminary\ndug across surface features. A map, prepared by the\nwork to determine the amount and direction of dis-","Introduction\n3\nplacement across the Sylmar segment of the San sive observational listings, the results of horizontal\ncrustal movements measured by the National Geo-\nFernando fault zone.\ndetic Survey of NOAA. Results were adjusted by\nGround displacement at the San Fernando Valley\nholding: (1) one position, station Cahuenga 2, fixed;\nJuvenile Hall was investigated by R. B. Fallgren and\n(2) all stations along the outer rim of the net fixed\nJ. L. Smith. They note that damage to the facility\nbetween surveys; and (3) fixed certain stations along\nresulted from severe shaking and differential ground\nthe western side of the net. N. L. Morrison presents\nmovement. The permanent ground displacements\nthe magnitude and extent of vertical crustal move-\nnear the Juvenile Hall are the result of settlement\nments, determined by comparing the results of level-\nand gradual migration of soft soils downslope in a\ning surveys before the earthquake and special surveys\nzone of narrow lateral extent during the earthquake.\nThe zone exists here as the combined effects of the\nafter the earthquake.\nselective deposition of soft soils in a lowland or\nFortuitously, the earthquake occurred at a time\ntrough formed by coalescing alluvial fans in a bed-\nwhen several hundred strong-motion seismographs\nrock depression, near-surface ground water, and past\nwere operating in the Los Angeles area. Abundant\ndisplacements of similar nature in the same area.\nunique acceleration data from 241 accelerographs\nT. L. Youd studied the origin of ruptures and dis-\nlocated at distances of 8 to 369 km from the earth-\nplacements in the Van Norman Lake vicinity. The\nquake's epicenter are reported by R. P. Maley and\nresults show that differential displacements were\nW. K. Cloud. They present detailed information for\nsmaller outside rupture zones than inside and that\n145 accelerograms. Maximum horizontal accelerations\nrelative horizontal displacements within rupture\nof 1.25g and maximum vertical accelerations of 0.72g\nzones were downslip and generally several times\nwere recorded at the abutment of the Pacoima Dam,\ngreater than corresponding vertical displacements.\n8 km from the epicenter. R. P. Maley, in a separate\nEarth ruptures and structural damage in a north\npaper, gives an account, and statistical summary, of\nSylmar housing development were studied by D. O.\naccelerograph performance. Seismoscope records ob-\nAsquith and F. B. Leighton. The investigation con-\ntained from 144 instruments, as reported by B. J.\nsisted of two phases, a surface mapping phase,\nMorrill, are a valuable complement to the accelero-\nfollowed by a subsurface exploration. Results are\ngraph records.\npresented for damage to construction caused by\nD. E. Hudson describes the processing of strong-\nground rupture and not associated with ground\nmotion accelerograms by the California Institute of\nfailure.\nTechnology Earthquake Engineering Research Lab-\nThe Engineering Geology and Survey Branches of\noratory in Pasadena. In view of the unusual potential\nthe Metropolitan Water District of Southern Cali-\nusefulness of the Pacoima Dam accelerogram to the\nfornia, which has been investigating the Sylmar-\nscientific and engineering profession, M. D. Trifunac\nSan Fernando area since 1962, presents information\nand D. E. Hudson provide details of the site geology\non the geology, earthquake damage, and fluctuations\nand operating condition performance and calibration\nof ground water levels.\nof the instrument. They conclude that the instrument\nThe Geodetic Section of the Department of\nperformed essentially to specifications and the re-\nCounty Engineer, County of Los Angeles, reviewed\ncorded acceleration traces may be adopted as repre-\nthe work of 11 agencies that conducted geodetic\nsentative of the actual motion of the instrument\nmeasurements in the earthquake-affected area and\nfoundation. Integration of the digitized accelerogram\nreported on horizontal and vertical land movements\nindicated tilt during the first 10 to 15 seconds after\nresulting from the earthquake. Based on preearth-\nit was triggered. Comments are offered about the\nquake and postearthquake constrained values, the\ncomputed relative velocity and displacement spectra\ngreatest movement of a first-order horizontal control\nwith a concluding statement that response spectra\nstation was at Pacoima L-1-with a movement of\ncurves alone cannot give a complete picture of the\n6.35 feet N.69°W. The greatest elevation change\neffects of the time duration of the acceleration\nof a precise bench mark was +4.72 feet at BM\nhistory. V. Perez analyzes response spectra at 5 per-\n03-00820-located near the intersection of Foothill\ncent of critical damping for five accelerograms and\nBoulevard and Hubbard Street. B. K. Meade and\nconcludes that the maximum relative velocity re-\nR. W. Miller report in great detail, and with exten-","San Fernando Earthquake of 1971\n4\nsponse spectrum is not necessarily caused by the\nW. K. Cloud, who comment on the frequency-domain\nmaximum ground acceleration and the maximum\namplification and time-domain amplification of the\nvelocity response is not necessarily proportional to\nseismic signals.\nmaximum acceleration. The response of the Pacoima\nIn the concluding report, J. E. O'Donnell and\nDam to eight aftershocks, as recorded at three sta-\nH. E. Kaufmann compare the magnetic field survey\ntions that were installed at the dam to record after-\nmade after the San Fernando earthquake and the\nshocks, is reported by W. V. Mickey, V. Perez, and\nrepeat survey of April 1 to 7, 1972.","Historical Seismicity of\nSan Fernando Earthquake Area\nThis contribution lists and briefly describes the\npast events that appear to be the most significant\nwith reference to past earthquake activity and future\nprobabilities for the area most affected by the San\nFernando earthquake. That area is considered to in-\nclude the western and central parts of the San Fer-\nnando Valley, the mountains north of it, and envi-\nrons of Newhall, Saugus, and Castaic.\nEarthquakes listed are of four main types: (1)\nThose originating within the given area; (2) those\nreaching notable intensity (sometimes damaging)\nwithin it, but centered outside; (3) large earth-\nquakes with distant center, but including the given\narea within the range of shaking perceptible to per-\nsons; and (4) disturbances of uncertain origin or\ncharacter, which may or may not have affected the\ngiven area.\nMagnitudes are given only for earthquakes which\nwere recorded by seismographs; prior to 1930, such\ndata are incomplete and imperfect. To reduce confu-\nsion, local intensities are not given in numerical\nform, as with the Rossi-Forel or the Modified Mer-\ncalli Intensity Scale, but are cited only in descriptive\nlanguage.\nBecause of the great difference in the amount and\nreliability of information available in earlier and\nlater years, the reader is earnestly advised not to use\nthis list for statistical purposes or to search for cycles\nor periodicities in occurrence. Any such studies\nshould be based on thorough critical study of the\nmuch larger body of historical and instrumental data\nfrom which the following items are extracted.\nMost of the given area was thinly populated until\ncomparatively recent years, and the mountainous\npart of the area is still unsettled. Historical data are\nCHARLES F. RICHTER\noften incomplete and fragmentary.\nSeismological Laboratory\nThe present listing does not include earthquakes\nCalifornia Institute of Technology\nthat affected the given area only in its southeastern\nPasadena, Calif.","6\nSan Fernando Earthquake of 1971\npart, namely, the southeast end of the San Fernando\nSanta Barbara, and La Jolla, and in 1929 at Tine-\nValley, including Burbank and Glendale; nor does it\nmaha and Haiwee in Owens Valley. This network\ninclude earthquakes of interest mainly for the effects\nwas extended gradually through the years and now\nin the central part of Los Angeles. In general, earth-\nincluded 15 routine stations. In 1937, administration\nquakes originating east of Los Angeles are omitted;\nof the program was taken over by the California In-\namong others, this excludes a number of moderate to\nstitute of Technology.\nmajor earthquakes on the San Andreas or San Ja-\nEntries for individual earthquakes follow.\ncinto faults, such as those of July 22 and December\n1769 July 28. The first credibly documented Cali-\n25, 1899, April 21, 1918, and July 22, 1923.\nfornia earthquake was experienced by the exploring\nCalifornia earthquake history begins with the first\nparty of Gaspar de Portolá when encamped on the\nSpanish land exploration in 1769. The mission at\nSanta Ana River not far from the site of the present\nSan Gabriel was founded in 1771, and the pueblo of\ntown of Olive. Light aftershocks were noted by the\nLos Angeles was established in 1781.\nparty during the following days as it proceeded\nThe mission of San Fernando Rey de España was\nwestward. Speculation is open as to where the epi-\nfounded in 1797; until the 20th century, the small\ncenter may have been, but it is unlikely that it was in\ntown of San Fernando, which grew up near it, was\nthe San Fernando earthquake area. One would\nthe only noteworthy center of population in the\nrather suspect the Whittier, Norwalk, Elsinore, or\nwestern San Fernando Valley. The eastern end of the\nSan Jacinto fault. Origin on the San Andreas fault\nvalley developed gradually toward the end of the\nis less likely, but not altogether to be excluded.\n19th century, with Burbank and Glendale as suburbs\nNOTE: Small earthquakes were SO frequent in the\nof Los Angeles.\nSan Gabriel Valley in the immediately following\nThe northern towns of Newhall and Saugus are of\nyears that Father Serra referred to it as el valle de los\nolder date, having benefited by early discovery of\ntemblores.\ngold and by oil developments. Entry of the railroads\n1812 December 8. This earthquake destroyed part\nin the 1880s added small settlements near some of\nof the mission church at San Juan Capistrano; it was\ntheir stations.\nseriously damaging at San Gabriel, but apparently\nMajor changes followed the bringing in of water\nnot at San Fernando. The same faults named in rela-\nfrom the Owens Valley by aqueduct in 1913. Several\ntion to the 1769 earthquake might be considered also\nnew towns were laid out at that time. Some of their\nfor this event.\nnames have changed; what were originally Lanker-\n1812 December 21. This major earthquake usually\nshim and Owensmouth are now North Hollywood\nis supposed to have originated under the Santa Bar-\nand Canoga Park.\nbara Channel, partly because of some reports (which\nAs for instrumental installations, the first continu-\nhave been questioned) that it caused high waves\nous earthquake recording in southern California\nalong the coast. It destroyed the mission at Purisima\nbegan in 1906 at Point Loma (near San Diego),\n(near Lompoc), and more or less damaged those at\nwith equipment of relatively low sensitivity. Compa-\nSanta Ynez, Santa Barbara, San Buenaventura, and\nrable instruments, or better, had been in operation\nSan Fernando.\nat Berkeley since 1887, but contribute little to our\ndata on earthquakes in southern California. Modern\nNote that California historical material of all\nseismographs began recording in 1910 at Berkeley\nkinds is scanty for its Mexican period, particularly\nand in 1911 at Mount Hamilton (Lick Observa-\nfrom the disestablishment of the missions, which\ntory) ; bulletins for these stations show useful entries\nbegan in 1834, to the American acquisition in 1848.\nfor large earthquakes in the south.\n1852 November 26. Strong shaking over a large\nA new period of recording and cataloging ensued\npart of southern California. Probably a major earth-\nwith the setting up of a seismological program, head-\nquake; possibly more than one event was involved.\nquartered in Pasadena, under the auspices of the\nHeavy shaking is reported for San Simeon, Los An-\nCarnegie Institution of Washington; Harry O. Wood\ngeles, and San Gabriel, but the most interesting item\nadministered the program as its chief. Regular re-\nis the reported opening of fissures for at least 30\ncording began in Pasadena in 1923; it was comple-\nmiles in Lockwood Valley. The valley of that name\nmented by stations set up in 1926-27 at Riverside,\nin Ventura County is on the course of the Big Pine","Historical Seismicity of Earthquake Area\n7\nMojave: \"This place was visited by four distinct\nfault. (There is a Lockwood in southern Monterey\nshocks of earthquake. Buildings were rocked for sev-\nCounty, but it is unlikely that this is intended.)\neral seconds, creating considerable fright. At Saugus\n1855 July 10. Strong at Los Angeles, where it\nchimneys were knocked down and dishes and other\nseems to have caused more damage than the great\nhousehold furnishings were broken. The impression\nearthquake of 1857 (see next entry) Bells at San\nis that the shock came from the northeast.\"\nGabriel Mission were thrown down. The Hugo Reid\nSan Bernardino: \"A heavy earthquake, moving in\nadobe, located almost directly on the Raymond\na southeasterly direction. No damage.\"\nfault, was wrecked.\nSanta Ana: \"A slight earthquake was felt, the\n1857 January 9. This event was the earliest of\nmovement seeming to be from west to east. The vi-\nthree known great shocks accompanied by faulting in\nbrations were SO slight, however, that many people\nCalifornia. Displacements occurred along the San\nwere not aware there had been any disturbance of\nAndreas fault, extending probably from Carrizo\nthe earth's surface.\"\nPlain in San Luis Obispo County southeast to a lo-\nLos Angeles: \"There was a slight earthquake of\ncality in San Gorgonio Pass, northeast of Banning.\nshort duration. The movement was from west to\nThis event often is termed the Fort Tejon earth-\neast. In observer Franklin's office the barometers\nquake because of strong shaking at the fort, then the\nwere well shaken, and continued to oscillate percep-\npoint of habitation nearest the fault; nearly all the\ntibly for 2 minutes at least. It lasted about 18 sec-\nbuildings were thrown down. In the town of San\nFernando, several houses were thrown down; the\nonds.\"\nSan Diego: \"A slight shock. It was felt only in the\nroof of the mission church of San Buenaventura col-\nupper stories. It shook the barometer at the signal\nlapsed; all the houses in Santa Barbara are reported\nto have been damaged.\noffice.\"\nDuarte: \"Light shock, east and west.\"\n1872 March 26. The second great California earth-\nquake caused faulting in Owens Valley along a belt\nVentura: \"Heavy.\"\nNordhoff: \"Heavy.\" (Nordhoff is now Ojai.)\nincluding the east base of the Alabama Hills. Heavi-\nLos Angeles: Newspaper account of April 8:\nest damage and casualties were at Lone Pine where\n\"Alarming reports of seismic disturbances have just\n27 were killed. The shaking was perceptible, but not\nbeen received from the oil region of Newhall, 35\nviolent, in and about Los Angeles.\nmiles from this city. Dating from last Tuesday, the\n1879 August 10. Light shock at Los Angeles. Re-\nday on which Los Angeles experienced a slight\nported as \"quite severe\" at San Fernando, whatever\nshake, there has been a terrifying series of temblors,\nthat means.\naccompanied by subterranean explosions. These dis-\n1893 April 4 (Tuesday) This, the Pico Canyon\nturbances have been frequent, and have been accom-\nearthquake, is of great interest for comparison with\npanied by landslides from the mountains of an\nthe 1971 event. The same general area was heavily\nalarming and dangerous description. A letter dated\nshaken, but the center of disturbance appears to\nfrom Pico Canyon, about 8 miles southwest from\nhave been farther west, and the magnitude was prob-\nNewhall, reads substantially as follows: 'I was driv-\nably less than in 1971. Nearly all the accessible infor-\ning this morning when my horse became frightened\nmation appears in Edward S. Holden's Catalog of\nwithout apparent cause, and there came a rumbling\nEarthquakes on the Pacific Coast, 1769-1806; it is\nsound which grew terrifying. I looked up and saw an\nhere transcribed in full, with slight rearrangements,\nawful sight. Landslides from every peak in sight\nomitting only (1) Holden's assignments of intensi-\ncame tumbling down, with huge boulders. The\nties on the Rossi-Forel Scale following each individ-\nmountains appeared as if myriads of volcanoes had\nual item, which add nothing to our knowledge of the\nburst forth. When I got to the long bridge I saw Mr.\nearthquake, and (2) reported times of occurrence.\nThomas standing dazed, holding to the railing, and\nThere was evidently only one large shock, for which\nothers came running across the bridge. The earth\nthe time is stated variously from 11:40 a.m. to a few\nopened in a number of places and the scene was in-\nminutes after 12 noon; these differences can only\ndescribable. Men cried, prayed, and swore. When I\nrepresent imperfect observation or inaccurate timing\nreached my house I found everything upset. Pictures,\ndue to clock error, etc. The earliest reported times\ndishes, and everything breakable were smashed, and\nare probably most nearly correct.","8\nSan Fernando Earthquake of 1971\ntwo stoves were broken all to pieces. All the after-\nquake of Tuesday (April 4) 'It was a few minutes\nnoon lighter shocks continued, and also through the\nafter 12 o'clock. The men had already left the der-\nnight.''' Another letter dated on Friday, April 7,\nricks. Suddenly there was a peculiar swaying of the\nsays: \"On Wednesday night, just as I had gone to\nground and an explosion which I can hardly de-\nbed, 'Crash!' came another great shock. All night\nscribe. It was heavier than any blast I ever heard. I\nlong they recurred, keeping up until morning; and\nwas on horseback, and the horse was frightened very\nall day Thursday they continued, each preceded by a\nbadly. At first I thought of a boiler, but looking\nheavy subterranean explosion. The house the fore-\nalong the San Fernando Range, as far as I could see\nman lived in was demolished this time. Last night\neast and west, there was a blinding cloud of dust. It\nwas less exciting, and at 3 o'clock this (Friday)\nrose directly up from the top of the range and was\nmorning we had another, which was fully as terrify-\nthick. All around me dust rose from the hills in the\ning as the first. The shocks were worse in the canyon\nnear vicinity and earth and boulders came tumbling\nhere than elsewhere, but at Newhall and all around\ndown. The shock lasted between 10 and 15 seconds.\nthis part of the county they have been terrifying.\"\nI looked across the valley and saw the same thing in\nLos Angeles: Newspaper account of April 9. \"The\nthe Castac [Castaic] Hills. That shock was the worst\nSan Fernando range of mountains, where the greater\nand it was accompanied by a rumbling sound. The\ndisturbance took place during the week, were pretty\nshocks since that time have been smaller ones. They\ngenerally shaken up every day, beginning with Tues-\nhave not affected the flow of oil. There was not the\nday. The last temblor, a slight one, was felt in the\nslightest disturbance in any of the wells. I have been\ncanyon about 10 o'clock Sunday night. There were\nhere for 19 years as superintendent of the oil wells,\nno shocks SO severe as the first one, and they grad-\nand this is the first time there has been an earth-\nually lessened in force and frequency. As far as can\nquake in this vicinity.'\nbe learned the area of the tremblors was not confined\n\"At the head of the canyon and at Mintryville,\nentirely to the San Fernando Range, but dipped\nwhich is nearly 2 miles below, the first shock played\nacross the big Newhall ranch, past Saugus and over\nhavoc with the crockery in nearly all the houses in\ninto the Castac [Castaic] and Piru mountains, north\nboth places, and a lot of milk pans full of milk, a\nof Newhall. Strange as it may seem, although New-\nquantity of eggs, and the stove and nearly every\nhall is only 8 miles from the Pico Canyon, where\nloose article in one house were thrown in a jumble\nthe shakes were more continuous than elsewhere, the\non the floor and mixed up with the ashes.\npeople in that town did not feel many of them.\n\"The schoolhouse had a large brick chimney, and\n\"The greatest disturbance was in and around the\nafter the shake there was not a whole brick left. An\noil wells of the Pacific Coast and San Francisco com-\nimmense stone came tumbling down a mountainside\npanies at the head of Pico Canyon. Mintryville is a\nand landed in among the pipelines and tanks below,\nlittle town with a schoolhouse, and is the residence\nsmashing things generally.\nof the superintendent of the oil companies. Scattered\n\"Strange to say, not one of the many huge derricks,\nabout are pretty little cottages, the homes of employ-\nwhich are from 40 to 70 feet in height, was over-\nturned, although they swayed in alarming manner.\nees.\n\"One who has not visited the peculiarly formed\n\"The motion in all the shocks was a swaying mo-\ncanyon can hardly have a clear conception of the\ntion, and the direction was from northwest to south-\nconsternation with which the earthquakes were re-\neast. An old and strong adobe house on what is\nceived by the 130 people who live in this vicinity.\nknown as the middle Newhall ranch, northwest of\nTemblors that would, as these did, tilt up great oil\nNewhall, was shaken completely down by one of the\ntanks full of oil, detach immense boulders from the\ntemblors.\"\nmountainsides weighing tons, and cause big surface\nThese reports, assembled by Holden, call for fur-\nfissures in the ground in various places, are not cal-\nther comment. The unreliability of times has been\nculated to make people rest well at night, and when\nnoted previously; the best time for the main shock\nthese disturbances continue at irregular intervals for\nis probably 11:40 a.m. That it was called a few min-\n5 days it is a wonder that the women and children in\nutes after 12:00, following the work break at noon,\nthe canyon bore the ordeal as bravely as they did.\nat the rather isolated community of Mintryville,\n\"Mr. Mintry gave his recollection of the big earth-\nprobably only means that the office clock was fast.","Historical Seismicity of Earthquake Area\n9\nDirections of apparent oscillation are noted at sev-\nnary perceptibility to persons; as is common near the\neral points. These, as usual, are of doubtful signifi-\nmargin for large earthquakes, the principal\ncance. Indoors, such observations are affected by the\nsensations were those of slow swaying, accompanied\noscillation of the structure itself. Outdoors, when re-\nby swinging of doors, suspended objects, etc.\nliable, they usually refer to directions transverse to\n1916 October 22. Magnitude 6. The strongest ef-\nthe line from point of observation to epicenter, and\nfects of this earthquake, barely reaching the damag-\nare probably due to waves of S-type.\ning level, were in the vicinity of Tejon Pass; field in-\nAlternate spellings \"Castac\" and \"Castaic\" have\nvestigators attributed it to the San Andreas fault.\nlong been in use; the latter is now preferred.\nNo surface faulting was found. The source possibly\nThere was probably only one really large shock;\nmight have been on one of the local faults north of\nthe San Andreas fault in that area; minor shocks\nsuggestions that following ones were nearly as strong\nare not very convincing. It is not unlikely that some\nhave been located there instrumentally, particularly\nof the aftershocks originated at very shallow depth,\nin 1941-42. Perceptibility to persons extended to\nwith correspondingly increased intensity near their\nLos, Angeles. A number of aftershocks, some possibly\nepicenters. The concluding note which concerned a\nfrom slightly different epicenters, were reported; a\nranchhouse probably means that it was damaged in\nnotable one occurred on November 1.\nthe main shock and failed gradually during the after-\n1919 February 16. This shock also is attributed\nshock sequence to the point of final collapse.\nwith some uncertainty to the San Andreas fault. An\nMintryville was probably not near the principal\nepicenter on the White Wolf fault near that of the\nepicenter. Equally strong shaking is indicated at New-\nmajor earthquake of 1952 would fit the data some-\nhall and Saugus, with landslides visible at a dis-\nwhat better. Perceptible shaking again extended to\ntance in the mountains, just as in 1971. The fact\nthe Los Angeles-San Fernando area.\nthat oil derricks were not damaged, nor production\n1920 June 21. This minor shock damaged typically\naffected, makes it unlikely that local shaking at Min-\nweak California masonry buildings in and near In-\nglewood. Perceptible shaking extended over a wide\ntryville was as intense or as strongly long period as\nwere the maximum motions of the 1971 earthquake.\narea, including most of the San Fernando Valley and\nIt is interesting that some small aftershocks felt at\nLos Angeles. This earthquake led Stephen Taber to\nidentify and name the active Inglewood fault. It has\nMintryville were not noticed at Newhall; this would\nsuggest that the epicenters of these, at least, were\nsometimes appeared in lists of large earthquakes, pre-\nnear Mintryville. Probably there was faulting of con-\nsumably because the maximum intensity of about\nsiderable extent.\nVIII on the Rossi-Forel Scale has been misread as a\nNote that the shaking was called \"slight\" at Los\nmagnitude 8. A review of the scanty evidence indi-\nAngeles. Except perhaps at Mojave, reports from dis-\ncates that the true magnitude was about 4.9.\ntant points generally indicate lower intensity than\n1925 June 29. Magnitude 6.3. Destructive at Santa\nfor the same localities in 1971, which supports the\nBarbara; perceptible generally in the Los Angeles\nidea that the main shock of 1893 was of lower mag-\narea.\nnitude than that of 1971.\n1926 February 18. Offshore? Fairly strong along\n1894 July 29. This appears to have been a consid-\nthe coast from Santa Barbara to Ventura, and nota-\nerable earthquake, but its center is uncertain. Shak-\nbly inland at Simi and Santa Susana. Slight at Santa\ning heavy enough to cause much excitement, but\nMonica and at Los Angeles.\napparently just below the level of damage, was re-\n1927 November 4. Magnitude 7.5. A major earth-\nported for Los Angeles, Pasadena, Santa Ana, San\nquake off the coast west of Point Arguello. A small\nBernardino, and Mojave, and the intensity was not\nseismic sea wave reached the coast. The tracks of\nmuch less at Santa Monica.\npart of the coast route of the Southern Pacific Rail-\n1906 April 18. Magnitude 8.3. The third of the\nroad were distorted SO that traffic was interrupted\ntemporarily. At Lompoc, numerous chimneys were\nknown great earthquakes of California, involving dis-\nplacements along the San Andreas fault from the\nwrecked. Shaking was perceptible to persons in most\nHumboldt-Mendocino region south past San Fran-\nof the Los Angeles area.\ncisco to near San Juan Bautista. The area of Los An-\n1930 August 30. Seismograms written at Pasadena\ngeles and San Fernando was near the limits of ordi-\nand auxiliary stations were used to locate the epicen-","10\nSan Fernando Earthquake of 1971\nter of this shock in the northern part of Santa Mon-\nglewood fault. The instrumentally determined epi-\nica Bay. The magnitude was placed at 5.2. Percepti-\ncenter, close to that of a foreshock on the previous\nday, is offshore between Newport Beach and Hun-\nble shaking extended over the whole metropolitan\narea. Scattered minor damage occurred near the\ntington Beach. Epicenters of aftershocks indicate\ncoast. Anomalously strong shaking and correspond-\nfaulting extended northwest to the vicinity of Long\ning damage occurred in the western San Fernando\nBeach and Signal Hill.\nValley, especially at and near Chatsworth and Ow-\nThere was serious damage, especially to weak ma-\nensmouth (later renamed Canoga Park) One of the\nsonry, over the whole of the Los Angeles Basin in\ntwo dams at the Chatsworth Reservoir was damaged\nLos Angeles and Orange Counties, extending into\nby settling and severe cracking. It was reconstructed\nthe old central area of Los Angeles city. In the San\nFernando Valley, damage was generally slight, in-\nthereafter, and the new dam passed through the\nearthquakes of 1933, 1952, and 1971 without dam-\ncluding bricks out of chimneys here and there. At\nSan Fernando, shaking was sufficient only to upset\nage.\nBecause earthquakes have originated in the Chats-\nsmall objects.\nworth area in later years, the question has been\n1952 July 21. The major Kern County earthquake\nraised whether there might not have been an error\nwas of magnitude 7.6 to 7.7. It originated on the\nin the placing of the epicenter in Santa Monica Bay.\nWhite Wolf fault. There was minor damage in the\nThe present writer undertook a careful remeasure-\nLos Angeles area, large in total amount, including\nment of the original seismograms, which confirmed\ninterior damage to business blocks in Los Angeles\nthe earlier determinations of recorded times. Even in\nand Long Beach. Much more damage occurred at\nthe light of better information on wave speeds and\nSanta Barbara. Slides were precipitated here and\ncrustal structures now available, it appeared that no\nthere over a large part of southern California. Some\nreasonable reinterpretation would allow an epicenter\nof these occurred in the mountains north of San Fer-\nmore than a few miles north of that previously as-\nnando Valley. The dam in Dry Canyon was cracked\nsigned. An epicenter in the Chatsworth area is defi-\nseriously.\nnitely in conflict with the data, particularly with the\n1952 August 22. The Bakersfield earthquake was\nwell-determined time of first recorded motion at La\nof magnitude 5.8. This was an aftershock of the July\nJolla.\n21 earthquake, but with its epicenter much nearer to\nSmaller earthquakes in later years have been lo-\nBakersfield, where it caused more apparent damage\ncated at epicenters in Santa Monica Bay near that\nthan the main shock; some of this, however, was a\nfound for the 1930 shock. For most of these, more\ncumulative effect on structures weakened in July.\nstations with better instrumentation have been avail-\nShaking was perceptible in most of the Los Angeles\nable than in 1930.\nand San Fernando area, but with practically no dam-\nIt is possible that the shock in Santa Monica Bay\nage.\nwas followed within less than 1 minute by a smaller\n1952 August 23. Magnitude 5.0. Its epicenter was\none centering in the Chatsworth area. Such a shock\nat N., 118°13' W., not far from Acton. This\ncould not be detected on the seismograms, where it\nalso was felt widely in the Los Angeles metropolitan\nwould be obscured by the preceding event. Faulting\narea. Coming only a few hours after the Bakersfield\nthat extends at depth from under Santa Monica Bay\nearthquake, it aroused much public excitement,\nnorthward would offer a possible explanation, but\nwhich was augmented by preliminary speculations\nthere is little other support for such a speculation.\nthat it had originated on the San Andreas fault-al-\n1931 April 4. This shock, magnitude 4, was felt\nthough instrumental recordings quickly showed that\nsharply in the San Fernando Valley, but without\nsuch was not the case. The above epicenter, within\ndamage. In view of the discussion on the earthquake\nlimits of accuracy, will fit a known fault mapped as\nof August 30, 1930, it is interesting that the epicen-\nbranching from the San Andreas system.\nter was close to Chatsworth, near a known and\n1954 January 12. The largest late aftershock of the\nmapped fault. Within limits of error, this epicenter\nKern County series was also generally perceptible in\nis the same as that for February 8, 1964.\nthe Los Angeles area.\n1933 March 10. The Long Beach earthquake, mag-\n1956 February 7. Two shocks, at an interval of 43\nnitude 6.3, was attributed to displacement on the In-\nminutes, were of magnitudes 4.2 and 4.6. The second","Historical Seismicity of Earthquake Area 11\none caused minor damage at Newhall and vicinity.\n1965 July 16. Magnitude 4. Noticed by many in\nthe San Fernando Valley. Epicenter was at 34°39' N.,\nThe epicenter, as revised in 1965, was at 33 33.3' N.,\n118°37.4\" W. This is north of Castaic, practically in\n118°31' W., east of Castaic.\nElizabeth Lake Canyon where slides occurred at the\nEpicenters for the numerous minor earthquakes\ntime. It is well outside the area of aftershock epicen-\nlocated in the given area from 1934 to 1970 show a\ngeneral scattering like that observed for almost any\nters of the 1971 earthquake.\n1964 February 8. Magnitude 3.7. Felt generally in\nequivalent area in southern California. There is no\nalignment or clustering that would suggest signifi-\nthe San Fernando Valley. Its revised location was at\n34°14' N., 118°351/2\" W., near Chatsworth. The shock\ncant activity on any of the known faults, including\nthose of the San Fernando group which were in-\nof April 29, 1931, can be referred to the same point.\n1964 August 30. Magnitude 4.0. Also, it was felt\nvolved in the 1971 earthquake. However, epicenters\nare notably lacking in the central parts of the San\ngenerally in the San Fernando Valley. Epicenter was\nFernando Valley, although they are normally numer-\nnear 34° 16' N., 118°27' W.; within the limits of ac-\ncuracy, this will fit the Mission Hills thrust fault.\nous around its periphery.","","San Fernando Earthquake:\nSeismological Studies and Their\nTectonic Implications\nABSTRACT\nImproved hypocentral locations have been ob-\ntained for the San Fernando earthquake and its\nlarger aftershocks through the use of data from port-\nable stations installed in and around the aftershock\narea subsequent to the main shock. The main shock,\nCONTENTS\nat 14:00:41.8 G.M.T. on February 9, 1971, is now\nPage\nassigned a magnitude (ML) of 6.4 and a location at\n13\nABSTRACT\n34°24.7' N., 118°24.0\" W., h = 8.4 km. Fifty-five\n13\nINTRODUCTION\naftershocks of magnitude 4.0 and greater had OC-\n14\nSEISMOLOGIC ENVIRONMENT\ncurred through December 31, 1971. The lunate-\n15\nHYPOCENTRAL LOCATIONS\n17\nMAGNITUDES\nshaped epicentral distribution of aftershocks is\n18\nFOCAL MECHANISMS AND TECTONIC\nconsistent with the idea of southward thrusting along\nINTERPRETATIONS\na disc-shaped fault surface, and aftershock depths as\n20\nACKNOWLEDGMENTS\n20\nREFERENCES\nwell as aftershock focal mechanisms suggest that the\nthrust surface dips about 35° toward N.20°E. How-\nAdapted from article prepared for publica-\ntion in California Division of Mines and\never, a distinct linear alignment of left-lateral strike-\nGeology Bulletin 196, Ch. 14. Contribution\nslip aftershocks parallel to the motion direction near\nNo. 2124, Division of Geological and Plane-\nthe west boundary of activity suggests that the fault\ntary Sciences, California Institute of Tech-\nsurface has a steep flexure along this line, down-\nnology.\nstepped to the west, and both the planar distribution\nof aftershocks and the local geology support this\nconcept.\nINTRODUCTION\nThe purpose of this paper is to describe the seis-\nmologic aspects of the San Fernando earthquake of\nFebruary 9, 1971, and its aftershocks, and to inter-\npret these earthquakes in terms of a tectonic model\nof the associated faulting. Several reports on these\nsubjects were prepared by the authors within 3\nweeks following the earthquake (Allen et al. 1971,\nCLARENCE R. ALLEN\nHanks et al. 1971, Whitcomb 1971a, and California\nTHOMAS C. HANKS\nInstitute of Technology 1971), , and this paper up-\nJAMES H. WHITCOMB\ndates these studies utilizing information recorded by\nSeismological Laboratory\nthe California Institute of Technology (C.I.T.) net-\nCalifornia Institute of Technology\nwork through December 31, 1971. By this time, the\nPasadena, Calif.\n13","San Fernando Earthquake of 1971\n14\nprincipal aftershock activity seems to have con-\n5 Lake Hughes\ncluded, although small aftershocks still continue.\nDuring the seismological investigations, particular ef-\nWSM\nPalmdale\nRTM\nfort has been made to gain an understanding of the\nPYR\nBQR\ntectonic mechanism of the earthquake-the configu-\nAGM\nration of the fault surface, the source mechanism of\nCastaic\n34°30'\nthe main shock and aftershocks, and the tectonic en-\nOActon\nvironment of the faulted region. Preliminary conclu-\nsoc\nIND\nGOK\nMLM\nsions on these topics are summarized herein, al-\nIRC\nthough it should be recognized that studies are\nNewhall\nOMM\nvigorously continuing and much detailed, substantiat-\nLTU\nSUS\ning evidence as well as possible modifications will be\nBRC\nUSan Fernando\npresented in subsequent papers.\nChatsworth\nBLA\n34°15'\nLa Crescenta\n405\nMWC\nVan Nuys\nBurbank\nSEISMOLOGIC ENVIRONMENT\nPAS\nPasadena\n(101)\nIn the years before 1971, the San Fernando area\nwas characterized by low to moderate seismic activity\nTopanga\nOTRP\nnot unlike that of many other parts of southern Cali-\nMalibu\nfornia. Indeed, the 1934-63 strain-release maps\nLos\nSanta Monica\n(Allen et al. 1965) indicated that the northern San\nAngeles\n34°00'\nFernando Valley was seismically less active than most\no\n10 km\nother parts of the greater Los Angeles area. Nothing\nthat has been recognized in the very recent seismic\nhistory seems to suggest that this area, more than any\nFigure 1.-Aftershock area of San Fernando earthquake (dotted\nline), showing locations of seismograph stations (triangles) that\nother area, was particularly likely to experience a\nwere used in epicentral locations of this study. Station data are\nmagnitude 6.4 earthquake. It should be kept in\ngiven in table 1.\nmind, however, that an earthquake of at least this\nmagnitude occurs somewhere in the southern Cali-\nAlthough most of the faults of the San Fernando\nfornia region on the average of about once every 4\narea had not been generally recognized by geologists\nyears (Allen et al. 1965), and in this sense the San\nand seismologists as \"active\" prior to 1971, abundant\nFernando earthquake was no great surprise. An\nunpublished evidence indicated that this was indeed\nearthquake of this same magnitude occurred in 1968\nthe case. Particularly along the Tujunga segment of\nin the Borrego Mountain area 220 km southeast of\nthe San Fernando fault, geologists of the Metropoli-\nLos Angeles, but damage was small because-unlike\ntan Water District had-long before the earthquake\nthe 1971 event-it occurred in a remote location.\n-carefully documented the thrusting of older rocks\nBetween 1934 and 1971, which is the interval dur-\nover very young gravels (Proctor et al. 1972) along\ning which epicentral locations of southern California\nthe same fault which broke on February 9. On the\nearthquakes have been listed by C.I.T., only about\nother hand, such evidence of geologically very recent\n10 earthquakes of magnitude 3.0 and greater OC-\ndisplacements is becoming more and more wide-\ncurred in the area that corresponds to the epicen-\nspread along many faults in coastal California, and\ntral region of the San Fernando earthquake (figs. 1\nthere was no known reason to have picked out the\nand 2) Before 1934, however, one earthquake is of\nSan Fernando fault more than many of the others as\nspecial importance; this is the so-called Pico Canyon\nearthquake of 1893 (Townley and Allen 1939),\nbeing a particularly likely candidate for an earth-\nwhich was apparently centered only slightly west of\nquake in 1971. The lesson is clear: Until we gain\nthe 1971 epicenter and was of only slightly lesser\nbetter geologic and seismologic understanding of the\nmagnitude. It does indicate, significantly, that mod-\nrelative activity of various fault zones, all of coastal\nerate earthquakes of this size were not unknown in\nCalifornia must be considered to be one of relatively\nthe region.\nhigh earthquake hazard.","Seismological Studies and Their Tectonic Implications\n15\nHYPOCENTRAL LOCATIONS\n34°30\nCastaic\nIn our earlier papers, Allen et al. (1971) summa-\no\n5\n10 km\nA\nrized the seismological data of the first 3 weeks based\nonly on the permanent stations of the C.I.T. net-\nwork, while Hanks et al. (1971) located much more\nSolemint\nMain Shock\nprecisely a number of aftershocks during a particular\nSaugus\n18-hour period on the basis of C.I.T. portable sta-\nNewhall\nValencia\ntions installed in the epicentral region within a few\nhours of the main shock. In this paper, we attempt\nX\nto use data from the C.I.T. portable stations, in ad-\ndition to those of several other agencies (table 1 and\nPacoima Dam\nSylmar\nfig. 1), to establish correction factors to make more\nLower San\nFernando Dam-\neffective use of the more distant permanent stations\nFAULT TRACE\nthat were the only source of seismic information dur-\nSan Fernando\nSunland\ning the first few hours when the great bulk of after-\nGrangda Hills\n34°15\nChatsworth\nTujunga\nshock activity occurred-as well as later in the after-\nA\nSun Valley\nNorthridge\nLa Crescenta\nshock sequence when most of the portable stations\n405\nhad been removed. For the purpose of presenting a\nCanoga Park\n5\nVan Nuys\nBurbank\nhomogeneous body of data, only shocks of magnitude\n101\n4.0 and greater have been listed in table 2 and por-\ntrayed in figure 2. We feel that this listing is rela-\ntively complete even within the first few minutes fol-\nFigure 2.-Earthquakes of the San Fernando series, magnitude 4.0\nand greater through December 31, 1971. Solid circles represent\nlowing the main shock, for which we relied heavily\n\"A\" locations (see text), open circles \"B\" locations, and heavy Xs\non the low-gain (4x, 100x) instruments of the Pasa-\n\"C\" locations. Dotted line shows limits of most aftershock activity\nincluding many smaller shocks than those shown. Cross section\ndena network as well as on the remarkable 6-min-\nA-A' is shown in figure 4.\nTable 1.-Seismographic stations whose data were used in epicentral locations shown in figure 2 and in table 2\nStation\nLongitude\nDistance Period of\nAgency\nLatitude\nNorth\nWest\noperation\nkm\nAGM\nAgua Dulce\nEML\n34 29.5\n118 19.3\n14.7\n2/10-4/24\n20.6\n3/02-present\nBLA\nBlayney\nCIT\n34 18.8\n118 26.7\n2/09-5/07\nBQR\nBouquet Canyon\nCIT\n34 33.5\n118 25.5\n18.9\nBRC\nBrown's Canyon\nCIT\n34 17.6\n118 35.4\n23.5\n2/09-5/07\nCSP*\nCedar Springs\nDWR\n34 17.9\n117 21.5\n97.2\nPermanent\nGOK\n11.4\n2/10-5/06\nGolden Oak Ranch\nCIT\n34 23.1\n118 28.3\nGSC*\nGoldstone\nCIT\n35 18.1\n116 48.3\n176.1\nPermanent\nIND\nIndian Canyon\nCIT\n34 25.2\n118 16.2\n15.2\n2/10-4/22\nIRC\nIron Canyon\nCIT\n34 23.3\n118 23.9\n9.3\n2/09-5/07\nISA*\nIsabella\nCIT\n35 38.6\n118 28.6\n139.0\nPermanent\nLTU\nLittle Tujunga\nUCSD\n34 17.7\n118 21.6\n16.0\n2/09-2/11\nMLM\nMill Creek Summit\nEML\n34 23.4\n118 04.8\n31.2\n2/10-4/24\nMWC\nMount Wilson\nCIT\n34 13.4\n118 03.5\n39.1\nPermanent\nOMM\nOat Mountain\nEML\n34 19.8\n118 36.0\n22.5\n2/25-4/22\nPAS\nPasadena\nCIT\n34 08.9\n118 10.3\n37.0 Permanent\nPLM*\nPalomar\nCIT\n33 21.2\n116 51.7\n184.5\nPermanent\nPYR\nPyramid\nDWR\n34 34.1\n118 44.5\n37.1\nPermanent\nRTM\nRitter Ranch\nEML\n34 35.8\n118 14.8\n26.7 2/10-4/22\nRVR*\nRiverside\nCIT\n33 59.6\n117 22.5\n105.6\nPermanent\nSBLG\nLaguna Peak\nUSGS\n34 06.6\n119 03.9\n70.2\nPermanent\nSOC\nSoledad Canyon\nCIT\n34 26.1\n118 21.7\n10.0\n2/10-5/06\nSUS\nWhite Oaks Park\nUSGS\n34 17.3\n118 39.8\n29.0\n2/12-4/24\nSYP*\nSanta Ynez Peak\nCIT\n34 31.6\n119 58.7\n145.5\nPermanent\nTRP\nTrippet Ranch\nUSGS\n34 05.4\n118 35.1\n40.4\n2/12-4/24\nWSM\nWarm Springs\nEML\n34 36.4\n118 33.5\n27.6\n2/10-4/24\n* Asterisk indicates distant stations used only for locations of\nEML, Earthquake Mechanism Laboratory of NOAA; UCSD,\nshocks during the first few hours before temporary stations were\nUniversity of California at San Diego; and USGS, National Center\nestablished. Agency designations are: CIT, California Institute of\nfor Earthquake Research of U.S. Geological Survey. Distance is that\nTechnology; DWR, California Department of Water Resources;\nto hypocenter of main shock.","San Fernando Earthquake of 1971\n16\nTable 2.-Shocks of San Fernando series of magnitude 4.0 and greater, February 9 through December 31, 1971\nDate 1971\nTime\nLatitude\nLongitude\nDepth\nQ\nMagnitude\nGMT\nNorth\nWest\nh m S\nkm\n2-09\n14 00 41.8\n34 24.7\n118 24.0\n8.4\nB\n6.4\n2-09\n14 01 08\n5.8\n2-09\n14 01 33\n4.2\n2-09\n14 01 40\n4.1\n2-09\n14 01 50\n4.5\n2-09\n14 01 54\n4.2\n2-09\n14 01 59\n4.1\n2-09\n14 02 03\n4.1\n2-09\n14 02 30\n4.3\n2-09\n14 02 31\n4.7\n2-09\n14 02 44\n5.8\n2-09\n14 03 25\n4.4\n2-09\n14 03 46\n4.1\n2-09\n14 04 07\n4.1\n2-09\n14 04 34\n4.2\n4.1\n2-09\n14 04 39\n2-09\n14 04 44\n4.1\n2-09\n14 04 46\n4.2\n2-09\n14 05 41\n4.1\n2-09\n14 05 50\n4.1\n4.0\n2-09\n14 07 10\n2-09\n14 07 30\n4.0\n2-09\n14 07 45\n4.5\n2-09\n14 08 40\n4.0\n2-09\n14 08 07\n4.2\n2-09\n14 08 38\n4.5\n2-09\n14 08 53\n4.6\n2-09\n14 10 21.5\n34 21.3\n118 19.0\n-2.0\nC\n4.7\n2-09\n14 10 28\n5.3\n2-09\n14 16 12.9\n34 20.3\n118 19.9\n11.1\nC\n4.1\n2-09\n14 19 50.4\n34 21.4\n118 24.4\n11.8\nC\n4.0\n2-09\n14 34 36.1\n4.9\n2-09\n14 39 17.7\n34 20.9\n118 23.9\n7.0\nC\n4.0\n2-09\n14 40 17.4\n34 26.0\n118 23.9\n-2.0\nC\n4.1\n2-09\n14 43 47.5\n34 20.8\n118 28.9\n5.9\nC\n5.2\n2-09\n15 58 20.9\n34 22.5\n118 20.1\n9.0\nB\n4.8\n2-09\n16 19 26.5\n34 27.4\n118 25.6\n-1.0\nC\n4.2\n2-10\n03 12 12.0\n34 22.2\n118 18.1\n0.8\nB\n4.0\n2-10\n05 06 35.7\n34 24.7\n118 19.8\n4.7\nB\n4.3\n2-10\n05 18 07.2\n34 25.5\n118 24.9\n5.8\nB\n4.5\n2-10\n11 31 34.6\n34 23.1\n118 27.3\n6.0\nB\n4.2\n2-10\n13 49 53.7\n34 23.9\n118 25.1\n9.7\nA\n4.3\n2-10\n14 35 26.7\n34 21.7\n118 29.2\n4.4\nA\n4.2\n2-10\n17 38 55.1\n34 23.8\n118 22.0\n6.2\nA\n4.2\n2-10\n18 54 41.7\n34 26.7\n118 26.2\n8.1\nA\n4.2\n2-21\n05 50 52.6\n34 23.8\n118\n26.3\n6.9\nA\n4.7\n2-21\n07 15 11.8\n34 23.5\n118\n25.6\n7.2\nA\n4.5\n3-07\n01 33 40.5\n34 21.2\n118\n27.4\n3.3\nA\n4.5\n3-25\n22 54 09.9\n34 21.4\n118 28.5\n4.6\nA\n4.2\n3-30\n08 54 43.3\n34 17.7\n118\n27.8\n2.6\nA\n4.1\n3-31\n14 52 22.5\n34 17.2\n118 30.9\n2.1\nA\n4.6\n4-01\n15 03 03.8\n34 24.7\n118 25.2\n7.1\nA\n4.2\n4-02\n05 40 25.1\n34 17.0\n118 31.7\n3.0\nA\n4.0\n4-15\n11 14 32.0\n34 15.9\n118 34.6\n4.2\nA\n4.2\n4-25\n14 48 06.5\n34 22.1\n118 18.9\n-2.0\nB\n4.0\n6-21\n16 01 08.5\n34 16.4\n118 31.9\n4.1\nB\n4.0\nNOTE: See text for explanation of Q (Quality).\nute-long accelerograph record from Pacoima Dam as the three U.S. Geological Survey (USGS) indi-\n(Trifunac and Hudson 1971)\ncated stations for a more limited number of shocks.\nTwenty-two aftershocks of magnitude 3.5 and\nAlthough the more distant stations of the C.I.T. net-\ngreater that were particularly well located by the\nwork (those indicated by an asterisk in table 1)\nportable stations were used to establish correction\nwere not used in the precise locations, time residuals\nfactors for the more distant permanent stations. In\nat these stations were calculated in each case, and the\ngeneral, the portable stations that were used in-\naverage traveltime correction factors thus obtained\ncluded most of the C.I.T. and Earthquake Mecha-\nfor these and the other permanent stations are as fol-\nnism Laboratory (EML) stations (table 1) as well\nlows:","Seismological Studies and Their Tectonic Implications\n17\ncomparison of some of our solutions with the largely\nStation\nSeconds\nindependent USGS solutions based on explosion cali-\nPAS\n+0.2\nMWC\n-.1\nbration (Wesson 1971)\nPYR\n-.2\nBecause of the difficulty in obtaining hypocentral\nSYP\n+.6\nsolutions for the numerous large aftershocks that OC-\nISA\n+.5\nGSC\n+.2\ncurred within the first 10 minutes following the\nCSP\n+.1\nmain shock (table 2) it is dangerous to attempt to\nPLM\n+1.3\ndraw conclusions about possible migrations in after-\nIn addition, correction factors were applied to some\nshock activity with time. It nevertheless may be sig-\nof the portable stations in the southwestern part of\nnificant that all of the larger aftershocks that we\nthe aftershock region, where considerable thicknesses\nhave located in the southwestern extremity of the af-\nof alluvium and sedimentary rocks are locally pres-\ntershock zone-near Chatsworth and Granada Hills\nent as contrasted to the basement rocks that closely\n(fig. 2) -occurred relatively late in the aftershock\nunderlie most of the rest of the area. These correc-\nperiod. The largest flurry of activity started almost 2\ntion factors, based on the local geology, were: BLA,\nmonths after the main shock and included the shal-\n-0.5; BRC, -0.3; OMM, -0.3; SUS, 0.2; LTU,\nlow, magnitude 4.6 shock of March 31 that locally\n-0.2 second. All of the above traveltime correction\ncaused more damage in Granada Hills than did the\nfactors were applied to a computer location program\nmain shock itself (Barrows et al. 1971-reprinted in\nbased on the three-layer southern California crustal\nthis volume)\nmodel of Press (1960) In actuality, this model is\nclearly a gross oversimplification; in their explosion\nMAGNITUDES\ncalibration of the USGS network in this same area,\nThe local magnitude (ML) of the San Fernando\nWesson and Gibbs (1971) demonstrated that the\nearthquake main shock was tentatively given as 6.6\nlocal geology and crustal structure are very compli-\nby Allen et al. (1971) and by the California Insti-\ncated and variable.\ntute of Technology (1971) on the basis of initial ex-\nOne effect of using both the traveltime correction\namination of the low-gain (4x) Wood-Anderson\nfactors and the larger number of close-in stations has\nN-S seismogram written at Pasadena. Subsequently,\nbeen to assign generally shallower hypocentral\nother low-gain instrumental records of the Pasadena\ndepths than those obtained earlier. Thus, for exam-\nnetwork have been examined in detail, and we\nple, the hypocenter of the main shock is now as-\nherein update our original estimate of M L on the\nsigned a depth of 8.4 km (table 2) instead of the\nbasis of records from Riverside, Cottonwood, and\nearlier 13.0 km (Allen et al. 1971) although the ef-\nSanta Barbara, in addition to Pasadena. All normal-\nfect on the location of the epicenter is less than 1\nmagnification (2800) Wood-Anderson instruments\nkm.\nwere off scale, such as those at Barrett and Tine-\nHypocenters obtained in this study have been di-\nmaha. Resulting magnitude assignments from the\nvided into three categories of accuracy (table 2) de-\nvarious low-gain instruments are as follows:\npending on the number and location of stations used\nin the solution and on the standard error of the com-\nML\nStation\nDirection\nMagnifi-\nputer solution. We feel that \"A\"-quality locations\ncation\nN-S\n4x\n6.7\nare generally accurate to within 2 km horizontally\nPasadena\nRiverside\nN-S\n4x\n6.5\nand 4 km vertically, \"B\"-quality hypocenters are felt\n6.3\nSanta Barbara\nE-W\n100x\nto be accurate to within 4 km horizontally and 8 km\n100x\n6.3\nCottonwood\nN-S\nCottonwood\nE-W\n100x\n6.3\nvertically, and \"C\"-quality solutions are still less ac-\nThe Pasadena determination is subject to the addi-\ncurate. Those hypocentral locations in the vicinity of\ntional uncertainty that the -log A correction (Rich-\nthe main shock probably are much better than these\nter 1958) is a very sensitive function of distance\nstandards, and the depths of the deeper shocks are\nfor epicentral distances of less than 50 km.\nmore accurately determined than those of shallow\nOn the basis of these determinations, we assign\nfocus. The figures represent somewhat subjective but\nM L = 6.4 to the San Fernando earthquake. This\nconservative judgments based on attempts at location\ncompares closely to the mean magnitude of 6.48 as-\nunder a wide variety of assumptions as well as on the","18\nSan Fernando Earthquake of 1971\nsigned by Bolt and Gopalakrishnan (1973) from\nfour stations of the Berkeley network. The Prelimi-\nnary Determination of Epicenters (PDE) listing by\nO\n5\n10 km\nthe National Earthquake Information Center\n(NEIC) of NOAA is Ms = 6.5, mb = 6.2, based on\n279 stations reporting.\nMagnitudes have been assigned to aftershocks\n(table 2) on the basis of readings from 11 standard\nWood-Anderson torsion seismometers at six widely\nspaced stations of the southern California network\n(Pasadena, Barrett, Cottonwood, Riverside, Santa\nBarbara, and Tinemaha) Most magnitudes have\nbeen determined by averaging the readings from at\nleast five of these stations. It is significant, however,\nthat the average standard deviation for individual\nstation readings for 20 aftershocks of magnitude 4.0\nand greater, each recorded at five or more stations,\nwas 0.30. Considering this large variation observed\nA\non standard instruments in a wide variety of azi-\nmuths from the epicenter, some of the discrepancies\nbetween C.I.T. and Berkeley magnitudes reported by\nFigure 3.-Earthquakes of \"A\" and \"B\" hypocentral accuracy\n(see text) for which good fault-plane solutions have been ob-\nBolt and Gopalakrishnan (1973) are not surprising.\ntained, indicating either left-lateral strike slip on north-striking\nplanes (squares) or thrusting on north-dipping planes (circles).\nA number of epicenters are shown here that are not on figure\nFOCAL MECHANISMS AND TECTONIC\n2 because some earthquakes down to magnitude 3.0 have been\nINTERPRETATIONS\nincluded. Dotted line is same as in figures 1 and 2.\nFault-plane solutions for the main shock have\nbeen carried out independently by several investiga-\nof the fault plane that slipped during the earth-\ntors (Canitez and Toksöz 1972, Dillinger and Espi-\nquake, and where stresses remained high following\nnosa 1971, Wesson et al. 1971, and Whitcomb\nthe main shock. Very few aftershocks occurred in the\n1971a) and they agree that the basic mechanism of\nvicinity of the surface break, presumably because\ninitial faulting was that of a thrust striking about\nstresses were completely relieved there. Two princi-\nN.70°W., dipping about 50°NE., and including a\npal areas of interest remain: (1) Aftershocks near\nsignificant component of left-lateral slip in addition\nGranada Hills and Chatsworth, at the southwest end\nto the thrust component. This agrees remarkably\nof the aftershock zone (fig. 2) are south of the pro-\nwell with the surface observations of faulting in the\njected trace of the thrust fault and, therefore, do not\nSylmar-San Fernando area, some 13 km farther\nfit SO simple a picture of thrusting; and (2) focal-\nsouth. Kamb et al. (1971), for example, report the\nmechanism studies of aftershocks (Whitcomb 1971a\noverall trend of the surficial fault break to be\nand 1971b) include many shocks of strike-slip char-\nN.72°W., with north dips averaging about 42°; they\nacter that demand an explanation more complicated\nalso report \"nearly equal amounts of north-south\nthan that of a simple thrust surface.\ncompression, vertical uplift (north-side up), and\nDisregarding momentarily those aftershocks near\nleft-lateral slip.\"\nGranada Hills and Chatsworth, it is clear from figure\nThe hypocentral locations of the main shock and\n4 that the average dip of the zone of faulting north\naftershocks presented herein support the idea of dis-\nfrom the fault trace is considerably less than the 50°\nplacement on a north-dipping thrust fault; and it\ndip indicated by the focal mechanism of the main\nseems particularly likely that the lunate-shaped dis-\nshock. One might explain this by systematic errors in\ntribution of aftershock epicenters (figs. 2 and 3,\nthe depth assignment of the hypocenters shown in\nAllen et al. 1971, Hanks et al. 1971, and Wesson et\nfigure 4, but substantiating evidence of the relatively\nal. 1971) reflects the edge of the disc-shaped segment\nshallow dip of the fault zone is given by the motion","Seismological Studies and Their Tectonic Implications\n19\nSurface\nfault trace\nA'\nA\n15\nxx\n5\n10\n10\n5\n5\no\n5\n15\nkm\n5\nFigure 4.-Vertical cross section along line A-A' of figures 2 and 3,\nwith hypocenters projected into plane of section. Symbols are\nsame as in figure 3, except that additional small crosses indicate\nwell-located earthquakes for which ambiguous or transitional\nfault-plane solutions have been obtained.\nFigure 5.-Schematic structural contour map showing simplified\nvectors of individual focal-mechanism solutions. For\ncontours (in km) on fault plane and showing monoclinal flexure\nthat might explain strike-slip aftershock mechanisms on steep\nsome 65 aftershocks, the motion vectors closely con-\nwest-dipping flank of flexure in fault surface.\ncentrate around an average plunge of 36° toward\nN.20°E., which corresponds closely to the dip of the\nmanded by the data of figure 4. It is significant,\nhypothetical fault surface passing through the hypo-\nhowever, that all but one of the few thrust-type af-\ncenter of the main shock and the main concentration\ntershocks deeper than the main shock (fig. 4) occur\nof aftershock hypocenters (fig. 4) We prefer to be-\nwithin and west of the flexural zone, suggesting that\nlieve, therefore, that the steep dip of the fault plane\nthe flexure is in essence a north-plunging, steep-\nportrayed by the focal mechanism of the main shock\nflanked monocline that simply steps down the thrust\nrepresents only the very initial motion, and that the\nplane to a somewhat greater depth west of the flex-\nfault displacement then propagated to the surface\nure, perhaps by 3 to 5 km.\nalong a zone dipping some 15° less steeply. The fo-\nIf indeed a flexure exists along the zone of strike-\ncal-mechanism data on which this and the following\nslip aftershocks, one geometric effect would be to dis-\narguments are based will be presented in detail in a\nplace the surface trace of the thrust fault to the\nseparate paper by Whitcomb (1973) ; the principal\nsouth on the west side of the flexure (fig. 5), and\nideas have already been presented in Whitcomb\nthis may be the explanation of the aftershocks near\n1971a and 1971b.\nGranada Hills and Chatsworth that are south of the\nIt is clear from figure 3 that the aftershocks of\ntrace of the fault as projected westward from the Syl-\ndominantly strike-slip character delineate a relatively\nmar and Tujunga segments. Furthermore, their pre-\nwell-defined north-trending zone west of the epicen-\ndominant thrust-type focal mechanisms are consistent\nter of the main shock. If the solutions portrayed\nwith their being west of the flexure, in analogy to\nright-lateral slip, this zone might be visualized as a\nthose thrust-type aftershocks at the very northwest\ntypical tear fault (Hills 1963) extending toward the\ncorner of the aftershock area (fig. 3) It is also sig-\nground surface, but their consistent portrayal of left-\nnificant that all of the thrust-type aftershocks west of\nlateral slip demands instead that the thrust surface\nthe flexure seem to have occurred well after the initi-\nturn downward along this zone. These strike-slip\nation of aftershock activity, on or after February 11;\nearthquakes typically occur on fault surfaces dipping\nthe larger shocks in the Chatsworth-Granada Hills\nsteeply westward, and we thus visualize a linear,\narea (fig. 2) all occurred after March 30-very late\nsteep flexure in the fault surface along this zone (fig.\nin the aftershock period.\n5) . Under this hypothesis, most of the strike-slip af-\nFurther support for the existence of a north-trend-\ntershocks should be deeper than the thrust after-\ning flexure comes from the mapped geology of the\nshocks to the east, and this is permitted but not de-","20\nSan Fernando Earthquake of 1971\narea (Wentworth et al. 1971, fig. 2) The trace of\nCaltech Earthquake Research Affiliates and by the\nthe Santa Susana thrust, which lies parallel to and\nNational Science Foundation (Grant GA29920)\nsome 4 km north of the San Fernando fault, makes a\ndistinct bend north of Granada Hills in exactly the\nREFERENCES\nmanner postulated for the San Fernando fault (fig.\n5) Further, the fact that basement rocks are widely\nAllen, Clarence R., Engen, G.R., Hanks, Thomas C., Nord-\nexposed in the San Gabriel Mountains east of this\nquist, J.M., and Thatcher, W.R., \"Main Shock and Larger\nzone, whereas only younger sedimentary rocks are ex-\nAftershocks of the San Fernando Earthquake, February 9\nposed to the west, strongly supports the concept of a\nThrough March 1, 1971,\" The San Fernando, California,\nflexural downstep to the west in this area.\nEarthquake of February 9, 1971, Geological Survey Profes-\nsional Paper 733, U.S. Geological Survey and the National\nThus we argue that the San Fernando earthquake\nOceanic and Atmospheric Administration, U.S. Department\nwas caused by displacement on a thrust fault-or\nof the Interior and U.S. Department of Commerce, Wash-\nzone of thrust faults-dipping about 35° N. and strik-\nington, D.C., 1971, pp. 17-20.\ning about N.70°W. Particularly where the surface\nAllen, Clarence R., St. Amand, Pierre, Richter, Charles F.,\ntrace trended more westerly, as along the Sylmar seg-\nand Nordquist, J.M., \"Relationship Between Seismicity and\nGeologic Structure in the Southern California Region,\"\nment, significant left-lateral slip occurred. A steep\nBulletin of the Seismological Society of America, Vol. 55,\nflexure in the thrust fault surface, parallel to (and\nNo. 4, Aug. 1965, pp. 753-797.\nprobably controlling) the direction of slip and\nBarrows, A.G., Kahle, J.E., Weber, F.H., Jr., and Saul, R.B.,\ndownstepped to the west, tended to limit the zone of\nMap of Surface Breaks Resulting From the San Fernando,\ninitial breaking on the west and led to numerous af-\nCalifornia, Earthquake of February 9, 1971, Preliminary Re-\ntershocks of left-lateral strike-slip character on the\nport II, Plate I, California Division of Mines and Geology,\nSacramento, 1971, scale 1:24,000.\nsteep west-dipping flank of the flexure. Some thrust\nBolt, B.A., and Gopalakrishnan, B.S., \"Magnitudes, After-\ndisplacements occurred later on the downstepped\nshocks, and Fault Dynamics,\" California Division of Mines\nsegment of the thrust fault west of the flexure, as in-\nand Geology Bulletin 196, Ch. 15, Sacramento, 1973? (to be\ndicated by aftershocks in the Chatsworth-Granada\npublished)\nHills area and in the northwestern extremity of the\nCalifornia Institute of Technology, Division of Geological and\naftershock zone north of Solemint. Whitcomb (1971a\nPlanetary Sciences, \"Preliminary Seismological and Geo-\nlogical Studies of the San Fernando, California, Earthquake\nand 1971b) has pointed out that many of the after-\nof February 9, 1971,\" Bulletin of the Seismological Society\nshocks east of the main epicenter have fault-plane so-\nof America, Vol. 61, No. 2, Apr. 1971, pp. 491-495.\nlutions which are consistent with normal faulting\nCanitez, Nezihi, and Toksöz, M. Nafi, \"Static and Dynamic\nalong steep northwest-trending faults; for simplicity,\nStudy of Earthquake Source Mechanism: San Fernando\nsuch shocks have not been shown in figures 3 and 4,\nEarthquake,\" Journal of Geophysical Research, Vol. 77,\nNo. 14, May 10, 1972, pp. 2583-2594.\nbut these events agree with the concept of compres-\nDillinger, W., and Espinosa, A.F., \"Preliminary Fault-Plane\nsional release resulting from a southward thrust to-\nSolution for the San Fernando Earthquake,\" The San Fer-\nward the San Fernando Valley.\nnando, California, Earthquake of February 9, 1971, Geo-\nlogical Survey Professional Paper 733, U.S. Geological Survey\nand the National Oceanic and Atmospheric Administration,\nACKNOWLEDGMENTS\nU.S. Department of the Interior and U.S. Department of\nCommerce, Washington, D.C., 1971, pp. 142-149.\nMany agencies and persons supplied data from\nHanks, Thomas C., Jordan, Thomas H., and Minster, J. Ber-\ntheir portable stations that have been used in our\nnard, \"Precise Locations of Aftershocks of the San Fernando\nstudy: Earthquake Mechanism Laboratory, NOAA\nEarthquake 2300 (GMT) February 10-1700 February 11,\n(Don Tocher) National Center for Earthquake Re-\n1971,\" The San Fernando, California, Earthquake of Feb-\nruary 9, 1971, Geological Survey Professional Paper 733, U.S.\nsearch, USGS (Robert Wesson and Willy Lee) Uni-\nGeological Survey and the National Oceanic and Atmos-\nversity of California at San Diego (James Brune)\npheric Administration, U.S. Department of the Interior and\nand California Department of Water Resources\nU.S. Department of Commerce, Washington, D.C., 1971,\n(Paul Morrison) At C.I.T., Gladys Engen, Mark\npp. 21-23.\nGaponoff, Jan Garmany, and John Nordquist read\nHills, E.S., Elements of Structural Geology, John Wiley &\nSons, New York, N.Y., 1963, 483 pp.\nmany of the records and carried out many of the\nKamb, Barclay, Silver, L.T., Abrams, M.J., Carter, B.A., Jor-\ncomputer solutions. This study was supported by the\ndan, Thomas H., and Minster, J. Bernard, \"Pattern of","Seismological Studies and Their Tectonic Implications\n21\nFaulting and Nature of Fault Movement in the San Fer-\nOceanic and Atmospheric Administration, U.S. Department\nof the Interior and U.S. Department of Commerce, Wash-\nnando Earthquake,\" The San Fernando, California, Earth-\nquake of February 9, 1971, Geological Survey Professional\nington, D.C., 1971, pp. 6-16.\nWesson, Robert L. (U.S. Geological Survey, Menlo Park,\nPaper 733, U.S. Geological Survey and the National Oceanic\nand Atmospheric Administration, U.S. Department of the\nCalif.) 1971 (personal communication)\nWesson, Robert L., and Gibbs, J.F., \"Crustal Structure in the\nInterior and U.S. Department of Commerce, Washington,\nVicinity of the San Fernando, California, Earthquake of\nD.C., 1971, pp. 41-54.\n9 February 1971\" (abstract), Transactions of the American\nPress, Frank, \"Crustal Structure in the California-Nevada Re-\ngion,\" Journal of Geophysical Research, Vol. 65, No. 3, Mar.\nGeophysical Union, Vol. 52, No. 11, Nov. 1971, p. 864.\nWesson, Robert L., Lee, W.H.K., and Gibbs, J.F., \"Aftershocks\n1960, pp. 1039-1051.\nof the Earthquake,\" The San Fernando, California, Earth-\nProctor, R.J., Crook, R., Jr., McKeown, M.H., and Moresco,\nquake of February 9, 1971, Geological Survey Professional\nR.L., \"Relation of Known Faults to Surface Ruptures,\n1971 San Fernando Earthquake, Southern California.\" Geo-\nPaper 733, U.S. Geological Survey and the National Oceanic\nand Atmospheric Administration, U.S. Department of the\nlogical Society of America Bulletin, Vol. 83, No. 6, June\nInterior and U.S. Department of Commerce, Washington,\n1972, pp. 1601-1618.\nRichter, Charles F., Elementary Seismology, W.H. Freeman\nD.C., 1971, pp. 24-29.\nWhitcomb, James H., \"Fault-Plane Solutions of the February\nand Co., San Francisco, Calif., 1958, 768 pp.\nTownley, S.D., and Allen, M.W., \"Descriptive Catalog of\n9, 1971, San Fernando Earthquake and Some Aftershocks,\"\nThe San Fernando, California, Earthquake of February 9,\nEarthquakes of the Pacific Coast of the United States, 1769\n1971, Geological Survey Professional Paper 733, U.S. Geo-\nto 1928,\" Bulletin of the Seismological Society of America,\nlogical Survey and the National Oceanic and Atmospheric\nVol. 29, No. 1, Jan. 1939, 297 pp.\nAdministration, U.S. Department of the Interior and U.S.\nTrifunac, Mihailo D., and Hudson, Donald E., \"Analysis of\nDepartment of Commerce, Washington, D.C., 1971a, pp.\nthe Pacoima Dam Accelerogram-San Fernando, California,\nEarthquake of 1971,\" Bulletin of the Seismological Society\n30-32.\nWhitcomb, James H., \"Focal Mechanisms of the San Fernando\nof America, Vol. 61, No. 5, Oct. 1971, pp. 1393-1411.\nAftershock Series\" (abstract), Transactions of the American\nWentworth, Carl M., Yerkes, R.F., and Allen, Clarence R.,\nGeophysical Union, Vol. 52, No. 11, Nov. 1971b, pp. 862-863.\n\"Geologic Setting and Activity of Faults in the San Fer-\nWhitcomb, J.H., \"The 1971 San Fernando Earthquake Series\nnando Area, California,\" The San Fernando, California,\nFocal Mechanisms and Tectonics,\" Reviews of Geophysics,\nEarthquake of February 9, 1971, Geological Survey Profes-\nsional Paper 733, U.S. Geological Survey and the National\nin press, 1973.","","Felt Area and Intensity of\nSan Fernando Earthquake\nINTRODUCTION\nEven though this earthquake was only of moderate\nmagnitude (6.4), it devastated buildings and dwell-\nings; major highways; dams, underground gas, water,\nand sewer systems; and electrical facilities and equip-\nment. With damage losses estimated at over $500\nmillion, it ranks as one of the major destructive\nCONTENTS\nshocks of the United States.\nPage\n23\nINTRODUCTION\nAlthough 58 persons were killed and over 2,000\n26\nINTENSITY IX-XI\nwere injured, clearly the time of occurrence\n26\nSan Fernando, Sylmar, and Environs\n(06:00:41.6 Pacific Standard Time) and the brief\nSummary of Faulting and Other\n26\nGround Effects\nduration of strong shaking (about 10 seconds) were\n27\nHighways and Roads\nextremely fortunate circumstances for a great many\n27\nDams\nother persons, as attested to by the collapsed freeway\n28\nUtilities\noverpasses, the collapsed or partially collapsed com-\n29\nBuildings and Dwellings\n34\nINTENSITY VIII\nmercial and industrial buildings, and the nearly de-\n34\nGranada Hills\nmolished Van Norman Dam.\n35\nMission Hills\nThe epicenter was located at latitude 34°24.7' N.\n36\nNewhall-Valencia Area\n36\nNewhall\nand longitude 118°24.0\" W., about 8.7 miles north-\n37\nValencia\nnortheast of San Fernando, in the San Gabriel\n37\nSaugus and Soledad Canyon Areas\nMountains south of Soledad Canyon; but the full\n38\nINTENSITY VII\nimpact of the shock's explosivelike force was felt in\n47\nREFERENCES\nthe San Fernando-Sylman area.\nA very violent vertical motion was reported by\nsome observers in the strongly shaken area, but, in\ngeneral, observers reported the direction of motion\nas either north-south or east-west.\nThe \"generally felt\" area was approximately\n80,000 square miles, but there were a few isolated in-\nstances of the shock being felt beyond this area:\nBridgeport, Stockton, and Yosemite National Park,\nCalif.; Tonopah, Nev.; and Beryl, Utah (fig. 1)\nThe felt area was determined primarily from almost\n2,000 reports received through the earthquake ques-\ntionnaire card canvass conducted by the Seismologi-\ncal Field Survey.\nIntensities ranging from VIII-XI (fig. 2) OC-\nNINA H. SCOTT\ncurred over approximately 190 square miles. A\nSeismological Field Survey\nmaximum intensity of XI was assigned to the Olive\nEarth Sciences Laboratories\nView Hospital in northern Sylmar area where por-\nEnvironmental Research Laboratories, NOAA\n23","2\n38°\n37°\n36°\n35°\n34°\n33°\n32°\nARIZONA\nUTAH\n113°\n113°\nBeryl\nKingman\n114°\n114°\n2e\nYYmm\n20\n20\nBlythe\nNeedles\nFigure 1.-Area affected by San Fernando, Calif., earthquake of February 9, 1971.\n:Desert Center\n115°\nLas Vegas\nLIMITS OF FELT AREA\n115°\n40\nCalexico\nNEVADA\nMEXICO\n04\n4\n05\n05\nAmboy\n40\n40\n116°\n22\nPalm Springs\nLathrop\n116°\n04\n5\n40 Wells\nSalton\n.5\nCity\n05\n05\n05\n5Big Bear City\nLucerne Valley\n.4\n40\n.5\n04\n20 Tonopah\n05\n03\nV\nCALIFORNIA\n117°\nBarstow\n05\n5e\n5.\nPalo\n117°\n6°\n6006\n05\n05\n05\n5°Boron\nSan Diego\nSanto Ana\n5\n05\n5\n40\n5\ne Lancaster\n118°\nVI\nPasadena\nOlancha\nCantil\n50\n05\n@San Fernando\n:\n05\n606\n5\n5\n05\n06\nVIII - XI\nAvalon\n118°\n05\nBishop\n4\n5.Wheeler Ridge 05\n04\n5. 05\nBakersfield\n60\n40\n7777\n4\n04\n04\n50\n119°\nCatalina\n5\nSanta\nIsland\nCastaic\n05\nVII\n240\nYosemite Natil Park\n150\n50\n2\n.4\n50\n5\nV\n50\nBridgeport\n119°\n05\n50\n05\n5.05\nHanford\n:\n05\n125\n200\n40\n30\n20Fresno\n05\nTaft 05\nFEBRUARY 9, 1971, 06:00:41.6 PST\nDOT WITHOUT NUMBER = NOT FELT\n05\n2\n3\nSEE FIG. 2 FOR VIII-XI AREA\n05\n05\n05\n120°\n2e\n50\n04\nSCALE IN KILOMETERS\n100\n160\n04\n4\n- IV\nSCALE IN MILES\n05\nMerced\n2\n04\nParkfield\n05\n40\n2\n30 Los Banos\n120°\n75\n120\n03\n2\nI\n50\n4e\nO\n30\n05\n5\n121°\n50\n80\n2\n2\nStockton\n4\n4\nKing City\n25\n40\n121°\n2\n122°\n0\n0\n122°\n38°\n37°\n36\n35°\n341\n33°\n32°","Felt Area and Intensity of Earthquake\n25\nCanyon\n8\nsoledod\nCanyon\nN\nSoledad\nHONBY\nRoad\n8\nSOLEMINT\n8\nSAUGUS\nEPICENTER\n8\n8\niron\nCanyon\nNEWHALL\nPiggerito\nBear Divide Ranger Station\nPocoimo\n10\n9\nVejerons Adm\n#: Hospital\nOlive View Hospitol\n(10\n(1)\nF\nJuvenile\n10\nHai\n10\nSylmar Electrical\nConverter Station\n10\n(8\n10\nSYLMAR\n10\nUpper\n9\nDam\niKart Holton\n10\nConyon\nStation\nSan Fernando\nIC\nPORTER\nRanger Station\nRANCH\nO\nAREA\nathill Nursing Home\nSAN/FERNANDO\n(IC\n10\n9\nLower Dam\nas\nPocaima Memorial\nHospital\nLutheran Hpspite\nRinoldi Street\n8\n(9)\nFootbill Freeway\n8\nGRANADA HILLS\nHansen\nLoke\nB\nPACOIMA\nMISSION HILLS\nSUNLAND\n7\nU.S Veterans\nHospital\n7\nNORTHRIDGE\n7\nSE\nULVEDA\n7\nPANORAMA\nCITY\nSUN VALLEY\n7\n8\nINDICATES INTENSITY\nEPICENTRAL AREA\n7\nBURBANK\nSAN FERNANDO EARTHQUAKE\nFEBRUARY 9, 1971\n7\nVAN NUYS\n1/2 0\nSCALE IN MILES\nFigure 2.-Epicentral area of San Fernando, Calif., earthquake of February 9, 1971.","San Fernando Earthquake of 1971\n26\ntions of new, reinforced concrete, earthquake-resis-\n\"Reports of fatalities have varied and are quoted\nfrequently as 64. These figures (58) have been pro-\ntive buildings collapsed. Intensities of IX-X gener-\nvided by the Medical Examiner-Coroner. They in-\nally were indicated in the Sylmar-San Fernando area\nwhere ground disturbances were varied and wide-\nclude only those who died as a direct consequence of\nthe earthquake. They do not include fatalities from\nspread (fissuring, sliding, slumping, and compres-\nheart attack occurring coincident with the earth-\nsion-ridging) freeway overpasses collapsed, support-\nquake or accidents while being transported from the\ning piers sustained great damage, and many other\nbridges were seriously damaged; two old earthfill\nscene.\"\nAn estimated 2,400 were injured.\ndams were damaged and must be rebuilt, with one\nDamage: Structures posted as unsafe, 1,489; dam-\non the verge of collapse; underground gas, sewer,\naged, 30,684, including mobile homes. (These fig-\nand water pipelines were completely out of service in\nsome areas as the result of the great number of\nures represent damaged dwellings, apartment build-\nings, commercial, industrial, etc.)\nbreaks; railroad tracks bent; electrical facilities were\ngreatly damaged; unreinforced concrete buildings\n\"Some additional structures were posted unsafe in\njurisdictions other than the cities of Los Angeles and\ncollapsed; and reinforced concrete buildings were se-\nSan Fernando and the county of Los Angeles. Most\nriously damaged. Buildings of all types-commercial,\nof the damage in these other jurisdictions was to\nindustrial, and dwellings-were damaged exten-\npre-1933 brick structures and chimneys. Hundreds of\nsively. Many were beyond repair and condemned.\nthe latter were damaged.\nIn the intensity VII zone, considerable damage OC-\n\"The damage inflicted by the earthquake has been\ncurred, but mainly to older buildings and dwellings.\nestimated to be over $500 million, and it has been\nSome were posted as \"unsafe,\" and others reportedly\nreported that approximately 850 homes, 65 apart-\nwill be demolished, notably in the Alhambra, Bev-\nment buildings, and 574 commercial-industrial\nerly Hills, Burbank, and Glendale areas. It was re-\nbuildings were SO damaged that they were vacated;\nported that a few large buildings sustained some\nsome 4,800 homes, 265 apartment buildings, and\nstructural damage, but damage to large or high-rise\n1,125 commercial buildings had appreciable damage;\nbuildings generally was minor-cracked partitions,\nand about 30,000 structures had lesser damage. It\nfallen plaster, and broken windows. There were nu-\nwas reported that about 1,700 mobile homes were\nmerous reports of inoperative elevators. Thousands of\ndamaged substantially in the earthquake area.\"\nchimneys were damaged.\nAll intensities in the sections that follow are rated\nDamage estimates:\naccording to the Modified Mercalli Intensity Scale of\nJurisdiction or agency\nPublic\nPrivate\nproperty\nproperty\n1931 (Wood and Neumann 1931) Descriptions for\nCity of Los Angeles\n$92,000,000\n$210,000,000\nintensity VI and below are not included in this\nCounty of Los Angeles\n100,000,000\n6,800,000\nOther local jurisdictions\n5,200,000\n30,000,000\npaper.\nState of California\n15,000,000\nThe following fatality, injury, and damage figures\nFederal Government\n10,000,000\nwere taken from Los Angeles County Earthquake\nMetropolitan Water District\n6,000,000\nGeneral Telephone\n4,700,000\nCommission (1971) : Relative to the four persons\nLos Angeles School District\n22,500,000\nkilled at other locations, it was reported by the press\nSouthern California Gas Company\n2,000,000\nthat a woman was killed by the collapse of her home\nSouthern California Edison\nCompany\n750,000\nat 13656 Borden Avenue in Sylmar; one child was\nkilled by the collapse of a commercial building at\nTotal\n$250,700,000\n$254,250,000\n1113 First Street in San Fernando; and a man was\nTotal (public and private). $504,950,000\nkilled by collapse of an old building (Mission Inn)\nin downtown Los Angeles. It is not known at this\nINTENSITY IX-XI\ntime just where the other fatality occurred.\nSan Fernando, Sylmar, and Environs\nFatalities:\nSummary of Faulting and Other Ground Effects\nOlive View Hospital\n3\nVeterans Administration Hospital\n49\nThe earthquake created a zone of discontinuous\nCollapse of freeway overpass\n2\nsurface faulting that extended from the Bee Canyon\nOther\n4","Felt Area and Intensity of Earthquake\n27\narea (west of Upper Van Norman Lake) roughly\nous shattered ridgetops, with the soil of previously\neastward across the Sylmar-San Fernando area to\nsmooth surfaces upthrown, overturned, and pulver-\nthe Big Tujunga Canyon area north of Sunland.\nized. This type of ground rupture was especially\nThe main rupture segment, designated the Sylmar\nexemplified west of Grapevine Canyon, in the hills\nsegment, extended eastward from the intersection of\nnorth of the Olive View Hospital, near Wallaby and\nHubbard Street and Glenoaks Boulevard in the\nRajah Streets in the northeasternmost corner of\nsouthern Sylmar-northern San Fernando area, across\nSylmar, west of Balboa Boulevard, east of Bartholo-\nFoothill Boulevard, to the Foothill Nursing Home.\nmaus Canyon, and on the ridges above Oliver and\nAlthough it was in this segment that the greatest and\nSchwartz Canyons.\nmost complex ground distortion and concentration\nof damage occurred, prominent ground displace-\nHighways and Roads\nments, fractures, and scarps were observed in other\nMost of the major and spectacular damage to high-\nsegments of the fault zone, notably in the Tujunga\nway structures and bridges occurred in an area along\nsegment that extended from the vicinity of the Foot-\nU.S. Highway 5 at the interchanges of Routes 5/210\nhill Nursing Home eastward into Big Tujunga Can-\nand 5/14, located about 1 mile apart. At the Route\nyon, and in the area north and northwest of Upper\n5/210 interchange (Foothill Boulevard and Golden\nVan Norman Lake. Surface faulting also occurred in\nState Freeway), three highway overpasses totally col-\nareas away from the main zones of faulting, includ-\nlapsed and two required rebuilding. Two men were\ning an area just east of the Veterans Hospital; in the\nkilled at this location when one of the overpasses col-\nLopez and Kagel Canyon areas; on Kagel Mountain\nlapsed onto their truck. Bridge columns failed. At\n(just east of Pacoima Reservoir) and in areas east\nthe Route 5/14 interchange (Golden State Freeway\nof Lower Van Norman Lake along the Golden State\nand Antelope Valley Freeway) two spans of a nine-\nFreeway. Landsliding and severe ground fractures\nspan bridge collapsed. A bridge also collapsed at the\nwere responsible for extensive damage in areas not\ninterchange between the Golden State Freeway and\nassociated with faulting. There was severe ground\nSan Diego Freeway. It was reported that almost all\ncracking in the Olive View Hospital area, in the\nremaining structures in the general vicinity of the\nsouthwestern Sylmar and San Fernando areas, in the\ninterchanges (possibly as many as 70) were damaged\nupper Granada Hills area west of Van Norman\nto some extent, many requiring extensive repair.\nLakes, and in many areas north and east of the Syl-\nBridges on the Antelope Valley, Foothill, and San\nmar-San Fernando area. There was extensive land-\nDiego Freeways also were damaged seriously, espe-\nsliding and slumping, along with numerous fissures\ncially along Foothill Freeway in the Sylmar-San Fer-\nand sand boils, in the Van Norman Lakes area. It\nnando area. The press reported that the Newhall\nwas reported that the appearance of the sand boils\nand Old Sierra Highways and Bouquet Canyon\nindicated liquefaction of soil in this area. The most\nRoad were closed by slides and bridge damage.\ndamaging slide (the Juvenile Hall slide) occurred\nThere was some bridge damage along the Soledad\nin the Upper Van Norman Lake area, where prac-\nCanyon Road areas east of Saugus. Many other roads\ntically all structures and facilities located in or cross-\nwere blocked by slides in the San Gabriel Moun-\ning this slide were damaged very severely-highway\ntains. Numerous roads and city streets in northern\noverpasses and bridges, railroad lines, pipelines, and\nSan Fernando Valley were made dangerous or im-\ncanals; Sylmar Converter Station; San Fernando\npassable by landslides, cracks, and upheaval. Rail-\nValley Juvenile Hall; Joseph Jensen Filtration Plant;\nroad traffic also was disrupted because of displace-\nand other structures and facilities. Landslides and\nment and distortion of rails and a collapsed overpass\nrockfalls were widespread and numerous, with high\nthat fell on the tracks. In front of the Juvenile Hall\nconcentrations in the foothills and mountainous\nfacilities, railroad tracks were twisted, broken, and\nareas. Massive rocks fell in the Pacoima Dam area.\ndisplaced as much as 52 inches.\nMany roads were blocked by landslides and rockfalls.\nOne of the larger slides, approximately 600 feet wide,\nDams\noccurred on the east side of Schwartz Canyon. The\nviolent, vertical motion of this earthquake also was\nThe old Upper and Lower Van Norman earthfill\nevident in the observance of widespread and numer-\ndams were damaged and require rebuilding. The","San Fernando Earthquake of 1971\n28\nLower Dam was SO close to complete failure that ap-\nUtilities\nThere was extensive and severe damage to under-\nproximately 80,000 persons were evacuated for sev-\nground waterlines, gaslines, sewers, tunnels, flood\neral days from the endangered areas below the dam.\ncontrol facilities, and electrical and power facilities\nThe reservoir keeper of Lower Van Norman Reser-\nand structures. It was reported that it will be neces-\nvoir reported the following: \"We live on the reser-\nsary to completely rebuild the sewer system in the\nvoir grounds at the bottom of the dam on the west\narea bounded by Hubbard Street, Glenoaks Boule-\nend (11729 Strandwood Avenue) No ground cracks\nvard, Harding Street, and Eighth Street. In the\naround house. Chimney badly damaged; one crack in\nUpper Van Norman Lake area, sections of several\nfoundation. Stove, refrigerator, and dresser shifted.\ncanals were badly damaged; several flood control\nNo broken plaster; no broken windows. Damage\nslight. My wife and child were up, getting ready for\ndikes suffered slumping. Reportedly, approximately\n$2.5 million damage was done to the Los Angeles\nschool. She heard the shock coming. I was asleep. I\ntried to get out of bed but couldn't, until the worst\nflood control facilities, and about one-half of this loss\nof it was over. I made a quick check on the family\nresulted from breakage of reinforced concrete open\nchannels and underground box channels. In one case,\nand a quick check of the house, then dressed and\nwent to check the dam. When I got to the main road\nbreakage extended for the length of a city block.\ngoing to the top of the dam, I could see through the\nSubstantial damage occurred to Wilson Canyon\ndust an irregularity of the crest of the structure\nChannel, Mansfield Avenue Storm Drain, Pacoima\nbelow, looking to the top. I drove to the top of the\nWash, Lopez Canyon Channel, and Glenoaks Boule-\ndam and around the west abutment and saw the\nvard Drain, all in the San Fernando-Sylmar area.\ndamage to the face. It was hard to believe what I\nLopez Debris Basin, north of Hansen Dam, was seri-\nously damaged. Damage was estimated at $6 million\nsaw.\"\nto the Metropolitan Water District of Southern Cali-\nIt was reported the Pacoima Dam, located about\nfornia facilities. At the Joseph Jensen Filtration Plant\n11/4 miles northeast of the San Fernando Veterans\n(about 1/4 mile northwest of Upper Van Norman\nHospital, sustained $1.5 million damage to its abut-\nLake), there was extensive ground cracking in the\nments. Massive rockslides blocked access roads to the\nplant area, with lateral movement of 1 foot or more\ndam. Waterlines were damaged. In view of the ap-\nat the plant site. The Balboa Inlet Tunnel (14 ft in\nparent high intensity in this area, the following, as\ndiameter) had about 300 feet of lining badly dam-\nreported by the caretaker of the dam, is of interest:\naged at a point about 1,500 feet in from its down-\n\"Caretaker's house is a one-story wood frame build-\nstream portal. It was reported the San Fernando\ning (built in 1953), situated on loose fill (fill done\nTunnel (18 ft in diameter, 29,000 ft long, and ex-\nin 1938) It is approximately 40 by 40 feet and rests\ntending from Magazine Canyon to Pacoima Wash)\n2 feet off the ground on a concrete perimeter foun-\ndation with wood plate around the foundation.\nexperienced a 61/2-foot vertical displacement between\nits portal and a point 41/2 miles into the tunnel. The\nThere was no damage to the concrete foundation\nFirst and Second Owens River Aqueducts were dam-\nand only minor damage to the wood support. The\naged. The Second Aqueduct was damaged in its Sau-\nbrick chimney was undamaged. There were hairline\ngus pipeline portion (pipes buckled and supports\ncracks in ceiling plaster and above doors; no doors\nwere out of plumb. Doors on a 6-foot-high hutch\nmoved) between Terminal Hill and Magazine Can-\nyon. Water service to the Granada Hills, Porter\nopened and the first row of glasses was thrown out;\nRanch, Sylmar, and other high-elevation areas in the\nthen the doors closed and rest of glasses did not\nbreak. Some objects fell in the house. Huge rock\nSan Fernando Valley was disrupted by the many\nrolled down and broke outside stucco but the rock\ntrunkline breaks on the Susana, Granada, and Ma-\ndid not come through into the house. An old nearby\nclay trunklines. On the Granada line, most of the 10\nhouse (built in 1937) had outside brick chimney\nor 12 breaks were in the Joseph Jensen Filtration\nseparate from frame but the chimney did not fall. At\nPlant area. The wood roof collapsed at the small Ma-\nthe dam, an empty tank (under construction)\nclay Reservoir on the Maclay High Line, and crack-\nshifted only about 6 inches off foundation.\" It was\ning occurred at the sides and corners of the basin.\nreported that Lopez and Hansen Dams sustained\nDamage at the Sylmar Converter Station (Pacific In-\nonly minor damage.\ntertie), just west of Upper Van Norman Lake, was es-","Felt Area and Intensity of Earthquake\n29\ntimated at approximately $22 million. It was re-\nter) broke and erupted in flames on Glenoaks Boule-\nported that the most severe damage to this plant\nvard between Hubbard and Bledsoe Streets, shutting\ninvolved electrical equipment and underground con-\noff service to 20,000 homes. Oilfield facilities and\nduits. Such equipment as converters, transformers,\nrelated structures sustained minor damage to tanks,\nand circuit breakers were damaged extensively.\nroads, pipelines, and a few wells in Aliso Canyon,\nHeavy outdoor electrical equipment, some weighing\nCascade, Castaic, Newhall, Newhall-Potrero, Oak\nmany tons, was overturned. Many cracks, separations\nCanyon, Placerita, and Ramona oilfields.\nof concrete walls, and other building damage were\nnoted. It was estimated that this facility would be\nBuildings and Dwellings\nout of operation for about 1 year. A power-generat-\nOlive View Hospital.-Major collapses of newly\ning plant, north of the station, was also seriously\nbuilt reinforced concrete buildings occurred and oth-\ndamaged. There was severe damage to electrical\ners were seriously damaged. The second story of a\nequipment at the Olive Switching Station, about\ntwo-story building dropped to ground level. Four\none-half mile west of the Sylmar Converter Station,\nfive-story wings pulled away from the main building;\nwhere insulator-supported equipment collapsed and\nthree were toppled. This damage was reported to\nseveral large transformers overturned. Severe damage\nhave been the result of severe ground shaking, not\nwas sustained at the Olive View Powerplant where\nfaulting. Three deaths occurred at this facility, one\nlarge boilers were shifted as much as 4 feet and\nfrom falling debris and two when power was cut off\nwhere tanks and motors were torn loose from an-\nfrom medical equipment. Ground and paving cracks\nchorages. Many elevated water tanks were damaged;\nand compression ridging were noted at the site.\nsome were shifted, overturned, and destroyed. A\nSan Fernando Veterans Administration Hospital.-\nlarge steel tank, just north of Olive View Hospital,\nMajor collapses of older unreinforced masonry build-\nwas ruptured. An elevated water tank, east of San\ning occurred at this facility. Forty-nine were killed;\nFernando Ranger Station in Lopez Canyon, was\nmany were injured.\nshifted from its pad and destroyed. A Fiberglas tank,\nHoly Cross Hospital.-This seven-story reinforced\nnear the northwest shore of Lower Van Norman\nLake, shattered when it hit the ground. A large tank\nconcrete building sustained major structural damage.\nat Granada Hills was damaged. Many water wells\nExtensive and severe cracking caused the building to\nwere damaged. In general, all utility facilities-gas,\nbe evacuated. Also, the nearby Indian Hills Medical\nelectrical, and water-in the severely damaged areas\nCenter building was badly damaged.\nof San Fernando and Sylmar were out of service. It\nPacoima Memorial Lutheran Hospital (about 13/4\nwas reported the water distribution system for the\nmiles southeast of Foothill Nursing Home) -Major\ncity of San Fernando was almost completely de-\nstructural damage to a four-story reinforced concrete\nstroyed by ground cracking and violent shaking. All\nbuilding occurred, causing it to be evacuated.\nreservoirs leaked; two could not be repaired. Many\nSan Fernando Juvenile Hall buildings.-There was\nunderground gaslines and waterlines were separated,\nsevere and extensive damage to practically all build-\nbuckled, or fractured. Nearly every pipeline in the\nings; some collapsed. Fissures 18 to 24 inches wide\nmajor ground-rupture zone was damaged. All tele-\nand 4 to 5 feet deep were noted at the site. The\nphone equipment in the Sylmar Central Office of the\nbuildings were evacuated.\nGeneral Telephone Company (Polk Street and Bor-\nSan Fernando Industrial Tract (east of the intersec-\nden Avenue) was totally destroyed. Damage to the\ntion of Foothill Boulevard and Arroyo Street) -Ma-\nbuilding and equipment was estimated at $4.5 mil-\njority of structures were posted as unsafe. Severe\nlion. In the Sylmar area, many pole transformers were\nground cracking, lurching, and compression ridging\nthrown down; insulators and crossarms were broken;\noccurred. Sidewalks were torn up and buckled.\nwires and poles were knocked down; and cable was\nsheared off in underground ducts. Four gas transmis-\nSylmar Industrial Tract (east of San Fernando\nsion lines, ranging in diameter from 12 to 26 inches,\nRoad in Bledsoe and Bradley areas) .Majority of\nwere damaged between Newhall and San Fernando,\nbuildings were posted as unsafe. Many roofs and\nresulting in loss of gas supply to the San Fernando-\nwalls collapsed. Considerable ground cracking and\nSylmar area. A main feeder gasline (16 in. in diame-\ncompression ridging occurred.","San Fernando Earthquake of 1971\n30\nhouses was between the Olive View Hospital and the\nFoothill Nursing Home (just east of Foothill\nVeterans Administration Hospital where some resi-\nBoulevard and about 1/3 mile south of San Fernando\ndences were damaged beyond repair and some were\nRanger Station) -The building, a one-story concrete\nin state of collapse, where many houses were shifted\nblock structure, was severely damaged. The curb and\noff foundations, and where practically all concrete\nsidewalk in front of the building were raised about 3\nblock walls and chimneys fell. Also, many dwellings\nfeet by surface faulting that also passed under the\nin various stages of construction in an area east of the\nbuilding.\nVeterans Administration Hospital were heavily dam-\nSchool buildings.-\"Most schools in the San Fer-\naged, and some collapsed.\nnando Valley were post-1933, and these experienced\nThe majority of the following reports were ob-\nlittle damage from shaking. Some wood frame build-\ntained through the questionnaire card canvass con-\nings were shifted on their foundations, and some\nducted by the Seismological Field Survey:\ncracking was experienced. The foundations of sev-\neral school buildings, such as Van Gogh Street Ele-\nSAN FERNANDO:\nmentary School and Sylmar High School, were dis-\n2043 Phillippi Street (about 1 3/4 miles southeast\nrupted by permanent ground displacements, but\nof Olive View Hospital) \"No one sound could be\nstructural damage was not such as to constitute an\ndistinguished. The building and everything in it\nundue hazard to occupants. However, in some cases,\nshook SO violently that the combined sounds were\nlight fixtures and ceilings supposedly designed to\ndeafening. In my block, streets split and were dis-\nwithstand earthquake shaking fell, and these would\nplaced in about 10 places; one place in street was\nhave been hazardous. The generally good behavior\nbuckled. Other streets in the area were split, cracked,\nof the school buildings in the San Fernando Valley\ntwisted, and buckled far worse than my street. My\nis due mainly to the fact that they were well-\nchimney top shot straight up, then fell on roof. It\nconstructed one- and two-story structures, mostly\nwas pulled straight up, with its reinforcement rods\nwood frame and plaster, that were significantly\nleft in main body of chimney, and pulled a segment\nstronger than the minimum requirements of the\nof the inside tile out of the main body of chimney.\nbuilding code. Of the pre-1933 schools, Morningside\nSwimming pools in area lost 5,000 gallons or more of\nSchool at Maclay Avenue and Fifth Street in San\nwater. One pool, two blocks away, was pushed under\nFernando was closest to the center of the earth-\ndecking nearly to the house foundation. Water in\nquake. One of the two structures at this site was a\ntoilet tank splashed all over the bathroom. Every sur-\ngood quality, two-story brick bearing-wall building\nface in house was cleared of contents. All bedroom\n(1928) which was very badly cracked by the ground\nfurniture in three bedrooms, except beds, was over-\nshaking. Although it would not have injured occu-\nturned. Every bottle lid was screwed off or loosened,\npants during the earthquake, it did appear after-\neven new bottles. Eighty-five percent of glass and\nwards to be in a most dangerous condition, and it\npottery broken, including 'Melmac.' Moderate-to-\nhas been demolished. Since the earthquake, most of\nsevere plaster cracks in walls and ceilings of every\nthe old buildings have been closed. A few were\nroom. Ninety-nine percent of block walls down, in-\njudged to be in a good condition and not unduly\ncluding reinforced walls. I have only slight damage\nhazardous to the occupants, and these will be used\nto my house, but [one-] half block away, every other\nfor a limited period of time.\"\nhouse is condemned; one block away, 90 percent of\nDwellings.-Severe and extensive residential dam-\nthe houses are condemned. All the waterpipes and\nage occurred in the area of permanent ground dis-\nmany of the gaspipes had to be replaced in a 36-\nplacement, beginning in the area of Glenoaks\nblock area of San Fernando where I live.\"\nBoulevard and Hubbard Street and extending east-\n1942 Chivers Street (northeast of Glenoaks Boule-\nward across northern San Fernando (north of Maclay\nvard, about 2 miles southeast of Olive View Hospi-\nAvenue) into the foothills to the east. Many houses,\ntal) -Fractures were in earth. \"According to the\nincluding mobile homes, were very badly cracked and\nU.S. Geological Survey, the lot was shortened by\nshifted from foundations. Many one- and two-story\nabout 1 foot. Water and gaslines in street broken.\napartment buildings were also extensively damaged.\nMost concrete block fences knocked down.\"\nAnother area of severe, extensive damage to residential","Felt Area and Intensity of Earthquake\n31\nFoothill Boulevard and Vaughn Street (about SYLMAR:\none-half mile east of San Fernando Airport) -\n12939 Gladstone Avenue.-Ground was cracked,\n\"Building about 6 months old. Floor is up and down\nlandslides occurred, and water was disturbed. Chim-\n12 inches in a rolling manner. Vaughn Street is\nneys and water tanks were cracked, twisted, and over-\nraised at least 12 inches near rear of the building.\nturned. Plaster and windows were cracked. Furniture\nSide walls torn loose from glued-laminated beams.\nwas broken. Damage was moderate to great. \"Land-\nRear lintel broken. Front wall (SW.) looks good.\nslides in the hills.\"\nWaterpipe in street (24-in. diameter) broken.\"\n13972 Sayre Street (between Borden Avenue and\nNortheast of Foothill Boulevard (about one-half\nFoothill Boulevard, near Phillippi Avenue, south-\nmile northeast of San Fernando Airport) \"Build-\nwest of Foothill Boulevard) -Ground was cracked,\ning (concrete tilt-up) at 12300 Gladstone moved 12\nlandslides occurred, and water was disturbed. Houses\ninches into building at 12314 Gladstone, ground and\nwere off foundations; cement slabs were cracked in\nall, at west corner. This was possible because it sat\nhalf and spread. Damage was moderate to observer's\nback about 12 inches behind adjoining building.\nhome.\nThe 12314 Gladstone building (concrete block) was\n14141 Foothill Boulevard (about three-fourths mile\nonly moved 4 inches off footings at west corner.\nsoutheast of Olive View Hospital) -Ground was\nFloor badly distorted. Compression lines in rear yard\ncracked, landslides occurred, and water was dis-\nrunning north-south. Building about 3 years old.\nturbed. Pipes were broken. Hot water heater was\nStreet buckled. At 12424 Gladstone (building about\ntorn from wall. Wall was moved. Plaster was\n1 year old), northeast rear wall failed because nails\ncracked, broken, and fallen. Furniture was over-\npulled through 1/2-inch plywood roof diaphragm.\nturned. Small objects were thrown. \"All animals pan-\nNails also pulled through plywood on southwest\nicked; horses broke corrals. The earthquake shook,\nwall. Southwest block wall, supported by frame and\nrolled, and heaved. Fires broke out everywhere. All\nstucco office in front, did not fail, but front block\nbirds left at dawn before the shock hit.\"\ncorners were completely broken. Building leaning 3\n13477 Bradley (northwest Sylmar area, between\ninches to west. Diagonal east-west cracks in floor 1\nRoxford Street and Foothill Boulevard).-\"Limbs\ninch wide.\"\non my trees were shaken off. My block wall fell.\n12401 Filmore (about 1 mile southeast of San\nVehicle moved about 2 feet. In the community there\nFernando Airport, Filmore and Foothill Boulevard,\nwere many chimneys down and some houses were off\nfoundations. Little plaster cracking in my home and\nnortheast of Glenoaks Boulevard) -Ground was\nno windows were cracked. Damage to my home was\ncracked, landslides occurred, and water was dis-\nslight.\"\nturbed. Chimneys were overturned. Furniture was\nbroken. Damage was great. \"Mobile home, 60 by 20\n15445 Cobalt (west Sylmar area, near San Fer-\nfeet, weight 11 tons (with wheels off), moved 4 feet\nnando Road, south of Roxford Street) -Ground\nand was broken apart. Water and gas pipes in\nwas cracked and water was disturbed. Chimneys and\nground were twisted and broken. Noise was over-\ntombstones were overturned. Damage was slight at\nwhelming. Personal feeling was one of resignation to\nresidence (mobile home) \"I was never SO frightened\nthe inevitable-surprised to be alive after shock was\nin all my life. I have never been a nervous person,\nbut during these last 2 months I get scared at the\nover. Also complete panic after the shock was over\nleast little movement.\"\ndue to no communication. Learned later that a fault\nwas located about 200 feet from our home.\"\n13597 Simshaw Avenue (about six blocks south of\nGlenoaks Boulevard, southeast of Hubbard Street\nthe southeast boundary of the Veterans Administra-\n(Brown's contracting yard) .Heavy lathe moved 9\ntion Hospital grounds) (Excerpted from a letter to\nfeet toward north, leaving straight skid mark. Loco-\nRobert D. Nason, Earthquake Mechanism Labora-\nmotive (1880 vintage), standing on rails and ties in\ntory, ERL, NOAA.) \"The first shock was sudden; no\nyard, was overturned (California Institute of Tech-\nwarning rumble. I thought it was an explosion. We\nnology 1971)\nwent up and down, with the noise and jolts acceler-","San Fernando Earthquake of 1971\n32\nbending the middle hinge badly. We were the first\nating. I can recall four very hard up-and-down mo-\nones out on our street. We stood on the lawn and\ntions, the last one being the hardest. The sound\nwatched Pacoima Dam light up with a hazy glow and\nseemed earsplitting-I thought my eardrums would\nthen fade. The light came from behind the front of\nburst. It was impossible to hear anyone, SO we just\nthe dam and was a steady light, not a flash, and there\ndidn't bother. My daughter said she was screaming,\nwere lots of slides and dust. We could hear lots of\nbut not one of us heard her. My husband, a large\nlarge rocks rolling down off the dam area, and\nstrong man, tried to force himself up from the bed\nthought the dam was breaking. We left the children\nbut was slapped down each time. Five times he tried,\nin the car, which was bouncing up and down with\nstraining with every muscle, until he was exhausted.\nevery shake. By now, people were starting to come\nI had trouble hanging onto the bed. We could hear\nout of their houses. I just sat in the middle of the\nnothing but the noise of the earthquake. The slapping\nyard, I was SO dizzy and dazed. The ground was\nmotion of the earth seemed to be in an east-west\nbumping up gently, and I noticed that I was sitting\ndirection, with the last slap ending in a hard motion\non one of the cracks in the yard but I just didn't\nto the west, toward Olive View Hospital. We were\ncare. I saw people who looked simply frightened 'out\nshaking between the up-and-down motions. Now we\nof their lives' and some who looked absolutely blank.\nstarted to roll. I was holding onto the bed for 'dear\nWe felt as though we had been through an explo-\nlife' to keep from being thrown into the furniture. I\nsion. It wasn't until we were in the aftershocks (in\ncould see the clock glide across the room. I looked\nthe hall) that I suspected it was an earthquake. We\nout the window from the bed. The window starts at\nreturned to the house a minute or two at a time to\n5 feet from the floor and goes to about 11/2 feet from\ngather shoes and robes. It took us 21/2 hours to find\nthe ceiling. I could clearly see the outline of the\nmy husband's glasses even though he knew where he\ntrees against the sky (it is a 360-acre area, rather\nhad left them. At daylight, we were amazed to find\nopen), the tops of the trees, the sky, the dark area of\nthe house structurally intact, as we had been think-\ngrowth, and the very dense area-I expected to see\ning it would be totally ruined. Inside, however, it\nthe ground any minute. This was repeated with\nwas a mess, taking over 3 weeks to straighten it up.\nevery roll. At one point I thought the house would\nThe house has a slab floor and dry walls, and stood\ngo over with the next roll, as each roll was worse\nup well. We had about $181 in structural glass dam-\nthan the last. That, I believe, was the end of the\nage, even the shower doors were broken. Our neigh-\nmajor motion, as my husband and I jumped out of\nbors on both sides of us were not SO lucky. In gen-\nbed almost simultaneously. It was when we were in\neral, things were scattered in a very even pattern\nthe rolls, north-south direction, that I could hear\nthroughout the house. I took a straight pin, which\neverything falling and breaking. The 'slaps' felt as if\nwas embedded about half way in, out of my bed-\none were being blown around and up in the air,\nroom wall. I have written down most of the details\nthen coming down hard, like being in the center of a\nas I remember them and given a lot of thought to\nbig explosion. The concussion was unbearable. Dur-\nthem, trying to be as exact as possible, if anyone\ning the rolls the sound was much more bearable.\ncould be exact through it. I asked my doctor how Pa-\nWhen we got to the bedroom door we found it was\ncoima Memorial Lutheran Hospital was and he said,\njammed with furniture, including the dresser, which\n'Bombed!' Somehow that just explains things per-\nweighs about 250 pounds, and the sewing machine,\nwhich was upside down. The minute I could get a\nfectly.\"\nfew inches gap in the door, I yelled to my children\n13284 Hubbard Street (about 1 mile south of the\nto get outside, and not to wait for us. My husband\nVeterans Administration Hospital) had just got-\nhad the door cleared in seconds. My four children\nten out of bed, and was immediately thrown to the\nwere huddled in the hall. We were now in the after-\nfloor. No warning at all-one minute I was standing\nshocks. The hall was leaning in first one way, then\nand the next minute I was on the floor. I couldn't\nanother. We pushed the children down the hall. We\nhave gotten up if I had wanted to. I don't remember\nwere thrown against each side of the wall all the way\nany ground noises, just the sound of furniture and\nto the front door. Then came another hard after-\nglass breaking. Almost everything of glass in the\nhouse was broken. Cupboard doors opened and all\nshock, and my husband could not get the door open.\ndishes fell out. Our heavy kitchen refrigerator was\nAs it eased up, he was able to jerk the door open,","Felt Area and Intensity of Earthquake\n33\nmoved nearly 11/2 feet; television tipped over; heavy\nThis one hit without warning. My service station\ngun cabinet tipped over. All the furniture was\nacross the street from me was not damaged either.\nmoved a foot or more from the walls. Our fish pond,\nAbout one-half mile south of me, near that new free-\n7 by 8 feet and 18 inches deep, was almost emptied.\nway that was being built and where SO many bridges\nI don't know what kind of ground we are on, but it\nwere lost, there is a mountain that is torn all to\nmust be pretty solid because the only damage to our\npieces-looks like it went through a grinder. The\nhouse was a few hairline cracks on the outside plaster\nnorth side of my place didn't seem to get hit as hard\nand one very small crack in the kitchen ceiling. We\nas the south side.\"\ndidn't even have a broken window. Our big pickup\nKAGEL CANYON AREA:\ntruck, with a big camper on it, was moved about 2\nLos Angeles Fire Station No. 74 (12587 North\nto 3 feet. All the chimneys in the area were shaken\nDexter Park Road, about 3 miles southeast of the\ndown and all the block walls were down. Some\nVeterans Hospital, in sec. 32, T. 14 W., R. 3 N.)\nhouses just across the street were damaged and de-\nGround was cracked, landslides occurred, and water\nclared unsafe. I would say the ground here is level.\nwas disturbed. Chimneys, tombstones, elevated water\nThere was no ground cracking on my property, but\ntanks, etc., were cracked, twisted, and overturned.\nthe street in front has cracks in the asphalt and all\nGas mains were broken. Power was turned off. Fur-\nthe street corner curbs seem to be cracked or broken.\nniture was overturned and broken. Violent motion\nI wouldn't go back in the bedroom for about 2\noccurred in all directions; also strong vertical mo-\nweeks because when the shock was going on I felt\ntion. Damage was great. \"This building was moved\ntrapped in there. The people in the community are\noff foundation approximately 12 inches and had to\nstill being frightened by the aftershocks.\"\nrise over sill at least 41/2 inches to settle down with-\nAbout 3 miles northwest of Sylmar (in canyon on\nout damage to the shingles.\" The following is an ex-\nHighway 14 at the Los Angeles city limits) \"I was\ncerpt from page 177 of the paper by Morrill (1971)\nreading the morning paper when the shock hit. All\n\"Firemen were resting in the wood frame quarters\nother earthquakes that I have experienced were of a\nbuilding.\nMr. J. White, duty fireman, stated that\nrolling motion, but this one felt as if the bottom fell\nhe was tossed out of bed onto the floor, and the bed\nout of everything. I felt a falling sensation, and\nlanded on top of him. Every object in the building\njumped up to try to get out, but I was knocked\nwas upset. Even the handset of a standard wall\ndown to my knees. I was sitting at the kitchen table\nphone came off its hook. Loud cracking and thun-\nwhen it struck. Everything began to fall; all dishes\nderlike noises added to the general confusion. The\nand glassware crashed to the floor; then in about 5\nbuilding was shifted off its foundation. Outside,\nseconds the light went out, and for 30 seconds I\nrocks were thrown off the ground, and large cracks\ncouldn't move. I put my hands over the back of my\nappeared in both soil and rock\nmany ground\nhead and stuck it under the table because bottles\ncracks appeared throughout the area. The surface of\nand everything else were falling and hitting me on\na hill adjacent to the building exhibited the 'shat-\nthe head. I thought it was the end of the world. My\ntered earth' effect\na few miles to the west. A\nwife hadn't gotten out of bed yet, and she began to\nnearby rock roadcut appeared to have exploded, and\nyell that 'the windows are breaking and the house is\nthe adjacent road was offset in many places. A 20-ton\nfalling down.\" I finally got to my feet, after about 30\nfire truck enclosed in the garage moved 6 to 8 feet\nseconds, and yelled to my wife to hurry down SO we\nfore and aft, 2 to 3 feet sideways without leaving vis-\ncould get outside. If we had been sitting on a big vi-\nible skid marks on the garage floor. The truck was in\nbrator, it couldn't have shaken us any harder. There\ngear, and the brakes were set. Damage to the truck\nwas no rolling or horizontal motion. It was a\nwas a bent rear step, broken windshield, shattered\nstraight-up-and-down motion. A big bookcase and a\nred light, and siren broken off. Also, a ladder and a\nlarge commode upstairs fell toward the east. We\nhook were broken. Marks which appear to have been\nhave two large china closets in the dining room and\nmade by the right rear tire were found on the door\nthere was not even a dish or glass broken in them\nframe 3 feet above the floor, while the metal fender\nduring the whole thing. This old house was built in\n1915 and is on pretty solid ground. There was no\nwas not damaged. The fender extends several inches\nnoise as in other earthquakes I have experienced.\nout beyond the upper portion of the tire. Four feet","San Fernando Earthquake of 1971\n34\nniture was overturned from north to south, east to\nabove the floor the hose rack was broken by the rear\nwest, and west to east. Refrigerator was out of posi-\nstep of the truck. The step was bent up, while the\ntion from south to north about 18 inches. Kitchen\nhose rack was broken downward. The rear of the ga-\ncabinets, from both north and south shelves, were al-\nrage was pushed outward 6 to 8 inches, and the final\nmost emptied. In living room, articles on north end\nposition of the truck was about 4 feet out the front\nof room slid off tables toward north, and on south\nof the garage, with the garage door resting on the\nend of room all books were dumped onto the floor\ncab.\" Morrill (1971) also suggests that the building\nfrom west to east. Most violent action seemed to be\naccelerated upward, with respect to the ground, at a\nfrom east to west, from final position of furniture.\"\nrate of at least 1g for about 0.1 second.\nKarl Holton Boys Camp (in Marek Canyon about\nKagel Canyon (from a letter by Doreen Russell,\n31/2 miles southeast of the Veterans Hospital) -Ex-\nSecretary, Kagel Canyon Civic Association)\ntensive damage occurred to buildings. One hundred\nmany of our homes have been totally destroyed,\nand fifty feet of 14-foot-high concrete block wall col-\nwhile others just next door had no real structural\nlapsed. Extensive landsliding and fracturing resulted.\ndamage. For example, our home had very slight dam-\nSevere structural damage occurred where ground\nage, but two of our immediate neighbors, one [who\ncracks passed through or were adjacent to the build-\nowns] a very new house and the other a much older\nings. The camp was evacuated.\nstructure, lost their homes. Severe ground scarp at\nGlen Haven Cemetery.\"\nLittle Tujunga Ranger Station (12371 North Lit-\ntle Tujunga Canyon Road, about 1/2 mile south of\nKagel Canyon (11825 West Trail, southern Kagel\nKarl Holton Boys Camp; report from Hugh E.\nCanyon) \"We were too busy to be scared, until\nMasterson, District Fire Control Officer) \"Ground\nlater. We were already up. Husband heard the shock\nheavily fractured. Water tank twisted. Concrete cess-\ncoming and thought it was a low-flying jet. Hard rat-\npool, waterlines, and pavement damaged. Everything\ntle first, then in 1 to 2 seconds I was thrown from\nupside down. Very heavy damage to all the buildings\nchair and my husband was dumped into the tub;\nat the station. Many inspectors have been at the sta-\nthen back-and-forth motion. I was able to reach the\ntion but no final estimate made of the damage; how-\nhall and get the children into a doorway until things\never, it will probably exceed $1 million. All crockery\nslowed down, then we went outside. Lights went out\nin the first movement. Water out but gas and tele-\nand china broken.\"\nphone were OK. Ground seemed to keep moving.\nLittle Tujunga Canyon Road-Bear Canyon Area\nWe have three acres (San Gabriel Range, first moun-\n(Bear Divide Ranger Station, NW 1/4, sec. 7, T.3\ntain by valley) with three houses. Lower house had\nR. 14 W., about 13/4 miles north-northeast of Pacoima\nlittle damage; no landslides or broken pipes. The\nDam) \"Rockslides on road up to 500,000 cubic\nsecond house, about 125 feet or SO higher, had a\nyards. Many ground cracks. Block wall broken. Mo-\ncracked foundation; 1-foot-thick walls cracked 1 to 4\nbile home dead-manned from concrete to 1/2-inch\ninches; four deep ground cracks, two under the\ncable to 3/g-inch eyebolts-eyebolts straightened out.\nhouse. Third house, about another 100 feet higher\nWater sloshed out of toilet bowls. Many cracks in fill\nup than the second house, had cement floors buckled\nground and solid ground. A giant up-and-down mo-\nand cracked; deep ground cracks; pipes separated;\ntion, changing to a north-south side motion.\"\nnew garage (side room) separated from house and\nslightly askew; 3/4-inch floor crack in cement; door\nwedged closed; everything dumped from cabinets,\nINTENSITY VIII\nand lots of stored glass windows broken. Garage was\nGranada Hills\na mess. Water main in front of this third house was\nbroken, separated 6 inches in five places, as it curves\nVan Gogh Street Elementary School in the upper\naround the corner.\"\nGranada Hills area sustained structural damage\ncaused by ground surface movement. Patrick Henry\nKagel Canyon (13706 North Kagel Canyon\nJunior High School in the lower Granada Hills area\nRoad) \"Water tank off foundation. Natural stone\nsustained structural damage caused by vibrational\nwall (no mortar) fell. Ground cracked. My husband\nwas awake and was thrown from north to south. Fur-\nmovement.","Felt Area and Intensity of Earthquake\n35\nment during the first part of the shock. It was almost\n17201 Courbet Street (about three-quarters mile\nimpossible to walk for the first few seconds. I tried\nwest of Upper Van Norman Reservoir) -Twisting\nto walk and felt as if I were walking uphill.\" Dam-\nand fall of chimneys, columns, and monuments OC-\nage was slight.\ncurred. Damage was great to masonry and concrete.\nDishes, windows, and furniture were broken. Cracks\n15832 Chatsworth Street.-Foundation, driveway,\nwere found in plaster, windows, walls, chimneys, and\nand water pipes were cracked. Chimney broke at\nground.\nroofline. Two ceilings of tile fell. One light fixture\nand all pictures and mirrors were down; shelves and\n16834 Bircher Street (southwest of Lower Van\ncupboards were emptied. \"Outside damage limited\nNorman Reservoir) \"Our tract (wood floors, lath,\nto west side. Our biggest bother was sorting and re-\nplaster, and stucco; one- and two-story homes) suf-\nturning several thousand books to shelves. The\nfered minimal damage. However, newer dwellings to\nshelves (fastened to the walls) were not damaged,\nnorth and northwest (slab, wallboard construction)\njust emptied. The later additions to the house were\nsustained major damage; many condemned. Holy\nfinished with wallboard-all seams cracked and must\nCross Hospital is about 21/2 miles east and the Van\nbe redone. All the plumbing in one bathroom\nGogh School is about 11/2 miles north of our home.\nbroke.\"\nMany commercial markets had major-to-minor dam-\nage; many business buildings marked 'unsafe.' Minor\n10342 Odessa Avenue.-Block wall was collapsed.\nground cracks north of our tract. Block fences fell.\nDriveway was cracked. Rock facing in decorative chim-\nChina cabinet overturned. Damage slight at my\nney was cracked. \"Our home and community is lo-\nhome.\"\ncated about 3 to 5 miles from the hardest hit areas of\nSylmar and San Fernando. The house faces in a\n10518 Encino Avenue.-Ground was cracked,\nnorthwesterly direction, and during the shock it\nlandslides occurred, and water was disturbed. Chim-\nseemed to move north-south. Our driveway break\nneys, tombstones, elevated water tanks, etc., were\n(minor) is also from north to south. The block wall\ncracked, twisted, and overturned. (This observer also\nwhich collapsed in yard runs east-west. Our neighbor\nreports only slight damage.)\nalso commented about the north-south movement, al-\n17608 Blackhawk Street.-\"No observed fissures,\nthough their home faces south and runs east-west.\nfaults, or landslides. Most 4-inch-thick concrete block\nBased upon the condition of the interior of house\nwalls in neighborhood (running north-south) are\n(fallen lamps, books, and dishes, etc.) , it seemed\ndown. East-west walls seem pretty good. All cup-\nthat the front side (west) of house moved more than\nboards on east-west walls emptied. Thirty-gallon\nthe back side. There was little displacement of ob-\nwater tank shifted 3 inches S.70°W Several 1/g-inch-\njects on eastern side, but much on western side. Af-\nthick cracks at attachment of garage to house and\ntershocks have also seemed to move the house north-\naround bottom plate. Damage moderate.\"\nsouth, with only occasional east-west shocks.\n12038 Bambi Place.-Ground was cracked. Chim-\nAlthough the aftershocks have decreased considera-\nneys were damaged in neighborhood. Bookcases were\nbly in the 3 weeks since the main shock, I find the\nmoved 6 to 8 inches.\nmost disconcerting problem now is the continual\npopping sounds in walls and cabinets, sometimes very\n12817 Neon Way.-Ground was cracked. Cement\nloud, and the creaking and springy feeling of the\nand plaster were cracked. Furniture was broken.\nfloors. I do believe SO many homes in our area came\n\"Everything affected.\" Damage was slight to moder-\nthrough the earthquake SO well because of our wall-\nate.\nboard interior walls. Many of our friends who have\n16939 Colven Road.-Block walls were cracked\nlath and plaster did not come through the shock\nand broken. Plaster was cracked and broken. Chim-\nnearly SO well.\" (There were also six reports of in-\nney and concrete block wall were cracked and\ntensity VI from Granada Hills.)\nknocked over. Toilet bowl was broken. Furniture\nwas overturned. \"Damage slight.\"\nMission Hills\n16329 San Jose.-Chimneys were overturned. Two\nNo address given.-Ground was cracked, land-\nfeet of water slopped from swimming pool. Plaster\nslides occurred, and water was disturbed. Chimneys,\nwas cracked. \"There was quite a lot of vertical move-","San Fernando Earthquake of 1971\n36\ntombstones, and elevated water tanks were cracked\n26961 B Avenue of the Oaks (northeast Newhall\nand overturned. Plaster cracked, broke, and fell.\narea, about 5 miles northeast of Newhall Post\nWindows were cracked. Furniture was broken. Dam-\nOffice) -Ground was cracked and water was dis-\nturbed. Side walls were lifted and shifted; retaining\nage was great.\nwalls were tilted. Drywalls had few cracks. Furniture\nMission San Fernando Rey (about one-half mile\nwas shifted and overturned. \"Shock was like a drop-\nsouth of the Holy Cross Hospital) -Adobe walls\nping motion, then a shift from northeast-southwest.\nwere severely cracked.\nLarge (19-in.) television thrown off 3-foot-high\n10222 Norwich Avenue.-Heavy objects (30-lb\nstand. Bookshelves and books on floor; lamps thrown\ntape recorder and large outside planter) were\nto floor; kitchen cupboards emptied of all contents,\nthrown 3 to 4 feet and overturned. Six-year-old boy\ncanned goods, dishes, etc. Refrigerator doors thrown\nwas thrown out of bed. Light objects were not\nopen and contents slid out on floor. Large dresser\nmoved. \"Noticed high-frequency, low-amplitude verti-\n(on short legs), full of material, shifted about 9\ncal motion at beginning of shock; low-frequency,\ninches on carpeted floor. Had to leave premises due\nhigh-amplitude lateral motion at end.\"\nto my wife being disturbed.\"\n24522 Walnut.-Ground was cracked, landslides\nNewhall-Valencia Area\noccurred, and water was disturbed nearby. Chim-\nNewhall\nneys, tombstones, and elevated water tanks were\ncracked, twisted, and overturned. Plaster was\nFour old buildings in downtown Newhall were\ncracked. Furniture was broken. Moderate damage OC-\ncondemned by the city engineer who estimated that\ncurred to house.\n90 percent of the fireplaces and chimneys on two-\n24736 Walnut.-\"We were not at home during the\nstory houses were damaged in the area. One concrete\nearthquake, but when we returned home we found\nwall was knocked down; most homes sustained only\nbeds, heavy bookcases, the stove, dressers, etc., had\nsuperficial damage (National Earthquake Informa-\nall shifted; one bookcase was overturned. Top of\ntion Center 1971). Gasline broke on Lyons Avenue.\nchimney, to about 4 feet below the roofline, broke\nAn observer at Honby reported the Newhall tele-\noff and fell, and made a dent in the lawn about a\nphone plant was flooded, the result of a broken\nfoot deep. All rooms except the kitchen have cracks\nwater main. A glass manufacturing company (be-\nin walls. Outside concrete slab is cracked. No broken\ntween Newhall and Saugus) sustained $10 million\nwindows.\"\ndamage to buildings, storage bins, and furnaces (Cal-\nNewhall Ranger Station (about 1 mile south of\nifornia Institute of Technology 1971). There was\nNewhall) -Ground was cracked; pipelines were bro-\nalso damage to oil refinery storage tanks and pipe-\nken. Chimneys were cracked and bricks \"rear-\nlines at the Newhall refinery located about 2 miles\nranged.\" Plaster was cracked. \"Cracks in plaster and\nsoutheast of Newhall. The bottom of one jet-fuel\npaneling of not much significance. Damage slight.\nstorage tank buckled, and there were scattered leaks\nThis site is a 1-acre area housing compound of the\nelsewhere in the refinery. The chief problem for the\nU.S. Forest Service administrative buildings. The\nrefinery was lack of water. Both sides of a booster\nstructures, two offices, one 6-bay garage, one bar-\npump on the waterline leading to the refinery were\nracks, several small outbuildings, and one residence,\nruptured. Minor damage was done to testing equip-\nwere constructed in 1934 and are of wood; very well\nment in the laboratory (Anonymous 1971).\nbuilt. All doors and cabinets in the residence and\n18909 Sierra Estates Drive (about 5 miles north-\noffices were thrown open and contents spilled to the\neast of Newhall Post Office, south of California\nfloor. Direction of thrust appeared to be to the\nHighway 14) -Water supply was cut off. Some\nsouth. No furniture of any appreciable size was\nchimneys were loosened from homes; cracks occurred\nknocked over, but very heavy pieces were shifted sev-\nin walls, concrete slabs, etc. China closet was over-\neral inches. Electricity, phone, and water services\nturned. Many windows were broken in stores. Dam-\nwere knocked out at impact. Hairline cracks are ap-\nage was great. This observer gives \"place\" as New-\nparent in and on all of the buildings, but appear to\nhall, Soledad, and entire area.\nbe the result of aftershocks.\"","Felt Area and Intensity of Earthquake\n37\n23405 La Glorita Circle.-Patio block walls were\noverturned to south. Bookcase was overturned and\nloosened. Piano and refrigerator were moved. Plaster\nothers moved. Plaster was cracked. \"All plasterboard\nwas cracked over windows and doors, but not very\njoints show cracks. Some vertical cracks in founda-\nextensive. Market, two blocks away, lost its windows.\ntion. No ground cracks here, but shopping centers\nclose by (300 yd) have cracks in blacktop parking\nDamage was slight.\nlots. Roof collapsed on north side of W. T. Grant\nValencia\nBuilding. Fifty to 70 percent of store windows\nbroke. Highway bridges need repairs to approaches.\n24200 Lyons Avenue (shopping center, east of\nElectricity off instantly, but it came back on again in\nGolden State Freeway) .-Suspended ceiling col-\nabout 20 minutes.\"\nlapsed. Nearly all glass in wall was broken (U.S.\nGeological Survey and the National Oceanic and\nHonby School.-Ground surface cracking was evi-\nAtmospheric Administration 1971)\ndent throughout the site. One crack passed through\none of the school buildings (U.S. Geological Survey\n25310 Via Calinda.-Chimneys were cracked,\nand the National Oceanic and Atmospheric Adminis-\ntwisted, and overturned. Water was disturbed. Chan-\ntration 1971)\ndelier fell. Television was overturned. Small amount\nof plaster was cracked. Windows were cracked in\n27430 Fairport Avenue.-\"All I have spoken with\nnearby houses. \"In the city of Newhall block walls\nsaid it felt as if their building would topple. We\nwere knocked over.\" Damage was moderate.\nhave a 16-foot trailer parked in driveway and it\ntwisted or jumped over a foot around. Block walls\n25349 North Avenida Ronanda.-Chimneys were\nfell. In the community, streets cracked, curbs broke,\ncracked, twisted, and overturned. Garden walls were\nand many buildings were condemned. I teach at the\ndown. Furniture was shifted and overturned. \"Sensa-\nHonby School (one-story building; six classrooms)\ntion of violent rotary motion.\"\n-over 1-inch-wide floor crack across center of slab;\n25657 Avenida Jolita.-Chimney was separated\nsection dropped about 11/2 inches; some doors will\nfrom house. Some plaster was cracked. Furniture was\nnot open and some will not close; new blacktop bro-\nshifted, overturned, and broken. Damage was slight.\nken and cracked. At my home (front faces west) a\nfront door latch (locked) broke off. The door was\nSaugus and Soledad Canyon Areas\nopened but held by safety catch. Many people have\nSaugus.-Ground was cracked. Trailer foundations\nasked for transfers for their children and are leaving\nwere cracked. Most light fixtures fell. Furniture was\nthe community.\"\nshifted, overturned, and broken. Plaster cracked,\n27416 Dewdrop.-Ground was cracked. Chimneys,\nbroke, and fell. Windows were broken. \"There were\ntombstones, elevated water tanks, etc., were cracked,\neight people working in the post office at the time.\ntwisted, and overturned. Many cracks were found in\nEveryone got out just in time to avoid falling light\nswimming pool. Plaster was cracked. Furniture was\nfixtures. Equipment was tossed around more in our\nbroken. Damage was moderate.\ntrailer complex (seven trailers placed together) than\n28189 Hot Springs Avenue (north Honby area)\nit was in our main office (brick building) The crew\n-Block walls were flattened. Chimneys were cracked\nmaintained their composure, as far as I could see,\nand twisted. Stucco was cracked. Small (1/4-in.)\nbut it was the general consensus that if the shock\nground cracks were evident. Building was bounced\nhad lasted much longer, panic would have resulted.\"\nin all directions. Locked doors swung open and\nSoledad Canyon Road Areas-Honby Area (about\nclosed. Damage was slight to building.\n31/2 miles east by north of Saugus)\n19419 and 19407 Soledad Canyon Road (North\nNear Soledad (10511 Soledad Canyon Road, about\nOaks and shopping center).-Roofs were collapsed.\n7 miles east by north of Honby) -Ground was\nCracks were found in nearby parking lot (U.S. Geo-\ncracked, landslides occurred, and water was dis-\nlogical Survey and the National Oceanic and Atmos-\nturbed. Chimneys were cracked, twisted, and over-\npheric Administration 1971)\nturned. Roof was split (wooden building) Furni-\nture was shifted, overturned, and broken. Water\n27327 Camp Plenty Road (just north of Soledad\nheater was torn loose. Damage was slight to house.\nCanyon Road) ,-Six-hundred-pound transmitter was","San Fernando Earthquake of 1971\n38\nSolemint (east of Honby) -Soledad Canyon\nshocks came with regularity every few minutes after\nSchool was damaged by ground surface movement.\nthe initial bump which definitely preceded the sway\nDiagonal ground cracking was observed throughout\nin Altadena. I would say we had between 10 and 20\nthe school site (U.S. Geological Survey and the Na-\nsmall aftershocks-sometimes no more than a queasy\ntional Oceanic and Atmospheric Administration\nvertigo-after the initial shock. At least four were of\n1971).\nfair violence.\" \"One piano in neighborhood escaped\ncaster cups.\" \"Water in pool splashed violently\nSolemint (in Iron Canyon southeast of Solemint)\nnorth-south.\" Plaster was cracked. The press re-\n-The press reported that house and land \"slipped\"\nported that powerlines were down. (Sixteen reports\nmore than 30 feet and that Head Road in Iron Can-\nof intensity VI and six reports of intensity V were\nyon \"dropped\" 15 feet.\nalso received from the area.)\nINTENSITY VII\nBeverly Hills.-TI following statistics (Stein-\nbrugge et al. 1971) do not include publicly owned\nAlhambra.-Chimneys were overturned. \"Earth-\nstructures: 135 buildings damaged; two commercial\nquake appeared to have long duration, about 10 to\nbuildings demolished or to be demolished; 1,000\n15 minutes, due to aftershocks. Noticeable up-and-\nchimneys damaged; and estimated total dollar loss at\ndown motion. Damage was light, except to old build-\n$800,000. (There were four reports of intensity VI\nings in business district where some (very few) plate\nand four reports of intensity V from the Beverly\nglass windows were broken; one old brick building\nHills area.)\nlost parapet walls and front.\" \"Damage was slight in\nthe Alhambra area. In wood frame buildings, dam-\nBurbank.-Chimneys were cracked, twisted, and\noverturned. \"Great damage to unreinforced brick.\"\nage was limited to cracked plaster and windows, and\nElectricity and phones were out. Plaster cracked and\nto broken dishes and knickknacks. Store buildings\nfell. Windows were broken. Heavy furniture was\nsuffered broken plate glass windows. Chimneys\nmoved. \"I have checked approximately 12 homes in\npulled away from some buildings. Several unrein-\nmy area (807 East Andover Drive) and found no\nforced brick parapets fell.\" The press reported that\npowerlines were down. The following statistics\nstructural damage. Only items of interest were the\nmovement of furniture, items falling out of cabinets,\n(Steinbrugge et al. 1971) do not include publicly\noff tables, dressers, etc., and broken windows. Damage\nowned structures: 55 buildings damaged; 15 posted\nunsafe; five commercial buildings demolished or to\nslight.\" \"The earthquake once it was over didn't seem\nbe demolished; 400 chimneys damaged; and estimated\nSO bad. We were alive and had suffered very little\ntotal dollar loss at $2 million. (Also, eight reports of\ndamage in comparison to others. The most frighten-\nintensity VI and four reports of intensity V were re-\ning part was the aftershocks-not knowing when\nceived from the area.)\nthey would come or how strong they would be. We\nlived in continual fear for the next few days.\" Ob-\nAltadena.-Chimneys fell. \"Almost solid after-\nserver at 209 North Naomi Street reported: \"This\nshocks for half an hour. Couldn't distinguish other\nneighborhood is located in southwestern Burbank.\nnoises due to general falling, crashing of objects.\nMotion in this area was an increasingly rapid, com-\nPower failure in a few minutes was worse than after-\nplex shaking for roughly 10 to 15 seconds, after\nshocks. Everything tall fell, lamps, etc. Left for work\nbeing awakened. After the motion had reached a\nat 6:58 a.m. No evidence of shock as I drove south\npeak, it began slowly to decrease in intensity; how-\non Lake Avenue. However, in Board of Education\never, ground motion did not seem to stop completely\nbuilding (in Pasadena), library shelves had fallen\nuntil after a considerable length of time. Brilliant,\nwest from against east wall. Books from shelves were\nquick flashes of light were seen in various directions\nalso tossed every which way. Things in cupboards in\n(apparently related to effect on powerlines or trans-\nhall fell. General problem. Big window at Bullocks,\nformers) Two roars (very prominently heard in this\nPasadena, shattered. I was on the phone to report\nneighborhood) were emitted from a powerplant 12/3\n'schools open' as fast as calls came in. General alarm\nreflected in phone calls but no panic of any kind.\nmiles from here as the quake caused valves to close\nEverything swung and teetered and crashed if unsta-\nas steam shot out. Power was knocked out in this\nble. Some people were afraid to come to work. After-\nneighborhood and remained out for slightly more","Felt Area and Intensity of Earthquake\n39\ntershocks had been felt up to June 21. The following\nthan 2 hours. In this house a number of things fell\nstatistics (Steinbrugge et al. 1971) do not include\nfrom shelves or tables, or were tipped over, or\npublicly owned structures: 445 buildings damaged;\nchanged positions (as happened, undoubtedly, at all\n25 posted unsafe; buildings demolished or to be de-\nhouses near here) A few knickknacks in precarious\nmolished include three residential, three commercial,\npositions seemed surprisingly virtually unaffected;\none church, and one school; 500 chimneys damaged;\nhowever, a water softener tank, just outside the\nand estimated total dollar loss at $4 million. (Eight\nhouse, jiggled off one of its three supports and tilted.\nintensity VI and three intensity V reports were re-\nThe tank is too heavy for one person to move with-\nceived from the area.)\nout great difficulty. Nothing in this house was bro-\nken. Glassware broke at next-door neighbor's house.\nCanoga Park.-Exterior building walls were\nProbably some things were broken at nearly every\ncracked. Windows were broken. Plaster was cracked.\nhouse around here. (Incidentally, relatives living in\nOne observer stated: \"The building is a small shop-\neastern foothills of Burbank reported figurines in\nping complex. One of the stores sells liquor and gro-\nglass dome were turned around even though dome\nceries. Damage to the bottles was extensive-40 per-\nitself was unaffected.) No windows were damaged at\ncent of the stock fell off the shelves, even though\nour house and none were damaged at most of the\nthere were wires to prevent this. The outside walls\nneighbors' houses. Many (although not most) plate\nof the building cracked and separated about three-\nglass windows at nearby business establishments were\nquarters inch at some places.\" The following is an\nbroken. A substantial number (about 10 percent) of\nexcerpt from Headlines (1971), a May Company\nchimneys in this neighborhood were cracked, several\npublication, reporting on damage at the May Com-\nSO severely that their upper portions had to be re-\npany Store in Topanga Plaza: \"Twenty-five plate\nmoved. A few chimneys were slightly separated from\nglass windows in the escalator well shattered. Ap-\nhouses, and the upper portions of a few were very\nproximately 50 percent of merchandise and display\nslightly twisted. Our house had no obvious damage.\nfixtures damaged or destroyed in china department.\nThe walls of our next-door neighbor's house devel-\nThe bedding and linen stockrooms were a tangle of\noped some narrow cracks in various places. Narrow\ntoppled shelving and merchandise. Ceiling tiles and\ncracks developed in walls, especially at corners of\ncomplete light casings fell. On the roof, four 4-ton\nwindows and doors, in many buildings in this neigh-\nfans were sheared from their bolts, and the fans\nborhood. One straight crack, clearly visible from the\nmoved 2 to 9 inches out of position. The lamp,\nstreet, extended from the base to the roof of a sin-\nmirror, picture, and television departments also re-\ngle-story library one-quarter mile to north, and sev-\nceived extensive damage to merchandise. The lower\neral long, conspicuous cracks formed in plaster inte-\nlevel and middle level also received damage. The\nrior walls of a church one-half mile to north of here.\nmajor problem was water. Three inches of water had\nSmall chips of plaster fell in several buildings. Some\nseeped into these levels by midmorning as the result\ngarden walls were cracked, several were significantly\nof damaged water pipes in an adjacent department\nweakened. Damage in other parts of Burbank: In-\nstore in the shopping mall. The building was care-\nstances of cracked walls, badly cracked chimneys,\nfully inspected by engineers and building inspectors\nshattered windows, and other damage were common\nbefore store members were permitted to enter. Dam-\nin much of Burbank. Some old buildings had exten-\nage to the structure was only surface damage, and\nsively damaged walls and ceilings and were consid-\nthe building was found to be in good condition.\"\nered unsafe. Some of the severe damage included the\n\"Movement seemed to be north-south and west-east.\"\nfall of portions of the exterior walls just below the\n\"Our home was shifting SO violently that it was diffi-\nroofs of a church and a rest home, both relatively\ncult to walk.\" Another observer reported: \"Water\nold buildings near downtown Burbank. The walls of\nescaped from street hydrants. Electricity off 1 hour.\nboth buildings were predominantly of brick. Al-\nAwakened by mild rolling shock of several seconds'\nthough the worst damage was typically to older\nduration, pause of a few seconds, then a sharp jolt\nbuildings, minor damage was common in newer\nfollowed by violent shaking in all directions, both\nones. In spite of much costly damage in places, at\nlateral and vertical. The intensity appeared to in-\nmany other places in town, damage was virtually\ncrease in a continuous manner, with a continuous\nnil.\" This observer reported that more than 120 af-","San Fernando Earthquake of 1971\n40\nEncino.-An observer reported: \"Two palm trees\nincrease in 'thumping-type' noise, and was followed\nby the steadily increasing noise from falling books,\nknocked over. Flagstone and concrete driveway\nthen louder crashing noise of objects falling. The\ncracked; concrete and flagstone pool deck raised one-\nintensity built up during a period of 30 to 60 seconds,\nhalf inch above pool tile; steel support column of\nthen abruptly stopped; then after a short pause was\nporch roof shifted 11/2 inches out of concrete base; 4-\nfollowed by more milder, rolling shocks. Electric\nby 12- by 20-[inch] garage-roof-support timber shifted\nabout 1 inch on north end. Damage about $4,000.\"\npower went out at the end of the violent shock\nperiod. Flashes of light observed during shocks. I\nWaterlines were broken. Plaster was cracked. Block\ngarden walls were broken. Yard was swamped with\nlost all sense of direction during violent shaking. It\nwas difficult to locate exit door in dark bedroom.\nwater from pool. Electricity was out. (Three inten-\nImmediately after the shock a check was made for\nsity VI reports were received from the area.)\ngas leaks, water leaks, broken electric cords or wires\nFillmore.-Chimneys and plaster were cracked;\nboth inside and outside-none were found. No neigh-\nwindows were cracked. One observer commented:\nbors observed outside. Power failure apparently gen-\n\"We lost one building in town, a dress shop, when\neral in the neighborhood. No structural damage\nthe roof caved in. Two other business buildings were\nnoted. Many books fell from tops of bookcases and\ndamaged: One furniture store lost part of the roof in\nfrom a shelf in one closet. Bookcases did not over-\nthe rear of the building and a hardware store lost\nturn. One table lamp, 3 feet tall, in corner of living\npart of the brick firewall on the north side of the\nroom, was found in middle of room about 10 feet\nbuilding. All of the grocery and liquor stores in\nfrom its original position. Other table lamp simply\ntown suffered losses when canned and bottled goods\ntoppled over. All fallen objects were from locations\nfell off the shelves and display counters. Electrical\non inside walls. Nothing along outside walls of house\nservice was out in the surrounding rural areas for a\nfell or moved. Water from aquarium spilled out and\nshort time, about 5 to 15 minutes.\" Another observer\nwater from neighbor's swimming pool sloshed out.\"\nstated: \"I was awakened by a terrific shaking of the\n\"Brick wall fell on neighbor's car. Store windows\nbed and a terrible noise. Seemed as if the house\nbroken. Lost 21/2 feet of pool water.\" Another ob-\nwould fall to pieces, but the only damage to the\nserver gave this account: \"I heard a rumbling noise\nstructure was to an outside brick chimney which was\njust prior to feeling the shock; then it hit. Pre-\nseparated from the house by about three-quarters\ndominantly east-west vibration with some north-south\ninch. About 21/2 city blocks away, the side of a two-\nmotion. Felt more like several quick vibrations, then\nstory brick building fell on a one-story frame roof\na little slower, then several quick motions, with a\nand demolished the smaller building. There was\ntotal response effort similar to a boat action in\nsome damage to an orange packinghouse. The lights\nwater.\" Still another observer told this story: \"No\nwere out for a few minutes.\"\ndishes, glasses in cupboards broken or noticeably\nFlintridge (southwest of La Canada; 34°11' N.,\nmoved. No books from bookcase fell. Lost about 11/2\n118°10' W.).-Heavy chimney sheared off at roofline.\ninches of water from 7-gallon fish tank; light hood\nPlaster cracked throughout interior. Minimum crack-\non fish tank bounced out of place but did not fall off.\ning of exterior stucco. Roof tiles shifted and broke.\nMany pictures on walls did not move or shift. The\nTorsion of building visually observed. Interior wood\nlarge, heavy, hanging lamp over dining table swung\nand lath and plaster failed (both horizontally and\nmore than moderately but not violently in an east-\ndiagonally) in shear and (vertically) in tension. Also\nwest direction. During the first aftershock, a half hour\nsome compression parallel to wave travel. Wall dam-\nor SO later, the lamp swung in a north-south direction\nage was extensive; ceiling damage was moderate.\nbut not as hard this time.\" \"Shock was felt for a\nWater sloshed from swimming pool. Small objects\nconsiderable length of time. Noises of rattling, creak-\nand books fell.\ning, etc., were continuous. Telephone and power\nwere out. Water was running, but during the day it\nGlendale.-Ground was cracked. Chimneys were\nbecame contaminated and remained SO for about 1\noverturned. Plaster and windows were cracked. Fur-\nday.\" (There were nine reports of intensity VI and\nniture was broken. Electricity was out; street lights\nfive reports of intensity V from the Canoga Park\nwere flashing. The press reported that the Glendale\narea.)\nPresbyterian Church, built in 1923, was severely dam-","Felt Area and Intensity of Earthquake\n41\naged. The First Methodist Church was not damaged,\nbuildings with brick and masonry facings. Portions\nbut in the 54-year-old former sanctuary behind it,\nof an old building, the Mission Inn, collapsed, kill-\ntowers fell through the roof. \"There was a complete\ning one person. Extensive damage occurred to some\nmess inside the apartment. Bookcases fell. Refrigera-\nof the old historic buildings on Olvera Street. The\ntor moved about 3 inches from wall. Bookcase on\npress reported \"unsafe\" and \"potentially unsafe\"\nsigns were posted at some buildings in \"Little\nwest wall; refrigerator on south wall. One brick from\nthe brick bookcase, quite heavy, was thrown about 7\nTokyo\" and along Main and Los Angeles Streets.\nfeet.\" The following statistics (Steinbrugge et al.\nConsiderable nonstructural damage occurred to some\n1971) do not include publicly owned structures: 31\nof the larger buildings and to some high-rise build-\nbuildings posted unsafe; buildings demolished or to\nings-plaster partitions were cracked; fall of plaster\nbe demolished include 13 residential, 23 commercial,\nand tile occurred; broken windows were numerous;\nand five churches and schools; 3,250 chimneys dam-\nand elevators were knocked out of service. It was re-\naged; and estimated total dollar loss at $2 million.\nported that the old Los Angeles High School would\n(Additional reports of eight intensity VI's and of 11\nbe demolished due to damage. There were reports of\nintensity V's were received from the area.)\nruptured gaslines in Highland Park; and in Eagle\nRock, it was reported a ruptured gasline blew a cra-\nLa Canada.-Chimneys were overturned. Low\nter in a freeway overpass bridge (California Institute\nfalse ceiling bent and fell. Plaster, windows, and\nof Technology 1971).\nwalls were cracked; plaster fell. Slab in patio was\nraised and cracked. Heavy objects were moved. Pool\nAbbey Hotel (825 West Eighth Street).\nwater was sloshed violently. The press reported that\npoorly built, four-story building. Section about 5 by\n8 feet fell away from lobby wall; waterpipe damage\npowerlines were down. \"There was a distinct feeling\nof significant vertical acceleration during the early\nat this break. Primary shock was moderate shaking\nmoments of the shock.\" (Nine reports of intensity\nfor first 5 to 10 seconds, then grew rapidly in inten-\nVI and seven reports of intensity V were received\nsity. Stayed at maximum about 40 seconds, with im-\nfrom the area.)\nmediate aftershocks of strong rolling motion, floating\nfeeling, and building noise almost ceased during this\nLa Crescenta.-Many false fronts of buildings\nperiod, only slight creaking noises. It seemed that\nwere badly damaged. Unreinforced parapet failures\nduring these aftershocks ground noises could be\noccurred. Some old stone walls were cracked. Chim-\nheard, resembling large masses of rock, at great\nneys were overturned. Water and furnace pipes were\ndepth, being shifted against one another. Some dam-\nbroken. Many windows were cracked in old and new\nage: Cracks, one-quarter to three-eighths inch in\nbuildings. \"Cracked concrete pool deck and dislo-\nwidth, opening on wall corners adjacent to stairway\ncated concrete and stone supporting wall.\" One ob-\nentrances on each floor; on ground floor (lobby),\nserver estimated damage to his house and contents at\nplaster fell from ceiling above last flight of stairs and\n$3,000. \"We had very little breakage from dishes and\nadjacent ceiling of area where wall fill and plaster\nknickknacks (5542 Pine Glen Road), probably due\nfell out. Lights in room flickered on and off during\nto the bedrock foundation. Other friends living out\nthe main shake, with floor lamp in great agitation.\nin the center of the canyon or on deeper alluvial\nDamage slight to building. Much masonry facing\ndeposits had considerable glass and dish breakage.\ndamage one block away; much window breakage and\nOne friend on third floor of wood frame apartment\nmasonry facing damage on taller buildings.\"\nbuilding had a wall-mounted air-conditioning unit fly\nhalfway across the room to the east. I tried to analyze\nMay Company Store (from Headlines (1971), a\ndirection of motion at my house from swinging of\nMay Company publication, Los Angeles, Calif.)\nlamps and displacement of objects and finally de-\n\"The downtown store was closed to store members\ncided it had to be east-west, even though swag lights\nearly Tuesday morning while building inspectors,\nin bedroom were swinging north-south.\" (One in-\nstore security, and engineers checked every area of\ntensity VI report and three intensity V reports were\nthe store. The building was considered structurally\nalso received from the area.)\nsound and safe for entry; but because of the damages\nLos Angeles.-Moderate damage occurred in\nto the interior, the store remained closed to custom-\ndowntown Los Angeles, especially to older type\ners. The 'back' stairwell, escalators, and elevator","42\nSan Fernando Earthquake of 1971\nof Civic Center) -The observer stated: \"Chimneys\nwells seemed to have suffered the most damage.\nin same block fell; some cracked and will be re-\nWalls surrounding the back stairs and the walls in\nmoved. Powerlines in rear of building flashing.\nthe adjacent halls sustained much surface damage in\ncracked and fallen plaster, and, in some cases, holes\nThere were reports of broken dishes in the area. We\nlive in four-family flat (old wooden building) We\nin walls and at corners were visible. Main wall sup-\nports were in good condition and were not damaged.\nhad nothing broken; one small mirror fell.\"\nThe escalators were extensively damaged. Exterior\nHollywood area.-Sidewalks were buckled. Win-\ndamage to the store was confined to display windows\ndows were broken. Chimneys cracked and fell. Build-\nand decorative treatment on the building. Well over\nings were damaged, especially brick buildings. The\n60 percent of the plate glass windows were shattered.\nfollowing accounts were received from observers:\nSome slight damage was noticeable on cornices and\n\"When we were awakened, it sounded as if a truck\nornamental trim.\"\nhad hit the motel. It also felt as if the furnace were\nabout to explode.\" \"After the earthquake, people\nOlympic and Alameda (about 2 miles south by\nwere outside on sidewalks and would not go back in-\neast of Civic Center) -One observer reported: \"The\nside because of the aftershocks. I thought the build-\nbuilding in which I work (Olympic and Alameda)\ning would disintegrate. Part of brick wall on roof\nsustained approximately 400 broken windowpanes,\n14 by 20 inch, all steel sash. Almost 100 percent of\nfell. Arch over building entrance cracked, creating\nthese were on the north and south sides of the build-\ndanger. Brick buildings seemed to be more damaged\ning. One or two freight-type elevators were inopera-\nthan single-structure cement buildings.\" \"At 6 a.m.,\ntive due to guide tracks warping and permitting\nheavy earthquake. For first 2 or 3 seconds thought it\nwould be the usual shake; then intensity increased\ncounterbalance weights to swing free.\"\nsuddenly. Thought all 'hell' was going to break loose.\n127 South Serrano Avenue (in area about 11/4\nBolted out of bed and stood under doorway. All\nmiles southwest of Los Angeles City College) .-Al-\nthoughts blank except when would the shock end-\nmost all nearby chimneys were badly fractured.\nseemed to last forever. Lights out almost immedi-\nMany new plaster cracks were found in all eight\nately and things overturned. Saw flashes of light from\nrooms of the house. Bookcase fell; dresser was\nshorted telephone pole transformers-thought the\nmoved. Pool water was splashed 20 feet horizontally.\nwhole city was ablaze. Got dressed and went outside,\n3812 Terry Street (in area about three-quarters\nsat in car, as I thought there would be aftershocks,\nmile northwest of Silver Lake) -Small objects flew\nand there were. Went back inside about 45 minutes\nthrough the air. Vehicles were rocked (cracked water\nlater; then went to work. Noted some traffic lights\nhose to radiator) Plaster cracked and fell; ceramic\nwere inoperative. People went outside after the\ntile was cracked. \"Everything in front apartment that\nshock, then tried or attempted to go back inside, but\nwas movable shifted. Heavy chest of drawers moved\naftershocks kept them outside for about 25 minutes.\n12 to 15 inches away from wall. I attempted to walk\nCars were driven and parked irregularly.\" From ob-\nacross room but was unable to do SO. Most dreaded\nserver at 1627 North Normandie Avenue: \"Older\nelement was the sound-as though every nail in the\nbrick buildings received the most damage. Chimneys\nbuilding were being wrenched out at once. Damage\ncracked. Heavy objects moved. Water sloshed from\nmoderate.\"\ntoilet bowls. This area where I live was apparently\n932 Maltman Avenue (Silver Lake area, about\njolted heavier than other sections of Hollywood. Per-\none-half mile from southwest shore) .C-ichimneys\nhaps adobe soil is responsible.\" \"Chimneys fell at\nwere cracked and overturned. Some plaster cracking\nHollywood-Wilshire area.\" \"Husband had parked\nwas noted; window was cracked. Damage was slight\ncar at work. Saw lightning in sky and over moun-\nto observer's home.\ntains and heard loud rumble before shock. Car shook\n4411 Los Feliz Boulevard (south of Griffith Park)\nstrongly, got out of car, earth moving up and down,\n-Chimneys were cracked, twisted, and overturned.\ngot back in car. People were running out of houses.\n\"Older masonry buildings generally damaged. Dam-\nMy husband drove back home and left for work\nage was moderate.\"\nlater. At home, 5191/2 North Heliotrope Drive (near\n2835 Sunset Place (about 21/4 miles west by north\nLos Angeles City College), people were also fright-","Felt Area and Intensity of Earthquake\n43\nened and ran from houses. So many aftershocks, SO\nthere were rumbling noises but not extremely loud.\nclose together, too many to count. Mostly sharp jerks\nClimbing out of bed during the shaking, I was able\non house, from east-west; some north-south shakes.\"\nto walk to my daughter's room. She was awake and\nwas not terrified. Oven and refrigerator displaced 4\n5238 College View Avenue (south of Ventura\ninches. Flat steel plates (25 1b each) were moved on\nFreeway and just southeast of southeast corner of\nuncarpeted surface of floor. General disruption in all\nGlendale city limits) .-Observer reported there was\nrooms. No readily observable cracks in ceilings or\nno damage to his 60-year-old, one-story home, but\nwalls. Cement block wall in yard cracked at ce-\nthat most neighbors' chimneys were cracked, twisted,\nmented joints, displacement about 1 inch. Immedi-\nand overturned.\nately after the shock subsided (lasted about 20 to 30\n5415 Wameda Avenue (Eagle Rock area) -\nseconds) I checked lights and phone-they still\n\"Damage considerable. Plaster fell. Furniture moved.\nworked. Water OK. I felt about five or six after-\nDishes flew out of cupboards and shattered. Air-raid\nshocks between about 6:09 and 6:19 a.m.; then I sat\nsiren short circuited. Whole house shook violently-\ndown to record more aftershocks.\" This observer re-\nhad to 'hold on.' My car fell off jack stands in garage.\"\nported he felt 34 shocks to 1:30 p.m., with the\n5151 State College Drive (California State Col-\nstrongest at 6:35, 6:44, 8:00, 8:30, 10:57, and 10:59\nlege, just northeast of northeast Monterey Park city\na.m., and at 12:57 p.m. He stopped keeping record\nlimits) \"On the California State College campus,\nafter 1:45 p.m. (Twelve reports of intensity VI and\nthe new eight-story Administration Building is built\nfour reports of intensity V were received from the\non about seven pairs of reinforced concrete columns\narea.)\n(no first floor) Column pairs one and seven exhibit\nNorthridge.-Walls were cracked; chimneys were\ntension cracks. No other columns show any damage.\noverturned; brick veneer was damaged. Exterior\nPlaster cracks, 45° diagonal, only in east-west walls.\nblock walls were down. Windows were broken. The\nCorners of rooms and steel doorframes show separa-\nfollowing is an excerpt from Lew et al. (1971)\ntion cracks. Bookcases fell if facing east-west; gener-\n\"Northridge Hospital, Roscoe Boulevard near Re-\nally did not fall if facing north-south.\"\nseda. Five-story steel frame structure with reinforced\n3566 Lowry Road (in area about one-half mile\nbrick masonry shear walls. The exterior cladding was\nsoutheast of Griffith Park, west of Golden State Free-\nof brick veneer. Damage to the veneer was extensive\nway) -\"Chimneys on older homes cracked and over-\non the east and west elevations. The shear walls in\nturned. Considerable glass damage in vicinity. Many\nthe first story were badly cracked at many places. All\npre-1933 masonry buildings severely damaged, some\nmechanical and electrical equipment was functioning\nafter the earthquake, including elevators.\" \"The\nbeyond repair, within a 2-mile radius of my house.\"\nsevere shaking seemed to last for a period of about 2\n(Also, 62 intensity VI and 101 intensity V reports\nto 3 minutes. Multistory wood frame stucco buildings\nwere received from the Los Angeles area.)\nin neighborhood (9723 Rathburn Avenue) suffered\nMontrose.-Chimneys and water tanks were\nextreme damage in shear walls but little damage in\ncracked, twisted, and overturned. Ground was\nhorizontal elements, such as floors and ceilings. Mod-\ncracked. Water was disturbed. Plaster was cracked\nern reinforced masonry buildings all seem damaged\nand broken. Windows were cracked. Damage was\naround corners at roof level.\" At 10027 Wish Ave-\nmoderate. The press reported that powerlines were\nnue, an observer reported: \"Ground motion was very\ndown. Damage was slight at 2261 Luana Lane, but\nviolent-seemed rippling-causing the house to tilt\nchimney across the street was overturned. (One in-\nabout 5°. Little or no structural damage or plaster\ntensity V report was received from the area.)\ncracking in the residences in our immediate vicinity.\nNorth Hollywood.-Water mains were broken.\nConsiderable damage to concrete block walls in the\nChimneys fell. Large plate glass windows were bro-\narea, particularly those oriented on an east-west axis.\nken. Outdoor block walls were cracked and dislo-\nApproximately 100 feet of wall totally destroyed on\ncated. File cabinet was overturned. The following is\nmy property. Floor lamps and table lamps were all\nfrom an observer at 7262 Farmdale, about five blocks\ntipped over; considerable breakage of dishes and\nnorthwest of Hollywood-Burbank Airport: \"I was\nbric-a-brac.\" At 10952 Etiwanda Avenue, near Chats-\nawakened at 6 a.m. The house shook and rolled, and","44\nSan Fernando Earthquake of 1971\nworth and Reseda, chimneys were cracked, twisted,\nerate. (Report from postmaster. Post office located at\nand overturned. Pool water was down 2 feet. Huge\nVan Nuys Boulevard, near Telfair Avenue.) Ob-\nbookshelves were broken loose; five-drawer steel file\nserver in the Arleta district, south of Pacoima, in\ncabinet was overturned. Damage was moderate. At\narea just east of Panorama City, reported: \"In our\n8419 Yolanda Avenue, block wall was cracked; above-\nhouse the refrigerator opened and everything fell\nground pool was damaged. Upright piano was\nout, also most things from the cupboards. Our next-\nmoved 8 inches east; refrigerator was moved 3 feet\ndoor neighbor's cupboards face the same direction as\nsoutheast. Damage was slight. At 10306 Sylvia Ave-\nours, with only a driveway separating the two houses,\nnue, block walls were topped and weakened; drive-\nbut she lost only one bottle of catsup. Our kitchen\nway was cracked; portable planters were moved; tele-\nhad to be cleaned out with a shovel. Most of the fur-\nvision was overturned; bed was moved 6 inches.\nniture in the family room moved at least 6 to 8\nDamage was slight. At 17527 Burton Street, water\ninches from the walls, including a large player piano.\nwas disturbed and dirty. Electricity was off 30 min-\nWe couldn't tell in which direction it was shaking-\nutes; phone was out 2 hours. Trailer fell off jacks.\nseemed to be both bouncing and swaying. We tried\nChest of drawers fell south. Movement was difficult.\nto walk through the house to get the children and\nMany aftershocks were felt for the first 2 days; sev-\nhad to hold onto the walls to keep from falling. Our\neral were felt thereafter. At 18822 Chase Street, patio\nblock fences are all cracked but still standing. We\ncement was cracked and old cracks were widened.\nhave many cracks outside, but few cracks inside. Fur-\nChimney toppled next door. Block walls were weak-\nniture broken. Water disturbed. Plaster and win-\nened and ready to topple. Plaster was cracked. Water\ndows cracked. Damage slight.\" (Two intensity VI re-\ncooler was broken; shower glass was cracked. No\nports were received from the area.)\nstructural damage was noticed. At 19530 Pine Valley\nPanorama City--Building at 14545 Lanark Street\nAvenue, chimneys were cracked, twisted, and over-\nwas reported as being very badly damaged; also dam-\nturned in vicinity. Wrought-iron fence was broken.\naged was a building at 8155 Van Nuys Avenue\nPlaster fell. Small overhang roof (tile) sagged and\n(from a letter by Superintendent of Buildings, De-\nmust be replaced. Damage was moderate. At 18098\npartment of County Engineer, Los Angeles) The fol-\nKirkcolm Lane (in Porter Ranch district, about 31/2\nlowing is an excerpt from Lew et al. (1971) \"Kaiser\nmiles due west of Lower Van Norman Lake), power\nFoundation Hospital, 13652 Cantara Street. Ten-\nwas out. No water was available for 4 days. Exterior\nstory reinforced lightweight concrete shear-wall\nblock walls were down. Windows were broken.\nstructure. There was severe cracking of the shear\nHoles were found in stucco walls and doors. Plaster\nwalls in the first, second, and third stories. The doors\nwas cracked. Furniture was shifted. Cabinets were\nto the interior stairwell on the second and third\nemptied. The following is from a report by California\nfloors were rendered inoperative due to the crushing\nInstitute of Technology (1971) It was reported that\nof the spandrel beam in the shear wall. The fourth-\n$245,000 damage was sustained at the San Fernando\nfloor slab, which is the transfer slab between the cir-\nState College, 18111 Nordhoff Street, and was due\ncular tower shear walls and the walls below, cracked\nprincipally to collapsing bookshelves, toppling furni-\nand displaced vertically. There was no apparent sign\nture, and falling glass from broken light fixtures and\nof structural damage above the fourth-floor level.\nbroken windows. \"Only very minor cracking of\nAbout 50 glass panels fell from the building. All the\nstructural members was found in the various build-\nelevators were out of service after the earthquake.\nings on this campus, which included an eight-story\nThe entire hospital remained in operation.\" Electric-\ndormitory and an eight-story office tower.\" (There\nity was off over the entire area. At 14861 Lorne\nwere reports of eight intensity VI's and two intensity\nStreet, damage was reported as slight. Stucco cracks\nV's from the Northridge area.)\nwere noted; waterline was broken between meter\nPacoima (excluding the more strongly shaken\nand house. \"Vertical motion of house was very pro-\nareas of northern Pacoima) -Ground was cracked.\nnounced, also lateral movement. Did not awaken 3-\nGaslines were broken. Chimneys were overturned.\nyear-old girl.\" At another location, furniture was\nOutside block walls were knocked down. Crack in\nshifted; plaster was cracked. (Two reports of intensity\nfloor the length of the building (post office) was re-\nVI and one report of intensity V were received from\nported. Furniture was overturned. Damage was mod-\nthe area.)","Felt Area and Intensity of Earthquake\n45\nPasadena.-At the Jet Propulsion Laboratory,\nfrom swimming pools. One observer stated: \"Our\n4800 North Oakgrove Avenue, an estimated $200,000\nfallen 6-foot block wall was not reinforced by steel.\nin minor damage to the Laboratory was reported by\nStucco cracks were widened by aftershocks. Asphalt\nan engineer: \"I arrived at work about 7:50 a.m. and\ndriveways cracked and some new sidewalk was\nmade numerous surveys of buildings on the Labora-\ncracked around power poles. Doors facing north or\ntory grounds to assess structural damage. Structural\nsouth on cupboards and on furniture flew open.\ndamage was superficial. Some spalling of concrete\nNothing fell from shelves running north-south, even\ncolumns and concrete block walls. Some cracking of\nfrom those near the ceiling. Windows in house are\nconcrete walls. Considerable damage to architectural\nall aluminum framed and did not break, though\nfinishes (plaster, suspended ceilings, and lighting fix-\nquite large. Some roofs in area buckled.\" (Five in-\ntures) Expansion joints and seismic joints had\ntensity VI reports and one intensity V report were re-\nworked [out] and caused buckling of threshold strips\nceived from the area.)\nand buckling and displacement of metal water stops\nSepulveda.-At the Holiday Inn, corner of Roscoe\nat joints. Some waterlines broken.\" At the Millikan\nBoulevard and Orion Avenue, the following was\nLibrary, California Institute of Technology, the fol-\nreported: \"Seven-story reinforced concrete building.\nlowing damage was reported: \"Nine-story reinforced\nExtensive damage to interior plaster walls, to the\nconcrete building. Many bookshelves collapsed on\nplumbing fixtures, etc., on the second, third, and\nthe upper floors and threw many books to the floor.\nfourth floors. The upper three floors were not dam-\nWith the exception of hairline cracking in the plas-\naged severely. The nonstructural damage had been\nter around some window panels, no damage to the\nestimated at approximately $250,000\" (excerpt, Cali-\nbuilding itself was observed\" (excerpt, California In-\nfornia Institute of Technology 1971) At the Veter-\nstitute of Technology 1971). Observers in several\nans Administration Hospital (about 2.5 miles south\nareas reported that chimneys were cracked, twisted,\nof the Lower Van Norman Reservoir), this report\nand overturned. Many windows were broken in busi-\nwas received: \"Buildings range from one to six sto-\nness district. Cracking and fall of plaster were re-\nries and are designed to resist earthquake forces.\nported at a number of locations. Heavy sloshing of\nOverall, there was only minimal structural damage\nwater from swimming pools was also reported. Ob-\nto the hospital. The operation of the hospital was\nserver at 1355 Daveric Drive (northeast Pasadena,\nnot interrupted. However, extensive elevator and\nnorth of Foothill Boulevard) reported that ground\nplaster repairs were required and a number of\nwas cracked. The following statistics (Steinbrugge et\nseismic joints required replacement\" (excerpt, Lew\nal. 1971) do not include publicly owned structures:\net al. 1971), At 9037 Burnet Avenue, an observer\n10 buildings damaged; four posted unsafe; buildings\ncommented: \"Telephone pole tilted east-west (across\ndemolished or to be demolished include one church\nstreet) Chimney cracked vertically where it lies\nand one school; 2,000 chimneys damaged; and esti-\nagainst house. Huge crack on cement foundation of\nmated total dollar loss at $2.5 million. Reports by\ngarage floor, running east-west across floor. Small\nPasadena city officials roughly estimated damage at\nchicken shed tilted south. The house was a mess in-\n$200,000 to public property, with the majority of the\nside. Anything on top of furniture (mantle, tables,\nloss attributed to road damage. The largest single\netc.) was thrown down and broken. Stove and icebox\nitem occurred on Park View Avenue, which runs\nmoved in kitchen. In the garage, a 6- by 6-foot book-\nparallel and east of Linda Vista Avenue. There, ap-\ncase, full of books, overturned. Garage had to be\nproximately 800 feet of retaining wall, standing 11\n'dug through to put things back in place. It suffered\nfeet high, was affected, with approximately 300 feet\nworse than the house. We inspected the house and\nof the wall reduced to rubble. Estimates for repair\ndid not see any new cracks, but since the aftershocks,\nof the wall made up the major portion of the $200,-\nwe have found many new cracks, running south-\n000 figure. (There were also 13 reports of intensity\nnorth, about the thickness of a razor blade. There\nVI and 19 reports of intensity V received from the\nare many old cracks running in the same direction.\nPasadena area.)\nAll of our cement porches (three) have shifted 1 to\none-half inch away from the house. We have found\nReseda.-Block garden walls fell. Some roofs were\ncracks outside both garage and house since the after-\nbuckled. Plaster cracked and fell. Heavy furniture\nshocks. In our house, all objects on north-south walls\nwas shifted and overturned. Water was sloshed","San Fernando Earthquake of 1971\n46\nfrom the Union Bank Building; 12-story reinforced\nfell; in neighbor's house (across street), all objects\nconcrete structure) the following damage occurred:\non their east-west walls fell, none on north-south\n\"There were cracks in the building frame over most\nwalls.\" At 10108 Gloria Avenue, 60 feet of outside\nof its height. These were especially pronounced in the\nblock wall fell and 150 feet was cracked; some inside\nconnection of the lightweight concrete beams to the\nand outside plaster-cracking was evident; damage was\nnormal weight concrete columns. This damage was\nmoderate. At 9752 Marklein Avenue, garden wall\nbeing repaired with epoxy\" (excerpt, Lew et al.\nwas cracked; furniture shifted; stucco was slightly\n1971). Observer at 3817 Cody Road reported: Un-\ncracked; minor kitchen-counter tile cracking was no-\nreinforced chimneys were cracked, twisted, and over-\nticed. \"Earth motion was definitely north-south.\nturned. Ground was cracked slightly. Plaster was\nHeavy books on north-south shelves fell sideways-\ncracked. Damage was slight. \"Major ground motion\nnot off shelves. Portable television against north wall\nappeared to be east-west. The major shock lasted\nfell to floor. Kitchen and both bathroom floors were\nabout 60 seconds. Very little damage to hillside\nlittered with broken glass. Hot water tank connec-\nhouses on rock in general vicinity. Houses on softer\ntions loosened, water leaked. China cabinet and re-\nsubstrata at lower elevations appeared to sustain\nfrigerator on east-west walls shifted 6 inches from\nlarger accelerations and damage.\" (There were six\nwalls. No structural damage.\" Postmaster reported\nintensity VI reports and eight intensity V reports re-\nslight, nonstructural damage to post office; ground\ncracked, landslides occurred, and water was dis-\nceived from the area.)\nSouth Pasadena.-Many chimneys were damaged\nturbed; and chimneys, plaster, and windows were\nand overturned. Large plate-glass windows in several\ncracked. Other observers reported: \"Water and gas\nstores were broken. Some old brick parapets fell in\nservice disturbed. Many windows cracked in area, in-\ncommercial area. \"One or two buildings of unrein-\ncluding a furniture store.\" \"One-third of water emp-\nforced masonry construction showed severe crack-\ntied from swimming pool.\" \"Slight spalling of side-\ning.\" Ground crack was observed on Monterey Road.\nwalk at pool joints.\" (Three intensity VI reports\nCommunity water tower leaked. Water sloshed 6 feet\nwere received from the area.)\non each side of swimming pool. The following statis-\nSherman Oaks.-The Union Bank Building\ntics (Steinbrugge et al. 1971) do not include\n(northeast corner of Sepulveda and Ventura), a 13-\npublicly owned structures: 20 buildings damaged; 1\nstory reinforced concrete structure, reportedly sus-\nposted unsafe; 300 chimneys damaged; and estimated\ntained some structural damage and considerable non-\ntotal dollar loss at $275,000. (In addition, there were\nstructural damage. \"The structure is 13 stories high\nover a two-level subterranean garage. Structural dam-\nseven intensity VI and four intensity V reports re-\nage was limited principally to the four-corner col-\nceived from the South Pasadena area.)\numns.\" Nonstructural damage was reported as: \"Ele-\nSunland.-At 8632 Le Berthon Street (northwest\nvators out of commission; several doors in the\nSunland area), observer reported: Block walls were\nsecond, third, fourth, and fifth floors were slightly\nthrown down. \"Our heavy plate-glass mirror in bed-\njammed, indicating some partition movement; con-\nroom was ripped off the wall, taking some plaster off\nsiderable areas of ceiling tile over the second floor\nthe wall. Built-in oven was sprung from the cabinet.\nfell; one drywall partition at the east end of the\nThe hutch in dining room was thrown down, break-\nbuilding buckled and showed horizontal movement:\ning all contents, and landed on the dining room\nsome steel stairlandings pulled away from their sup-\ntable; badly damaged.\" At 10734 Nassau, rocks in\nports but were still functional; five large panes of\ngarden rolled. Damage to furniture and dishes was\nglass in the first floor cracked or broke; marble ve-\nin excess of $900. At 10114 McBroom Street (west\nneer in the first-floor lobby cracked and fell away\nSunland area), furniture was shifted; glasses, food,\nfrom the walls and had to be replaced. The upper\netc., fell from cupboards, but no damage was re-\nfloors showed the least damage, and the penthouse\nported. \"Shock was violent enough to knock one off\nshowed no damage. The mechanical equipment in\nhis feet if not holding onto something solid.\" At\nthe penthouse was intact and securely mounted\" (ex-\n8442 Oswego Street, plaster, walls, chimneys, and\ncerpt, U.S. Geological Survey and the National\nground were cracked. Plaster and walls fell. Dishes,\nOceanic and Atmospheric Administration 1971) At\nwindows, and furniture were broken. Damage was\nthe Bank of California Building (across the street","Felt Area and Intensity of Earthquake\n47\nslight to brick. (Two reports of intensity VI were re-\nVerdugo City.-\"Major damage to buildings in\nceived from the area.)\narea. Many windows and dishes broke. Without lights\nuntil 10:20 and limited telephone service for most\nSun Valley.-Chimneys were cracked, twisted, and\nof the day.\" Plaster cracked. Small objects fell. Fur-\noverturned. Outside reinforced concrete wall was\nniture shifted. Water sloshed from toilet.\ncracked. Heavy furniture was moved east-west. Water\nin street was due to sloshing of swimming pools. \"I\nVernon.-T following statistics (Steinbrugge et\nwas standing at the time; motion was a violent\nal. 1971) do not include publicly owned structures:\nnorthwest-southeast shaking. Dining room fixture\n30 buildings damaged; five posted unsafe; and esti-\n(4-ft chain) swung to the ceiling. Glass and crystal\nmated total dollar loss at $100,000. Postmaster re-\nfell from every china closet in neighborhood.\"\nported there was no damage at the post office.\n\"Many people thought it was a bomb.\" (Reports of\nWoodland Hills.-At 22233 Buenaventura, cement\nthree intensity VI's and one intensity V were re-\nwork, especially pool decking, was severely cracked.\nceived from the area.)\nTree was leaning. One-half of the pool water was\nTarzana.-At 18525 Linnet Street, house founda-\nsloshed out. Plaster was cracked. Furniture was over-\ntion was cracked. Waterpipe was broken. Plaster\nturned. Damage was moderate. At 20513 Rhoda\nand windows were cracked. Toilet and bathtub line\nStreet, few branches were broken off trees. Big tele-\nwas damaged. Damage was moderate. \"There are still\nvision and stereo sets were moved a few inches. Ceil-\n(March 9) numerous strong aftershocks.\" Other ob-\ning, floor, and walls were cracked; more cracks were\nservers reported: Plaster cracked and fell. Cracks\nfound in outside floor but not serious. Damage was\nwere widened in pavement and asphalt drives. Pool\nslight. Other observers reported: Blocks in cement\nwater was sloshed. (Two intensity VI and four in-\nblock fence were loosened; plaster was cracked; and\ntensity V reports were also received from the area.)\npool water was sloshed out. \"No electricity for 1 hour\nand 15 minutes. Electric power went out within sec-\nTujunga.-Ground was cracked. Minor cracking\nonds after start of shock. Gas and water supply re-\nof pavement occurred. Chimneys were cracked,\nmained OK. No telephone communication for 7\ntwisted, and overturned. Plaster and windows were\nhours.\" \"Aftershocks seemed to be, in general, a\ncracked. Electrical wires were down. \"Most of the\nrolling, wavy motion, causing a good shake. However,\ndwellings in the area suffered only minor damage.\nabout one of four aftershocks seemed like a roll at\nSome older dwellings suffered moderate to major\nfirst, then a big thud and dropping sensation. Per-\ndamage, but these were very few. Many commercial\nsonally, I feel as if the ground and building were\nbuildings had broken plate-glass windows. A few\nwaving and moving all the time.\" (Also, there were\ncommercial buildings suffered moderate damage.\"\nfive intensity VI reports and seven intensity V re-\nMany aftershocks were felt. (There was one report\nports received from the Woodland Hills area.)\neach of intensities VI and V received from the area.)\nVan Nuys.-Ground was cracked. Chimneys were\nREFERENCES\ncracked, twisted, and overturned. Water was muddy\nAnonymous, \"Oil Escapes Heavy Damage in California Quake,\"\nfor about 5 days. Outside block walls were cracked.\nThe Oil and Gas Journal, Vol. 69, No. 7, Tulsa, Okla., Feb.\nSlab floor was cracked. Plaster was cracked. Heavy\n15, 1971, pp. 44-45.\nfurniture was shifted. Pool water sloshed over top of\nCalifornia Division of Mines and Geology, \"The San Fer-\nnando Earthquake, 1971,\" California Geology, Vol. 24,\nhouse. \"People here were very frightened, but kept\nNos. 4-5, Sacramento, Apr.-May 1971, pp. 57-96.\ncontrol. In our general area, 8183 Lesner Avenue,\nCalifornia Institute of Technology, Earthquake Engineering\nwest of Van Nuys Airport, near Balboa Boulevard,\nResearch Laboratory Report EERL 71-02, Pasadena, June\nloss was mostly to dishes and personal items. Parts of\n1971, 512 pp.\nblock walls came down; water heaters moved, some\nLew, H.S., Leyendecker, E.V., and Dikkers, R.D., \"Engineering\noff elevated stands, and most were inside houses in\nAspects of the 1971 San Fernando Earthquake,\" Building\nScience Series 40, National Bureau of Standards, U.S. De-\nservice porch area. Some people were thrown out of\npartment of Commerce, Washington, D.C., Dec. 1971, 419\nbed. Some cars rolled out of driveways or garages.\npp.\nTraffic became a major problem.\" (Reports of seven\nLos Angeles County Earthquake Commission, San Fernando\nintensity VI's and 16 intensity V's were received\nEarthquake, February 9, 1971, County Board of Supervisors,\nfrom the area.)\nLos Angeles, Calif., Nov. 1971, 45 pp.","San Fernando Earthquake of 1971\n48\nMorrill, B.J., \"Evidence of Record Vertical Accelerations at\nSteinbrugge, Karl V., Schader, E.E., Bigglestone, H.C., and\nKagel Canyon During the Earthquake,\" The San Fernando,\nWeers, C.A., San Fernando Earthquake, February 9, 1971,\nCalifornia, Earthquake of February 9, 1971, Geological Sur-\nPacific Fire Rating Bureau, San Francisco, Calif., 1971, 93 pp.\nvey Professional Paper 733, U.S. Geological Survey and the\nU.S. Geological Survey and the National Oceanic and At-\nNational Oceanic and Atmospheric Administration, U.S.\nmospheric Administration (Publishers), The San Fernando,\nDepartment of the Interior and U.S. Department of Com-\nCalifornia, Earthquake of February 9, 1971, Geological Sur-\nmerce, Washington, D.C., 1971, pp. 177-181.\nvey Professional Paper 733, U.S. Department of the Interior\nNational Earthquake Information Center, Earthquake Infor-\nand U.S. Department of Commerce, Washington, D.C., 1971,\nmation Bulletin, Vol. 3, No. 2, National Ocean Survey, Na-\n254 pp.\ntional Oceanic and Atmospheric Administration, U.S. De-\nWood, Harry O., and Neumann, Frank, \"Modified Mercalli\npartment of Commerce, Rockville, Md., Mar.-Apr. 1971,\nIntensity Scale of 1931,\" Bulletin of the Seismological So-\n27 pp.\nciety of America, Vol. 21, No. 4, Dec. 1931, pp. 277-283.","Focal Mechanism of\nSan Fernando Earthquake\nABSTRACT\nBody-wave focal plane solutions for the San Fer-\nnando earthquake of February 9, 1971, have been\ncomputed using long-period P-wave data and S-\npolarization angles, including solutions with com-\nbined P- and S-wave data. The long- and short-period\nCONTENTS\nP-wave data give essentially the same result. The P-\nPage\nwave data reported to the National Earthquake In-\n49\nABSTRACT\nformation Center (NEIC) give a solution that agrees\n49\nINTRODUCTION\nwell with data carefully read by the author. The\n64\nP-WAVE SOLUTIONS\nNEIC-reported data do give a larger percent error,\nS-WAVE AND COMBINED SOLUTIONS\n65\nwhich is reflected in the larger error limits shown for\n66\nCONCLUSIONS\nthis solution; however, the solution is good and\n67\nREFERENCES\ndemonstrates the feasibility of using reported P-wave\ndata on a routine basis for earthquakes with M > 6.0.\nThe best solution selected using combined P- and\nS-wave data for this earthquake gives one plane with\nstrike N.65° W. dipping 55° to the northeast which\nis well determined, and a second plane with a strike\nN.40°W dipping 37.7° to the southeast which is not\nas well determined. This solution gives excellent\nagreement with the observed field evidence found in\nthe source region for horizontal compressional forces\nand the thrusting up of the San Gabriel Mountains.\nINTRODUCTION\nThe San Fernando earthquake of February 9,\n1971, caused extensive damage in the Los Angeles\nand San Fernando areas. Many Federal agencies re-\nsponded to this earthquake by initiating studies of\nthe effects. The Seismological Research Group of the\nEnvironmental Research Laboratories (ERL) sent a\nrequest to many cooperating stations around the\nworld for use of their seismograms. Over 170 stations\nW. H. DILLINGER\ncooperated by loaning their seismograms. The com-\nSeismological Research Group\nplete set of seismograms was filmed by the Environ-\nEarth Sciences Laboratories\nmental Data Service (1971) . Copies can be obtained\nEnvironmental Research Laboratories, NOAA\n49","50\nSan Fernando Earthquake of 1971\nfrom the National Geophysical Data Center at Ashe-\ntional P-wave data, which were obtained after the\nville, N.C.\ndeadline for the previous report, but the study is pri-\nHypocenter parameters used in this study were re-\nmarily improved by the use of S-polarization angles,\nported to NOAA by the California Institute of\nwhich allow the determination of an independent S-\nTechnology as follows:\nwave solution and a combined P- and S-wave solu-\ntion.\nOrigin time: 14 00 41.6 GMT\nEpicenter:\nOne of the focal planes of this earthquake, striking\n34.4°N., 118.4°W.\nDepth:\n13 km.\nN.65°W. and dipping 55° to the northeast, is very\nThe body-wave magnitude Mb reported by the Na-\nwell determined by P-wave first motions as shown in\ntional Earthquake Information Center (NEIG) is\nfigure 1. Using P-wave first motions alone, the sec-\n6.2, and the surface-wave magnitude MS is 6.5.\nond plane is determined very poorly, having an al-\nEven though there was extensive damage locally, this\nlowable variation in strike of about 60° to 70°. The\nwas only a moderate size earthquake in terms of\n\"combined maximum likelihood solution\" (solution\nsource dimensions and radiated energy. Conse-\nNo. 1 of table 1) shown in figure 3, using the tech-\nquently, the S-wave motion was not exceptionally\nniques developed by Dillinger et al. (1971) gives a\nwell recorded at most of the stations between dis-\nsolution for the second plane with a strike of\ntances of 40° and 80° This earthquake is on the\nN.40°T W. and dipping 37.7° to the southeast. These\nlower limit for determining the orientation of the\nresults are in good agreement with the P-wave first\nfocal mechanism from S-wave data with current tech-\nmotions. The residuals for the S-polarization angles\nniques.\nare about 10 percent higher than would be allowed\nThe P-wave first motion was also difficult to inter-\nby the 95-percent fiducial limits of the corresponding\npret at low-magnification stations where the signal-\nS-wave solution. As the magnitude of this earthquake\nto-noise ratio was poor, such as some of the stations\nis probably marginal for the use of S-waves, these\nin Mexico and Central America, which might other-\nhigh S-residuals were not considered too important,\nwise give important information on the focal mecha-\nand solution No. 1 was considered \"best\" primarily\nnism of California earthquakes. The shallow depth\nbecause of the better distribution of P-wave data.\nof this earthquake, placing it in the upper crust, cer-\nThis solution also gives good agreement with the ob-\ntainly added to the complexity of both the P- and S-\nserved geological evidence in the source regions,\nwave signals.\nwhich indicates horizontal compressional forces and\nShortly after this earthquake, a preliminary solu-\nvertical uplift of the San Gabriel Mountains.\ntion was computed by Dillinger and Espinosa\nAn alternate possibility (solution No. 2 of table\n(1971) using only P-wave data. This study uses addi-\n1) shown in figure 6b, with one plane striking\nTable 1.-San Fernando focal mechanism solutions\nP-wave\nRp\nPole of A-plane\nPole of B-plane\nfidu-\nfidu-\nSolution\nN\nRp\nRs\nR (95%)\ncial\ncial\nA\nB\na\nAzimuth\nDip\nAzimuth\nDip\nre- bound-\ngion\nary\no\no\nO\nO\nPercent\nSolution No. 1:\nP-wave\n10.00\n40.00\n209.28\n51.62\n180\n155\n96.4\n153\nS-wave\n195.00\n70.00\n328.22\n27.99\n20\n6527.7\n19.60\n10213.9\nCombined\n205.00\n55.00\n50.04\n37.70\n154\n11734.1\n1.82\n0.00130\nSolution No. 2:\nP-wave\n0.00\n40.00\n192.96\n50.73\n96\n91\n97.8\n90\nS-wave\n220.00\n45.00\n79.23\n52.24\n18\n1611.4\n10.37\n2671.7\nCombined\n215.00\n45.00\n74.23\n52.24\n91\n1771.3\n2.90\n00465\nSolution No. 3:\nP-wave\n5.00\n50.00\n207.63\n42.27\n134\n119\n98.7\n117\nSolution No. 4:\nP-wave\n10.00\n50.00\n212.63\n42.27\n91\n79\n98.3\n76\nS-wave\n190.00\n65.00\n322.19\n34.78\n19\n2037.3\n11.28\n3274.9\nCombined\n45.00\n40.00\n205.72\n51.62\n78\n6712.2\n1.88\n00393\nSolution No. 5:\nP-wave\n0.00\n40.00\n205.41\n52.84\n149\n136\n99.3\n134\nSolution No. 6:\nS-wave\n315.00\n75.00\n200.85\n33.23\n19\n3390.5\n14.56\n5450.2","a","S HOVE SOLUTION","","125.00 STRIKE\n90.00 DIP\nFigure 4.-Profiles of S-wave error surface for 20-station solution on left and 18-station solution on right. These are for solutions Nos. 1 and 2, respectively, from table 1.\n180.00\n110.57\n160.00\n76.00\n140.00\n94.32\n62.97\n120.00\n74.23\n52.24\nDIP 45.00\nANGLE OF ROTATION\n100.00\n49.00\n45.86\n21.00\n45.86\nb\n80.00\nSTRIKE 215.00\n355.77\n52.24\n60.00\n335.68\n62.97\n40.00\nINITIAL PLANE\n319.43\n76.00\n20.00\n305.00\n90.00\n0.00\n00\n115.00 STRIKE\n90.00 DIP\n180.00\n103.21\n160.00\n73.73\n140.00\n89.30\n58.23\n120.00\n70.19\n44.81\nDIP 55.00\nANGLE OF ROTATION\n100.00\n42.09\n36.22\n36.22\n80.00\na\n7.91\n205.00\n339.81\n44.81\n60.00\nSTRIKE\n320.70\n58.29\n40.00\nINITIAL PLANE\n306.79\n73.73\n20.00\n295.00\n90.00\n0.00\n00","Focal Mechanism of Earthquake\n55\nplotting a particle motion diagram from which the\nN.55°W. and dipping NE, for the well-deter-\nmined plane and N.16.8°W. and dipping 2.2°SW.\npolarization angle was measured.\nThe computer procedure used for finding the best\nfor the second plane, is also a good solution. This so-\nfitting focal planes is incremental. The orientation of\nlution uses only what was considered to be the very\nfocal planes giving the highest score determined\nbest data. The long-period data were used for the P-\nfrom maximum likelihood is selected as the best SO-\nwave observations; and the two S-polarization angles,\nlution. The P- and S-scores are combined with con-\nwhich gave the highest residuals to the preceding SO-\nstants determined from maximum likelihood statis-\nlution, were discarded.\ntics to find the best combined solution. The fiducial\nOne problem which occurred when looking at\nlimits for the P- and S-wave solution are contoured\nsuch a large number of original records was that, on\non an equal-area projection of the focal sphere. For\na small percentage of the records, there was some\nthe S-wave solutions, the contours are 95-percent fidu-\nquestion about the polarity of the instrument. A\ncial limits. The P-wave maximum likelihood surface\nbrief inspection of figures la and 8a shows several\nis a step function because of the discrete nature of\ncases of inconsistent observations in the middle of\nthe data. Thus, it is seldom possible to contour an\nmany consistent observations nearby. While some of\nexact 95-percent limit because the score which is con-\nthese may be errors in the readings, some were clear\ntoured is the value which gives the next highest per-\narrivals and even had records similar to nearby sta-\ncent likelihood above 95 percent. A complete discus-\ntions, except they were reversed in phase. This prob-\nsion of these techniques can be found in Dillinger et\nlem could be resolved easily if more attention would\nbe paid by the station operators and managers to the\nal. (1971)\nSeveral solutions were run to determine if\npolarity of their instruments, including making a\ndifferent data sources would give significantly differ-\nclear indication on the record of the polarity.\nent answers. The computed results are given in table\nThe fact that the worldwide station at Mexico\n1. In each case, the solution given for the best P-\nCity was not operational during this earthquake and\nwave solution is not unique. There is always a con-\nthat there is a lack of other high-quality data from\ntinuous range over which the focal planes may be\nthe region in northern Mexico were real disadvan-\nvaried while keeping the same number of consistent\ntages. The occurrence of three dilatational obser-\nobservations of P-wave first motion. The P-wave so-\nvations from Mexico (seen in the fourth quadrant of\nlution printed in table 1 is the first solution found\nfig. la) gave the author the first impression that\nby the computer which has a score equal to the best\nthe second plane was well defined and dipping south.\nscore found. For the more important solutions, con-\nTo resolve any focal plane which was dipping steeply\ntoured limits on the allowable variation of the P-\nsouthward for a southern California earthquake,\nwave solution are presented. From these diagrams, it\nsome high-quality stations with long- and short-\nis easy to see the range in orientation possible for the\nperiod instruments would be needed in Mexico.\nP-wave nodal planes.\nThe data read by the author for this earthquake\nThe contours shown on illustrations of P-wave so-\nand the reported data are given in table 2 along with\nlutions (figs. 1b, 5b, 7b, 8b, and 9b) have two levels.\nthe distance, azimuth, and angle of departure for the\nThe outer contour is of the fiducial limit. The per-\nP-wave. The azimuth is measured clockwise north\ncent likelihood contained within the fiducial limit\nthrough east, as are the azimuths given in table 1.\nfor each solution is given in table 1. The inner con-\nThe first motions listed under NEIC were those\ntours closest to the given solution are the limits over\navailable to the Center by approximately March 1,\nwhich the pole can vary and still have the same\n1971. The first motions read by the author are fol-\nvalue as the given solution, that is, the same number\nlowed by a relative quality factor: E = excellent; G\nof agreeing and disagreeing observations.\nThe contours presented for the combined solu-\n= good; F = fair; and P = poor. All of the read-\ntions in figures 3b, 6a, and 9b are not computed fidu-\nings with the exception of those labeled poor are\ncial limits of a known percent likelihood as is pre-\nprobably good enough not to be arbitrarily discarded\nsented for the individual P- and S-wave solutions.\nwithout reinterpreting the record. The S-polarization\nHowever, as with fiducial limits, they are equal like-\nangles were determined by digitizing the horizontal\nlihood boundaries and are contoured at equal incre-\ncomponents of the long-period instruments and by","San Fernando Earthquake of 1971\n56\nTable 2.-Observed data for San Fernando earthquake\nSense of motion1\nAmplitude\nS-wave\nStation\nAngle of\nStation\npolarization\nT3\nmagni-\nDistance\nAzimuth\ndepar-\nLP\nSP\nNEIC\nA1\nA2\nfication\nture\nSeconds\nkm\no\nmm\nmm\nAAE\nC F\nC G\n131.7\n30.9\n6.4\nADK\nC G\nC E\nC\n44.7\n311.5\n28.2\nAFI\n-51.5\n69.8\n236.1\n20.8\nALB\nD F\n15.6\n344.2\n49.3\nALE\nC G\nC G\nC\n-177.0\n13.0\n38.0\n8.8\n3900\n51.8\n8.0\n26.4\nALI\nC G\n87.5\n44.1\n16.3\nALQ\nC G\nD P\nC\n1.5\n9.0\n12.4\n375\n9.8\n83.4\n53.6\nANP\nC\n97.9\n307.7\n15.3\nAPP\nC G\n77.6\n22.0\n19.0\nAQU\nC E\nC E\n3.2\n7.5\n10.4\n3000\n91.8\n33.6\n15.6\nARE\nC E\nC E\nC\n-59.7\n5.0\n14.3\n9.2\n1500\n67.4\n130.6\n21.6\nASP\nC\n117.1\n258.8\n6.2\nATH\nC\n99.9\n29.5\n15.7\nATL\nC G\nC G\n10.0\n31.0\n12.0\n3000\n28.2\n82.2\n31.8\nAVE\nC G\n86.6\n51.6\n16.6\nBCN\nD G\n3.3\n60.4\n56.1\nBEC\nC E\n-14.5\n4.5\n11.0\n8.0\n1500\n44.5\n76.9\n28.3\nBHP\nC G\nC F\nC\n135.7\n43.7\n116.2\n28.3\nBLA\nC G\nC G\n6.0\n15.0\n13.2\n1500\n30.8\n73.6\n31.0\nBLC\nC G\nC G\nC\n8.5\n31.5\n8.8\n3800\n32.9\n17.8\n30.6\nBLG\nD\n0.6\n243.6\n88.8\nBMN\nD\n6.1\n8.4\n55.8\nBMO\nD E\nD E\n10.5\n4.2\n53.3\nBNG\nC G\nD\n124.1\n55.2\n6.4\nBNH\nC\n37.3\n59.8\n29.4\nBNS\nC G\nC G\n1.8\n4.8\n9.6\n1000\n82.5\n31.3\n17.7\nBRK\n4.7\n319.1\n56.0\nBRW\n42.2\n342.7\n28.8\nBTY\n2.8\n27.5\n56.6\nBUH\n84.6\n32.3\n17.0\nBUL\nC G\nC G\n147.6\n72.6\n5.4\nBUT\nD P\nD F\n12.4\n19.2\n51.7\nCAR\nC E\nC E\nC\n-23.0\n10.0\n27.3\n12.8\n3000\n52.5\n104.2\n26.0\nCHI\nC G\n25.2\n63.6\n33.6\nCLE\nC F\n29.8\n65.2\n31.6\nCMP\nC\n94.1\n24.9\n15.6\nCOL\nC E\nC G\nC\n4.5\n13.0\n9.2\n1500\n35.3\n338.8\n29.9\nCOM\nC G\n29.7\n120.9\n31.6\nCOP\nC G\nC G\nC\n2.5\n6.5\n10.0\n1500\n81.0\n25.7\n17.9\nCOR\nC G\nC P\nD\n10.9\n341.1\n53.0\nCPO\nC E\nC G\n14.0\n62.0\n17.3\n2200\n26.8\n78.0\n32.4\nCPP\nC\n76.4\n137.1\n19.1\nCPX\nC\n3.2\n36.2\n56.1\nCSC\nC\n30.8\n80.0\n31.0\nCUM\nD F\nC\n54.4\n102.1\n25.6\nDAL\nD E\nC P\nC\n20.7\n87.5\n8.0\n1500\n18.1\n88.8\n47.7\nDBN\nC\n80.8\n31.4\n18.0\nDBQ\nC E\nC E\n12.0\n12.5\n4.4\n23.1\n61.2\n34.6\nDEN\nD E\nD F\n11.9\n59.3\n52.2\nDUG\nD E\nD E\nC\n95.0\n256.0\n32.0\n3000\n7.3\n35.9\n55.1\nEKO\nD\n6.7\n17.2\n55.4\nELK\nD G\nD\n6.8\n20.6\n55.4\nEPT\nC F\nD F\n10.3\n101.4\n53.4\nESA\nC G\nC G\nC\n.8\n1.6\n2.4\n96.1\n262.4\n15.4\nESK\nC G\nC G\n165.5\n2.5\n5.5\n10.0\n750\n74.9\n32.4\n19.8\nEUR\nC\n5.4\n20.2\n55.5\nFAY\nC\n19.8\n78.2\n40.6\nFBC\nC E\nC G\nC\n9.8\n33.5\n9.2\n2800\n42.2\n30.4\n28.8\nFCC\nC E\nC G\n8.5\n43.0\n7.2\n4500\n29.2\n26.1\n32.0\nFFC\nC E\nC G\n19.0\n4600\n23.4\n24.5\n34.6\nFHC\nC\n7.8\n326.9\n54.8\nFLO\nC E\nC E\n15.2\n51.5\n13.2\n1500\n22.9\n70.7\n35.1\nFOR\nC G\nC F\n35.5\n66.2\n29.8\nFSJ\nC G\nC G\nC\n3.5\n59.0\n14.8\n3300\n20.5\n350.2\n37.5\nFÜR\nD\n86.3\n31.1\n16.7\nGCA\nD P\nD\n6.1\n63.1\n55.8\nGDH\nC G\nC G\n170.3\n4.2\n15.5\n9.2\n1500\n49.4\n25.1\n26.8\nGEO\nC\nC\n33.3\n70.0\n30.7\nGLA\nC\n113.2\n3.3\n56.1\nGMA\nC\n38.8\n329.6\n29.3\nGOL\nD E\nD P\nD\n33.0\n65.0\n32.0\n1500\n11.7\n59.2\n52.5\nGRC\nC\n83.2\n35.8\n17.5\nGRF\nD G\nC G\nC\n12.0\n37.0\n16.8\n85.1\n30.1\n17.0\nGSC\nD\n1.6\n54.6\n56.7\nSee footnotes at end of table.","Focal Mechanism of Earthquake\n57\nTable 2.-Observed data for San Fernando earthquake-Continued\nSense of motion 1\nAmplitude\nS-wave\n2\nStation\nAngle of\nStation\npolarization\nT3\nmagni-\nDistance\nAzimuth\ndepar-\nLP\nSP\nNEIC\nA1\nA2\nfication\nture\nSeconds\no\nkm\nO\nmm\nmm\nGUA\nC E\nC G\n3.0\n7.0\n8.0\n750\n87.9\n284.9\n16.2\nGWC\nC\n34.9\n40.6\n30.0\nHFS\nC G\n77.9\n22.3\n18.6\nHHM\nD G\nD G\nD\n14.3\n11.8\n50.1\nHLW\nC F\n109.9\n27.8\n6.4\nHNR\nC G\nC G\nC\n5.0\n13.5\n16.8\n1500\n88.5\n257.6\n16.3\nHUA\nC G\n61.7\n130.6\n23.4\nHVO\nC\n35.9\n255.1\n29.6\nIFR\nC G\nC\n87.9\n50.2\n16.2\nINK\nC G\nC G\nC\n10.5\n29.0\n9.2\n3300\n35.0\n350.3\n30.0\nISA\nD\n1.2\n356.5\n88.8\nJAS\nD\nD\n3.9\n335.6\n56.1\nJCT\nC E\nC E\n12.0\n57.0\n11.2\n1500\n16.2\n98.8\n48.3\nJER\nC F\n109.6\n23.7\n6.4\nJOL\nC\n2.8\n307.4\n56.5\nKBL\nC G\n111.1\n353.4\n6.2\nKDC\nD F\n32.7\n326.2\n30.6\nKEV\nC E\nC E\n- 175.2\n3.2\n9.5\n10.0\n1500\n73.1\n11.9\n20.0\nKHC\nC\n86.5\n29.3\n16.6\nKIP\nC P\nC E\nC\n1.0\n3.2\n12.0\n375\n37.1\n260.1\n29.4\nKIR\nC G\n73.5\n15.1\n19.8\nKJN\nC E\nC F\n-16.0\n6.0\n16.5\n8.0\n1500\n78.2\n14.5\n18.8\nKLG\nC\n130.1\n256.5\n6.4\nKNB\nD G\n5.2\n58.4\n55.5\nKRL\nC\n84.4\n32.0\n17.0\nKTG\nC G\nC G\nC\n164.8\n2.0\n6.0\n8.0\n750\n60.1\n22.7\n23.6\nLAC\nC G\nC\n1.6\n89.5\n56.7\nLAO\nD G\n15.4\n33.2\n49.7\nLHC\nC E\nD G\n14.4\n55.0\n12.4\n3000\n25.8\n48.2\n33.1\nLIS\nC G\n82.1\n48.2\n17.7\nLJU\nC G\n16.0\n89.4\n30.7\nLMP\nD\n67.7\n275.1\n21.5\nLON\nD E\nC G\n12.6\n349.2\n51.5\nLPA\nC G\n1.5\n4.5\n8.8\n750\n89.2\n134.3\n16.1\nLPB\nC E\nC E\nC\n- 121.6\n4.0\n12.0\n12.0\n1500\n69.6\n128.1\n20.8\nLPS\nC\n33.1\n120.0\n30.7\nLPZ\nC E\n69.6\n128.1\n20.9\nLWI\nC F\nD P\n135.8\n50.9\n6.0\nC E\nC F\n4.5\n12.0\n1500\n86.3\n47.4\n16.7\nMAL\n8.4\nC G\n18.3\nMAT\nC G\n10.0\n31.0\n10.0\n3000\n79.7\n307.2\nMBC\nC E\nC E\nC\n6.0\n15.8\n49.0\n8.8\n3900\n41.9\n359.7\n28.7\nMCV\nD\n3.0\n40.4\n56.5\nMDC\n4.5\n321.7\n56.1\nC\nMDZ\nC\n40.9\n77.7\n28.7\nMEK\nD\n130.9\n262.9\n6.4\n56.1\nMHC\nC\n4.0\n319.1\n6.5\n337.6\n55.6\nMIN\nC\nMLF\nC F\n27.6\n70.1\n32.1\nC F\n5.4\n97.1\n55.5\nMMA\nMNT\nD F\nC\n11.0\n21.0\n24.8\n35.6\n58.2\n29.7\nMNV\nD G\nD\n4.0\n2.6\n56.4\nMRG\nC G\nC\n31.0\n68.9\n31.0\nMUN\n134.7\n257.1\n6.3\nD\n0.3\n121.1\n93.0\nMWC\nC\nD E\nC F\n14.0\n29.0\n16.4\n1500\n13.9\n3.5\n50.3\nNEW\nNIL\nC G\n2.8\n8.2\n12.0\n1500\n111.4\n349.6\n6.4\n60.7\n131.9\n23.4\nNNA\nC G\nC\nNOL\n24.3\n92.6\n34.8\nC P\nNOR\nC G\nC G\nC\n174.6\n2.6\n7.6\n9.2\n750\n57.9\n9.8\n23.9\nNOU\nC E\n90.9\n243.5\n15.5\n5.3\n347.7\n55.5\nNRR\nD F\n14.3\n3.8\n50.1\nNTI\nC G\nNUR\nC E\nC G\n5.0\n13.0\n9.6\n1500\n80.7\n17.5\n18.0\nOLC\nC\n5.1\n316.9\n55.5\nORV\nC P\n5.7\n335.1\n55.5\nOTT\nC E\nC F\nC\n5.0\n24.5\n12.0\n3200\n34.2\n58.3\n30.3\nOXF\n23.9\n81.4\n34.6\nOXM\nC G\n22.4\n127.4\n35.5\n35.5\n65.9\n29.8\nPAL\nC E\n5.5\n17.0\n16.0\nPAS\nD\n0.3\n143.1\n93.0\n32.2\nPBJ\nD G\n27.3\n125.2\nPEL\nC E\nC G\nC\n9.6\n8.0\n1500\n80.7\n141.0\n18.0\n3.5\nPIM\nD G\n21.8\n133.3\n36.0\nPKF\nC\n2.2\n312.5\n56.9\nSee footnotes at end of table.","San Fernando Earthquake of 1971\n58\nTable 2.-Observed data for San Fernando earthquake-Continued\nAngle of\nAmplitude 2\nStation\nSense of motion 1\nS-wave\nT3\nmagni-\nDistance\nAzimuth\ndepar-\npolarization\nStation\nA2\nfication\nture\nLP\nSP\nNEIC\nA1\nO\nSeconds\nkm\no\nmm\nmm\n1.6\n128.7\n56.7\nC\nPLM\n98.9\n264.7\n15.3\nC P\nPMG\n30.6\n1.8\n7.5\n8.8\n1000\n33.5\n333.7\nPMR\nC G\nC G\n69.2\n128.2\n21.0\nC\nPNS\n14.9\n356.9\n49.8\nD P\nPNT\nC F\n126.1\n345.6\n6.2\nC\nPOO\n84.3\n35.6\n17.1\nC\nPOU\n2.6\n313.8\n56.7\nD\nPRI\n86.2\n28.3\n16.7\nC\nPRU\n1500\n81.0\n46.0\n17.9\nC E\nC G\n-20.5\n6.5\n15.0\n8.0\nPTO\n50.8\n124.1\n26.3\nC\nQUI\n1.0\n2.5\n18.4\n750\n91.9\n266.2\n15.6\nC F\nC F\nRAB\n7.2\n7.5\n86.5\n50.7\n16.6\nC G\n3.0\nRBA\n2.8\n4.0\n2.4\n1500\n15.2\n46.0\n49.9\nD G\nD G\nRCD\n5.3\n347.9\n55.5\nD F\nREN\n10.6\n33.5\n8.0\n3400\n42.0\n9.1\n28.7\nRES\nC E\nC G\nC\n-5.0\n12.4\n21.7\n73.0\n36.1\nC G\nD G\n9.0\n40.0\nROL\n740\n31.6\n61.0\n31.0\nC E\n1.9\n6.2\nSCB\n40.9\n43.8\n28.7\nC E\nC\nSCH\n1500\n132.7\n78.1\n6.3\nC P\n1.6\n4.2\n8.2\nSDB\nC F\n13.6\n348.6\n50.5\nC F\nSEA\n3500\n16.9\n16.4\n47.6\nC\n3.0\n6.3\n4.0\nSES\nD G\nC G\n1900\n37.6\n55.6\n29.4\nC\n3.0\n12.5\n12.0\nSFA\nC E\nC G\n25.7\n89.8\n33.2\nC F\nSHA\nC G\n1500\n84.5\n308.3\n17.0\nC G\n4.0\n10.5\n8.4\nSHK\nC G\nC G\nC\n127.0\n2.7\n7.6\n8.8\n750\n49.1\n95.5\n26.9\nSJG\nC E\n3.5\n320.1\n56.1\nD\nSLD\n77.5\n22.3\n18.8\nC G\nSLL\n23.0\n71.2\n35.0\nC G\nSLM\nC E\n3.0\n25.2\n56.1\nC\nSMN\n75.2\n13.3\n19.6\nC F\nSOD\n8.4\n950\n49.9\n53.8\n26.6\nC G\nC G\nC\n150.0\n4.2\n10.2\nSTJ\n17.0\n2.0\n5.0\n10.0\n750\n84.5\n32.6\nSTR\nC\nC F\n30.7\n55.5\n31.0\nC E\nSUD\n1.3\n276.4\n56.7\nC\nSYP\n106.4\n12.5\n6.4\nC\nTAB\n22.7\n126.3\n35.3\nC F\nTAC\n83.5\n60.0\n17.4\nC\nTEN\n14.1\n2000\n5.9\n89.0\n55.5\nC E\n6.7\nTFO\nC E\n3.8\n14.1\n56.1\nD\nTNP\n31.1\n17.3\nC G\n83.6\nTNS\n17.0\nC E\nC\n4.0\n13.2\n12.8\n1500\n84.4\n44.8\nTOL\nC F\n3.8\n14.1\n56.1\nC\nTPH\n23.0\n126.8\n34.6\nD G\nTPM\n31.3\n16.0\n11.5\n10.0\n3000\n89.3\nC G\nC G\nC\n4.0\nTRI\n56.9\n100.3\n24.9\n-50.8\nTRN\n71.7\n14.5\n20.5\nC\nTRO\n35.6\n62.9\n29.8\nC F\nTRY\n18.8\n7.5\n17.6\n8.8\n78.6\n306.1\nTSK\nC E\n1500\n6.7\n105.9\n55.4\n7.5\n38.0\n11.2\nTUC\nC E\nC\n80.2\n9.6\n1500\n18.5\n78.8\n45.8\nC E\nC G\n19.5\nTUL\n13.1\n346.2\n50.8\nD F\nTUM\n9.2\n47.3\n54.0\nUBO\nD\nD\nD\n81.3\n32.7\n17.8\nC G\nUCC\nC G\n77.9\n22.4\n18.6\nC G\nUDD\n6.1\n322.2\n55.8\nC E\nUKI\n5500\n76.8\n17.5\n19.0\nC G\nC G\n17.0\n35.0\n8.8\nUME\n79.3\n20.9\n18.5\nC G\nC G\nC\n8.0\n16.0\n10.0\n1700\nUPP\n0.4\n167.1\n93.0\nD\nUSC\n2.1\n6.0\n9.2\n750\n73.6\n37.8\n19.8\nC G\nC G\n-21.0\nVAL\n25.9\n126.1\n33.1\nC G\nVHM\n89.0\n22.0\n2500\n14.6\n346.6\n49.9\nD G\nD P\n29.5\nVIC\n88.3\n28.4\n16.3\nC G\nVKA\n37.4\n63.4\n29.4\nC G\nC\nWES\n33.2\n69.7\n30.7\nC\nWSC\n30.0\n16.0\n2250\n28.2\n3.8\n31.8\nC E\nC\n6.5\nYKC\nLP = long period, SP = short period, NEIC = National Earthquake Information Center (NOAA), C = compressional, D = dilata-\ntional, E = excellent, F = fair, G = good, P = poor.\n2 A1 = Amplitude of first 1/2 cycle on long-period record; A2 = peak-to-peak amplitude of first full cycle on long-period record.\n3 T = Period of first cycle.","revenue\nNOTIONS","60","","","","San Fernando Earthquake of 1971\n64\nwhich is sampled, the likelihood is computed. Then\nments down from the maximum likelihood solution.\nthese likelihoods are summed starting with the value\nBecause the percent likelihood contained within\nfor the maximum likelihood solution and moving\nthese contours is not known, the relative size cannot\ndown until the first value greater than or equal to 95\nbe compared from one solution to another. The pur-\npercent is found. Because the long-period data are\npose of these contours is to show the trend of the\nvery consistent, allowing only one additional station\nlikelihood surface in the vicinity of the solution.\nto be in error determines the fiducial limit; however,\nfor the reported data, three additional stations must\nP-WAVE SOLUTIONS\nbe considered in error before reaching the fiducial\nlimit of 98.3-percent likelihood. Thus, the contoured\nThe sources of P-wave data are long- and short-pe-\nfiducial limits allow reasonable comparisons of re-\nriod records read by the author and data reported to\nsults from high-quality data with data for which the\nthe NEIC. Several solutions were run to evaluate\nquality may not be as good, but where distribution\nthese various types of data and to find if they would\nmay be better.\nproduce similar results. As can be seen from the con-\nThe solution with the most consistent data set is\ntoured fiducial boundaries for the various P-wave SO-\nobtained using long-period data read by the author\nlutions, they have all produced very similar and com-\n(solution No. 2 of table 1). This solution gives 95-\npatible results. The short-period and reported data\npercent agreement, which is the type of result that\ndo contain a larger percent of error in the observa-\none would expect from long-period data all read by\ntions, but the fiducial limits are smaller and the re-\nthe same individual. However, the data distribution\nsults are in agreement with the long-period data.\nis such that the solution may lie in a broad region\nIn the following discussion, the contoured bounda-\n(figs. 5a and 5b) Thus, it is possible that there are\nries of the fiducial limits are used to evaluate and\nnot many observations near the nodal planes where a\ninterpret the various solutions. These boundaries are\ngreater amount of error would be expected.\nprimarily a function of three things: the distribution\nSolution No. 1 of table 1 was obtained using the\nof data, the quality of the data, and the number of\nalternate possibilities which exist in the data. The\nshort-period data read by the author and supple-\ndistribution of the data is, of course, important.\nmented by the reported data. This is essentially a\nshort-period solution, since it is doubtful that much\nWhere there is a region of the focal sphere with no\nreported data would come from long-period instru-\nobserved data, the focal planes can vary continuously\nments. If the reported observation disagreed with\nover this region without being restricted. Such a re-\ngion may be large or small, depending on the distri-\nthat of the author, then the reading of the author\nwas used. The agreement was 86 percent for this so-\nbution of the data. If the data contained no error,\nlution, which is the lowest of those reported here.\nthere would only be one such region within which\nHowever, it can be seen from figure 1 that this solu-\nthe planes could be located. However, because there\ntion has the smallest fiducial limits of those obtained\nis always some possibility of error, each region de-\nfrom P-wave data. Also, by comparing figures 1b and\nfined by the data has some probability of containing\nthe solution. This probability, which is also the like-\n5b, we can see that the contours of the short-period\nlihood, is computed from the probability of an ob-\nlimits overlap those of the long-period limits, giving\na result which agrees with the long-period data.\nservation being correct; this latter probability is the\nThus, solution No. 1 might be considered the \"best\"\nnumber of correct observations in the maximum\nlikelihood solution divided by the total number of\nin that it has smaller limits and is in agreement with\nobservations. The probability of an observation\nthe long-period observations.\nbeing correct is given in table 1 for each P-wave so-\nThe two preceding cases describe the orientation\nlution. If this value is multiplied by 100, it becomes\nof the focal mechanism of the San Fernando earth-\nthe percent of the data in agreement with the maxi-\nquake, particularly when they are combined with the\nS-wave polarization angles for the combined maxi-\nmum likelihood solution.\nThe boundaries of the fiducial limits are found by\nmum likelihood solution. There are, however, some\ncontouring the number of agreeing observations on\ninteresting observations which can be made from the\nthe focal sphere. The value to be contoured is deter-\nother three P-wave cases presented. The short-period\nmined as follows. For each region on the focal sphere\nreadings made by the author were used in solution","Focal Mechanism of Earthquake\n65\nplanes. This gives certain advantages in handling the\nNo. 3, which is shown in figure 8. While more data\nare available in this case, the percent error is also\nS-wave solution. The maximum likelihood S-wave so-\ngreater, which causes the fiducial limits to become\nlution turns out to be a least-squares solution. This\nmakes the statistical analysis easier, and the fiducial\nlarger. This result was not expected, but with consid-\neration it seems quite reasonable and builds confi-\nlimits can be determined in much the same manner\nas in usual least-squares problems. The quantities\ndence in the statistical analysis.\ncomputed and contoured are therefore the sum of\nIt would be desirable to get a good solution which\nsquared residuals for the S-polarization angle. This\nuses reliable data and restricts the variation of the\nnodal planes as much as possible. For this purpose,\nalso allows the calculation of the value for an exact\n95-percent fiducial limit, which cannot be done in\nsolution No. 5 was run. This included all the data\nread by the author, long and short period, with\nthe P-wave case. All of the S-wave solutions presented\nin table 1 contain the following: N, the number of\nlong-period observations used when the two were dif-\nferent. The nodal planes are only slightly more re-\nobservations used; o, the standard deviation of an\nstricted than for the long-period data (compare figs.\nobservation; Rs, the sum of squared residuals for the\nmaximum likelihood solution, and the value of the\n5b and 9b) Thus, it is only when reported data are\nused, as in solution No. 1, that the distribution of\ncontour for the 95-percent fiducial limit.\nthe observations is improved enough to improve the\nThe continuous nature of the S-polarization angles\nsolution significantly.\nmeans that it should be possible to get a solution\nwith fewer observations than in the P-wave case, and\nA very interesting result was found when only the\ndata which had been reported to the NEIC by ap-\nthe data points need not be near the nodal planes.\nproximately March 7, 1971, were used. This solution\nIn practice, it turns out that S-polarization angles are\nwas run to evaluate the reported data and to see if it\nnot too sensitive to the orientation of the focal\nwould produce results comparable to the data read\nplanes. This is easily seen from figure 4, which shows\na profile of the error surface as one plane is held\nby the author (see solution No. 4 of table 1) The\nfixed while the other plane is rotated through 180°.\nobservations give 87-percent agreement, which is not\nThe value plotted is the sum of squared residuals.\nfar different from the 89 percent given by the short-\nperiod data read by the author. When comparing the\nThe very broad nature of the minimum regions seen\nlimits on this solution shown in figure 7 with the\nin these figures is characteristic of the S-wave error\nsurface. These broad minima are probably due pri-\nlong-period results (fig. 5b), we see that the accepta-\nble regions overlap to a large extent. The reported\nmarily to the difficulty of determining the polariza-\ndata restrict fiducial limits in strike considerably, but\ntion angle accurately. Two things are worth noting\nallow the limits to spread out more in the dip.\nin these figures. In figure 4a, which is for solution\nThese reported data contain more close-in observa-\nNo. 1 and uses all 20 polarization angles, it is easy to\ntions that were reported to the NEIC, but for which\nsee that there are two minima. These also are seen in\nthere was no opportunity to look at the records. It is\nthe contours shown in figure 2b. Secondary minima\nof this type could cause problems for iterative tech-\nthese close-in data which restrict the strike of the\nniques of finding the solution. The other interesting\nplanes the most. The best solution found, using the\npoint is how much narrower the minimum shown in\ndata reported to the NEIC, falls within the limits of\nfigure 4b becomes for solution No. 2 for which the\nthe long-period data; thus, it can be seen that re-\nported data can produce good results compatible\nobservations, giving the two largest residuals, were\nwith the best available data and, when statistically\ndiscarded.\nproduced fiducial limits are provided, it is easy to\nThe use of all 20 S-polarization angles shown in\nevaluate the strength and weakness of the results.\nfigure 2a gives a broad fiducial region, and the best\nS-wave solution in the \"least-squares\" sense does not\nagree with the P-wave solution. However, two sec-\nS-WAVE AND COMBINED SOLUTIONS\nondary minimum areas within the fiducial region are\nseen in figure 2b to be close to the fiducial limits of\nThe S-wave observational data are different from\nthe P-solution. It is this section of the S-likelihood\nthe P-wave case in that S-polarization angles are a\nsurface which is enhanced when combined with the\ncontinuously varying function over the focal sphere,\nwhereas the P-wave data change only at the nodal\nP-data and causes the selection of the combined solu-","San Fernando Earthquake of 1971\n66\ntion shown in figure 3a. This combined maximum\nThe resulting S-wave solution using AFI is not ac-\nlikelihood solution is in agreement with the P-wave\nceptable, as it is in complete disagreement with the\ndata.\nP-wave data. However, it is very encouraging to see\nTwo stations, AFI and LPB, have very high resid-\nthat, when the combined solution is found using the\nuals for the S-wave and combined solutions, as can\nP-data also, the secondary minimum of the S-likeli-\nbe seen in table 3 under solution No. 1. Discarding\nhood surface is picked up and the result is in agree-\nthese two observations produces S-wave solution No.\nment with the P-wave data.\n2, shown in figure 6a, which agrees to a much larger\nA single-couple solution was made for this earth-\ndegree with the P-wave solutions and the resulting\nquake, and the results were reasonably good\ncombined solution. Removing these two observations\n(solution No. 6 of table 1) The standard deviation\nalso reduces the standard deviation significantly and\nof the single couple is not much greater than a dou-\ngives the narrower minimum discussed previously.\nble-couple solution using the same data, which can\nTwo solutions were run to find the independent ef-\nbe seen by comparing solution No. 6 with solution\nfect of AFI and LPB. It was found that discarding\nNo. 4. The S-wave solution alone does not agree\neither station will improve the standard deviation al-\nwith the P-wave data; however, when combined with\nmost as much as removing both. Although the con-\nthe P-data, a good result is obtained which gives\ntoured fiducial regions are not shown, it was found\nagreement with both sets of data.\nthat LPB does not change the character of the fiducial\nregion much from that obtained with both stations\nCONCLUSIONS\nremoved. It does, however, enlarge the region. This\nis most likely due to LPB being in disagreement\nThe procedures used have proved to be very satis-\nwith nearby stations which \"average out\" its influ-\nfactory for determining the combined P- and S-wave\nence. The effect of AFI is roughly seen by compar-\nsolution. The fiducial limits on the individual P-\ning figures 2b and 6a. Since LPB did not change\nand S-wave solutions are seen to be very helpful in\nfigure 6a significantly, almost all of the difference in\nevaluating and comparing various solutions. In de-\nthe shape of the fiducial regions between these two\ntermining the combined solution, the P-wave data\nsolutions is due to AFI. This observation probably\nseem to be dominant. This is probably due to the\nhas such a strong influence on the solution because it\nbroad insensitive minimums which are shown in\nstands alone in the center of the opposite half of the\nfigure 4 for the S-wave data. When the most incon-\nfocal sphere from the other data.\nsistent S-observations are removed, the minimum re-\nTable 3.-S-wave residuals (0-C)\nSolution\nSolution\nSolution\nSolution\nStation\nObserved\nNo. 1\nNo. 2\nNo. 4\nNo. 6\npolarization\nS-wave\nCombined\nS-wave\nCombined\nS-wave\nCombined\nS-wave\nAFI\n-51.5\n-3.6\n-68.7\n-4.6\n-59.2\n24.3\nALE\n-177.0\n-1.3\n-7.4\n4.2\n4.8\n2.4\n-6.4\n-5.1\nARE\n-59.7\n5.1\n-4.6\n0.2\n-8.7\n-15.2\n-29.1\n12.2\nBEC\n-14.5\n36.9\n24.8\n17.7\n20.6\n28.4\n21.1\n19.4\nBHP\n135.7\n10.5\n7.2\n4.9\n4.6\n-9.7\n-5.2\n12.0\nCAR\n-23.0\n34.5\n29.7\n25.6\n27.6\n17.8\n21.5\n28.1\nESK\n165.5\n2.4\n-5.2\n-0.1\n2.1\n2.9\n-5.8\n-6.8\nGDH\n170.3\n3.4\n-7.7\n-4.8\n-2.8\n5.3\n-7.7\n-7.0\nKEV\n-175.2\n2.7\n-0.9\n12.7\n13.7\n5.2\n-0.3\n-1.2\nKJN\n-16.0\n-16.0\n-19.5\n-6.2\n-5.0\n-13.9\n-19.0\n-20.3\nKTG\n164.8\n-5.6\n-14.3\n-8.7\n-6.9\n-3.7\n-14.2\n-14.0\nLPB\n-121.6\n-56.4\n-63.7\nMBC\n6.0\n-6.5\n-10.7\n5.3\n4.9\n-1.8\n-9.1\n-7.0\nNOR\n174.6\n-8.3\n-14.0\n-2.6\n-1.8\n-4.9\n-13.2\n-12.4\nPTO\n-20.5\n7.1\n-0.3\n2.8\n5.5\n5.8\n-1.8\n-3.4\nRES\n-5.0\n-7.5\n-15.4\n-5.9\n-5.2\n-3.6\n-14.4\n-12.2\nSJG\n127.0\n3.1\n-3.8\n-9.4\n-7.0\n-11.2\n-10.0\n-7.6\nSTJ\n150.0\n7.8\n-6.0\n-10.6\n-7.7\n5.1\n-7.9\n-9.5\nTRN\n-50.8\n6.9\n1.4\n-2.7\n-0.4\n-8.2\n-5.8\n-1.3\nVAL\n-21.0\n0.6\n-7.6\n-4.2\n-1.7\n0.4\n-8.5\n-9.7\nNOTE: O-C = observed minus computed.","Focal Mechanism of Earthquake\n67\nThe San Fernando earthquake indicates that this\ngions become narrower (fig. 4b) and the standard\nproblem may not occur in southern California; how-\ndeviation of an S-wave polarization angle is reduced\never, a study of the long- and short-period data for\nconsiderably. It would appear that for S-wave solu-\nmore earthquakes will be necessary to determine if\ntions to become independently reliable, the standard\ndeviations of S-wave polarizations would have to be\nthis is always true.\nimproved over current capabilities. Nonetheless, the\nmost consistent of the S-wave data gives good agree-\nREFERENCES\nment with the P-wave first motions even if the S-\nwave data are not very sensitive to the precise orien-\nAkasche, B., and Berckhemer, H., \"Focal Mechanism of Deep\ntation of the focal planes.\nand Shallow Earthquakes as Derived From Short and Long\nThe P-wave data provide some interesting results\nPeriod Seismograms,\" Proceedings of the X Assembly of the\nin themselves. The long- and short-period data pro-\nEuropean Seismological Commission (ESC), Leningrad, 3-11\nvide essentially the same result for this earthquake;\nSeptember 1968, Vol. II, Academy of Sciences of the USSR,\nSoviet Geophysical Committee, Moscow, 1970, pp. 334-357.\nwhen reported observations are compared with the\nDillinger, William H., Pope, Allen J., and Harding, Samuel\nshort-period data read by the author, they are seen to\nT., \"The Determination of Focal Mechanisms Using P- and\nbe almost as good. This indicates that reported data\nS-Wave Data,\" NOAA Technical Report NOS 44, National\nare certainly good enough to be used in computing\nOcean Survey, National Oceanic and Atmospheric Adminis-\nP-wave solutions, especially if the results are pre-\ntration, U.S. Department of Commerce, Rockville, Md.,\nsented with statistically evaluated fiducial limits on\nJuly 1971, 56 pp.\nDillinger, W., and Espinosa, A.F., \"Preliminary Fault-Plane\nthe variation of the focal planes.\nSolution for the San Fernando Earthquake,\" The San Fer-\nThe excellent agreement that was found between\nnando, California, Earthquake of February 9, 1971, Geo-\nthe long- and short-period data would appear to\nlogical Survey Professional Paper 733, U.S. Geological Survey\nimply that there is no difference in the long- and\nand the National Oceanic and Atmospheric Administration,\nU.S. Department of the Interior and U.S. Department of\nshort-period solutions. For some earthquakes in a\nCommerce, Washington, D.C., 1971, pp. 142-149.\nfew areas of the world, Akasche and Berckhemer\nEnvironmental Data Service, \"The February 9, 1971, Califor-\n(1970) show solutions which give decidedly different\nnia Earthquake and Complete Set of Seismograms From\nresults from the long- and short-period data. An\nMore Than 170 Stations,\" National Geophysical Data Cen-\ninspection of their plots shows that there can be no\nter, U.S. Department of Commerce, Asheville, N.C., 1971\nquestion of the difference if the data are reliable.\n(microfilm)","","Seismograms, S-Wave Spectra, and\nSource Parameters for Aftershocks of\nSan Fernando Earthquake\nABSTRACT\nA high sample-rate, high dynamic-range digital-\nrecording system was used to obtain broadband, high\nsignal-to-noise ratio seismograms and S-wave spectra\nof 167 aftershocks to 41/2) of the February\n9, 1971, San Fernando earthquake. The character-\nCONTENTS\nistics of the spectra-a relatively constant amplitude\nPage\nat low frequencies, a well-defined corner frequency,\n69\nABSTRACT\nand a high-frequency asymptote with a slope from\n69\nINTRODUCTION\n- 1 to - 3 on a log-log plot-apparently represent\n70\nEQUIPMENT AND SITES\n71\nDATA AND ANALYSIS\nseismic source properties and have been interpreted\n77\nGENERAL SPECTRAL CHARACTERISTICS\nusing the Brune model, giving seismic moments of\n77\nFITTING THE SPECTRA TO A MODEL\n1018 to 1022 dyne-cm, source dimensions of 50 to\n79\nSOURCES OF ERROR\n79\nS-Wave Sample Length\n500 m, and stress drops of 1 to 300 bars. An apparent\n79\nPropagation-Path Effects\nupper limit in stress drop (more than an order of\n79\nUncertainties of Spectra\nmagnitude greater than stress drops previously re-\nInterpretation\n79\nRadiation Pattern, Scattering, and\nported for small earthquakes) may represent the\nFocusing Effects\nregional effective stress, while the range in stress\n80\nEstimate of Combined Errors\ndrops may correspond to a range in fractional stress\n80\nANALYSIS OF RESULTS\ndrops.\n119 CONCLUSIONS\n120 ACKNOWLEDGMENTS\n120\nREFERENCES\nINTRODUCTION\nThis paper presents seismograms and corrected\nS-wave spectra for 167 aftershocks of the February 9,\n1971, San Fernando earthquake. The Richter magni-\ntude of these aftershocks ranged from about 1/2 to\n41/2. Except for eight events in December 1971, all\nevents were recorded during the first 8 days follow-\ning the main shock. This data set is more complete\nBRIAN E. TUCKER\nand more reliable than any similar set previously\nInstitute of Geophysics and Planetary\nobtained for several reasons: (1) The corrections for\nPhysics\npropagation effects were small because the average\nUniversity of California, San Diego, Calif.\nhypocentral distance was short (12 km) and the\npropagation path was through granitic rock; (2) the\nJAMES N. BRUNE\nrecords were made on well-calibrated, high sample-\nScripps Institution of Oceanography\nrate (150/sec), high dynamic-range (90-dB) digital\nLa Jolla, Calif.\n69","San Fernando Earthquake of 1971\n70\nequipment; and (3) an estimate of experimental 2 days of operation, the amplifier was bypassed to\nerrors could be made because of the large number\navoid clipping on large events. A two-stage, low-pass\nof events recorded and because of the simultaneous RC filter between the amplifier and the A-D was\nrecording of 24 events at two different sites.\nused (almost always) to reduce aliasing. The maxi-\nmum output of the A-D was + 16,384 \"counts,\"\nwhich corresponds to an input of + 10 volts. The\nEQUIPMENT AND SITES\noutput of the A-D was recorded 150 times a second;\nA high sample-rate, high dynamic-range digital-\nhence, the Nyquist frequency (one-half the sampling\nrecording system was necessary to obtain broadband\nrate) was 75 Hz.\nspectra with high signal-to-noise ratios. Two record-\nThe system was calibrated in five independent\ning systems were operated, each consisting of a\nways: (1) lifting a known weight from the seismom-\nRanger seismometer, an amplifier, an analog-to-\neter mass; (2) using a well-calibrated shake table;\ndigital converter (A-D) , and a digital tape recorder.\n(3) measuring the seismometer's coil constant; (4)\nThe seismometer was operated in the horizontal\nusing a Willmore-Bridge; and (5) driving the seis-\nmode with about 70-percent critical damping and a\nmometer, using its calibration coil, and optically\n1-Hz natural frequency. The amplifier gain (25 to\nmeasuring the motion of the mass. The resulting re-\n3,150) could be varied in 6-dB steps. During the first\nsponse (curve 1, fig. 1) is estimated to have an accu-\n6\n1\n2\n3\n4\n4\n2\n0\n-2\n0.4\n0.6\n0.8\n1\n2\n40\n4\n6\n8\n10\n20\n60\n80\nFREQUENCY (cps)\nFigure 1.-The basic recording system- horizontal, approximately 0.7 critically damped Ranger seismometer (1-Hz natural frequency),\nan amplifier, an analog-to-digital converter (A-D) and a digital tape-recorder-was calibrated to an estimated accuracy of +1 6 per-\ncent by means of five essentially independent methods, mentioned in the text. The resulting response (curve 1) was used to calculate\nthe response of the system including a two-stage, low-pass RC filter (between the amplifier and A-D) with cutoff frequency 60\n(curve 2) and 50 Hz (curve 3) while the response of the basic system excluding the amplifier (curve 4) was obtained from a separate\ncalibration experiment. The amplifier's internal filters and the damping effect of the amplifier's input impedance on the seismometer\ncause the difference in shape of curves 1 and 4 for frequencies less than 2 Hz. Response units are A-D output (counts) per input\nground motion (microns).","Source Parameters for Aftershocks\n71\nracy of +6 percent. The response with the low-pass\nDATA AND ANALYSIS\nfilter (curve 2 for 60-Hz cutoff frequency; curve 3\nThe data tapes were computer-searched for signals\nfor 50-Hz cutoff frequency) was calculated from\nexceeding a certain threshold. Selected signals were\ncurve 1. The response of the system with the ampli-\ncopied onto a composite tape and plotted. Noise\nfier bypassed (curve 4) was obtained from a separate\nbursts, electronic artifacts, and earthquake signals\ncalibration experiment. The amplifier's internal fil-\nunusable because of either poor signal-to-noise ratio\nters and the damping effect of the amplifier's input\nor electronic saturation were excluded. This left 220\nimpedance on the seismometer cause the difference\nseismograms for 167 earthquakes-27 of the earth-\nin shape of curves 1 and 4 for frequencies less than 2\nquakes were recorded on two orthogonal horizontal\nHz.\nseismometers located at the same site, and 25 were\nTo minimize propagation effects, the two record-\nrecorded at both the Bear Divide and Dillon Ranch\ning sites-Bear Divide and Dillon Ranch-were lo-\nsites. The California Institute of Technology\ncated on granite outcroppings close to the epicenters\n(C.I.T.) and the U.S. Geological Survey (USGS)\n(fig. 2) The hypocentral distances ranged from 3 to\ndetermined the epicenters (fig. 2) and depths of 91\nof these events.\n28 km.\nN\n99\n34° 25' N\nNEWHALL\n6\nBEAR DIVIDE\nDILLON RANCH\nMAIN SHOCK\nPacoima Reservoir\nOLIVE VIEW\nV.A.\nSIGNAL\n22 100\nHOSPITAL\nHOSPITAL\nNOISE\n~ 10\nRECORDING SITE\nSAN\nFERNANDO\nVan Norman\nLakes\n405\n5\n0\n10\nKILOMETERS\n34°15 N\nFigure 2.-Map of San Fernando area with locations of several well-known landmarks, our two recording sites, and the epicenters\n(obtained from C.I.T. and USGS) of the main event and 91 aftershocks studied in this paper.","San Fernando Earthquake of 1971\n72\nTwo hundred and twenty seismograms and their\ncomputational ease) This series (x1, k = 0, 1,\ncorrected S-wave spectra are presented in figure 5.\nN - 1) was transformed using a Cooley-Tukey\nScales for time, logio (frequency), and relative log10\nFast-Fourier-Transform program which calculated\n(amplitude spectrum) are given on each page. Each\nN-1\nxx==\"\nseismogram-spectrum pair has been given an identifi-\ncation number. Those events recorded on two instru-\nk=0\nments have two seismogram-spectrum pairs, each\n1, 2,\nN-1.\nwith the same identification number. For events re-\nThe amplitude spectrum was obtained by correct-\ncorded at both Bear Divide and Dillon Ranch, the\ning for instrument response and propagation-path\nnumbers are followed by B or D, respectively, to\nattenuation. With N equal to 1,536 and a Nyquist\nspecify the site; for events recorded on orthogonal\nfrequency of 75 Hz,\ninstruments located at the same site, the subscript\nE-W or N-S specifies the component of ground mo-\ntion recorded. For events numbered 1-22, E-W\nmeans W.37°S. and N-S means N.37°W.; otherwise,\nE-W and N-S mean true east-west and true north-\nj=0,1,\n768,\nsouth, respectively.\nwhere Lj, Xj, and L, are, respectively, the values of\nTable 1 summarizes pertinent information for 216\namplitude spectrum, S-wave Fourier transform, and\nof the seismogram-spectrum pairs in figure 5. Using\ninstrument response at frequency (j/768) 75 Hz,\nthe notation described above, the recording site and\npropagation-path attenuation is compensated for by\ncomponent of motion recorded are indicated in the\nthe exponential factor, where R is the hypocentral\nSite and Orientation columns, respectively. The\ndistance (in km), B is the S-wave velocity (3.5 km/\nmore accurate origin times (those given to the near-\nsec), and Q is the quality factor (250) For one of\nest second) were obtained from C.I.T. and USGS.\nthe two spectra calculated for event 73 in figure 5,\nThe hypocentral distances were calculated from the\nthe individual values of S are plotted separately; in\nS P times, using a P-wave velocity of 6.0 and a S-\nthe other spectra, the values are connected by\nwave velocity of 3.5 km/sec. When the P-wave arrival\nstraight lines. The minimum frequency of each spec-\ntime is uncertain, the corresponding distance esti-\ntrum is the reciprocal of the length of the S-wave\nmate is in parentheses. For determining the absolute\nsample; the maximum frequency is 75 Hz.\namplitude of each seismogram, the column Range\nOccasionally, events recorded at the same site on\ngives the difference (in counts) between the maxi-\nthe same instrument component have spectra that\nmum positive and negative amplitudes, the Response\nare remarkably alike in detail. Seven pairs of events\ncurve column identifies the appropriate curve in fig-\nhaving such spectra are: 27, 28; 30, 77; 62, 63; 118,\nure 1, and the column Attenuation specifies the\n119; 125, 127; 129, 130; and 133, 134. The likeness\namplifier's attenuation (in decibels) relative to that\nis most pronounced between 1 and 10 Hz and can\ncurve. Blank spaces are equivalent to ditto marks;\nbe seen by overlaying comparable spectra on a light-\ntherefore, the fifth row reads, from left to right:\ntable. Similarities may result from like-scattering\n5, N-S, D, 2/10/71, 1131 34, 8.13, etc.\neffects because, in every case where similar events\nTo obtain each S-wave spectrum in figure 5, we\nhave been located, their hypocenters are identical\ncalculated a Fourier transform of that part of the\n(within experimental errors) and because spectra of\nseismogram underlined. A typical S-wave sample was\nthe same earthquake recorded at different sites are\nabout 1.5 seconds long (225 data points) ; its begin-\nnot similar. Two spectra obtained from recordings\nning and ending were chosen SO that the numerical\nof an event on orthogonal seismometers at the same\nvalues of the first and last data points were close to\nsite typically do not show strong similarity, although\nthe zero-level of the signal immediately preceding the\nthey share general characteristics. In fact, there is\nP-wave. This zero-level was subtracted from the\noften a striking difference in the appearance of\nnumerical value of each point of the sample. The\nseismograms of an earthquake recorded either at\npoints preceding the sample were set to zero, and\ndifferent sites or on orthogonal components located\nother zero points were added to the end of the sample\nat the same site; for example, compare the two\nto make each time-series 1,536 data points long (for\nseismograms of event 6 (orthogonal components at","Range\n1679\n1359\n646\n858\n810\n1449\n3796\n1233\n1595\n1488\n720\n867\n422\n543\n4355\n1263\n863\n1238\n837\n795\n644\n1039\n796\n326\ncounts\n2941\n5751\n648\n1761\n1050\n794\n622\n749\n835\n1231\n1111\n1081\n1291\n687\n28260\n3946\n2551\n16597\n4466\n5108\n5963\n10404\n5755\n8317\n5013\n4057\n5554\n20680\n23820\n6045\n8374\n5491\ntenu-\nation\nAt-\ndB\n0\n42\n0\n6\n6\nsponse\n(fig. 1)\ncurve\nRe-\n4\n1\n4\n2\n2\nSlope\n3\n2\n3\n3\n3\n2\n3\n3\n2\n3\n2\n3\n3\n3\n2\n3\n1\n2\n3\n2\n2\n3\n3\n2\n2\n2\n3\n3\n2\n3\n2\n2\n2\n1\n3\n3\n3\n2\n2\n2\n2\n2\n2\n3\n2\n2\n3\n3\n2\n2\n3\n3\n1\n2\n3\n3\nQuality\n(2)\n2\n2\n2\n2\n2\n2\n1\n2\n2\n3\n2\n2\n2\n3\n2\n3\n2\n2\n2\n3\n2\n2\n1\n3\n2\n2\n2\n2\n2\n2\n2\n1\n2\n1\n3\n3\n3\n3\n3\n2\n3\n2\n2\n2\n2\n3\n3\n3\n2\n2\n3\n2\n1\n1\n3\n220.92\n124.33\n216.77\n167.12\n146.25\n75.10\n145.35\n59.32\n65.33\n154.30\n92.57\n169.48\n288.66\n236.85\n78.57\n59.35\n271.75\n228.98\n75.89\n53.73\n232.52\n65.58\n8.64\n54.26\n156.04\n192.05\n40.13\n219.52\n20.40\n45.67\n34.28\n12.16\n56.75\n76.55\n21.77\n18.96\n100.24\n76.04\n.58\n2.94\n1.55\n9.69\n1.22\n8.93\n16.22\n10.99\n82.81\n54.51\n1.33\n2.40\n18.30\n1.22\n10.12\n20.32\n7.75\n2.96\nStress\ndrop\nso\nbar\nTable 1.-Summary of information for seismogram-spectrum pairs in figure 5\n8.377E-04\n7.646E-04\n5.068E-04\n5.519E-04\n7.310E-04\n8.600E-04\n1.911E-03\n9.163E-05\n2.978E-03\n2.029E-03\n3.430E-03\n2.558E-03\n8.897E-04\n1.672E-03\n4.509E-04\n1.356E-03\n6.808E-04\n1.068E-03\n5.742E-04\n5.359E-04\n9.055E-05\n4.735E-04\n4.322E-04\n2.265E-04\n7.679E-04\n1.184E-04\n1.102E-03\n8.959E-04\n1.829E-03\n2.189E-03\n9.300E-04\n3.225E-04\n4.508E-04\n8.994E-04\n5.282E-04\n2.837E-03\n6.120E-04\n9.925E-04\n4.570E-03\n4.265E-03\n3.118E-06\n1.575E-05\n2.561E-06\n2.663E-06\n2.847E-06\n8.509E-06\n2.748E-06\n1.995E-06\n4.719E-06\n1.318E-06\n3.560E-06\n6.536E-06\n9.637E-06\n5.581E-06\n2.445E-06\n7.423E-06\ncm-sec\n5(10)\n9.557E 20\n1.728E 20\n8.504E 20\n1.708E 20\n8.929E 20\n8.149E 20\n4.272E 20\n2.233E 20\n6.081E 20\n8.500E 20\n9.960E 20\n2.970E 19\n4.829E 18\n5.021E 18\n5.370E 18\n1.605E 19\n1.580E 21\n1.442E 21\n1.041E 21\n1.379E 21\n1.622E 21\n3.604E 21\n5.616E 21\n3.826E 21\n6.468E 21\n4.825E 21\n1.678E 21\n3.154E 21\n2.557E 21\n1.284E 21\n2.014E 21\n1.083E 21\n1.011E 21\n1.448E 21\n2.078E 21\n5.182E 18\n3.762E 18\n8.899E 18\n2.485E 18\n6.712E 18\n1.233E 19\n1.817E 19\n1.052E 19\n4.612E 18\n1.400E 19\n1.689E 21\n3.450E 21\n4.129E 21\n1.754E 21\n1.696E 21\n5.349E 21\n1.154E 21\n1.872E 21\n8.617E 21\n5.879E 18\n8.042E 21\nMoment\ndyne-cm\nM\ndimension\nSource\n146.3\n171.8\n124.5\n139.7\n160.4\n211.4\n221.4\n108.4\n335.0\n221.4\n312.7\n231.8\n136.5\n179.9\n167.9\n266.1\n127.4\n156.7\n179.9\n184.1\n201.9\n96.6\n118.9\n175.8\n278.7\n226.5\n121.6\n156.7\n335.0\n201.9\n335.0\n179.9\n221.4\n393.6\n197.3\n312.7\n285.2\n350.8\n335.0\n359.0\n110.9\n61.0\n124.5\n92.3\n51.9\n76.8\n54.3\n164.1\n164.1\n53.1\n142.9\n164.1\n92.3\n61.0\n63.8\n127.4\nm\nr\nHypocentral\ndistance\n(16.4)\n(4.0)\n(13.0)\n(16.0)\n(13.9)\n(15.8)\n(12.5)\n(15.5)\n8.0\n7.8\n10.8\n11.8\n13.0\n8.6\n12.8\n16.8\n17.7\n7.4\n7.3\n9.6\n9.6\n14.2\n9.3\n9.3\n13.0\n13.0\n12.1\n13.8\n7.1\n9.1\n8.3\n10.6\n9.9\n3.2\n10.6\n7.3\n12.1\n13.7\n13.7\n13.8\n13.3\n12.8\n14.4\n14.3\n11.6\n13.8\n12.3\n13.8\n15.9\n14.3\n13.0\n13.7\n14.4\n12.9\n15.1\n13.3\nkm\nR\n1.413E-03\n9.333E-04\n1.288E-03\n1.413E-03\n1.000E-03\n3.467E-04\n3.467E-04\n6.918E-04\n4.365E-04\n2.344E-03\n4.467E-04\n7.244E-04\n3.311E-03\n3.090E-03\n2.344E-06\n1.230E-05\n1.778E-06\n1.862E-06\n2.455E-06\n6.166E-06\n1.820E-06\n1.622E-06\n3.548E-06\n9.550E-07\n2.239E-06\n4.571E-06\n7.413E-06\n4.074E-06\n1.698E-06\n5.754E-06\n1.047E-03\n7.079E-04\n3.090E-04\n4.677E-04\n5.623E-04\n1.000E-03\n2.692E-03\n2.291E-04\n2.291E-03\n1.585E-03\n2.042E-03\n1.445E-03\n1.202E-03\n2.291E-03\n2.818E-04\n1.413E-03\n4.898E-04\n6.761E-04\n6.310E-04\n6.457E-04\n7.244E-05\n4.467E-04\n4.365E-04\n7.079E-04\n7.244E-04\n1.622E-04\ncm-sec\nSo\nfrequency\nCorner\n7.59\n10.47\n9.33\n8.13\n6.17\n5.89\n12.02\n3.89\n5.89\n4.17\n5.62\n9.55\n7.24\n7.76\n4.90\n10.23\n8.32\n7.08\n6.46\n13.49\n10.96\n7.41\n4.68\n5.75\n10.72\n7.24\n8.32\n3.89\n6.46\n3.89\n7.24\n5.89\n3.31\n6.61\n4.17\n4.57\n3.72\n3.89\n3.63\n7.94\n7.94\n11.75\n21.38\n10.47\n14.13\n25.12\n24.55\n9.12\n16.98\n23.99\n7.94\n14.13\n21.38\n20.42\n10.23\n8.91\nHz\nfc\n0920 54\n0952 20\n1502 42\n1622 44\n0546 39\n0550 27\n0628 02\n0629 09\n0541 40\n0700 45\n1129 25\n1131 34\n1242 19\n1349 54\n1435 27\n1511 26\n1738 55\n1854 42\n1906 06\n2342 29\n0924 37\n0924 40\n0925 23\n1132 56\n1421 21\n1643 32\n0809 31\nOrigin\ntime\nGMT\n0552\n0553\n0557\n0558\n0604\n0610\n1330\n1500\n2125\n0613\n0616\n0622\n0636\n0643\n0645\n2/10/71\n2/11/71\n2/12/71\n2/13/71\n2/13/71\nDate\nSee footnotes at end of table.\nSite\nD\nB\nB\nIdenti- Orien-\ntation\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nnumber\nfication\n22³\n24\n10\n12\n15\n16\n17\n18\n19\n20\n25\n26\n27\n28\n29\n30\n32\n39\n40\n42\n1\n2\n4\n5\n6\n7\n8\n9\n11\n13\n14\n21\n31\n33\n34\n35\n36\n37\n38\n41\n43\n44","Range\n3635\n7182\n12882\n28720\n10676\n7312\n10555\n8807\n6838\n10253\n7850\n4630\n23070\n16859\n31569\n5024\n6500\n14997\n5876\n12579\n7949\n8325\n32199\n5713\n5436\n3650\n10544\n5125\n6593\n6274\n12737\n7404\n32768\n32768\n3643\n1892\n6626\n10137\n7997\n10137\n8691\n3437\n14686\n14131\n13421\n4698\n28639\n27769\n15095\n32768\n8791\n19540\n13391\n10254\n29929\n5071\ncounts\ntenu-\nation\nAt-\n30\n30\ndB\nsponse\n(fig. 1)\ncurve\nRe-\n3\nSlope\n2\n2\n3\n2\n2\n2\n2\n1\n2\n3\n3\n3\n2\n2\n3\n2\n2\n3\n3\n1\n3\n1\n2\n2\n2\n3\n2\n2\n3\n3\n2\n2\n2\n3\n2\n2\n3\n2\n2\n2\n2\n2\n2\n3\n3\n2\n3\n3\n2\n2\n3\n2\n2\n2\n2\n2\nQuality\n(1)\n(2)\n(2)\n(2)\n(3)\n(2)\n(2)\n(2)\n3\n2\n2\n3\n2\n2\n2\n3\n2\n2\n1\n2\n2\n3\n2\n2\n2\n2\n3\n2\n3\n2\n3\n2\n2\n2\n3\n2\n1\n2\n2\n3\n1\n2\n2\n2\n2\n3\n3\n2\n2\n2\n2\n2\n2\n2\n2\n2\n.63\n9.50\n4.60\n.73\n.75\n2.92\n1.50\n6.62\n4.60\n13.12\n10.03\n2.44\n7.33\n1.02\n9.05\n15.65\n3.83\n1.29\n.94\n.95\n2.14\n4.96\n16.64\n9.49\n16.76\n5.34\n1.99\n6.09\n4.45\n6.51\n11.67\n1.22\n3.09\n1.20\n9.74\n2.35\n2.57\n11.65\n29.86\n18.84\n17.85\n54.38\n14.56\n35.89\n50.69\n44.55\n61.50\n13.43\n8.28\n12.40\n17.52\n44.85\n51.49\n3.81\n2.11\n1.91\nStress\ndrop\nTable 1.-Summary of information for seismogram-spectrum pairs in figure 5-Continued\nso\nbar\n2.096E-06\n3.441E-06\n4.087E-06\n5.535E-06\n3.731E-06\n1.922E-05\n1.139E-05\n7.762E-06\n4.379E-06\n3.138E-06\n2.401E-06\n8.652E-06\n5.674E-06\n2.925E-06\n2.486E-06\n2.474E-06\n6.343E-06\n7.919E-06\n2.302E-05\n2.307E-05\n9.427E-06\n3.022E-05\n1.160E-05\n4.896E-06\n5.080E-05\n1.490E-05\n9.464E-06\n4.647E-06\n1.201E-06\n1.330E-05\n1.492E-05\n9.563E-06\n1.686E-05\n1.607E-06\n2.607E-05\n4.155E-06\n3.964E-06\n2.125E-05\n6.298E-06\n2.627E-06\n1.430E-04\n1.300E-04\n1.637E-04\n2.695E-04\n4.210E-05\n3.564E-04\n3.190E-05\n2.108E-05\n5.102E-04\n3.074E-04\n2.075E-05\n1.469E-05\n7.626E-05\n1.154E-04\n1.204E-04\n1.049E-04\nS((10)\ncm-sec\n3.953E 18\n6.489E 18\n7.707E 18\n1.044E 19\n7.036E 18\n3.625E 19\n2.147E 19\n1.464E 19\n8.258E 18\n5.918E 18\n4.527E 18\n1.631E 19\n1.070E 19\n5.515E 18\n4.688E 18\n4.666E 18\n1.196E 19\n1.493E 19\n4.342E 19\n4.351E 19\n1.778E 19\n5.698E 19\n2.187E 19\n9.233E 18\n9.580E 19\n2.809E 19\n1.785E 19\n8.764E 18\n2.264E 18\n2.508E 19\n2.814E 19\n1.803E 19\n3.180E 19\n3.031E 18\n4.916E 19\n7.836E 18\n7.476E 18\n4.006E 19\n1.188E 19\n4.953E 18\n2.697E 20\n2.451E 20\n3.086E 20\n5.082E 20\n7.940E 19\n6.720E 20\n6.015E 19\n3.974E 19\n9.621E 20\n5.797E 20\n3.913E 19\n2.770E 19\n1.438E 20\n2.176E 20\n2.270E 20\n1.977E 20\nMoment\ndyne-cm\nM o\ndimension\nSource\n139.7\n66.9\n90.2\n142.9\n133.4\n61.0\n272.3\n201.9\n226.5\n124.5\n62.4\n113.5\n124.5\n63.8\n121.6\n179.9\n160.4\n146.3\n48.4\n103.5\n184.1\n160.4\n175.8\n184.1\n98.9\n92.3\n58.2\n58.2\n86.1\n50.7\n110.9\n171.8\n142.9\n164.1\n90.2\n139.7\n121.6\n130.3\n94.4\n216.3\n260.1\n153.1\n192.8\n231.8\n211.4\n86.1\n272.3\n90.2\n70.0\n160.4\n108.4\n113.5\n171.8\n175.8\n130.3\n118.9\nm\nr\nHypocentral\ndistance\n(15.8)\n(16.3)\n(14.6)\n11.0\n13.7\n11.0\n11.3\n15.2\n12.7\n12.2\n10.0\n11.0\n12.8\n13.7\n13.5\n13.4\n13.3\n6.7\n11.9\n10.8\n14.2\n15.6\n14.8\n8.4\n13.8\n15.7\n15.6\n6.7\n10.7\n12.7\n9.2\n13.2\n11.4\n15.0\n14.0\n10.2\n11.7\n13.1\n14.1\n10.7\n14.3\n13.0\n13.0\n12.9\n11.8\n9.2\n9.5\n10.4\n10.4\n10.1\n9.2\n9.5\n9.6\n9.6\n12.9\n12.9\nkm\nR\n1.905E-06\n2.512E-06\n3.715E-06\n4.898E-06\n2.455E-06\n1.514E-05\n9.333E-06\n7.762E-06\n3.981E-06\n2.291E-06\n1.778E-06\n6.457E-06\n4.266E-06\n4.365E-06\n2.089E-06\n2.291E-06\n4.467E-06\n5.012E-06\n1.413E-05\n1.479E-05\n6.457E-06\n2.042E-05\n1.380E-05\n3.548E-06\n3.236E-05\n9.550E-06\n1.413E-05\n3.631E-06\n1.122E-06\n1.047E-05\n1.622E-05\n7.244E-06\n1.479E-05\n1.072E-06\n1.862E-05\n4.074E-06\n3.388E-06\n1.622E-05\n4.467E-06\n2.455E-06\n1.000E-04\n1.000E-04\n1.259E-04\n2.089E-04\n4.169E-05\n3.020E-04\n3.467E-05\n2.291E-05\n5.370E-04\n3.236E-04\n1.995E-05\n1.413E-05\n7.943E-05\n1.202E-04\n9.333E-05\n8.128E-05\ncm-sec\nLo\nfrequency\nCorner\n9.33\n19.50\n14.45\n7.08\n8.13\n15.14\n10.47\n20.42\n10.72\n7.24\n7.41\n7.08\n13.18\n14.13\n22.39\n22.39\n9.12\n9.77\n21.38\n25.70\n11.75\n7.59\n9.12\n4.79\n6.46\n5.75\n10.47\n20.89\n7.94\n14.45\n11.48\n8.13\n26.92\n12.59\n10.00\n8.91\n13.80\n6.03\n6.76\n5.62\n15.14\n4.79\n5.01\n9.33\n10.72\n8.51\n14.45\n18.62\n6.17\n8.13\n12.02\n11.48\n7.59\n10.00\n10.96\n7.41\nHz\nfc\n0746 46\n0820 48\n0821 07\n0821 59\n0826 45\n0841 21\n0930 32\n0937 15\n0957 08\n1206 28\n1325 20\n1349 23\n1406 03\n1524 34\n1534 52\n0428 53\n0429 22\n0731 58\n0600 21\n0720 53\nOrigin\nGMT\ntime\n0649\n0656\n0659\n0738\n0746\n0805\n0919\n0923\n0924\n0927\n0929\n0711\n0715\n0722\n0724\n0812\n0832\n0842\n0903\n0904\n0907\n0936\n0945\n1004\n1014\n0721\n0725\n0727\n0732\n0737\n0951\n2/14/71\nDate\nSee footnotes at end of table.\nSite\nIdenti- Orien-\ntation\nEW\nEW\nEW\nEW\nEW\nNS\nNS\nNS\nNS\nNS\nnumber\nfication\n45\n46\n47\n48\n49\n50\n52\n53\n54\n55\n56\n72\n73\n74\n76\n79\n51\n57\n58\n59\n60\n62\n61\n63\n64\n65\n66\n67\n68\n69\n70\n71\n75\n77\n78\n80\n81\n82\n83\n84\n85\n86\n87\n88\n89\n90\n92\n91\n93\n94\n95","Range\n2525\n2788\n284\n369\n449\n455\n4759\n8402\n1154\n1042\n2248\n324\n656\n792\n749\n694\n626\n895\n1034\n939\n826\n362\n734\n305\n624\n6712\n5743\n7680\n12804\n10678\n9739\n11483\n1029\n27939\n2234\n680\n759\n935\n1148\n3577\n748\n2280\n2472\n6220\n7571\n1221\n1623\n1451\n1221\n766\n7691\n427\n462\n400\ncounts\n10011\n1031\ntenu-\nation\nAt-\ndB\n30\n36\n42\n1)\nsponse\ncurve\nRe-\n(fig.\n3\nSlope\n3\n3\n3\n2\n2\n2\n2\n3\n2\n3\n3\n3\n3\n3\n3\n3\n2\n2\n1\n1\n2\n1\n3\n3\n3\n3\n3\n3\n3\n2\n2\n3\n2\n2\n2\n2\n1\n3\n3\n3\n3\n3\n3\n3\n3\n3\n3\n3\n2\n3\n3\n3\n3\n3\n3\n3\nQuality\n(3)\n3\n3\n3\n2\n3\n2\n2\n2\n2\n2\n3\n2\n3\n2\n3\n2\n2\n2\n2\n2\n2\n2\n3\n3\n3\n2\n2\n2\n2\n2\n2\n2\n2\n2\n2\n2\n2\n2\n3\n3\n2\n2\n3\n3\n2\n2\n3\n3\n1\n2\n2\n2\n2\n2\n3\n37.37\n60.03\n38.50\n2.15\n12.54\n3.72\n6.52\n6.98\n17.54\n35.32\n34.14\n126.00\n22.83\n14.26\n23.48\n12.58\n19.94\n18.19\n63.90\n19.14\n4.31\n56.75\n15.48\n16.09\n20.76\n27.70\n22.28\n30.62\n8.11\n8.17\n1.67\n99.50\n54.19\n116.06\n7.82\n11.84\n82.66\n13.72\n9.15\n74.92\n184.06\n24.24\n18.57\n35.16\n291.17\n14.74\n102.49\n29.62\n168.53\n13.49\n15.14\n22.33\n16.29\n68.45\n49.54\n253.91\nStress\ndrop\nbar\nso\nTable 1.-Summary of information for seismogram-spectrum pairs in figure 5-Continued\n2.298E-04\n6.415E-04\n5.424E-04\n2.634E-05\n1.436E-04\n4.258E-05\n1.750E-05\n1.632E-05\n1.358E-05\n1.279E-05\n1.706E-04\n9.104E-05\n1.341E-05\n1.919E-05\n1.948E-05\n7.387E-06\n1.156E-05\n1.615E-04\n6.181E-05\n1.149E-04\n4.750E-05\n2.587E-05\n2.359E-05\n1.171E-04\n8.616E-05\n1.500E-05\n1.627E-05\n1.221E-05\n1.798E-05\n6.586E-05\n9.091E-05\n6.816E-05\n8.581E-05\n5.038E-04\n3.822E-04\n2.925E-04\n3.856E-04\n5.375E-06\n2.363E-05\n2.258E-03\n5.667E-05\n8.210E-06\n1.124E-05\n9.498E-06\n1.011E-04\n1.963E-04\n6.417E-05\n1.287E-04\n1.700E-04\n1.720E-04\n1.945E-05\n1.256E-05\n1.281E-04\n8.929E-06\n2.846E-05\n4.612E-04\ncm-sec\n52(10)\n4.334E 20\n4.967E 19\n2.560E 19\n2.412E 19\n3.218E 20\n1.717E 20\n2.528E 19\n3.619E 19\n3.673E 19\n1.393E 19\n2.180E 19\n3.045E 20\n1.166E 20\n2.167E 20\n8.957E 19\n4.878E 19\n4.449E 19\n2.209E 20\n1.625E 20\n2.829E 19\n3.068E 19\n2.303E 19\n3.391E 19\n1.242E 20\n1.714E 20\n1.285E 20\n1.618E 20\n9.501E 20\n7.207E 20\n5.516E 20\n7.271E 20\n1.014E 19\n4.456E 19\n1.069E 20\n1.548E 19\n2.120E 19\n1.791E 19\n1.907E 20\n3.702E 20\n1.210E 20\n2.427E 20\n3.206E 20\n3.243E 20\n3.667E 19\n2.368E 19\n2.416E 20\n1.684E 19\n5.367E 19\n8.696E 20\n1.210E 21\n2.708E 20\n1.023E 21\n8.030E 19\n3.301E 19\n3.078E 19\n4.259E 21\nMoment\ndyne-cm\nM\ndimension\nSource\n171.8\n206.6\n78.5\n226.5\n216.3\n211.4\n211.4\n130.3\n124.5\n66.9\n160.4\n84.2\n78.5\n103.5\n130.3\n254.2\n70.0\n84.2\n139.7\n160.4\n78.5\n65.3\n375.9\n298.6\n142.9\n285.2\n78.5\n63.8\n216.3\n124.5\n47.3\n78.5\n75.0\n133.4\n82.2\n153.1\n101.2\n167.9\n94.4\n106.0\n88.1\n167.9\n76.8\n70.0\n197.3\n86.1\n88.1\n184.1\n384.7\n73.3\n73.3\n184.1\n164.1\n78.5\n76.8\n78.5\nm\nr\nHypocentral\ndistance\n(19.1)\n(19.8)\n(15.8)\n(16.8)\n(16.4)\n(14.7)\n(17.0)\n(17.2)\n14.5\n12.8\n14.6\n12.9\n28.0\n11.4\n7.8\n7.4\n7.2\n8.0\n6.6\n9.3\n6.5\n17.3\n17.0\n10.2\n10.2\n13.6\n13.6\n14.2\n14.2\n14.0\n14.0\n5.5\n12.4\n8.2\n7.3\n5.9\n7.9\n6.9\n5.0\n7.6\n9.0\n13.3\n10.1\n17.1\n8.7\n18.1\n14.1\n15.6\n12.1\n12.1\n12.1\n12.1\n15.0\n15.9\n16.4\n16.1\nkm\nR\n1.585E-04\n5.012E-04\n3.715E-04\n2.042E-05\n5.129E-05\n3.020E-05\n1.122E-05\n1.349E-05\n1.122E-05\n1.122E-05\n2.188E-04\n1.230E-04\n1.862E-05\n2.399E-05\n2.951E-05\n7.943E-06\n1.778E-05\n9.333E-05\n3.236E-05\n6.761E-05\n2.399E-05\n2.138E-05\n1.950E-05\n7.413E-05\n5.129E-05\n1.000E-05\n1.023E-05\n7.586E-06\n1.096E-05\n6.457E-05\n8.913E-05\n5.012E-05\n6.310E-05\n3.548E-04\n2.692E-04\n2.089E-04\n2.754E-04\n9.772E-06\n1.905E-05\n2.754E-03\n7.762E-05\n8.128E-06\n1.905E-05\n1.202E-05\n6.166E-05\n1.148E-04\n4.365E-05\n1.479E-04\n1.000E-04\n1.000E-04\n2.818E-05\n2.512E-05\n7.079E-05\n1.175E-05\n3.162E-05\n3.467E-04\ncm-sec\nSo\nfrequency\nCorner\n7.59\n5.75\n14.79\n16.60\n10.00\n5.13\n7.08\n3.39\n17.78\n17.78\n18.62\n7.08\n7.94\n15.49\n16.60\n16.98\n16.60\n9.33\n8.13\n16.60\n19.95\n3.47\n4.37\n9.12\n20.42\n6.03\n10.47\n27.54\n16.60\n17.38\n9.77\n15.85\n7.76\n13.80\n12.30\n14.79\n7.76\n16.98\n18.62\n4.57\n16.60\n8.51\n12.88\n6.61\n6.31\n6.03\n6.17\n6.17\n10.00\n10.47\n15.14\n19.50\n8.13\n15.49\n16.60\n12.59\nHz\nfc\n0246 35\n0256 47\n0333 52\n0335 00\n0335 53\n0340 22\n0444 44\n0449 12\n0624 52\n0803 32\n1807 50\n1943 42\n1946 34\n2030 49\n2225 22\n2231 23\n0032 00\n0110 50\n0520 41\n0748 01\n1324 35\n1753 58\n2128 41\nOrigin\nGMT\ntime\n0412\n0433\n0637\n0644\n1919\n1920\n0743\n1732\n0111\n0341\n1741\n1927\n2233\n0027\n0040\n0057\n2/15/71\n2/14/71\nDate\nSee footnotes at end of table.\nSite\nD\nD\nD\nD\nD\nD\nD\nD\nD\nD\nD\nD\nD\nD\nD\nD\nB\nB\nB\nB\nB\nB\nB\nB\nB\nB\nB\nB\nB\nB\nB\nB\nIdenti- Orien-\ntation2\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nnumber\nfication\n119\n120\n128\n129\n130\n132\n96\n97\n98\n99\n100\n102\n121\n122\n123\n124\n125\n126\n127\n131\n133\n134\n101\n103\n104\n105\n106\n107\n108\n109\n110\n115\n116\n117\n118\n111\n112\n113\n114","Range\n4276\ncounts\n13737\n5515\n859\n1564\n588\n1302\n1475\n841\n2801\n2871\n3583\n2266\n1268\n2918\n6717\n455\n708\n2781\n367\n605\n938\n588\n3175\n218\n281\n272\n353\n10182\n1072\n30169\n906\n5485\n7329\n1513\n1551\n8989\n1777\n1179\n9681\n18017\n2253\n5835\n2295\n4033\n2817\n3404\n6813\ntenu-\nation\nAt-\ndB\n42\n6\n(fig. 1)\nsponse\ncurve\nRe-\n3\nSlope\n3\n3\n3\n2\n3\n3\n2\n2\n3\n2\n3\n2\n2\n2\n3\n2\n3\n3\n3\n2\n3\n3\n2\n3\n2\n2\n3\n3\n3\n2\n3\n2\n1\n2\n2\n1\n1\n3\n1\n3\n2\n1\n2\n2\n2\n2\n2\n2\nQuality\n(2)\n3\n3\n3\n3\n2\n3\n3\n3\n2\n2\n2\n3\n3\n2\n2\n2\n2\n2\n2\n2\n2\n2\n2\n2\n2\n2\n2\n1\n1\n2\n2\n2\n2\n2\n2\n2\n2\n2\n2\n2\n2\n2\n2\n2\n2\n2\n2\n3 There is no event 23.\n12.02\n228.25\n210.37\n7.91\n55.48\n156.67\n112.47\n2.68\n29.07\n35.51\n102.93\n8.11\n16.67\n19.30\n158.53\n21.30\n144.03\n14.17\n12.32\n4.90\n22.61\n37.03\n11.07\n68.49\n2.45\n6.83\n21.53\n41.49\n289.24\n21.83\n343.92\n3.67\n9.37\n59.14\n1.63\n2.11\n21.89\n112.26\n6.17\n141.29\n5.34\n.76\n1.74\n.53\n.92\n.52\n.56\n2.19\nStress\ndrop\nbar\nTable 1.-Summary of information for seismogram-spectrum pairs in figure 5-Continued\nso\n9.974E-06\n4.648E-04\n3.033E-04\n5.214E-05\n4.603E-05\n7.479E-05\n1.230E-04\n4.040E-05\n4.459E-05\n7.803E-05\n7.437E-05\n1.852E-04\n9.565E-05\n9.646E-05\n7.568E-05\n6.875E-04\n4.143E-04\n9.336E-05\n5.490E-06\n6.150E-06\n9.400E-06\n3.292E-05\n3.918E-05\n6.990E-05\n3.446E-05\n2.972E-05\n2.050E-05\n1.849E-05\n5.890E-04\n6.728E-05\n2.115E-03\n1.360E-04\n6.467E-04\n5.137E-04\n2.251E-04\n1.788E-04\n5.001E-04\n3.460E-04\n1.510E-04\n5.117E-05\n1.891E-05\n2.331E-06\n1.232E-05\n3.259E-06\n6.518E-06\n3.969E-06\n5.536E-06\n7.739E-06\ncm-sec\n52(10)\n1.881E 19\n8.765E 20\n5.719E 20\n9.833E 19\n8.680E 19\n1.410E 20\n2.319E 20\n7.618E 19\n8.408E 19\n1.472E 20\n1.402E 20\n3.493E 20\n1.804E 20\n1.819E 20\n1.427E 20\n7.813E 20\n1.760E 20\n1.035E 19\n1.160E 19\n1.773E 19\n6.207E 19\n7.389E 19\n1.296E 21\n1.318E 20\n6.498E 19\n5.604E 19\n3.867E 19\n3.486E 19\n1.269E 20\n1.111E 21\n3.988E 21\n2.565E 20\n9.687E 20\n4.244E 20\n3.371E 20\n1.219E 21\n9.431E 20\n6.525E 20\n2.847E 20\n9.648E 19\n3.566E 19\n4.395E 18\n2.322E 19\n6.146E 18\n1.229E 19\n7.484E 18\n1.044E 19\n1.459E 19\n2 For events 1-22, E-W means W.37°S. and N-S means N.37°W.\nMoment\ndyne-cm\nMo\ndimension\nSource\n118.9\n106.0\n175.8\n73.3\n96.6\n130.3\n84.2\n167.9\n298.6\n133.4\n175.8\n88.1\n231.8\n101.2\n90.2\n142.9\n94.4\n88.1\n266.1\n160.4\n73.3\n71.6\n101.2\n70.0\n226.5\n118.9\n153.1\n92.3\n71.6\n136.5\n171.8\n312.7\n384.7\n192.8\n484.3\n412.2\n136.5\n136.5\n179.9\n171.8\n266.1\n272.3\n66.9\n142.9\n179.9\n201.9\n184.1\n142.9\nm\nr\nHypocentral\ndistance\n(14.2)\n(15.9)\n(16.9)\n6.9\n15.2\n12.8\n13.9\n13.3\n9.5\n11.5\n13.1\n12.3\n12.2\n7.4\n14.6\n14.7\n20.9\n6.6\n6.9\n9.4\n10.9\n11.3\n8.8\n14.7\n15.2\n16.6\n16.8\nkm\n15.1\n13.1\n17.1\n16.1\n13.6\n11.5\n11.5\n14.2\n14.2\n8.3\n8.3\n15.1\n15.1\n13.7\n16.5\n17.0\n15.6\n16.0\n15.8\n14.9\n15.8\nR\n1.445E-05\n3.548E-04\n1.995E-04\n4.074E-05\n3.311E-05\n5.623E-05\n1.000E-04\n3.311E-05\n6.026E-05\n5.495E-05\n4.677E-05\n1.950E-04\n8.318E-05\n6.607E-05\n5.012E-05\n5.248E-04\n2.818E-04\n4.467E-05\n8.318E-06\n8.913E-06\n1.000E-05\n3.020E-05\n3.467E-05\n7.943E-05\n2.344E-05\n1.738E-05\n1.349E-05\n1.148E-05\n3.548E-04\n3.981E-05\n1.259E-03\n1.000E-04\n5.623E-04\n4.467E-04\n1.585E-04\n1.259E-04\n6.026E-04\n4.169E-04\n1.000E-04\n3.388E-05\n1.380E-05\n1.413E-06\n7.244E-06\n2.089E-06\n4.074E-06\n2.512E-06\n3.715E-06\n4.898E-06\ncm-sec\nSo\nfrequency\nCorner\n14.79\n10.96\n12.30\n7.41\n14.79\n17.78\n13.49\n5.62\n12.88\n10.00\n15.49\n4.90\n7.76\n8.13\n17.78\n4.37\n9.77\n18.20\n12.88\n18.62\n14.45\n9.12\n13.80\n5.75\n14.13\n18.20\n10.96\n9.55\n7.59\n4.17\n7.41\n3.39\n8.51\n6.76\n2.69\n3.16\n4.90\n9.55\n4.79\n19.50\n9.12\n9.55\n7.24\n7.59\n7.24\n7.08\n6.46\n9.12\nHz\nfc\n0653 43\n0656 16\n0656 16\n0705 25\n0723 33\n0806 55\n0839 41\n0840 18\n0846 54\n0947 32\n1026 55\n1038 32\n1129 26\n1225 04\n1048 01\n1246 37\n1302 52\n1303 42\n1536 40\n0240 06\n0257 19\n1137 59\nOrigin\nGMT\ntime\n0652\n0952\n1007\n0923\n2300\n0026\n0110\n0530\n0533\n0540\n0732\n0736\n1 Blank spaces are equivalent to ditto marks.\n2/15/71\n2/18/71\n12/23/71\n12/24/71\nDate\nSite\nD\nD\nD\nB\nB\nD\nB\nD\nD\nD\nB\nB\nD\nD\nB\nB\nD\nD\nD\nB\nD\nD\nB\nB\nB\nB\nB\nB\nB\nIdenti- Orien-\n2\ntation\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nEW\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nNS\nnumber\nfication\n135\n136\n137\n137\n138\n139\n141\n142\n143\n144\n145\n146\n147\n148\n149\n150\n151\n152\n153\n154\n155\n156\n157\n158\n159\n160\n161\n162\n163\n164\n165\n166\n167\n168","Source Parameters for Aftershocks\n77\nthe same site) or those of event 146 (different sites)\nbecause it is predominantly noise that has been arti-\nFrom the Range column in table 1, it is seen that\nficially corrected for attenuation over a 12-km path.\nthe peak-to-peak amplitude of the seismograms 6N-S\nThe hypothetical amplitude spectrum 3e was ob-\nand 6E-W are 3,796 and 1,449, respectively, while\ntained by dividing 3d by frequency; it has character-\nthose of seismograms 146B and 146D are 708 and\nistics similar to those of the observed spectra (fig. 5)\n367, respectively (the instruments had the same\nIn the absence of noise, this hypothetical spectrum\nresponse and attenuation). Thus, the difference in\nwould have a constant amplitude for frequencies\nthe appearance of the seismograms is caused primarily\nfrom zero to the \"corner\" frequency (fc) and a slope\nby the large spike at the beginning of the S-waves in\nof -2 for higher frequencies. In the presence of\n6N-S and 146B.\nnoise, it has a negative slope for frequencies less than\nf1 and a positive one for frequencies greater than f2.\nThe values of f1 and f2 depend on the signal-to-noise\nGENERAL SPECTRAL CHARACTERISTICS\nratio and, indirectly, on fc. The rate of increase of the\nspectrum above f2 depends on the hypocentral dis-\nFigure 3 illustrates the general characteristics of the\nspectra in figure 5. All plots are log-log and have\ntance because this part of the spectrum is pre-\nbeen shifted vertically for clarity; slopes are indi-\ndominantly noise that has been multiplied by an\ncated. Figure 3a is the response of the recording sys-\nexponential factor to compensate for attenuation over\nthis distance.\ntem to ground velocity. The bold line in 3b is a\nhypothetical input velocity spectrum of the S-wave\nof a signal that has traveled 12 km through a medium\nFITTING THE SPECTRA TO A MODEL\nwith a Q of 250. The dashed line in 3b represents\nthe spectrum of the same signal traveling through a\nThe spectra shown in figure 5 characteristically\nmedium with infinite Q. The dashed line merges\nhave a constant amplitude at low frequencies, a\nwith the bold line at low frequencies. The spectrum\ncorner frequency, and a high-frequency asymptote\nof the hypothetical background noise is indicated by\nwith slope from to Deviations from this\nthe thin line. The shape and relative levels of these\ngeneral character almost always can be attributed to\nhypothetical signal and noise spectra are typical of\nnoise. We have ignored the narrow minima that\nobserved spectra. For frequencies less than f1 and\noccur throughout the spectra, assuming they are the\ngreater than f2, the noise level exceeds the signal\nresult of phase interference that we are not attempt-\nlevel, whereas between f1 and f2, the input is pre-\ning to interpret. Such phase interference could be\ndominantly signal. The actual spectrum of the seis-\ncaused by complexities in the source, scattering, or\nmometer output was obtained by multiplying the\nreflection.\nresponse curve 3a by the input (signal plus noise)\nTo determine the effect of background noise on a\nspectrum 3b and is represented by the dotted line in\nparticular spectrum, a sample of the record (equal\n3c. The solid line in 3c represents the spectrum calcu-\nin length to the S-wave sample and, typically,\nlated from a discretely sampled section of the S-wave.\nimmediately preceding the event) was Fourier-\nThe lowest frequency, fL, equals the reciprocal of the\ntransformed and corrected for attenuation in the\nlength of the S-wave section; and the highest (Ny-\nsame way as was the S-wave spectrum. In general,\nquist) frequency, fn, equals one-half the sampling\nthe effect of the noise on the S-wave spectra is as\nrate. The solid line coincides with the dotted line\nshown in figure 3. When noise exceeds signal at low\nexcept for frequencies greater than about f2 where\nfrequencies, the slope of the spectrum is negative;\naliasing errors cause the calculated spectrum to ex-\nand when the noise exceeds signal at high fre-\nceed slightly the actual spectrum. The dashed line of\nquencies, the slope increases at a rate proportional to\n3c represents the calculated spectrum after correcting\nhypocentral distance. Contamination of the S-wave\nfor propagation-path attenuation. The apparent in-\nspectra by P-wave energy was insignificant. Events\nput velocity spectrum 3d is obtained by dividing the\nwith clipped seismograms (indicated by a \"(c)\" be-\ncorrected output spectrum (dashed line in 3c) by the\nlow their identification numbers in fig. 5) , had\nresponse curve 3a. The solid line in 3d and the\nanomalous spectra at high frequencies (e.g., 28 E-W,\ndashed line in 3b are identical except for frequencies\n102, 140B, and 140D) Several of the spectra of\ngreater than f2 or less than f1, where 3d is greater\nevents recorded at Dillon Ranch on February 14 and","San Fernando Earthquake of 1971\n78\n15, 1971, have a peak (at about 33 Hz) that is not 149). They may have been caused by resonance of\npresent in the associated noise spectra. These peaks nearby trees or buildings.\nwere considered anomalous because they are narrow-\nA curve with a constant low-frequency amplitude\nband and missing in spectra for the same earthquakes and a variable high-frequency slope was fit to\n216\nrecorded at Bear Divide (e.g., 138, 144, 146, and spectra (of 165 aftershocks) in figure 5; the remain-\na\nLOG\nVELOCITY\n+2\nRESPONSE\n(counts/u)\nSIGNAL\nb\nLOG\nACTUAL VELOCITY\n+1\n-1\nSPECTRUM\n(u/cps)\nNOISE\nC\n-1\nLOG\n+1\nOUTPUT\nSPECTRUM\n(counts/cps)\n+3\n+2\n-1\nLOG\nd\n+1\nAPPARENT VELOCITY\nSPECTRUM\n(u/cps)\ne\n-1\nLOG\nAPPARENT AMPLITUDE\nSPECTRUM\n(u/cps)\n-2\nUNIT\n1\n10\n100\nfL\nf1\nfc\nf2\nfN\nFREQUENCY (cps)\nFigure 3.-Illustration of the effect of background noise and propagation-path attenuation on amplitude spectra, All plots are log\n(frequency) versus relative logarithmic units of response or of spectral density (u = ground amplitude, ii = ground velocity,\n\"counts\" = output of recording system); slopes are indicated on each plot. The input S-wave velocity spectrum of an attenuated\n(Q = 250, hypocentral distance = 12 km) signal (bold line in b) merges at low frequencies with that of an unattenuated signal\n(dashed line in b). The hypothetical, but typical, signal and noise (thin line in b) spectra are equal at frequencies f, and f2 The\nactual spectrum of the recording system output (dotted line in c) is obtained by multiplying the recording system response (a) by\nthe hypothetical input spectrum (sum of the solid lines in b). The spectrum of a discretely sampled section of the S-wave (solid line\nin c) begins at fL (the reciprocal of the length of the S-wave section) and ends at fN (the Nyquist frequency); correction for atten-\nuation (dashed line in c) and system response give the apparent velocity spectrum (d). The combined effect of noise and attenuation\non the corresponding amplitude spectrum (e)-a negative slope below f1 and a slope which increases at a rate proportional to hypo-\ncentral distance above f2-can be seen in the observed spectra (fig. 5).","Source Parameters for Aftershocks\n79\ning four spectra (3, 11N-S, 140B, and 140D) were\ncorner frequencies observed. We found no significant\nnot interpreted because their general shape was not\ndependence of corner frequency on the hypocenter's\nwell approximated by such a curve. The fit was per-\ngeographical location or depth. Thus, circumstan-\nformed by adjusting the curve's low-frequency ampli-\ntial evidence suggests that the observed corner fre-\ntude (no), corner frequency (fc) and high-frequency\nquencies and high-frequency slopes are not a result\nslope to average the amplitude (not log amplitude)\nof propagation-path effects.\nof the spectra. Allowance was made for the fact that\nUncertainties of Spectra Interpretation\nthe density of spectral estimates, (si), increases with\nlog (frequency) and therefore the character of the\nExamination of the spectra and dashed lines in\nspectra between 10 and 20 Hz, for example, is more\nfigure 5 shows that, in some cases, there is consider-\nreliably determined than that between 1 and 2 Hz.\nable uncertainty in the choice of No, fc, and slope.\nThose parts of the spectra judged to be noise were\nFor example, by fitting a spectrum with a steeper\nignored. Results of this process are indicated by the\nhigh-frequency slope, one often can increase corner\ndashed lines on the spectra in figure 5 and by the\nfrequency. Some spectra seem to have two corner\nvalues of So, fc, and slope in table 1.\nfrequencies (e.g., event 25N-S at 4 and 20 Hz, event\n57 at 8 and 20 Hz, event 58 at 10 and 40 Hz, and\nevents 96E-W and 96N-S at 6 and 15 Hz) Except\nSOURCES OF ERROR\nin the few cases (like events 58 and 25N-S) where\nS-Wave Sample Length\nthe ratio of the two corner frequencies is large\n(>4) and the smaller value was used, the spectra\nThe level and shape of the spectra do not depend\nwere interpreted with an intermediate corner fre-\ncritically on the length of the S-wave sample, pro-\nquency. In general, interpretations of the spectra\nvided the frequencies of interest are greater than the\nreciprocal of the sample length. This fact is illus-\nwith steep slopes and/or high signal-to-noise\nratios (100 to 1,000 at fc) are less ambiguous than\ntrated by comparing the spectra of two samples, of\nthose of the spectra with shallow slopes (-1)\ndifferent length, of the S-wave of event 73 (fig. 5)\nThe arrowheads under the seismogram indicate the\nand/or low signal-to-noise ratios (<20 at fc). The\nambiguity of the fit of each spectra has been esti-\nendings of the two samples; the longer sample in-\nmated and is indicated in the Quality column in\ncludes the shorter. The spectrum of the longer is\ntable 1. The least ambiguous interpretations have a\nplotted as individual points and that of the shorter\nquality of 3, the most ambiguous a quality of 1, and\nas a continuous curve. It is seen that the dashed curve\nthe average a quality of 2. When a seismogram is\nfits both spectra equally well. Many such comparisons\nclipped, the associated quality estimate is in paren-\nhave been made with similar results.\ntheses.\nPropagation-Path Effects\nAn upper limit for the errors in No and fc, resulting\nfrom ambiguity in interpretation, was estimated by\nOur correction for propagation-path attenuation\nmaking two alternate interpretations of 59 of the\naffects the spectra most strongly at high frequencies\nmost ambiguous spectra. For each pair of alternate\n(fig. 3c) Therefore, if our choice of Q (250) were\ninterpretations, we calculated the variance of the\ngrossly in error or if scattering were seriously affect-\ninterpretations from their mean. The average of these\ning our data, we would expect a marked dependence\n59 determinations of variance corresponds to a stand-\nof corner frequency and of slope of the spectrum at\nard deviation in No or fc of about 75 percent. The\nhigh frequencies on hypocentral distance. As a check,\nstandard deviation for the other 157 less ambiguous\nthe corner frequency and high-frequency slope of\nspectra was estimated to be 10 percent. A weighted\neach of the 216 spectra in table 1 were plotted\naverage of the two corresponding variances indicates\nagainst distance. The spectra were considered collec-\nthat the standard deviation in No or fc resulting from\ntively and in groups with comparable No's; no corre-\nambiguities in the fitting procedure is 25 percent.\nlation was found.\nAlthough the effect of near-site attenuation or scat-\nRadiation Pattern, Scattering, and Focusing Effects\ntering would be independent of hypocentral\ndistance, it seems improbable that such attenuation\nBecause we recorded at only one or two stations, it\nand scattering alone could explain the wide range of\nwas impossible to average the spectra over azimuth","San Fernando Earthquake of 1971\n80\nand thereby to eliminate the effects of radiation pat-\nor f as a result of all errors is about 50 percent. This\ntern, scattering, and focusing. To a certain extent,\nmay somewhat underestimate the total errors because,\nthis difficulty was overcome by recording a large num-\nin many cases, the two sites did not sample grossly\nber of events at various azimuths (fig. 2)\ndifferent parts of the radiation pattern.\nEstimate of Combined Errors\nANALYSIS OF RESULTS\nThe combined effect of all the errors mentioned\nabove has been estimated by comparing the two\nFigure 4 is a plot of our interpretations of 216\nvalues of No and fc obtained for each of the 24\nS-wave spectra of 165 San Fernando aftershocks. This\nearthquakes that were recorded at both the Bear\nplot is similar to the Hanks and Thatcher (1972)\nDivide and Dillon Ranch sites. Each event has two\nNo - fc diagrams. The top abscissa is corner fre-\nspectra which were: (1) interpreted independently;\nquency, and the righthand ordinate is S2 (10) -the\n(2) calculated from S-wave samples of different\nlow-frequency spectral amplitude (no) corrected to\nlengths; (3) corrected for attenuation over different\na distance of 10 km (s) (10) = N.R/10 where R is\npropagation paths; and (4) affected differently by\nhypocentral distance) The type of symbol used to\nradiation pattern, scattering, and focusing. The esti-\nrepresent each of our spectra indicates the slope of\nmated standard deviation of a determination of No\nthe spectrum's high-frequency asymptote (see legend\nCORNER FREQUENCY (cps)\n40\n30\n20\n15\n10\n7\n6\n5\n4\n3\n24\nTRIFUNAC (1972)\nA\nSLOPE 22 -3\n-2 O\nOUR DATA\n-1 X\n100\nA\n2\n22\n-3\n-3\n20\n5\n6\n18\n7\n30\n40\n50\n70\n100\n150\n200\n300\n400\n500\n700\n1000\nSOURCE DIMENSION (meters)\nFigure 4.-Observed spectral parameters-corner frequency, S2(10) SLOR/10, where S20 is low-frequency amplitude and R is hypocentral\ndistance (km)], and slope of high-frequency asymptote (see legend)-and our interpretation (using the Brune (1970) model) in terms\nof source parameters-source dimension, seismic moment, and stress drop. Results of Trifunac's (1972) study of accelerogram records\nof 13 large aftershocks are included. Error bars were obtained by comparing spectra of earthquakes simultaneously recorded at the two\ndifferent recording sites (fig. 2); the larger set applies to all the data, the smaller applies only to those having high-frequency slopes\nof 3. Significance is attached to the sharp cutoff of stress drops at about 300 bars and, more speculatively, to the correlation between\nstress drop and spectral slope.","Source Parameters for Aftershocks\n81\n60 bars; Wyss and Hanks (1972) estimated 7 X 10 25\nin fig. 4) Only about 7 percent of the spectra have\ndyne-cm and 14 bars, respectively.\nhigh-frequency slopes of - 1; the rest are about\nThe error bars on figure 4 represent + 1 standard\nevenly divided between those with slopes of - 2 and\ndeviation in our log M, log fc, and log Ao determina-\nthose with slopes of - 3.\ntions (it was necessary to estimate the errors in Ao\nTo interpret these data in terms of source\nseparately because the errors in Mo and r are not\nparameters, we have used the Brune (1970) model\nnecessarily independent) The unlabeled set of error\n(with corrections from Brune 1971) Our measure-\nbars was obtained using the procedure described\nments of So, fc, and slope can be interpreted using\nunder Estimate of Combined Errors. The smaller\nany other model relating corner frequency to source\nset, labeled -3, was obtained using the same pro-\ndimension, for example, Kasahara (1957), Berck-\ncedure, with only those examples for which both\nhemer and Jacob (1968), Haskell (Savage 1972),\nevents had spectra with slopes of - 3.\nand Aki (1972) Results of Hanks and Wyss (1972)\nWe feel that, in large part, the range of values\nand Wyss and Hanks (1972) indicate that for\nplotted on figure 4 represents a real variation in\nmoderate-size earthquakes, source parameters de-\nsource dimension, moment, and stress drop. (See:\nrived from the Brune (1970) model are in good\nNote Added in Proof.) The range is too large to be\nagreement with field observations. There is no reason\naccounted for entirely by the known errors, and the\nto believe the model does not apply to the smaller\nsymbols are not normally distributed about a point\nevents studied here; however, our understanding of\nor line. There is no correlation between the source\nsource mechanism is inadequate to decide with cer-\nparameters and quality estimates given in table 1.\ntainty what model should be used for small earth-\nEvents with moments less than 101s dyne-cm are\nquakes. Our choice of the Brune (1970) model is\nmissing from our data because their signal-to-noise\none of convenience. In the Brune (1970) model, the\nlevels were small. The upper limit of observed stress\nsource parameters, seismic moment (M0), source\ndrops (300 bars) and the upper and lower limits of\ndimension (r), and stress drop (Ao) are defined as\nobserved corner frequencies (30 Hz and 3 Hz, re-\nfollows:\nspectively) cannot be explained by any known experi-\nmental limitation. (Events with some of the largest\nr\nstress drops had peak amplitudes 30 times less than\n4R\nthe dynamic range of the instrument.) The com-\nM.\nbination of Trifunac's (1972) data (which include\nsome of the largest aftershocks that occurred) and\nAo\nour data (which include events down to magnitude\nwhere B is shear-wave velocity (3.5 km/sec), R is\n1/2 or less) is probably a representative sample of all\nhypocentral distance (table 1) p is density (2.8\nSan Fernando aftershocks having moments greater\ngm/cm3, Rep is the root mean square (rms) average\nthan 1018 dyne-cm.\nof the radiation pattern (0.4), and k is a correction\nIt is important to note that our sample of events\nfactor for amplification upon free-surface reflection\nhas been influenced strongly by our choices of the re-\n(taken to be 2, as for SH-waves). The lower\ncording system gain. The data set does not include\nabscissa of figure 4 is source dimension, the left-hand\nall events that occurred within the range of the plot-\nordinate is seismic moment, and the diagonal lines\nted points. When the amplifier gain was large, some\nare lines of constant stress drop. Table 1 lists the r,\nlarge events were missed because of clipping; when\nM, and Ao.\nthe gain was small (or the amplifier bypassed) nu-\nIn addition to our data, figure 4 includes points\nmerous small events were missed because of low sig-\nfor 13 San Fernando aftershocks studied by Trifunac\nnal level. If the system had been operated the entire\n(1972) Trifunac used the Brune (1970) model to\n8 days with the amplifier bypassed, our sample of\ninterpret Pacoima Dam (fig. 2) accelerogram records\nevents would have included only a few large, high-\nof the largest aftershocks (M L = 4.3 to 5.5) occurring\nstress events. On the other hand, if the system had\nduring the 6 minutes following the main event. For\nbeen operated at its highest gain during the entire\nthe main event, Trifunac (1972) estimated a seismic\nperiod, the sample would have consisted of over a\nmoment of 1.5 X 10 dyne-cm and a stress drop of","82\nSan Fernando Earthquake of 1971\nthousand small events with generally small stress\nhave smaller, fractional stress drops. Although the\ndrops.\nBrune model does not predict slopes of for azi-\nThere is a general correlation of stress drop with\nmuthally averaged (rms) spectra, it does not pre-\nmoment; events with moments of about\nclude slopes of 3 at particular azimuths. In fact, it\ndyne-cm have stress drops, on the average, of 1 to 10\nis reasonable that the effect of rupture might lead to\nbars, whereas events with moments greater than 1021\nthe observed correlation of steeper slopes with\ndyne-cm have stress drops of 100 bars on the average.\nhigher corner frequencies. In the direction of rup-\nLarger values of stress drop estimated for San Fer-\nture propagation, the corner frequency is increased\nnando aftershocks are several orders of magnitude\nbecause high-frequency energy is focused in this\nlarger than those previously estimated for small\ndirection. However, such focusing would be expected\nearthquakes, although the smaller values are compa-\nto be ineffective at frequencies much higher than the\nrable to stress drops obtained by Wyss (1970) for af-\ncorner frequency because of incoherence. Thus,\ntershocks of the 1968 Borrego Mountain earthquake\nsteeper slopes would be correlated with higher corner\nand to those obtained by Douglas and Ryall (1972)\nfrequencies and higher stress drops. The relatively\nfor Nevada microearthquakes. The large stress-drop\nlarge number of high-slope events would remain to\nevents have corner frequencies that are from 5 to 30\nbe explained, however. We cannot determine for cer-\ntimes greater than those predicted by the recently\ntain whether the slopes in our spectra are the re-\nproposed scaling laws of Aki (1972) and the fault-\nsult of propagation-path effects or of source effects-\nlength versus magnitude curve of Wyss and Brune\nsuch as rupture propagation and those described by\n(1968) In fact, these large stress-drop aftershocks\nSavage (1972) The lack of correlation of high-fre-\nare more consistent with the early source-dimension\nquency slope with distance is an argument against\nversus magnitude curve of Press (1967) This fact\npath effects as the explanation. The correlation be-\nhas important implications for seismic discrimination\ntween steeper slopes and higher stress drops could be\nbetween underground explosions and earthquakes\ncaused partly by a bias in the fitting process; if the\nbecause these higher stress-drop events tend to have\nspectra are forced to fit steeper slopes, the resulting\nsource parameters similar to those of explosions.\ncorner frequencies and stress drops are increased.\nHowever, this effect was estimated above to be about\nOne of the most striking features of the data in\n25 percent in fc and is therefore too small to ex-\nfigure 4 is the apparent upper limit of about 300\nbars for stress drop. Because the effect of errors\nplain entirely the observed correlation.\nwould be to extend the data beyond any such limit\nFinally, our data are further evidence of a large\nin stress drop, the actual upper limit represented by\nrange in stress drops of small earthquakes. The fact\nthese data is probably about 100 bars. This conclu-\nthat many of the San Fernando aftershocks had very\nsion is based on the Ao error bars for spectra with\nhigh stress drops might suggest that parts of the\nslopes of (because most of our data near this\nsource region were under a relatively high state of\nboundary have slopes of -3) Thus, we interpret\nstress because of strain changes induced by the main\nthe data in figure 4 as representing a range of stress\ndrops from less than 1 bar to an upper limit of\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks.\nThe amplitude spectrum scale is relative, logarithmic units; time\nabout 100 bars.\nand log (frequency) scales are given at the bottom of each page.\nWe speculate that this upper limit of 100 bars in\nSpectra were obtained by Fourier-transforming the underlined\nstress drop is equal to the actual effective stress oper-\npart of each seismogram and correcting for instrument response\nating; thus, events with stress drops of less than 100\nand attenuation (assuming a Q of 250 and calculating hypocentral\ndistance from S - P times). Events recorded on two instruments,\nbars are fractional stress-drop events. This specula-\neither at different sites (Bear Divide (B) and Dillon Ranch (D))\ntion is consistent with Trifunac's (1972) estimates of\nor on orthogonal components (EW and NS) at the same site, have\nan effective stress of 85 bars and a stress drop of\ntwo seismogram spectrum pairs, each with the same ID number\nbut subscripted to indicate the site or component. A \"c\" below\nabout 60 bars for the main shock. It is also consistent\nan ID number indicates that the corresponding seismogram was\nwith an interpretation, using the Brune (1970)\nclipped. All but four spectra were fit to a curve having a constant\nmodel, of the tendency on figure 4 for events with\nlow-frequency amplitude and a high-frequency asymptote with a\nlarge stress drops to have steep slopes. In that model,\nslope from -1 to -3, resulting in the dashed curves through\nthe spectra and the inferred values of low-frequency amplitude\nspectra with slopes of have stress drops equal to\n(520), corner frequency (fc), and high-frequency slope (table 1 and\nthe effective stress while those with slopes of 1\nfig. 4).","Source Parameters for Aftershocks\n83\n1\n2\n3\n1 UNIT\n4\n5EW\n5NS\n1 SEC\n40 60\n20\n6 8 10\n4\n1\n2\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks.","","Source Parameters for Aftershocks\n85\n9NS\n10EW\n10NS\n11EW\n1 UNIT\n11 NS\n12\n1 SEC\n6 8 10\n40 60\n1\n2\n4\n20\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","86\nSan Fernando Earthquake of 1971\n13EW\n13NS\n14EW\n14NS\n15\n1 UNIT\n16EW\n1 SEC\n1\n2\n4\n6\n8 10\n20\n40 60\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","Source Parameters for Aftershocks\n87\n16NS\nmy\nmemorying\n17\n18\nMany\n19\nhm\n20\n1 UNIT\n21\n1 SEC k\n2\n1\n4\n6\n8\n10\n20\n40\n60\nFREQUENCY (cps)\nFigure 5.--Seismogram-spectrum pairs of San Fernando aftershocks-continued","San Fernando Earthquake of 1971\n88\n22EW\n22NS\n**\n241EW\n24/NS\nWhitten\n1 UNIT\nMyhomes\nthe\n25EW\n25NS\n1 SEC\n1\n2\n4\n6\n8\n10\n20\n40\n60\n** There is no event 23.\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","Source Parameters for Aftershocks\n89\n-\n26EW\n26NS\n27EW\n27NS\n1 UNIT\n28EW\n(c)\nmillion\n28NS\nM\n1 SEC\n4 6 8 10\n40 60\n20\n1\n2\nFREQUENCY (cps)\nFigure 5.-Seismogran-spectrum pairs of San Fernando aftershocks-continued.","San Fernando Earthquake of 1971\n90\n29\n30\nThey\n31\n-\n32\n1 UNIT\n33\n34\nSEC\n6 8 10\n40 60\n20\n2\n4\n1\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","Source Parameters for Aftershocks\n91\n35\n36\n37\n38\n1 UNIT\n39\n40\n1 SEC\n1 2 FREQUENCY (cps)\n40 60\n6 8 10\n20\n4\n5 5.--Seismogram-spectrum. pairs of San Fernando aftershocks-continued.\nFigure","San Fernando Earthquake of 1971\n92\n41\n42\n43\n44\n1 UNIT\n45\n46\n1SEC\n1\n6 8 10\n2\n4\n20\n40\n60\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","93\n48\n49\n50\n1 UNIT\n51\n52\n2/1SEC\n10\n20\n40\n60\n2\n4\n(cps)","San Fernando Earthquake of 1971\n94\n53\n54\nW\nMy\n55\n56\nyou\n57\n1 UNIT\n58\nAM,\nprincipal\n1SECK\n4 6 8 10\n20\n40\n60\n1\n2\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks continued.","95\n59\n60\n62\n1 UNIT\n64\n1 SEC\n40\n60\n2\n4","San Fernando Earthquake of 1971\n96\n65\nMn\n66\n(c)\n67\n(c)\n68\nmy\n69\n(c)\n1 UNIT\n70\n1 SEC\nk\n40 60\n8 10\n1\n2\n4\n6\n20\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","Source Parameters for Aftershocks\n97\n71\n(c)\n72\n73\n14\n74\n75\nM\n1 UNIT\n76\n1 SEC\n40 60\n1\n2\n4\n6\n8\n10\n20\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","San Fernando Earthquake of 1971\n98\n77\n(c)\nwww.\n78\n/ 79\n80\n1 UNIT\nT\n81\n82\n(c)\n1\nSEC\n4 6 8 10\n40 60\n1\n2\n20\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","Source Parameters for Aftershocks\n99\n83\nin\n84\n85\n86\n1 UNIT\n87\nharms\n88\n1SEC\n40 60\n6 8 10\n20\n1\n2\n4\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","San Fernando Earthquake of 1971\n100\n89\n90\n91EW\n1 UNIT\n91 NS\n92EW\n(c)\n92NS\n(c)\n1SEC\n2\n6 8 10\n40 60\n1\n4\n20\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","Source Parameters for Aftershocks\n101\n93EW\n93NS\n94EW\n94NS\n95EW\n1 UNIT\n95NS\n1 SEC\n60\n10\n20\n40\n4\n6\n8\n1\n2\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","San Fernando Earthquake of 1971\n102\n96EW\n96NS\n97EW\n97NS\n1 UNIT\n98EW\n98NS\n1 SEC\n4 6 8 10\n40 60\n1\n2\n20\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","Source Parameters for Aftershocks\n103\n99EW\nMr.\n99NS\nmm\n100\nfrom\n101\n1 UNIT\nI\n102\n(c)\n103\nbyth\n1 SEC\n40 60\n20\n4\n6\n8\n10\n1\n2\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","104\nSan Fernando Earthquake of 1971\n104\n105\n106\n107\n108\n1 UNIT\n109\nk\n1SEC\n1\n2\n4\n6\n8\n10\n20\n40\n60\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","Source Parameters for Aftershocks\n105\n110\n1/4/1\n111\n112\n113\n114\ninh\n1 UNIT\n115\n1SEC\n4 6 8 10\n40 60\n20\n1\n2\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","San Fernando Earthquake of 1971\n106\n)\n116\n117\nmy\n118B\n-\n118D\n1 UNIT\nT\n119B\nM.\n119D\n1SEC\n4 6 8 10\n40 60\n2\n1\n20\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","Source Parameters for Aftershocks\n107\n120\n121\nWAN\nManagement\n122B\n122D\n123\n1 UNIT\n124B\n1SEC\n40 60\n6 8 10\n20\n4\n1\n2\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","San Fernando Earthquake of 1971\n108\n124D\n125B\n125D\n126\n127B\n1 UNIT\n127D\n1 SEC -\n6 8 10\n1\n2\n4\n40 60\n20\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","Source Parameters for Aftershocks\n109\n128B\n128D\n129B\n129D\n130B\n1 UNIT\n130D\n1SEC\n40 60\n4 6 8 10\n20\n1\n2\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","San Fernando Earthquake of 1971\n110\n131B\nMAM\n-\n131D\n132B\n132D\nsmm\n133B\n1 UNIT\nT\n133D\n1 SEC\n40 60\n1\n2\n4\n6\n8\n10\n20\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","Source Parameters for Aftershocks\n111\n134B\n-\n134D\n135\n/\n136B\n136D\n1 UNIT\n137B\n1 SEC\n40 60\n4 6 8 10\n20\n1\n2\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","San Fernando Earthquake of 1971\n112\n137D\n138B\n138D\n139B\n139D 1 UNIT\n140B\n(c)\n1SEC\n4 6 8 10\n1\n40 60\n2\n20\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","Source Parameters for Aftershocks\n113\n140D\n(c)\n141B\n141D\n142B\nMr\nMyp\n142D\n1 UNIT\n143B\n1SEC\n40 60\n6 8 10\n20\n4\n1\n2\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","114\nSan Fernando Earthquake of 1971\n143D\n144B\n144D\n145\n146B\n1 UNIT\n146D\n1\nSEC\n1\n2\n4\n6\n8\n10\n20\n40 60\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","Source Parameters for Aftershocks\n115\n147\n148\nHA\n149B\n149D\n150B\n1 UNIT\n150D\n1SEC\n40 60\n6 8 10\n20\n1\n2\n4\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","116\nSan Fernando Earthquake of 1971\n151\n152\n153\n154\n1 UNIT\n155\n(c)\n156\n1 SEC\n1\n2\n4\n6\n8\n10\n20\n40 60\nFREQUENCY ( cps )\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","Source Parameters for Aftershocks\n117\n157EW\n157NS\n158 p EW\n158NS\n159EW\n1 UNIT\n159NS\nMY\n1 SEC\n40 60\n2\n8\n10\n20\n1\n4\n6\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued","San Fernando Earthquake of 1971\n118\n160EW\nm\n160 NS\n161\n162\n163\n1 UNIT\n164\n1 SEC\n1\n6 8 10\n2\n4\n20\n40 60\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.","Source Parameters for Aftershocks\n119\n165\n166\n167\n168\n1 UNIT\n1SEC\n40\n60\n4\n6\n8\n10\n20\n1\n2\nFREQUENCY (cps)\nFigure 5.-Seismogram-spectrum pairs of San Fernando aftershocks-continued.\nfrequencies, a well-defined corner frequency, and an\nshock. Alternatively, these high stress-drop events\nestimated high-frequency asymptote with slope from\ncould have had, for some presently unknown reason,\n- 1 to - -3. About 7 percent of these spectra had\nhigher fractional stress drops, with the effective stress\nhigh-frequency slopes of - 1, with the rest about\nfor all events near 100 bars. It is interesting to note\nevenly divided between those with slopes of - 2 and\nthat the eight events recorded in December 1971, 10\nthose with slopes of -3. Circumstantial evidence,\nmonths after the main shock, all had stress drops of\nbased on comparisons of spectra of earthquakes si-\nless than 10 bars.\nmultaneously recorded at two different sites and on\nlack of dependence of corner frequency and high-fre-\nCONCLUSIONS\nquency slope on hypocentral distance, indicates that\nthe spectral parameters No, fc, and slope represent\nMore than 98 percent of the 220 S-wave spectra we\nseismic-source properties. Interpretation of these pa-\ncalculated had a relatively constant amplitude at low","120\nSan Fernando Earthquake of 1971\nrameters using the Brune (1970) model gave seismic\nmore typed the manuscript. Tom Hanks, Wayne\nmoments of 1018 to 1022 dyne-cm, source dimensions\nThatcher, Peter Molnar, and Jim Savage participated\nof 50 to 500 m, and stress drops of 1 to 300 bars.\nin helpful discussions; Peter Molnar also assisted in\nThe higher stress drops are several orders of magni-\nfield operations.\ntude greater than obtained in previous studies of\nThis research was supported by National Science\nsmall earthquakes and the corner frequencies are\nFoundation Grant NSF-GA-30765, Seismic Data\nabout an order of magnitude greater than predicted\nAnalysis.\nby the scaling laws of Aki (1972) and by the fault-\nlength versus magnitude curve of Wyss and Brune\nREFERENCES\n(1968) There is a general correlation of stress drop\nwith moment; events with larger moments have, on\nAki, Keiiti, \"Scaling Law of Earthquake Source Time-\nFunction,\" The Geophysical Journal of the Royal Astro-\nthe average, larger stress drops. A relatively sharp\nnomical Society, Vol. 31, Nos. 1-3, Dec. 1972, pp. 3-25.\ncutoff of calculated stress drops around 300 bars and\nBerckhemer, H., and Jacob, K. H., \"Investigation of the\na correlation between high-frequency slope and stress\nDynamical Process in Earthquake Foci by Analyzing the\ndrop can be interpreted as indicating that the effec-\nPulse Shape of Body Waves,\" Final Scientific Report AF 61\ntive stress for the San Fernando aftershocks was\n(052) -801, Institute of Meteorology and Geophysics, Uni-\nabout 100 bars and that the estimated range in ac-\nversity of Frankfurt, Germany, Apr. 1968, 85 pp.\nBrune, James N., \"Tectonic Stress and the Spectra of Seismic\ntual stress drops (100 to 1 bar) corresponds to a\nShear Waves From Earthquakes,\" Journal of Geophysical\nrange in fractional stress drop (100 to 1 percent, re-\nResearch, Vol. 75, No. 26, Sept. 10, 1970, pp. 4997-5009.\nspectively) (See: Note Added in Proof.) Our data\nBrune, James N., \"Correction,\" Journal of Geophysical Re-\nand interpretations are consistent with Trifunac's\nsearch, Vol. 76, No. 20, July 10, 1971, p. 5002.\n(1972) results for the main shock and 13 large after-\nDouglas, Bruce M., and Ryall, Alan, \"Spectral Characteristics\nand Stress Drop for Microearthquakes Near Fairview Peak,\nshocks.\nNevada,\" Journal of Geophysical Research, Vol. 77, No. 2,\nNote Added in Proof: Recent experiments with\nJan. 10, 1972, pp. 351-359.\nspontaneous dislocations in foam rubber models sug-\nHanks, Thomas C., and Thatcher, Wayne R., \"A Graphical\ngest another explanation for the apparent low stress\nRepresentation of Seismic Source Parameters,\" Journal of\ndrops. Many of the slips in foam rubber models are\nGeophysical Research, Vol. 77, No. 23, Aug. 10, 1972,\nmultiple events along essentially the same slip sur-\npp. 4393-4405.\nface, causing the overall time function to be con-\nHanks, Thomas C., and Wyss, Max, \"The Use of Body-Wave\nSpectra in the Determination of Seismic-Source Parameters,\"\nsiderably longer than for single events. This tends\nBulletin of the Seismological Society of America, Vol. 62,\nto shift the corner frequency to lower values than\nNo. 2, Apr. 1972, pp. 561-589.\nwould be observed for a single event, thus giving\nKasahara, K., \"The Nature of Seismic Origins as Inferred\nerroneously large estimates of source dimension and\nFrom Seismological and Geodetic Observations,\" Bulletin\nerroneously low estimates of stress drop (propor-\nof the Earthquake Research Institute, Vol. 35, Part 3,\ntional to the inverse cube of the estimated source\nTokyo, Japan, Sept. 1957, pp. 473-530.\nPress, Frank, \"Dimensions of the Source Region for Small\ndimension) Further study is necessary to determine\nShallow Earthquakes,\" Proceedings of the VESIAC Con-\nif such a mechanism is common in natural earth-\nference on the Current Status and Future Progress for\nquakes.\nUnderstanding the Source Mechanisms of Shallow Seismic\nEvents in the 3 to 5 Magnitude Range, La Jolla, California,\nACKNOWLEDGMENTS\n22-24 March 1965, Willow Run Laboratories of the Institute\nof Science and Technology, University of Michigan, Ann\nThe authors are particularly indebted to Don\nArbor, Feb. 1967, pp. 155-163.\nMiller who developed and maintained the recording\nSavage, James C., \"Relation of Corner Frequency to Fault\nsystem and to Dick Haubrich who gave critical ad-\nDimensions,\" Journal of Geophysical Research, Vol. 77,\nvice on spectrum analysis and statistics. Rob Wesson\nNo. 20, July 10, 1972, pp. 3788-3795.\n(USGS) and Tom Hanks and Jim Whitcomb (C.I.T.)\nTrifunac, Mihailo D., \"Stress Estimates for the San Fernando,\nprovided the locations and origin times of after-\nCalifornia, Earthquake of February 9, 1971: Main Event\nand Thirteen Aftershocks,\" Bulletin of the Seismological\nshocks in figure 2; Gabette Hamlin assisted in data\nSociety of America, Vol. 62, No. 3, June 1972, pp. 721-750.\nreduction and preparation of figures; Bob Winsett\nWyss, Max, \"Observation and Interpretation of Tectonic\ndrafted the figures; Terry Barker wrote the computer-\nStrain Release Mechanisms,\" Ph. D. thesis, California Insti-\nsearch program; and Irma Lieras and Elaine Black-\ntute of Technology, Pasadena, 1970, 239 pp.","Source Parameters for Aftershocks\n121\nWyss, Max, and Brune, James N., \"Seismic Moment, Stress,\nWyss, Max, and Hanks, Thomas C., \"The Source Parameters\nand Source Dimensions for Earthquakes in the California-\nof the San Fernando Earthquake Inferred From Teleseismic\nNevada Region,\" Journal of Geophysical Research, Vol. 73,\nBody Waves,\" Bulletin of the Seismological Society of\nNo. 14, July 15, 1968, pp. 4681-4694.\nAmerica, Vol. 62, No. 2, Apr. 1972, pp. 591-602.","","Increased Seismic Shaking\nAbove a Thrust Fault\nINTRODUCTION\nThe San Fernando earthquake involved some of\nthe highest intensity of seismic shaking ever re-\ncorded. The high intensity of shaking also was shown\nin building failures (Steinbrugge et al. 1971), shat-\ntered earth (Nason 1971), and other unusual effects\nCONTENTS\n(Morrill 1971) . Most, if not all, of the high-intensity\nPage\nshaking occurred to the north of and above the\n123 INTRODUCTION\nnorth-dipping earthquake thrust fault (U.S. Geologi-\n123\nSEISMIC SHAKING\ncal Survey and the National Oceanic and Atmos-\n123 INTERPRETATION\npheric Administration 1971). This paper presents\n124\nASYMMETRIC ELASTIC-STRAIN RELEASE\ntwo possible mechanisms that would produce in-\n124\nMULTIPLE REFLECTION OF SEISMIC\ncreased seismic shaking above an earthquake thrust\nWAVES\n124 CONCLUSIONS\nfault.\n126\nREFERENCES\nSEISMIC SHAKING\nIn the San Fernando earthquake, very strong\nseismic shaking occurred in the region north of the\nsurface fault traces. This shaking produced: record\naccelerations, exceeding 1g at the Pacoima strong-\nmotion instrument (Maley and Cloud 1971) ; very\nheavy damage to some buildings and highway con-\nstruction; and marked surficial geologic effects such\nas landslides, widespread soil cracking, and shattered\nearth (Nason 1971 and Barrows et al. 1971) as well\nas multiple-surface thrust faults. The shattered-earth\neffects are particularly impressive, for they indicate\nseismic shaking strong enough to destroy the internal\nstructure of competent soil (figs. 1 and 2) The shat-\ntered-earth effects suggest a possible seismic Modified\nMercalli intensity XII in very localized areas. These\neffects occurred over a wide area north of the surface\nfault traces (fig. 3) , almost always on the tops of\nlocal ridges.\nINTERPRETATION\nROBERT NASON\nThe earthquake was generated by north-side up-\nEarthquake Mechanism Laboratory\nward movement on a north-dipping thrust fault\nEnvironmental Research Laboratories, NOAA\n123","San Fernando Earthquake of 1971\n124\nplacement above the thrust fault is because the verti-\ncal movement of the upper block is not confined at\nthe ground surface, while the lower block is tightly\nconfined by other rock at its lower edge. This com-\npares with a partial confinement of movement on a\nstrike-slip fault (confined by undisplaced rock at ei-\nther end of the active fault segment) Asymmetric\ndisplacement on the San Fernando thrust fault is\nshown well by leveling data (Burford et al. 1971).\nBecause the movement of the upper fault block is\nnot confined, the upper fault block will have much\nmore complete elastic-strain relief than the lower\nfault block or a strike-slip fault block. As the seismic\nwave energy is produced by the release of elastic-\nFigure 1.-Shattered earth effect at Wallaby Street, Sylmar.\nstrain energy, the greater elastic-strain relief above\nCollapsed unfinished houses in background.\nthe thrust fault will mean production of more\nseismic energy per unit of rock volume. This, in\nturn, will mean more energetic seismic waves above\nthe thrust fault and, thus, increased seismic shaking\nabove the thrust fault as observed at San Fernando.\nThis mechanism would operate with any shallow\nearthquake thrust fault.\nMULTIPLE REFLECTION OF SEISMIC\nWAVES\nThe ground surface and the inclined thrust fault\nplane form a wedge shape for the upper fault block,\nwith the tip of the wedge at the surface fault trace.\nThis wedge shape might partially \"trap\" seismic\nwave energy and cause a concentration of seismic en-\nergy near the tip of the wedge. The thrust fault\nFigure 2.-Shattered earth effect at Wallaby Street, Sylmar.\nwould be a surface of at least partial reflection of the\nVeterans Administration Hospital is behind hill at upper left.\nseismic waves and perhaps total reflection during the\ndynamic fault movement. The seismic waves in the\n(U.S. Geological Survey and the National Oceanic\nblock above the thrust fault would reflect back and\nand Atmospheric Administration 1971). The region\nforth between the fault surface and the ground sur-\nof strongest seismic shaking was north of the surface\nface, as shown in figure 5. This multiple reflection\nfault traces and thus was above the north-dipping\nwill cause an increased amount of shaking at the\nthrust fault. Did the special conditions of thrust-fault\nground surface. The long duration of the strong\ngeometry and movement contribute to increased\nshaking in the Pacoima record may represent accu-\nseismic shaking above the inclined fault?\nmulation of trapped seismic-wave energy caused by\nmultiple reflection.\nASYMMETRIC ELASTIC-STRAIN RELEASE\nStudies of dislocation models of movement on in-\nCONCLUSIONS\nclined thrust faults have shown that the fault move-\nBoth the effects of unconfined elastic-strain release\nment is asymmetric, with greater displacement above\nthe thrust fault than below the fault (Savage and\nabove a thrust fault and of multiple reflection of\nHastie 1966), as shown in figure 4. The greater dis-\nseismic waves at the thrust fault may have contrib-","34°25'\n34°15'\n118°15'\nN\nFigure 3.-Map of shattered earth localities and surface fault traces, San Fernando earthquake (after Barrows et al. 1971).\n°0\nACCELEROMETER\nEPICENTER\n80\nPACOIMA\n8\nVeterans\nHospital\nOlive View\nHospital\nVan Norman\nDam\n118°30'","San Fernando Earthquake of 1971\n126\nuted to the high intensity of seismic shaking above\nREFERENCES\nthe north-dipping thrust fault at San Fernando.\nBarrows, A.G., Kahle, J.E., Weber, F.H., Jr., and Saul, R.B.,\nThese effects also might be expected to apply to\nMap of Surface Breaks Resulting From the San Fernando,\nother earthquakes caused by thrust fault movement\nCalifornia, Earthquake of February 9, 1971, Preliminary Re-\nanywhere in the world, for example, in Alaska\nport II, Plate I, California Division of Mines and Geology,\nSacramento, 1971, scale 1:24,000.\n(1964) or Assam in India (1897).\nBurford, R.O., Castle, R.O., Church, J.P., Kinoshita, W.T.,\nKirby, S.H., Ruthven, R.T., and Savage, James C., \"Pre-\nliminary Measurements of Tectonic Movement,\" The San\nFAULT\nFernando, California, Earthquake of February 9, 1971, Geo-\nEPICENTER\nTRACE\nUNCONFINED\nlogical Survey Professional Paper 733, U.S. Geological Survey\nGROUND SURFACE\nand the National Oceanic and Atmospheric Administration,\nU.S. Department of the Interior and U.S. Department of\nCommerce, Washington, D.C., 1971, pp. 80-85.\nMaley, R.P., and Cloud, W.K., \"Preliminary Strong-Motion\nResults From the San Fernando Earthquake of February\n9, 1971,\" The San Fernando, California, Earthquake of\nFebruary 9, 1971, Geological Survey Professional Paper 733,\nU.S. Geological Survey and the National Oceanic and At-\nmospheric Administration, U.S. Department of the Interior\nand U.S. Department of Commerce, Washington, D.C., 1971,\nFOCUS\npp. 163-176.\nMorrill, B.J., \"Evidence of Record Vertical Accelerations at\nKagel Canyon During the Earthquake,\" The San Fernando,\nFigure 4.-Diagram showing greater uplift and thus greater elastic-\nCalifornia, Earthquake of February 9, 1971, Geological Sur-\nstrain release in the block above a thrust fault (after Savage and\nvey Professional Paper 733, U.S. Geological Survey and the\nHastie 1966).\nNational Oceanic and Atmospheric Administration, U.S.\nDepartment of the Interior and U.S. Department of Com-\nmerce, Washington, D.C., 1971, pp. 177-181.\nNason, Robert D., \"Shattered Earth at Wallaby Street, Sylmar,\"\nS\nN\nThe San Fernando, California, Earthquake of February 9,\n1971, Geological Survey Professional Paper 733, U.S.\nPACOIMA\nFAULT\nTRACE\nGeological Survey and the National Oceanic and Atmos-\nEPICENTER\nDAM\npheric Administration, U.S. Department of the Interior and\n45\nU.S. Department of Commerce, Washington, D.C., 1971,\npp. 97-98.\nSavage, James C., and Hastie, L.M., \"Surface Deformation\nAssociated With Dip-Slip Faulting,\" Journal of Geophysical\nResearch, Vol. 71, No. 20, Oct. 15, 1966, pp. 4897-4904.\nSteinbrugge, Karl V., Schader, E.E., Bigglestone, H.C., and\nWeers, C.A., San Fernando Earthquake, February 9, 1971,\nPacific Fire Rating Bureau, San Francisco, Calif., 1971, 93\npp.\nU.S. Geological Survey and the National Oceanic and At-\nmospheric Administration (Publishers), The San Fernando,\nFOCUS\nCalifornia, Earthquake of February 9, 1971, Geological Sur-\nvey Professional Paper 733, U.S. Department of the Interior\nFigure 5.-Seismic-wave paths from earthquake focus, with reflection\nand U.S. Department of Commerce, Washington, D.C., 1971,\nat ground surface and thrust fault, showing difference of seismic-\n254 pp.\nwave intensity on each side of fault.","Map of Surface Breaks Resulting\nFrom the San Fernando, California,\nEarthquake of February 9, 1971\nINTRODUCTION\nOn February 9, 1971, at 6:01 a.m., PST, an earth-\nCONTENTS\nquake of magnitude 6.6 [6.4] struck the Sylmar-San\nPage\nFernando area of southern California. Geologists\n127\nINTRODUCTION\nfrom the California Division of Mines and Geology\n128\nMAJOR ZONES OF SURFACE FAULTING\ncommenced field investigations at once. Preliminary\n128\nSanta Susana Fault Zone\n128\nSan Fernando Fault Zone\nresults, based on reconnaissance, were published by\n128\nMission Wells and Sylmar\nKahle and others (1971) shortly after the earth-\nsegments\nquake, as were results obtained by other organiza-\n129\nTujunga segment\n130\nLakeview segment\ntions (Kamb and others 1971; U.S. Geological Sur-\n131\nADDITIONAL SURFACE FAULTING\nvey Staff 1971)\n131\nSURFACE EFFECTS IN OTHER AREAS\nCalifornia Division of Mines and Geology staff\n131\nJuvenile Hall and Upper Van\nbegan detailed field mapping of the geology, includ-\nNorman Lake area\n132\nOlive View Hospital area\ning surface effects, immediately after the initial\n132\nSouthwestern Sylmar area\nreconnaissance. Information obtained through August\n132\nSouthwestern San Fernando area\n133\nGranada Hills area\n1971 is given in this report.\n133\nSURFACE EFFECTS OF MARCH 31 AFTER-\nThe following discussion includes sections on sur-\nSHOCK\nface faulting, surface effects other than faulting, the\n133\nSHATTERED RIDGE TOPS\n133\nTRENCHES ACROSS SURFACE BREAKS\nGranada Hills aftershock of March 31, 1971, and\n134 REFERENCES\nfindings from a series of backhoe trenches dug across\nsurface features. No attempt has been made to in-\nPrepared in cooperation with the Los Angeles\nclude landslide and cutbank failure information on\nCounty Engineer and the Los Angeles County\nthis map except in the area of the Juvenile Hall. For\nFlood Control District. Initially published in\n1971; reprinted by permission of California\ndiscussions of landsliding see Morton (1971a; 1971b)\nDivision of Mines and Geology. Map of sur-\nand Youd (1971) Although most of the surface\nface breaks is in pocket inside back cover.\ngeologic effects of the earthquake are found within\nthe area of this map, minor landsliding and forma-\ntion of settling cracks did occur elsewhere. Informa-\ntion about geological structures or stratigraphic units\nA. G. BARROWS\nreferred to in the following discussion can be found\nJ. E. KAHLE\non the Los Angeles Sheet of the Geologic Map of\nF. H. WEBER, JR.\nCalifornia (Jennings and Strand 1969) or in reports\nR. B. SAUL\nby Oakeshott (1958) and Wentworth and others\nCalifornia Division of Mines and Geology\n(1971)\nSacramento, Calif.\n127","San Fernando Earthquake of 1971\n128\nTo the southwest of the freeway and beyond an\nMAJOR ZONES OF SURFACE FAULTING\nancient landslide (3), the fault break is clearly de-\nAt any given locality it may be difficult to dis-\nfined. For example, a line on the road to St. Vincent\ntinguish surface breaks due to faulting from those\nde Paul Camp was displaced left laterally about 12\ndue to other causes such as lurching, differential set-\ninches (30 cm) (4). From this area the trace of\ntling, landsliding, or shaking. The criteria used to\nground rupture extends west-northwest toward Bee\nidentify surface faulting are primarily continuity\nCanyon where it seems to be absorbed along the\nand linearity of fracture, displacement of rock units,\nstrike of bedding, and where abundant shattered\nand fresh movements along bedding planes in sedi-\nridges and landslides may have obscured fault move-\nmentary rocks. When the surface evidence is in un-\nment (5).\nconsolidated material, the most common case, the\nmost important characteristic is continuity combined\nSan Fernando Fault Zone\nwith any or all of the other criteria.\nThe San Fernando fault zone, as designated by the\nSurface faulting during the earthquake extended\nU.S. Geological Survey (U.S. Geological Survey Staff\nfrom the Bee Canyon area of the Santa Susana Moun-\n1971) was divided by the Survey into these segments\ntains eastward across the Sylmar-San Fernando area\nwhich are, from west to east: Mission Wells, Sylmar,\nof the northern San Fernando Valley to Big Tujunga\nand Tujunga segments. That portion of the San Fer-\nWash in Sunland. The major surface breaks are\nnando fault zone between Little Tujunga and Big\nexpressions of thrust faulting whereby land on the\nTujunga Canyons, formerly considered part of the\nnorthern side was lifted above that on the south and\nTujunga segment, is herein renamed the Lakeview\nshoved or thrust obliquely toward the southwest. The\nsegment because it coincides with the Lakeview thrust\nfollowing is a discussion of the major zones of fault-\nfault (Proctor 1970), making a total of four seg-\ning proceeding from west to east across the area. The\nments considered in this report.\nzones include the Santa Susana fault zone in the Bee\nCanyon-San Fernando Pass area and the San Fer-\nMission Wells and Sylmar segments\nnando fault zone.\nThe Mission Wells segment strikes north-northeast\nSanta Susana Fault Zone\nfrom Osceola School, bends northeastward, and ex-\nRelatively small, left-lateral displacement occurred\ntends to a point in alluvium about half a mile\nalmost continuously along the principal fault of this\n(0.8 km) from the southwest end of the Sylmar seg-\nzone for about 1.5 miles (2.4 km), from the San\nment. At least part of this gap between the two\nFernando Pass area on the northeast to Bee Canyon\nsegments is marked by a slight, south-facing break in\non the southwest. The fault break is mostly in un-\nslope, suggesting an older fault scarp (6). The al-\ndeveloped land and damage along it was restricted\nluvium in the gap area is deeper (45 feet\nmainly to the Golden State Freeway (including Bal-\nthan to the west and east, as described by the Cali-\nboa Boulevard bridge) and several power lines and\nfornia State Water Rights Board (1962), which\nnamed this underground feature the Sylmar notch.\ntowers.\nAbout 300 feet (92 m) northeast of the freeway,\nProbably much of the earthquake energy from the\nthe fault is well exposed (1), with left oblique dis-\nfault below was dissipated into this relatively deep\nplacement of 3 to 4 inches (8 to 10 cm) here the\nalluvium before it reached the surface. As a result of\nfault dips about 20° northwest, with nearly vertical\nthe earthquake, elevations increased to the north of\nbeds of the lower Sunshine Ranch Member of the\nthe gap relative to the south just as they did relative\nSaugus Formation overlying younger, gently south-\nto the active segments according to measurements of\neast-dipping beds of the upper unnamed member of\nBurford and others (1971, p. 81).\nthe Saugus Formation. To the southwest, along the\nLeft-lateral offset, shortening, and downthrow on\nfreeway (2), abundant ground and concrete cracks\nthe south side occurred along the Mission Wells seg-\nsuggest several smaller faults parallel to the Santa\nment but are less pronounced than along the Sylmar\nSusana fault, at least one with left-lateral offset.\nsegment, as was the damage. The Mission Wells seg-\nment is best exposed along a cut in back of houses\n1 Bold numbers identify locations of surface breaks shown as\non the northwest side of Osceola Street (7), where\ncircled numbers on Map of Surface Breaks in pocket insert.","Map of Surface Breaks\n129\nof the segment, strata dip about 35° north. Indicative\nit seems to dip 50° to 60° northwest. Just southeast\nof previous very late Pleistocene or Holocene fault\nof here, moderately south-dipping strata, probably of\nmovement in the immediate area, but inactive in the\nthe Modelo Formation of late Miocene age, are ex-\npresent earthquake, is a nearly vertical fault exposed\nposed. Their presence here suggests left-lateral dis-\non Gladstone Street 200 feet (61 m) north of the\nplacement of perhaps 1,200 feet (360 m) or more of\nprincipal break. Here, older alluvium is faulted down\nthe contact between Modelo Formation and younger\nat least 2 feet cm) to the south against Towsley (?)\nTertiary rocks to the west. Some activity is implied\nFormation. Similar faults are exposed to the west\non this segment during the March 31 aftershock, as\nalong the cuts of the Foothill Freeway-one of which,\na tension crack just west of the fault on Osceola\nhaving a total reverse offset of 50 feet (15 m) or\nStreet opened considerably wider at that time.\nmore, was active during the earthquake.\nThe Sylmar segment of the San Fernando fault\nAbout a quarter mile (12) north of the\nzone represents perhaps the most spectacular surface\nSylmar segment, in the vicinity of Harding School\nexpression of tectonic activity in the entire earth-\nand Alta Mesa Convalescent Hospital (formerly\nquake region. Cracks and welts in asphalt parking\nHighland Sanitarium), is an area of faults and\nlots and streets, mole tracks in lawns, and other fea-\nground cracks in older alluvium. The breaks trend\ntures of breaking and twisting of structure extend\nessentially east, parallel to the strike of the bedding\nnortheast in alluvial deposits from the southeast side\nof the Saugus Formation that is exposed nearby\nof Hubbard Street opposite the former Carewell\nbeneath thin, older alluvium. The faults are com-\nConvalescent Hospital (now called The Gables),\nmonly slightly right lateral and down slightly on the\nthrough the severely damaged commercial area (in-\nnorth; they extend east toward Lopez Dam but are\ncluding Boys Market, now razed) along Glenoaks\nobscure there. The dip of the faults was not deter-\nBoulevard (8). The segment continues northeast as\nmined, but may be along bedding planes of the\na zone or swath as much as 1,200 feet (360 m) wide,\nSaugus Formation, which dips about 70° north. Dam-\nwith severe damage to many houses in Sylmar and\nage to structures in the area was minor to moderate.\nSan Fernando. It bends gently almost due east, and\ncontinues to Foothill Boulevard where a modern\nTujunga segment\napartment building (now razed) was severely dam-\nThe surface features that comprise the Tujunga\naged, and extends spectacularly across the Foothill\nfault segment extend from the vicinity of the San\nFreeway (9). From here the segment narrows, and\nFernando Industrial Park (13) eastward along Foot-\nextends along the base of a low hilly area, across the\nhill Boulevard where, just east of Vaughn Street, the\nconcrete channel in Pacoima Wash, and bends south-\nnortheast sidewalk and curb were lifted abruptly\neast along the base of a ridge of the foothills east of\nseveral feet relative to the pavement (14). The\nSylmar where it apparently dies out. Projected south,\nbreaks continue across the mouths of Lopez, Kagel,\nthe segment would extend toward the Tujunga seg-\nand Little Tujunga Canyons and disappear near the\nment and probably comes to the surface in the San\nmouth of Cassara Canyon. In some places (15) (16)\nFernando Industrial Park (10).\nthe breaks of the Tujunga segment define a single,\nWhere exposed by trenches, the dip of the fault\ncontinuous fault-line scarp, whereas in other places\ngenerally is obscure because of the relatively poorly\nthe segment consists of numerous, interrupted, locally\nconsolidated nature of the material cut by the fault\nmultiple (17), scarps and cracks that very closely\nat the surface, even where trenches cut prominent\napproximate the change in slope at the base of the\nsouth-facing scarps; but, in one backhoe trench just\nfoothills. Asymmetrical compression ridges and mole\nnortheast of the Foothill Freeway (T13) a crushed\ntracks are the southernmost surface features of the\nzone implies a dip of 52° north on the fault. To the\nthrust faulting. Abundant tensional cracks and high-\neast of this locality, the segment strikes essentially\nangle fault scarps are common immediately north of\nparallel to the bedding of the Towsley (?) Formation\nexposed locally just north of the segment; and the\nthe thrust-fault scarps.\nAn average of five measurements of the approxi-\ndip of the fault segment may be similar to the dip of\nmate amount of shortening across the thrust fault in\nthese rocks. On Gladstone Street (11), about 100\nthe orange groves of Middle Ranch (16) is 3.6 feet\nfeet (30 m) northwest of the segment, strata dip\n(1.1 m) The lateral component of slip for faults\nabout 55° to 60° north; and, very near the east end","130\nSan Fernando Earthquake of 1971\nof the Tujunga segment is predominantly left-lateral\ncrosses ridge tops, hillsides, and canyon bottoms.\n(18) (19) (20).\nLandslide complications along the trace at first led\nThe scarps of the Tujunga segment attain their\nus and other workers in the area (U.S. Geological\ngreatest height, exceeding a yard (1 m), near the\nSurvey Staff 1971, p. 71) to discount the possibility\nwestern end (14). In general, the scarp is between\nof fault movement here. However, detailed mapping\n16 inches (40 cm) and 20 inches (50 cm) high over\nof the surface effects has indicated that significant\nthe most continuous stretches and it diminishes to-\nmovement did indeed occur on the Lakeview seg-\nward the east.\nment with as much displacement as measured on the\nThe low-angle dip, ranging from 10° north to 40°\nother segments of the San Fernando fault zone.\nnorth, can be observed where the trace of the thrust\nSome imbricate or sympathetic movement can be\nfault crosses stream canyons (21) (22) (23). Accu-\ndetected below the main trace between the breccia\nrate, near-surface measurement of the attitude of the\nunit and the boulder gravel (27) and in a few places\nfault plane was made in several trenches (T3) (T4)\nthere seems to have been differential movement of\n(T8) A few feet beneath the surface the fault plane\nthe rocks on adjacent blocks above the thrust (28).\nparallels the bedding in the Modelo shale, sandstone,\nAn accumulated horizontal thrust component of at\nand siltstone but flattens out to horizontal (T8) or\nleast 1,450 feet (442 m) can be measured on the\neven slightly south-dipping (T4) where details were\nfault near Oliver Canyon. The age of the alluvial\nrevealed in trenches. Slickensides bearing N. 50°E.\ngravel under the thrust is not known. However, this\nplunge 22° N. on clayey layers (T8) that coincide\nmuch displacement could have taken place in 25,000\nwith the fault plane.\nto 70,000 years from a series of similar earthquakes\n(4- to 6-ft displacement) occurring at intervals of\nLakeview segment\n100 to 200 years.\nIn the coarse alluvium of Big Tujunga Wash the\nSurface breaks along the Lakeview segment can be\nscarps locally resemble erosional cut banks but the\ntraced eastward from the ridge west of Kagel Canyon\ncontinuity of the trace which traverses sand deposits,\nto the northernmost scarp across Little Tujunga\ngravel deposits, bulldozer cuts (29), bridle trails, and\nCanyon and with some discontinuity through the\nfoothills, across Cassara, Oliver, and Schwartz Can-\nvegetation covered areas (30) of the flood plain\nmakes it easy to follow. Cracks occurred in soft sand\nyons about 1,400 feet (0.41 north of their mouths\nand soil along the trace and debris fell down the face\nto Big Tujunga Wash. Scarps can be followed for an\nadditional 1.5 miles (2.4 km) in the alluvium of\nof the scarp. Considerable ponding of the alluvium\nhas occurred where the fault crosses the stream (31).\nthe wash.\nFrom Kagel Canyon the surface trace can be fol-\nAt the base of the cliff near the mouth of Ebey\nlowed eastward as far as the east side of Little Tu-\nCanyon (26) a scarp with a vertical displacement of\njunga Canyon where it dies out at the base of the\nabout 3 feet (1 m) and vertical slickensides formed\nhills. Where exposed by a small slide just to the west\nbetween bedrock and the alluvium. Caving obliter-\nof Little Tujunga Road (23), the trace shows shale\nated much of this evidence within three months after\nof the Modelo Formation lying on top of uncon-\nthe earthquake. The scarp can be traced farther east-\nsolidated bouldery cobble gravel. These units are in\nward through the alluvium to where there was a\nfault contact and, although the fault did move in\nleft-lateral displacement of about 3 feet (1 m) on\nthis earthquake, it did not move an amount sufficient\nOro Vista Avenue. The vertical component of move-\nto account for the total thrust component of at least\nment is much less here than farther west and appears\n12 feet (3.8 which can be measured here.\nto decrease eastward. A bedding-plane fault is visible\nThe fault trace can again be found on the first\non the north side of the hill on which Bill Lane\nridge east of Little Tujunga from where it can then\nCamp is situated (32).\nbe traced with some confidence to Big Tujunga\nSeveral kinds of evidence have been found which,\nWash. In this stretch of the fault, the surface traces\nwhen considered together, substantiate movement on\nare much more continuous than the gaps.\nthe Lakeview segment. Firstly, the well-defined sur-\nMovement has taken place on a fault plane that\nface trace is nearly continuous, and surface displace-\ndips northward from nearly horizontal in some places\nment is consistent on ridge tops and in canyon\n(25) to 60° in others (26). The sinuous fault trace\nbottoms-always up on the north. However, old","Map of Surface Breaks\n131\nthe greatest vertical offset (41) (42) along ridge\nlandslides and thick accumulations of slope wash\ncrests whereas there was commonly no surface rup-\nhave masked the surface trace along some hillsides.\nture in the canyon bottoms except in Bartholomaus\nSecondly, distinctive landslides, restricted to the\nCanyon (43). On Kagel Mountain (44), west of\ntrace, occurred at the time of the earthquake (33)\nCassara Canyon (40), and along Yerba Buena Ridge\n(34). Shale of the Modelo Formation was thrust out-\n(45) faults developed that appear to displace bed-\nward on the slope enough to drop as rockfalls. Debris\nrock and cross ridge tops with the displacement up\nand dust partially cover the slope below the trace,\non the downslope side. The scarps (40) west of\nsimulating \"skin-type\" slides or soil failures. Com-\nCassara Canyon may be related to an adjacent ancient\nmonly, the slope below the break is undisturbed\nalthough, in some places, the material both above\nlandslide.\nand below the thrust plane has been exposed.\nWest-southwest of the Mission Wells segment lies\nThirdly, the rock unit under the thrust is in some\na zone of faulting which damaged the Golden State\nplaces a breccia and elsewhere is a mixture of breccia\nand San Diego Freeways. On the west end of the\nand alluvium. The breccia consists exclusively of\nzone, the fault activity may have extended into frac-\nangular chips and debris derived from the Modelo\ntured, clayey beds which dip south and strike west-\nFormation. In the mixed unit the breccia is similar\nsouthwest into the lake area (46). Faults mapped in\nand the alluvium consists of layers of interbedded\nthis area previously by Oakeshott (1958) and others\nwell-rounded pebbles and sand grains. Weathering\nhave been projected toward Lower Van Norman\nhas changed the appearance of the breccia unit and\nDam.\nthe shales above the fault plane since the earthquake.\nTo the northwest (47) are two fault breaks, nu-\nThe color contrast has been enhanced-the shale\nmerous ground cracks, cracks in the Golden State\nturning dark brown and the breccia nearly white or\nFreeway, and shaking effects. The faults and ground\nlight gray. Under the breccia unit there is an older\ncracks mainly strike west-northwest, parallel to the\nalluvial unit consisting of unconsolidated, horizon-\nstrike of bedding in the Saugus Formation, whose\ntally bedded, boulder conglomerate, greater than 30\ndip ranges from 25° to 60° northeast.\nfeet (10 m) thick, with well-rounded clasts derived\nfrom the basement complex of the San Gabriel\nSURFACE EFFECTS IN OTHER AREAS\nMountains.\nJuvenile Hall and Upper Van Norman Lake area\nADDITIONAL SURFACE FAULTING\nConsiderable ground cracking and damage OC-\ncurred in the area from Van Gogh School eastward\nFaults other than thrusts also were active during\nbeyond the San Fernando Valley Juvenile Hall, a\nthe earthquake at places away from the major zones\ndistance of nearly 2 miles (3 km) The cracks occur\nof thrusting. A type of fault in which the dip and\nmostly in deposits which range from sand to fine\nstrike of the fault parallel the dip and strike of en-\nsand and gravel, and to a lesser extent in fill. The\nclosing strata is known as a bedding-plane fault. It is\narea overlies the Olive View fault as projected south-\nexemplified by the Veterans fault (35) (Kamb and\nwest through the area from exposures northeast of\nothers 1971, p. 51) and by the Oak Hill fault (T1)\nOlive View by Merifield (1958, plate 1) it also\n(Kamb and others 1971, p. 48) in Lopez Canyon\noverlies the projected northeast trace of the Mission\nwhere a very prominent, partly overhanging, 32-inch\nHills syncline shown by Oakeshott (1958, plate 1)\n(80 cm) scarp was formed. In these examples the\nand by Merifield (1958, plate 1) None of the cracks\nnorth side moved up in north-dipping strata. Else-\ncan be attributed directly to faulting although at\nwhere (36) (37) the north side moved down in\ndepth beneath alluvium faulting may have been a\nnorth-dipping strata by amounts equal to or greater\nfactor; no major activity occurred on northeast-\nthan south-side-down faults.\ntrending faults where they are exposed northeast of\nSeveral faults that transect bedding also moved\nOlive View (48). The cracking was attributed by\nduring the earthquake (38) (39) (40). The Kagel\nYoud (1971, pp. 105-109) to sliding along water-\nfault (Hill 1930) was active over a stretch 1.75 miles\nsaturated layers near the ground surface within the\n(2.8 km) long. The surface breaks along the trend\ngeneral area where the water table is high. Such\nof the Kagel fault are not continuous and exhibit","132\nSan Fernando Earthquake of 1971\nlayers subsequently were exposed in backhoe trenches\nslides on steeper slopes occurred on the low hill in\ndug at the Juvenile Hall (49), which was severely\nthe northeast corner of the Olive View grounds.\ndamaged by sliding as well as by shaking. The Juve-\nSlides occurred in fill used for the Foothill Freeway\nnile Hall slide extends southwest toward Upper Van\nsouth of the grounds. A west-northwest trending\nNorman Lake and also includes the Southern Pacific\nzone of relatively strong street and ground cracks ex-\nrailroad tracks, which were dramatically bent, a por-\ntends 1 mile (1.6 km) or more southeast of the\ntion of the Golden State Freeway, and also the\nhospital area. The cracks are mostly displaced down\nstrongly shaken Pacific Intertie Terminal (50).\non the south and may have resulted from movement\nSevere sliding also occurred all around the edges of\nalong a fault here (59).\nthe northern part of Upper Van Norman Lake (51).\nLandslide-type cracks also occur in the heavily dam-\nSouthwestern Sylmar area\naged Van Gogh School area and for about half a mile\nAdditional ground and asphalt cracks occur in the\nto the north-northeast (52); also to the east in the\narea of the heavily damaged Sylmar Industrial Park\nfill for the Jensen Filtration Plant (53); and directly\nand the El Dorado Avenue School (60). Most of the\nnorth of the Juvenile Hall area and probably to the\ncracks are in asphalt streets, parking lots, and the\nnorth-northeast for about half a mile (54), although\nschool playground, but some extend into the allu-\nthese latter cracks might be attributed to faulting,\nvium, especially just northeast of San Fernando Road\nas they are aligned in a north-northeast to northeast\n(60). Northeast of Herrick Avenue lies a well-defined\ndirection. Such landslide-type cracks also occur at\nbut relatively weak fault break which trends north-\nlocality (55), where two houses were severely dam-\nwest (T14)\naged. Cracks possibly attributable to landsliding are\nOne relatively prominent crack, formed at the time\nin the area around locality (56). One section of the\nof the earthquake, cuts across Roxford Street (61).\nGolden State Freeway and a northeastern part of\nThere are other parallel, west-northwest trending\nLower Van Norman Lake also may have slid (57).\ncracks, mostly from just south of Bradley Avenue to\nJust southeast of Upper Van Norman Dam, a\nabout midway to Herrick Avenue; these all seem to\ntrench for a water line exposed two fairly strong re-\npredate the earthquake, though some were active\nverse faults offsetting the contact between Saugus\nduring the event.\nFormation and Pacoima Formation (older allu-\nvium ?) of late Pleistocene age; apparently they were\nSouthwestern San Fernando area\nnot active during the February 9 earthquake (58).\nSome street and ground cracks, trending mostly\neast, are in the western part of San Fernando. Dam-\nOlive View Hospital area\nage here occurred especially to older houses and to\nSevere tensional and compressional cracking of\nsome churches (62). The area, underlain by older (?)\nasphalt roads and parking lots occurred on the\nalluvium, is approximately at the projected, con-\ngrounds of the Olive View Hospital; very few co-\ncealed junction of the Mission Wells fault from the\nincided with significant ground cracks. The most\nnorth, the Mission Hills fault from the west, and the\nsevere ground cracks occurred around the founda-\nVerdugo fault from the southeast (as shown on the\ntions of the new main hospital building or were\nLos Angeles Sheet of the Geologic Map of Cali-\nassociated with the Los Angeles Department of Water\nfornia) To the southeast, the hills at Jessup Park\nand Power Maclay Aqueduct which traverses the\nwere examined but no fault activity could be seen\nground from west to east. All cracks appear to be the\n(63). To the west (64) only surficial pavement\nresult of severe shaking in soft alluvium which is\ncracking occurred above the projected trace of the\nknown from borings to be greater than 40 feet\nMission Hills fault, though considerable damage OC-\ndeep. Cracking could not be ascribed directly\ncurred at Alemany High School, Holy Cross Hospital,\nto faulting although the possibility that faulting OC-\nand at the new Indian Hills Medical Center build-\ncurred at depth cannot be discounted and it may\ning. The high school was also damaged during the\nhave contributed to the severity of the shaking in\nMarch 31 aftershock. New cracks also opened then\nthis area. One very low-angle slide was seen in allu-\nat the corners of the sidewalks at the base of the\nvium or fill in the center of the grounds and some\nRinaldi Street overpass of the San Diego Freeway at","Map of Surface Breaks\n133\nlayers of the Saugus Formation, it is almost absent at\nRinaldi Street. In the downtown shopping area of\nthe contact immediately east and west of Kagel\nSan Fernando (65), intense damage is attributed to\nshaking of older buildings on alluvium, as only sur-\nCanyon (72).\nficial cracking in pavement occurred.\nTRENCHES ACROSS SURFACE BREAKS\nGranada Hills area\nBrief descriptions of the findings in 15 backhoe\nIn the area of Granada Hills west of Lower Van\ntrenches logged by the California Division of Mines\nNorman Lake and, generally along Balboa Boulevard,\nand Geology in cooperation with F. Beach Leighton\nmany houses were damaged (66). Here ground crack-\n& Associates are listed below. Logs of the trenches\ning cannot be related to faulting. The cracks are\nwere made by E. G. Heath and R. H. Dickey of F.\nmainly along or near contacts of fills with bed-\nBeach Leighton & Associates, who independently\nrock (67).\ndug Trench 1, and by J. E. Kahle and A. G. Barrows\nof the Division of Mines and Geology. Logs of the\nSURFACE EFFECTS OF MARCH 31\ntrenches may be consulted in the Los Angeles office\nAFTERSHOCK\nof the Division of Mines and Geology.\nThe impact of the damaging March 31 after-\nshock was most severe in the vicinity of Rinaldi\nTrench 1: Lopez Canyon. Trench across the Oak\nStreet and Wilbur Avenue in Granada Hills (75),\nHill fault scarp. Bedding plane fault strikes\nalthough the epicenter of this event was reported to\nN. 75°W. and dips 62°N and is nearly coinci-\nbe about 2.5 miles (5 km) to the south-southeast.\ndent with attitude of sandstone, siltstone, and\nThe magnitude was 4.6 as reported by the California\nconglomerate strata. Displaced base of slope wash\nInstitute of Technology. Ground cracks opened in\nand alluvium is 32 inches (81 cm) down on the\nolder alluvium south of Rinaldi in the vicinity of\nsouth side.\nYolanda Avenue where two houses were severely\nTrench 2: Lopez Canyon. Trench across mole track\ndamaged; cracks opened between bedrock and fill\nof Oak Hill fault in unconsolidated fill and\nnorth of Rinaldi along Yolanda. In addition, some\nalluvium. Although surface is cracked no fault-\ncracks that opened during the February 9 earth-\ning was observed in the trench.\nquake were reactivated during this one. Surface\nTrench 3: Ridge north of Carl Street. Trench\neffects of the aftershock may lie along the general\nacross compression ridge exposed well-defined\ntrend of the Devonshire fault zone as mapped to the\nsingle fault plane that strikes east-west and dips\nnorthwest in bedrock and projected southeast be-\n44° N. and coincides with attitude of bedding.\nneath alluvium by Saul (1971)\nFault juxtaposes shale of the Modelo Formation\non the north over conglomerate with coarse\nSHATTERED RIDGE TOPS\nsandy matrix which may be an alluvial fan\ndeposit.\nSome ridge crests in the foothills have a striking\nTrench 4: Ridge west of Blue Star Trailer Court\n\"exploded\" appearance resembling plowed fields\nand north of Paxton Street. Trench across 2-foot-\nwhere the soil looks as if it had been heaved upward\nhigh (60 cm) scarp in soil exposed near-surface\nby a sharp blow from below. Such shattering is most\naspect of fault plane that separates debris of the\ncommon along those crests underlain by sandstone\nModelo Formation containing shale chips, peb-\nand conglomerate strata that have a soil cover com-\nbles, and cobbles on the north from old alluvium\nmonly less than 2 feet (60 cm) thick (68) (69) (70).\nwhich is poorly bedded. Fault plane dips north\nBetween Lopez and Little Tujunga Canyons shatter-\n15° near northern end of trench, bends over\ning is either localized along certain strata (71) (72)\nnear the surface, and dips shallowly southward.\nor concentrated where there is especially angular\nTrench 5: Pacoima Wash near Newton Street.\ntopography locally (73) (74). An excellent example\nTrench across 1-foot (30 cm) scarp of Sylmar\nof the latter is around Camp Karl Holton in Marek\nfault segment. Fault could not be seen in the un-\nCanyon. Elsewhere, shattering is localized along the\nconsolidated, bouldery alluvium. Caving limited\nuppermost sandstone layers of the Towsley (?) For-\nexposure to 4-foot (1.2 m) depth.\nmation. In the overlying coarser, clastic, sedimentary","134\nSan Fernando Earthquake of 1971\nTrench 6: Big Tujunga Wash, south of creek.\nface during formation of the sand boil. Its total\nTrench across 20- to 24-inch (50-60 cm) scarp\ndepth is unknown.\nin modern, flat-lying, bouldery alluvium. Di-\nTrench 12: Vacant lot at 12670 Gladstone Avenue,\nrectly beneath the surface offset, a jumbled zone\nSylmar. Trench across surface cracks aligned\ndips approximately 45° northward but coarse-\nwith fault scarps east and west of lot. No sig-\nness of material and lack of marker units made\nnificant breaks could be seen in the unconsoli-\nit difficult to determine whether or not faulting\ndated pebbly to bouldery conglomerate and\noccurred.\ninterlayered sand strata although strata appeared\nTrench 7: Big Tujunga Wash, north of creek.\nto bend to conform to surface warp or scarp.\nTrench across 15-inch (38 cm) scarp. Flat-lying\nTrench 13: North shoulder of Foothill Freeway,\nto shallowly south-dipping, sandy and bouldery,\nwest of Maclay Avenue. Trench across 1-foot (30\nmoist alluvial layers which are overlain by soil\ncm) east-west scarp or warp. Fault plane dipping\nand fill vaguely appear to be folded beneath\n52° could be traced as a zone of looser mate-\nscarp. May represent a dispersion of a discrete\nrial separating gravelly and cobbly deposits with\nfault plane in unconsolidated materials.\na reddish, sandy matrix on the north from adobe-\nTrench 8: Blue Star Trailer Court, west side of\nlike material of possible mudflow origin on the\nLopez Canyon. Trench across 2.3-foot (70 cm)\nsouth.\nscarp in graded bedrock surface. Movement dur-\nTrench 14: West side of Tyler Street, 200 feet\ning earthquake took place on two parallel fault\n(60 m) northeast of Herrick Avenue, Sylmar.\nplanes that coincide with the N.80° W. strike\nTrench across northwest-striking crack. Not pos-\nand 32°N. dip of bedding in Modelo siltstone\nsible to trace crack in loose trash and fill exposed\nand sandstone. Near the surface, however, the\nin walls of trench.\nnorthernmost fault plane bends over and be-\nTrench 15: West of road to St. Vincent de Paul\ncomes horizontal. Trench also exposed shallowly\nCamp, east of Bee Canyon. Trench across minor\ndipping, undisturbed fault contact between over-\ncracks possibly coinciding with the trace of the\nlying, highly contorted Modelo sandstone strata\nSanta Susana fault. Not possible to follow cracks\nand reddish-brown mudflow-like alluvial mate-\nin loose, powdery soil exposed in walls of trench.\nrial.\nTrench 9: San Fernando Valley Juvenile Hall\nREFERENCES\ngrounds. Trench across main trace of northern\nset of cracks in football field. Main crack could\nBurford, R.O., Castle, R.O., Church, J.P., Kinoshita, W.T.,\nbe traced in moist sandy and silty soil contain-\nKirby, S.H., Ruthven, R.T., and Savage, J.C., \"Preliminary\nMeasurements of Tectonic Movement,\" The San Fernando,\ning abundant roots to a depth of 5.5 feet (1.7 n\nCalifornia, Earthquake of February 9, 1971, Geological Sur-\nto the upper surface of a gravelly layer where it\nvey Professional Paper 733, U.S. Geological Survey and the\nappeared to stop. This may suggest that move-\nNational Oceanic and Atmospheric Administration, U.S.\nment took place along the surface of the gravelly\nDepartment of the Interior and U.S. Department of Com-\nlayer.\nmerce, Washington, D.C., 1971, pp. 80-85.\nTrench 10: San Fernando Valley Juvenile Hall be-\nCalifornia State Water Rights Board, \"City of Los Angeles\nVS. City of San Fernando, et al.,\" San Fernando Valley\ntween inner and outer compound. Trench across\nReference Report of Referee No. 650079, Superior Court,\ntrace of southern set of cracks. Main crack strikes\nLos Angeles County, Calif., Vol. I, 258 pp., 36 pls.; Vol. II,\nN. .0°W. and extends nearly vertically 9 feet\nvarious pages, July 1962.\n(2.75 m) to bottom of trench through layers of\nHill, M.L., \"Structure of the San Gabriel Mountains North of\nsilty sand, many with high organic content.\nLos Angeles, California,\" California University Publications\nin Geological Sciences, Vol. 19, No. 6, University of Cali-\nTrench 11: South of San Fernando Road opposite\nfornia Press, 1930, pp. 137-170.\nSan Fernando Valley Juvenile Hall. Trench in\nJennings, C.W., and Strand, R.G., Geologic Map of California,\nopen field across sand boil. Light brown, sand-\nOlaf P. Jenkins Edition, Los Angeles Sheet, California\nfilled crack could be traced 9 feet (2.75 m) from\nDivision of Mines and Geology, Sacramento, 1969, scale\ncenter of sand boil to bottom of trench in dark\n1:250,000.\nbrown silty sand. The filled crack represents the\nKahle, J.E., Barrows, A.G., Weber, F.H., Jr., and Saul, R.B.,\nfracture through which material traveled to sur-\n\"Geologic Surface Effects of the San Fernando Earthquake,\"","Map of Surface Breaks\n135\nProctor, R.J. (Compiler), \"Geologic Map and Sections Along\nCalifornia Geology, Vol. 24, No. 4-5, 1971, pp. 75-79.\nthe 4.4-Mile Sunland Tunnel,\" B-20262, Metropolitan\nKamb, Barclay, Silver, L.T., Abrams, M.J., Carter, B.A.,\nWater District of Southern California, Los Angeles, July\nJordan, T.H., and Minster, J.B., \"Pattern of Faulting and\n1970 (unpublished map, scale 1:12,000)\nNature of Fault Movement in the San Fernando Earth-\nSaul, R.B., \"Effects of the San Fernando Earthquake in the\nquake,\" The San Fernando, California, Earthquake of\nOat Mountain Quadrangle,\" California Geology, Vol. 24,\nFebruary 9, 1971, Geological Survey Professional Paper 733,\nU.S. Geological Survey and the National Oceanic and\nNo. 4-5, 1971, p. 83.\nU.S. Geological Survey Staff, \"Surface Faulting,\" The San\nAtmospheric Administration, U.S. Department of the In-\nFernando, California, Earthquake of February 9, 1971,\nterior and U.S. Department of Commerce, Washington,\nGeological Survey Professional Paper 733, U.S. Geological\nD.C., 1971, pp. 41-54.\nSurvey and the National Oceanic and Atmospheric Ad-\nMerifield, P.M., \"Geology of a Portion of the Southwestern\nministration, U.S. Department of the Interior and U.S.\nSan Gabriel Mountains, San Fernando and Oat Mountain\nDepartment of Commerce, Washington, D.C., 1971, pp.\nQuadrangles, Los Angeles County, California,\" M.A. thesis,\n55-76.\nUniversity of California, Los Angeles, 1958, 61 pp.\nWentworth, Carl M., Yerkes, R.F., and Allen, Clarence R.,\nMorton, D.M., \"Seismically Triggered Landslides Above San\n\"Geologic Setting and Activity of Faults in the San Fer-\nFernando Valley,\" California Geology, Vol. 24, No. 4-5,\nnando Area, California,\" The San Fernando, California,\n1971a, pp. 80-82.\nEarthquake of February 9, 1971, Geological Survey Pro-\nMorton, Douglas M., \"Seismically Triggered Landslides in the\nfessional Paper 733, U.S. Geological Survey and the Na\nArea Above the San Fernando Valley,\" The San Fernando,\ntional Oceanic and Atmospheric Administration, U.S. De-\nCalifornia, Earthquake of February 9, 1971, Geological Sur-\npartment of Commerce, Washington, D.C., 1971, pp. 6-16.\nvey Professional Paper 733, U.S. Geological Survey and the\nYoud, T. Leslie, \"Landsliding in the Vicinity of the Van\nNational Oceanic and Atmospheric Administration, U.S.\nNorman Lakes,\" The San Fernando, California, Earth-\nDepartment of the Interior and U.S. Department of Com-\nquake of February 9, 1971, Geological Survey Professional\nmerce, Washington, D.C., 1971b, pp. 99-104.\nPaper 733, U.S. Geological Survey and the National Oceanic\nOakeshott, Gordon B., \"Geology and Mineral Deposits of\nand Atmospheric Administration, U.S. Department of the\nSan Fernando Quadrangle, Los Angeles County, California,\"\nInterior and U.S. Department of Commerce, Washington,\nCalifornia Division of Mines Bulletin 172, Feb. 1958, 147\nD.C., 1971, pp. 105-109.\npp.","","Effects of\nSan Fernando Earthquake\nas Related to Geology\nSUMMARY\nThe epicenter of the moderate (magnitude 6.4)\nCONTENTS\nSan Fernando earthquake was located only 4 miles\nPage\nnortheast of the urbanized San Fernando Valley; the\n137\nSUMMARY\n138\nGEOLOGIC SETTING\nearthquake was the first in historic time to be accom-\nCOMPARISON WITH BORREGO MOUNTAIN\n141\npanied by tectonic ruptures of the ground surface in\nEARTHQUAKE\nthe metropolitan Los Angeles area. The ruptures\n141\nTRANSITORY EFFECTS\n142\nPERMANENT EFFECTS\nwere caused by left-oblique reverse movement on the\nTectonic Ruptures\n142\nSan Fernando fault, which dips about 35° NE. be-\nSan Fernando Fault and Related\n142\nneath the northern part of the valley (and the south-\nRuptures\nwesternmost San Gabriel Mountains) thus account-\n143\nLakeview Thrust\nLower Santa Susana and Related\n144\ning for the relatively intense shaking effects north of\nFaults\nthe fault. Although the attitude and movement of\nVeterans Fault\n146\nthe San Fernando fault are dissimilar to those of\n146\nHonby Ruptures\nCamp Holton Rupture\n147\nSan Andreas-type faults, the faulting was in response\nZones of Bending\n147\nto the same stress system and was the most recent ex-\nUplift, Tilting, and Horizontal\n147\npression of a long-established pattern.\nDisplacement\nPermanent surface deformation accompanying the\n147\nLandslides\nfaulting included: the east-trending zone of tectonic\nSan Fernando Reservoir Landslides\n147\nJuvenile Hall Landslide\n147\nruptures that traversed the urbanized valley floor\nOlive View Landslides\n148\nand that coincided with evidence of prior faulting;\nCamp Holton Slope Failures\n148\nuplift, tilting, and southwestward shifting of an area\nKagel Mountain Landslide\n148\nOther Ground Failures\n148\nof more than 75 square miles of the southwestern-\nShattered Ground\n149\nmost San Gabriel Mountains; and numerous slope\n149\nStructural Damage\nfailures. Transitory effects included the most severe\nEstimates of Average Loss\n151\nground motions ever recorded; the strong motions\nDistribution of Damage\n151\nwere recorded more extensively than for any pre-\nEffects of Deformation\n152\nCorrelation and Implications\n152\nvious earthquake.\nPREDICTING THE FAULTING\n152\nUnusually severe shaking, locally exceeding 50\n153\nCONCLUSIONS\npercent of g, characterized the mountain-front belt\n153\nREFERENCES\nabout midway between the epicenter of the main\nshock and the surface ruptures. Shaking strong\nPublication authorized by Director,\nU.S. Geological Survey.\nenough to severely test pre-1933 structures, accompa-\nnied by measured horizontal accelerations of 10 to\n20 percent of g, extended southward into the down-\nR. F. YERKES\ntown areas of Los Angeles and Pasadena 25 miles\nU.S. Geological Survey\nfrom the epicenter. More than 25 percent of all\nMenlo Park, Calif.\n137","138\nSan Fernando Earthquake of 1971\ndwellings in the area of heavy shaking north of the\nGEOLOGIC SETTING\nrupture zone had losses exceeding 5 percent of\nThe San Fernando earthquake occurred in the\npreearthquake market value. Damage was concen-\nsouthwesternmost San Gabriel Mountains, in the\ntrated along the rupture zone and along boundaries\ncentral part of the Transverse Ranges geomorphic\nbetween relatively unconsolidated alluvial deposits\nprovince of southern California (fig. 1) The promi-\nand harder, denser rocks; such boundaries in this\nnent east-trending ranges and valleys of the province\narea commonly coincide with east- and southeast-\ncontrast sharply with the northwesterly trends of the\ntrending, north-dipping reverse faults of the Santa\nCoast Ranges to the northwest and the Peninsular\nSusana and Sierra Madre systems that bound the San\nRanges-Los Angeles Basin on the south. The pres-\nGabriel Mountains on the south.\nent-day geometry of the crustal blocks in this region\nThe San Fernando fault is not known to have\nis such that the San Gabriel Mountains block south-\nruptured previously during historic time, and al-\nwest of the San Andreas fault is constrained and\nthough segments of it had been mapped, no evalua-\ncompressed against the crustal block north of the\ntion of their potential activity had been attempted.\n\"great bend\" of the San Andreas where it forms the\nAbundant evidence of geologically recent faulting\nnorth boundary of the San Gabriel Mountains. Such\nalong the same trend indicates the activity of the\nzone. The San Fernando earthquake is one of the\ncompressive deformation over the last 5 to 10 mil-\nsmaller events produced by the same stress system\nlion years has thrust the mountain block relatively\nthat produced the 1857 Fort Tejon (magnitude 8 +)\nsouthward up and over adjoining lowlands such as\nand 1952 Kern County (magnitude 7.7) earth-\nthe Los Angeles Basin and San Fernando Valley\nquakes.\nalong systems of reverse or thrust faults such as the\n121\n120°\n1198\n118°\n117°\nCOAST\nO RANDSBURG\nBAKERSFIELD\nPleito\n+35°\n1952\n+\n+\nRA\nN\n1852\n1857\nFrazier\nSVERSE\nYnez\n1977\nCoyerano\nRANGES\nRidge\nSusona:\nOo\nVENTURA\nSAN FERNANDO\nVALLEY\nN\nModre\nRaymond\nSierra\nMalibu\n+34°\nLOS ANGELES\nSta.Cruz\n+\n+\nSta Rosa\nPENNNSULAR\n16\no\n16\n32\n48\n64 MILES\nRANGES\nFigure 1.-Index map of major faults in southern California, showing relation of San Fernando Valley, February 9 (1971) earthquake\nepicenter and rupture zone to Transverse Ranges, San Andreas fault, and larger earthquakes (shown by stars and dates), and historic\nruptures (jagged lines), attributable to same stress system as the San Fernando earthquake. Arrows show inferred principal component\nof relative movement. Adapted from Hill (1954, fig. 1).","Effects of Earthquake as Related to Geology\n139\nsimilar evidence relating to the Sierra Madre system\nSanta Susana and Sierra Madre. The most impressive\neast of Pasadena had been recognized and published\nproduct of this deformation is the bold southern\n(Wentworth et al. 1970)\nfront of the San Gabriel Mountains, which rises\nThe San Fernando Valley area (fig. 2) is located\n5,000 to 9,000 feet above the lowland surface to the\nin a depositional basin that dates from middle Mio-\nsouth. Thus, the February 9, 1971, earthquake and\ncene time (about 15 million years ago) the basin is\nreverse faulting were expressions of a long-estab-\nfloored and bounded on the north, east, and south\nlished pattern.\nby crystalline basement rocks (Wentworth and\nThe San Fernando earthquake is attributed to dis-\nYerkes 1971) The basin is inferred to be 15,000 to\nplacement on a buried north-dipping fault beneath\n20,000 feet deep in its central part; the upper 50 to\nthe southwesternmost San Gabriel Mountains, north\n1,000 feet of basin fill are relatively unconsolidated\nof the San Fernando Valley. The map pattern of epi-\nalluvial sands and gravels (Q1, Q2 of structure sec-\ncenters (see epicentral area, fig. 4) is bisected by the\ntion, fig. 3)\nsurface trace of the San Gabriel fault, an important\nThe valley is bounded on the north and northeast\nmember of the San Andreas fault system. The map\nby prominent east-to-southeast-trending reverse and\ntrend of the San Fernando fault is similar to that of\nthrust faults of the Sierra Madre-Santa Susana sys-\nthe San Gabriel and San Andreas faults in this area,\ntem. At and near the surface, these faults form prom-\nN.65°-70°W., but instead of being nearly vertical,\ninent topographic and geologic boundaries such as\nthe fault is inclined about NE. toward the San\nsteep, eroded scarps in sedimentary rocks, north-dip-\nAndreas, and thus passes beneath the trace of the\nping contacts along which crystalline basement rocks\nSan Gabriel fault. The dip of the San Fernando\nhave been thrust over young sediments, and impedi-\nfault is such that it intersected the surface as a zone\nments to the flow of ground water in alluvium (fig.\nof tectonic ruptures along the north margin of San\n3). Several faults, such as the Verdugo, also coincide\nFernando Valley where it coincides with evidence of\nwith pronounced residual Bouguer gravity gradients\nearlier faulting.\n(Corbató 1963, fig. 7), indicating that the surface\nThe sense of displacement was also dissimilar to\ndensity contrasts extend to considerable depth. Sub-\nthat characteristic of the San Andreas; instead of\nsidiary faults, such as the east-trending Northridge\nright-lateral (horizontal shear) movement on a\nHills and Mission Hills faults (figs. 2 and are\nnear-vertical fault, the displacement was reverse in\nrecognized on the basis of surface evidence and\nnature-the mountainous block north of and above\nground water impediments in young materials, both\nthe fault moved relatively southwestward, up and\nof which indicate recent geologic activity.\nover the San Fernando Valley south of the fault. As\nThe Sylmar area, where damage was most intense,\nmeasured by total displacement across the 1971 rup-\nis underlain by a thin veneer of unconsolidated al-\ntures, the mountain block was uplifted as much as 7\nluvial deposits, which in turn overlies steeply north-\nfeet and shifted westward as much as 6 feet relative\ndipping sand and gravel beds of the Saugus Forma-\nto the valley block on the south. Horizontal (com-\ntion (included in Q2, figs. 2 and 3) The Saugus in\npressive) shortening normal to the trend of the rup-\nthis area forms an east-trending syncline; its north\ntures was as much as 3.5 feet. Resurvey of a preearth-\nlimb is overturned and overthrust by older rocks of\nquake net of gravity stations in the area shows that\nthe mountain block along the Olive View fault and\nthe significant gravitational changes attributable to\nother faults of the Santa Susana system (see north\nthe faulting occurred in the mountain block north\nend of section, fig. 3) The south limb of the syn-\nof the rupture zone and that the changes (decreases\ncline is interpreted as being cut by another north-dip-\nin attraction of 0.1 to 0.36 mgal) are consistent with\nping reverse fault, a segment of the San Fernando\nthe measured uplift of the mountain block (Oliver\nfault, which ruptured during the February 9 earth-\n1973)\nquake.\nAlthough many segments of the mountain-front\nIn the San Fernando city area, the February 9\nfault system had been mapped and interpreted in the\nzone of tectonic ruptures closely followed the surface\ncontext of this geologic history, the abundant but\ntrace of a ground water impediment that had been\nrelatively unobtrusive evidence of late geologic activ-\nmapped previously (figs. 3 and 6) Along the eastern\nity along the trace of the February 9 ruptures had\npart of this segment, the ruptures also followed an\nnot been widely recognized or appreciated. However,","140\nSan Fernando Earthquake of 1971\neroded fault scarp at the south edge of an uplifted furnish strong evidence of geologically recent activity\narea of old stream terrace deposits (Q2, east of the\nalong this segment of the San Fernando fault.\nnorth part of section line N-S, fig. 2) . The displaced\nIn the fall of 1970, ground water was at depths ex-\nwater table and surface scarps in alluvial deposits\nceeding 50 feet below the surface throughout most of\n118°30'\n118°15'\n118°\nEXPLANATION\nQ1s Alluvium\nQ2 Terrace deposits and upper\nMiocene to Pleistocene\nsedimentary rocks\nSANFA\n6.4\nEpiceater,\nT, Upper Cretaceous and Tertiary\nMain Shock\nsedimentary rocks, minor\nmiddle Miocene volcanic rocks\nSUSANA\nBasement complex\nNormal, reverse, or strike-slip fault\nFERNANDO\nThrust or detachment fault\nHILLS\nMISSION\nFAULT\n34°\n15\nSAN\nFERNANDO\nVALLEY\nSANTA\nMONICA\nMTS\nLOS\nSANTA\n34\nMONICA\nANGELES\nBAY\nBASIN\n5\n0\n5\nMILES\nFigure 2.-Generalized geologic map of Los Angeles-San Fernando Valley area showing epicenter (box) and rupture zone along San\nFernando fault, February 9, 1971. Geologic section (fig. 3) along line N-S. Adapted from Jennings and Strand (1969).","Effects of Earthquake as Related to Geology\n141\ntem) ; this earthquake had only minimal effects in\nSan Fernando Valley (fig. 3) , except in the vicinity\nthe Los Angeles metropolitan area. Although compa-\nof the San Fernando Reservoirs. With that excep-\nrable in magnitude, the effects of the two earth-\ntion, saturation of near-surface materials by ground\nquakes were quite dissimilar, especially in maximum\nwater apparently did not contribute significantly to\nfault displacement, size of affected area, and maxi-\nthe earthquake damage.\nmum intensity (table 1)\nCOMPARISON WITH BORREGO MOUNTAIN\nTRANSITORY EFFECTS\nEARTHQUAKE\nIn addition to forming the first historic tectonic\nThe San Fernando earthquake was comparable in\nruptures within the Transverse Ranges, the San Fer-\nmagnitude (6.4) to the Borrego Mountain earth-\nnando earthquake made engineering history by\nquake of 1968 (6.5) , which was the last large earth-\nbeing not only unusually well and widely recorded,\nquake to affect southern California. That latter\nbut also by being unexpectedly intense and thus\nearthquake occurred 145 miles southeast of Los An-\nmuch more destructive than might have been antici-\ngeles on the margin of the Imperial Valley on the\npated. The more prominent transitory effects in-\nCoyote Creek fault, a vertical (?) fault of the San\ncluded: about 7 seconds of very strong shaking\nJacinto fault zone (a part of the San Andreas sys-\nN\nMission Hills segment,\nOlive View\nSan Fernando fault\nfault\nInferred extension,\nSan Gabriel\n(Ruptured 2/9/71)\nNort hridge Hills\nMountains\nFault\nQ2\n1500\ng\nT\nof ground water, 1970\n-1000'\nGround water\nQ1,Q2\nQ2, T\nimpediments\n- 500'\nApprox. trace,\nO\naxial surface\nof syncline\n-500'\nS\nSanta Monica\nMountains\nSan\nFerrando Valley\n1000'\nQ\n500\nT\nTop of ground water, 1970\nQ1, Q2\no\n0\nMILE\nVERTICAL 4x HORIZONTAL\n-500\nFigure 3.-North-south geologic section across San Fernando Valley, showing thickness of valley fill (Q1, Q2) and relation to late Tertiary\nsedimentary (T) and basement rocks (g), faults, ground-water impediments, and top of ground water as of fall 1970. Based on\nCalifornia State Water Rights Board (1962, pls. 5B and 6) and unpublished data supplied by the Los Angeles Department of Water\nand Power.","San Fernando Earthquake of 1971\n142\nTable 1.-Comparison of the Borrego Mountain and San Fernando\nStaff (1971), Barrows et al. (1971), and Kamb et al.\nearthquakes\n(1971)\nBorrego Mt.¹\nSan Fernando\nSan Fernando Fault and Related Ruptures.-Al-\nApr. 8, 1968\nFeb. 9, 1971\nthough a rather broad zone of tectonic ruptures\n6.4\nRichter magnitude\n6.5\nEstimated focal depth\n12 mi\n5 mi\nformed in the Sylmar-San Fernando area (location\nMaximum measured horizontal\n14% g at 40\n1+ g at 4 mi\nA, fig. 5; fig. 6) the largest displacements were con-\nacceleration and epicentral\nmi\ndistance\ncentrated along the ruptures in the southern part of\nLength of surface rupture\n20 mi\n9.5 mi\nDip of fault\nvertical(?)\nabout 35°NE.\nthis zone. This part of the zone coincides very closely\nright-lateral\nleft-oblique\nType of movement\nwith the previously mapped trace of a ground water\nreverse\nMaximum displacement (net slip)\n1.25 ft\n7.9 ft 2\nimpediment (fig. 6), interpreted to have been\nMaximum intensity (Modified\nVII\nVIII-XI\nformed by repeated faulting along the same trend\nMercalli)\nArea of intensity VII or greater\n550 sq mi\n975 sq mi\n(Wentworth et al. 1971, p. 13)\n1 Data from summary, Youd and Castle (1970).\nThe broad area of short ruptures just west of Pa-\n2 Components of net slip: 4.92 feet of reverse dip slip, 6.25 feet\nof left-lateral, and 2.0 feet of transverse (shortening normal to\ncoima Wash and north of the main rupture zone (lo-\ntrend).\ncation B, fig. 5) is underlain by an upfaulted ero-\n(Modified Mercalli intensities VIII-XI and meas-\nsional remnant of semiconsolidated stream terrace\nured horizontal accelerations greater than 25 percent\ngravels (Q2 in fig. 2) The eroded fault scarp at the\nof g) over an area of about 140 square miles cen-\nrupture zone along the south margin of this remnant\ntered on Sylmar (fig. 4) ; and about 10 seconds of\nis about 25 feet high. The ruptures in this area\nmoderately strong shaking (intensity VII and meas-\nnorth of the main zone are chiefly tensional, down-\nured horizontal accelerations between 8 and 25 per-\nthrown on the north, and most show small compo-\ncent of g) over an additional area of about 835\nnents of right-lateral separation (fig. 6)\nsquare miles that includes all of San Fernando Val-\nThe most prominent and continuous ruptures east\nley, the northern part of the Los Angeles Basin, and\nof San Fernando formed along the base of the hills\nnearby parts of the Santa Clara River Valley.\nbetween San Fernando and the mouth of Big Tu-\njunga Canyon 7 miles to the east. However, the con-\ntours of uplift (fig. 7) show that the east-trending\nPERMANENT EFFECTS\naxis of the zone of uplift continues directly eastward\nThe most significant permanent effect of the San\ninto the foothills along the trend of the Mission\nFernando earthquake, one not previously recorded\nWells-San Fernando segment of the rupture zone.\nin the metropolitan Los Angeles area, is the zone of\nThe prominent ruptures in Lopez Canyon, about 0.5\ntectonic ruptures that extends across the north margin\nmile north of the canyon mouth (location C, fig. 5),\nof the main San Fernando Valley from its west edge\nmay thus represent the main or dominant fault trace.\nat Mission Wells eastward to the mouth of Big Tu-\nThis trace is difficult to locate in the hills because it\njunga Canyon (fig. 5) Other important permanent\nis obscured by numerous slope failures and patches\neffects include movement on a segment of the lower\nof shattered earth; the only recognizable scarp along\nbranch of the Santa Susana thrust fault west of Syl-\nits trend was formed in the bottom of Lopez Can-\nmar; formation of surface warps or narrow zones of\nyon. This zone of ruptures also consistently dips\nlateral bending without ruptures; regional uplift and\nmuch more steeply northward than does that at the\ntilting of the land surface north of the rupture zone;\nsouth margin of the hills (65°-72° versus 15°-37°)\ndestructive landslides in the Olive View area and in\nthe dips are subparallel to bedding in adjoining bed-\nthe vicinity of the San Fernando Reservoirs; local\nrock in each case. The hill-front zone of ruptures\ndifferential settling, lurching, and failure of alluvium\n(location D, fig. 5) may thus be a secondary effect,\nand artificial fill; and numerous small areas of in-\nthe response of the frontal segment of hills to thrust-\ntensely shattered soil on ridge tops around the north\ning of the main mass to the north.\nmargin of the valley.\nEvidence of at least two earlier events of similar\nfaulting along the hill-front zone of ruptures is ex-\nTectonic Ruptures\nposed in a cut bench just west of the mouth of\nThe following review of the tectonic ruptures is\nLopez Canyon. Each of these faults thrust surficial\nbased on field studies by the U.S. Geological Survey\ndeposits or bedrock over younger material. Neither","Effects of Earthquake as Related to Geology\n143\nLakeview Thrust.-A preexisting fault, the Lake-\nof them was disturbed by the faulting of February 9,\nwhich instead formed a new rupture just upslope\nview thrust of Proctor (1970), was reactivated along\nthe hill front near the mouths of Oliver and\nfrom the older ones.\n118°30'\n118°15'\n118\nEXPLANATION\nQ1' unconsolidated sand and gravel\nQ2' semiconsolidated sand and gravel\nT, sandstone, pebbly sandstone, or\nVIII\nsiltstone\nSANFA\n6.4\nMetamorphic or plutonic rocks\nNA\nEpicentral area; contains more than\n95% of 700+ well-located aftershocks;\nbox indicates main-shock epicenter\nX(40+)\nM.T.S\n125\nLocation and value (% G) of maximum\nX29\nmeasured horizontal ground\nacceleration\nApproximate boundary and inferred\n(50)\n(VII)\nintensity of shaking\n34°\n15\nSAN\n28\nFERNAND 0\n12\nVII\nX24\nVALLEY\nX23\nx22\nX18\nx28\n18\nSANTA\nMONICA\nMTS\n16\nx\n12\nX13\nx20\nX9\nx\n20\n8X\nLOS\nSANTA\n34\nMONICA\nANGELES\nX4\nBAY\nX6\nBASIN\n5\n0\n5\nMILES\nFigure 4.-Map of transitory effects of February 9 (1971) earthquake. Epicentral area contains more than 95 percent of more than 700\nwell-located aftershocks recorded between time of main shock and April 23, 1971 (data from Allen et al. 1971, Wesson et al. 1971,\nand written communications). Measured maximum horizontal accelerations from Hudson (1971, table 1); those shown in parentheses\nare estimates based on interpolation of a seismoscope record (Seed et al. 1971) and analysis of failure of Olive View Hospital (Structural\nEngineers Association of Southern California 1971). Inferred intensity of shaking and approximate boundaries from N.H. Scott (1971).","San Fernando Earthquake of 1971\n144\nSchwartz Canyons, about 2 miles east of Little Tu-\ngin of this rupture includes its coincidence with a\njunga Canyon (location E, fig. 5) . In this area, Mio-\npreviously mapped thrust fault that locally cut\ncene siltstone previously had been thrust over young\nstream terrace deposits, local continuity across ridges\nterrace deposits (T over Q2, fig. 2) that underlie the\nand valleys, and movement not clearly attributable\nridges between these canyons. Although details are\nto slope failure. Soil on many of the ridge tops above\nobscured by landsliding, the 1971 faulting involved\nthe fault was shattered severely. Opposed to a strictly\nthrusting with vertical displacements as great as 5.3\ntectonic origin, on the other hand, is the fact that\nfeet on a fault that dips northward between 15° and\nthe lower Santa Susana thrust is penetrated by sev-\n45°.\neral wells in the Cascade oilfield immediately to the\nwest, none of which was disturbed by movements\nLower Santa Susana and Related Faults.-A mile-\nsufficient to cause damage.\nlong segment of the lower Santa Susana thrust west\nof Sylmar ruptured discontinously during the earth-\nA shorter, subparallel rupture formed near the\nquake, offsetting a road about 1 foot in a left-lateral\nnorth end, but about 0.3 mile east of that described\nsense (location F, fig. 5) . Evidence for a tectonic ori-\nabove (location G, fig. 5) . Movement on this rup-\n2.4% M\n119\n30\n118\n22\n30\n42C\nTectonic rupture, showing dip; ball on\n650\nAmount of horizontal shortening (inches)\ndownthrown side, number shows\n20\nvertical separation (inches)\nacross rupture zone\nDirection and amount (inches)\n30\n34°\nFissure or scarp bounding landslide;\nof horizontal separation\n22\n30\"\n34°\nhachures on downslope side\n22'30'\nZone of lateral distortion; arrows\nx\nshow direction of bending\nShattered earth on ridge top\nP\nx\nX\nX X X\nwas\nL\nfor\n46.°\nX\nx\nX\nX\nx\n75°\n72°\nX\n#F\n65°\n31.5\nX\nX\n75,\n19.6\nA\nX\n24C\nX\n18\n39,4\n65°\n23\n57.°\n6\n31°\n35°\n12\n18\n12.6\n39.4\nas\n25\n42C\nD\n12.\n28C\n19°\n20\n50°\n55°\n18\n24\nGranada\n24\n23\nHills\n118\n15\n340\n15\nMILES\nValle\n118°30'\n118\n22\n30\"\nFigure -Map of permanent effects of the February 9 (1971) earthquake, showing zones of surface ruptures, lateral distortion, and slope\nfailures. Underlined letters refer to text, Data from Youd (1971) and field investigations by Sharp and Yerkes.","Figure 6.-Map of Sylmar-San Fernando area showing tectonic ruptures, zones of lateral distortion, and damaging landslides along foothills north of Sylmar. Also shown\nslide; hachures on downslope side\nshows vertical separation (inches)\nZone of lateral distortion; arrows\nof horizontal shortening across\nFissure or scarp bounding land-\n12\nTectonic rupture, showing dip; ball\n65° 31.5\nDirection and amount(inches) of\nhorizontal separation; R, right\nDirection and amount (inches)\n58.7\nIOR\n2R\nis the map trace of Mission Wells-San Fernando ground-water impediment (from California State Water Rights Board 1962, Vol. II, appendix A, fig. A-1).\non downthrown side, number\n15\nshow direction of bending\n40\n24\n31°\n28C\n4\n*2\n25\n9\n37°\ntoe\nlinear feature\n28°\n22\n48\nA\nL, left\n*\n2.8\n39,\n42C\n22C\n65\n2\n31\n95L\n40\n30\n1.6\n0.4\n0.4\n23\nMILE\n0.8\n0.4\n0.8\n13.3\nII8 25\n0.9\n0.4\n0,8\n31.5C\n2.4\n11\n0.8\n0.8\nIT\n(TOTAL)\n95L,24C\n0.4\nSAN FERNANDO\n0.5\n95L,22C\n(TOTAL)\n0.5\nAVG.72°\n0.8\n(TOTAL)\n95L\nO\nGround water\nimpediment\n(TOTAL)\n40L,126\nfrom\n.08\n18\n74°\n.4\nIf\n118° 27 30\n2\nM\nLower San Fernando\n6.3\n13\n579\nReservoir\n30'\n34°\n17","146\nSan Fernando Earthquake of 1971\n118°30'\n118° 22' 30\"\n34°\n22\n30\"\n340\n22'30\nMOMANL\nGABRIER\n+1.0(3.28)\n18\n+0.5(1.64)\nchernando\n18\nGranada\n(Held)\nHills\n118\n34°\n34\no\n5\n10 FEET\nL\n1\nVECTOR SCALE\no\nMILES\n118 of 30'\n118° 22' 30\"\nFigure 7.-Map of northern San Fernando Valley area, showing elevation changes since 1960 or 1963 in meters (and ft) relative to bench\nmark labeled \"Held\" (data from Burford 1971) and observed horizontal displacements showing vectors in feet (data from Savage 1971).\nture could be attributed to local slope failure, but\nrupture thus may be a secondary effect along a\nthe rupture also traversed ridges and valleys and is\npreexisting fault.\nparallel to faults of the Santa Susana system.\nHonby Ruptures.- unique instance of ground rup-\nVeterans Fault.-An east-trending rupture about 0.3\nture occurred in alluvium north of the Santa Clara\nmile long, the Veterans fault of Kamb et al.\nRiver at Honby (location M, fig. 5, north border)\n(1971), formed at the north-dipping, previously\nThis narrow zone of discontinuous en echelon rup-\nfaulted contact between the stream terrace deposits\ntures is about 1 mile long and trends about N.25°E.,\nand the Saugus Formation just west of the mouth of\nsubparallel to and nearly coincident with the north-\nPacoima Canyon (location H, fig. 5) . Movement was\nwest margin of the aftershock pattern. Vertical dis-\nreverse and vertical displacement of the north block\nplacement across ruptures was as much as 4 inches up\nwas about 7 inches. Although the rupture intersected\non the west, and right-lateral displacement was as\nseveral houses and streets, most of the considerable\nmuch as 2.5 inches. Considerable minor damage, such\ndamage in this particular area is attributable to the\nas rupturing of pavement, curbs, and sidewalks, ac-\nintense shaking along this mountain-front zone; this\ncompanied the displacement. Along the same trend","Effects of Earthquake as Related to Geology\n147\ntrending axis which coincides with the main rupture\non both sides of State Highway 14, south of Santa\nzone in San Fernando and continues eastward into\nClara River, considerable localized structural damage\nthe foothills about 0.5 mile north of their south mar-\naccompanied failure of artificial fill and cracking of\ngin. Relative subsidence as great as 4 inches was\nnatural ground.\nmeasured south of the foothill rupture zone, gener-\nCamp Holton Rupture.-A preexisting north-dip-\nally within the area bounded by the zero contour.\nping fault in bedrock just north of Camp Karl\nIn addition to the uplift, that part of the moun-\nHolton Juvenile Facilities, 1.5 miles northeast of the\ntain block north of the San Fernando rupture zone\nmouth of Little Tujunga Canyon (location N, fig. 5)\nwas shifted generally southwestward between 2 and 4\nshowed evidence of movement involving about 6\nfeet relative to the valley block south of the rupture\ninches of left-lateral displacement, which accounts\nzone (fig. 7)\nfor severe damage to the gymnasium building. Al-\nthough the fault cuts across the south end of a steep\nLandslides\nridge of bedrock, it is not certain that the movement\nSeveral destructive landslides occurred during the\nshould be considered tectonic.\nearthquake; the most significant of these occurred\naround the San Fernando Reservoirs and locally\nZones of Bending\nalong the mountain front north of Sylmar.\nA unique feature of the surface deformation asso-\nSan Fernando Reservoir Landslides.-At the lower\nciated with the earthquake was the formation of sev-\nand larger dam of the San Fernando Reservoir com-\neral narrow zones of horizontal bending, either as Z-\nplex (location J, fig. 5), the embankment, parapet\nshaped connections between offset rupture zones, as\nwall, dam crest for a length of about 1,400 feet, most\nat the west end of the hill-front zone east of San Fer-\nof the upstream face, and part of the downstream\nnando (location I, fig. 5; fig. 6) or as extensions of\nslope slid into the reservoir (California Division of\nrupture zones. Because of their obscurity relative to\nSafety of Dams 1971) About 30 feet of dam height\nthe ruptures, these zones of bending were not noted\nwas lost, leaving a critically reduced freeboard of\nuntil after the preliminary field investigations had\nabout 4 feet. Perhaps as much as 29,600 cubic yards\nbeen concluded; the zones were mapped chiefly on\nof dam embankment was displaced; the resulting\nthe basis of distorted horizontal or vertical lines asso-\nslide extended as much as 650 feet northward into\nciated with structures such as curb lines, building\nthe reservoir and covered an estimated 670 square\nwalls, or pole lines. Distortion across these zones of\nyards of the floor. The landslide is attributed by\nbending includes formation of compressive welts as\nSeed et al. (1971) to liquefaction of the hydraulic\nmuch as 23 inches high and lateral distortion of at\nfill on the upstream side of the dam; these investiga-\nleast 0.05 percent over a zone 700 feet wide. The east\ntors estimate that maximum accelerations of 40 to 50\nend of the Z-shaped zone of bending at locality I\npercent of g were attained in parts of the dam dur-\nmay be related to lateral spreading of the adjacent\ning the earthquake.\nhill; this interpretation is supported by the anoma-\nThe upper dam at the reservoir complex is about\nlously large westward displacement of the triangula-\nthe same size as the lower dam, but it impounds a\ntion station on the hill (fig. 7)\nmuch smaller reservoir. The crest of the dam shifted\nas much as 5 feet downstream and settled about 3\nUplift, Tilting, and Horizontal Displacement\nfeet vertically during the earthquakes (California\nDivision of Safety of Dams 1971)\nRegional uplift and tilting affected an area of at\nOther smaller landslides and slumps affected the\nleast 75 square miles north of the rupture zone in\nalluvial materials and fill around much of the mar-\nthe northern San Fernando Valley-southwestern San\ngins of the reservoirs; one scarp on the west shore of\nGabriel Mountains area. The affected area extends\nthe lower reservoir is more than 0.5 mile long and\nfrom west of the San Fernando Reservoirs eastward\nwas associated with a linear array of sand boils\nto Big Tujunga Canyon and northward from the\n(Youd 1971, fig. 1)\nbase of the foothills east of San Fernando to beyond\nJuvenile Hall Landslide.-Another very destructive\nthe mouth of Pacoima Canyon (fig. 7) Maximum\nlandslide extended northeastward from the northeast\nuplift of about 7.5 feet occurred along an east-","148\nSan Fernando Earthquake of 1971\nshore of the upper reservoir (location K, fig. 5)\nwere damaged severely by slope failures in natural\nCracking, fissuring, and lateral movement of the\nand filled ground at the base of the mountains north\nground surface downslope (generally toward the res-\nof Sylmar (location L, fig. 5) These failures OC-\nervoir), associated with shaking resulting from the\ncurred on terraced slopes about 0.5 mile long, ex-\nearthquake, severely damaged parts of a major elec-\ntending about 0.2 mile southward from the base of\ntricity converter station, a major juvenile detention\nthe hills and include cuts along the new Foothill\nfacility, railroad trunklines, a major boulevard and\nFreeway. In addition, landslides on the west and\nan interstate freeway, and several pipelines and ca-\nsouth slopes of the small hill 0.2 mile northeast of\nnals. The affected area is tongue-shaped in plan and\nthe new hospital severely damaged the older build-\nabout 4,000 feet long and 900 feet wide at the down-\nings there. In none of these cases can the ground\nslope, southwest margin. Topographic relief between\nfailures be attributed to surface movement along the\nthe lake level at the toe and the land surface at the\nOlive View fault, which trends northeastward be-\nhead was about 60 feet, an average effective gradient\ntween the two areas.\nof about 1.5 percent.\nCamp Holton Slope Sailures.-Destructive slope fail-\nThe landslide is bounded by relatively linear\nures affected both natural and artificial materials at\nzones of discontinuous ruptures, locally en echelon\nthe Camp Karl Holton Juvenile Facilities, 1.5 miles\n(for details, see Volume III paper by Youd,\nnortheast of the mouth of Little Tujunga Canyon\n\"Ground Movements in Van Norman Lake Vicinity\n(location N, fig. 5) A preexisting north-dipping\nDuring San Fernando Earthquake\") Relative dis-\nfault in bedrock immediately northeast of the camp\nplacement across the zone of ruptures bounding the\nshowed evidence of movement involving about 6\nnorth margin is consistently right lateral and as\ninches of left-lateral displacement; this movement ex-\nmuch as 2.8 feet; displacement across the south\ntended westward into the gymnasium and accounts\nmargin is consistently left lateral and as much as 1.9\nfor the most severe structural damage at the camp.\nfeet; vertical separations across fissures are as much\nSlosson (1971) attributes this damage to shaking\nas 7 inches; and fissures that intersected buildings at\nonly and does not cite the fault movement.\nthe detention facility are open as much as 15 inches.\nA number of postearthquake borings show that\nKagel Mountain Landslide.-A large landslide OC-\nthe area is underlain by silt and silty sand. This rela-\ncurred on the north face of Kagel Mountain, 0.65\ntively fine-grained material was deposited in a topo-\nmile due east of Pacoima Dam (location P, fig. 5)\ngraphic depression at the confluence of several small\nIndividual fissures at the head of the slide extend for\nalluvial fans.\nmore than 0.3 mile along the east and west shoulders\nThe north margin of the slide is generally coinci-\nof the mountain, which is underlain by jointed, frac-\ndent with the trace of the Olive View fault (fig. 2)\ntured, and foliated diorite and gneiss of the base-\nas projected from the northeast; and although tec-\nment complex. Although fissures locally cut across\ntonic displacement of the ground surface along the\nthe crest of the mountain, they are attributable to\nfault trend is not evident on the basis of careful\nfailure of the north slope rather than to tectonic\ninspection, survey data indicate up to 0.40 foot of\nmovement (compare with Barrows et al. 1971, loca-\nright-lateral displacement of the areas bounding the\ntion 44)\nslide on the north and south (paper by Youd) Ex-\nOther Ground Failures.-Numerous other instances\namination of predevelopment topography of this\nof ground failure, attributable to lurching, differen-\narea (such as the 6-minute Sylmar quadrangle at\ntial settling, and related effects, caused considerable\n1:24,000, 5-foot contour interval, 1935) clearly shows\ndamage in marginal areas of the San Fernando Val-\nGrapevine Creek to be deflected about 500 feet in a\nley. Chief of these is the area west of the San Fer-\nright-lateral sense near the north boundary of the\nnando Reservoir complex (location Q, fig. 5) gener-\npresent failure, strongly suggesting that this is a re-\nally along the trend of the Olive View fault, where\ncurring process. The failure is considered to be re-\na number of destructive fissures formed on gentle\nnewable in the event of another similar earthquake\nslopes in alluvial and fill materials. These fissures\n(Fallgren and Smith 1971, pp. 38-39)\ngenerally trend subparalle] to the contours of local\nOlive View Landslides.-Many of the older build-\nslopes and are not directly attributable to surface dis-\nings north and west of the new Olive View Hospital\nplacement on the fault.","Effects of Earthquake as Related to Geology\n149\nstone and conglomerate with a relatively thin soil\nShattered Ground\ncover. A relatively dense concentration of the shat-\nNumerous examples of closely spaced, randomly\ntering is associated with the axis of the Little Tu-\noriented fissures are present in the soil on the tops of\njunga syncline, which trends northwest from Little\nmany ridges around the west, north, and east mar-\nTujunga Canyon about 2 miles northeast of its\ngins of San Fernando Valley (Barrows et al. 1971)\n.\nmouth, and which is underlain by very steeply dip-\nThe fissuring produced large, tilted, and overturned\nping sandstone and conglomerate beds.\nclods and blocks of soil in areas of finely pulverized\nsoil. The effect is especially well developed just\nStructural Damage\nabove the lower branch of the Santa Susana thrust in\nThe plots of damage (figs. 8 and 9) are intended\nthe foothills west of the San Fernando Reservoirs,\nto represent primarily the areal distribution and\nalong the mountain front north of Sylmar, and in\ndensity of significant damage to structures; they are\nthe foothills east of San Fernando. Barrows et al.\nbased on field observations and on lists supplied by\n(1971) associate the shattering with especially angu-\nthe cities of Los Angeles and San Fernando, Los An-\nlar topography and with ridges underlain by sand-\n118°22'30\"\n118°30'\nH-Hospital or nursing home\nS-School\n-Pre-Field Act school\nseverely damaged\n6.4\nX - Apartment OF dormitory\nHouse or commercial building\n.\n-\n34°\n-Dam\n22'30\nF-Freeway overpass\nQuaternary deposits\nTectonic ruptures\n(Inset of figure 9)\nBoundary of epicentral area\nFAUL\nSUSANA\n34°\n15\n2\no\n2\n4 MILES\n0\n2\n4\n6 KILOMETERS\nFigure 8.-Map of northern San Fernando Valley area, showing distribution of structural damage\nrelative to geology. Base from Wentworth et al. (1971).","150\nSan Fernando Earthquake of 1971\n118°30'\n118°15'\n118\nEXPLANATION\n&1' unconsolidated sand and gravel\nO2' semiconsolidated sand and gravel\nSANTA\nT, sandstone, pebbly sandstone, or\nsiltstone\nMetamorphic or plutonic rocks\nSUSANA\nN\nDamaged school building\nMTS\nPre-1933 school building damaged\nbeyond economic repair\nDamaged house, apartment, or\ncommercial building\n(See figure 8)\n34\n15\nXX\nSAN\nX\nFERNANDO\nX\nX\nx\nx\nVALXEY\nX\nx\nX\nX\nx\nX\nX\nSANTA\nX\nMONICA\nMTS\nX\nX\nX\nS\nSANTA\n34\nMONICA\nANGELES\nBAY\nBASIN\n5\n0\n5\nx\nMILES\nFigure 9.-Map of San Fernando Valley-Los Angeles Basin area, showing distribution\nof structural damage relative to geology. Base same as figure 2.\ngeles City School District, and Los Angeles County.\nNone of the lists indicate the age or type of con-\nOnly one of these lists separates structural from ar-\nstruction. Thus, it was impossible to normalize the\nchitectural damage; others give only the estimated\ndata satisfactorily; instead, the plots include all indi-\ncost of repairs to the structures or identify only those\nvidual structures intended for some degree of occu-\nstructures that were posted as unsafe for occupancy.\npancy for which repairs were estimated to equal or","Effects of Earthquake as Related to Geology\n151\ndamaging deformation-vertical and lateral displace-\nto exceed $2,000. Eight pre-1933 school buildings\nment and compressive horizontal shortening normal\nthat were damaged beyond economic repair are dif-\nto the trend of the zone-occurred chiefly within a\nferentiated; the plots also include the wood frame\nband about 200 feet wide along the south margin of\ndwellings in the northern San Fernando Valley that\nthe zone. The northern part of the zone shows chiefly\nwere examined and plotted by Steinbrugge et al.\nextensional features: open cracks and small fissures\n(1971, 16)\nwith relatively small vertical displacements.\nEstimates of Average Loss.-The loss caused by the\nThe mountain-front belt of intense shaking dam-\nmoderate San Fernando earthquake to private\nage north of Sylmar is about 0.75 mile wide and ex-\nhomes is of interest because the geology of the north-\ntends at least 7 miles from the alluvial area west of\nern San Fernando Valley area approximates that\nthe Upper San Fernando Reservoir eastward to Pa-\nalong the entire northern margin of the Los Angeles\ncoima Dam. This belt includes the area of landslid-\nBasin.\ning around the east end of the Upper San Fernando\nSteinbrugge et al. (1971) summarize data on\nReservoir, the Olive View medical facilities, the Vet-\nearthquake-related damage to 12,037 wood frame\nerans Administration Hospital facilities, and several\ndwellings in the heavily shaken area of San Fer-\nintervening tracts of houses. Only one short segment\nnando Valley north of the rupture zone. The average\nof presumed tectonic rupturing occurred in this belt\nloss of each dwelling, based on estimates of preearth-\n(about 0.5 mile east of the Veterans Administration\nquake market value and repair costs, is 6.6 percent.\nHospital, near the mouth of Pacoima Canyon-see\nAs based on the values of the Los Angeles County\nlocation H, fig. 5) although the fault intersected\nAssessor and the estimated losses for 1,088 dwellings\nsome structures, the most severe damage along its\nuniformly distributed in the same area, the average\ntrend appears to be the result of shaking. In addi-\nloss was 21.5 percent (Steinbrugge et al. 1971) In\ntion, failure caused by landsliding was extensive and\nJune 1971, the Small Business Administration had\nvery damaging at places along the belt, as at the San\napproved loans for earthquake repairs to 11,815\nFernando Valley Juvenile Facility and the older parts\ndwellings (type not specified) in the northern San\nof the Olive View facility.\nFernando Valley area (U.S. Congress 1971, p. 41)\nNo evidence of significant ground failure has been\nThe loans averaged $3,860, representing 24.6 percent\nnoted in the failures of the new hospital and psychi-\nof the $15,700 average value (as based on the figures\natric units at Olive View, where vertical and lateral\nof Steinbrugge et al. 1971) or 27.2 percent of the av-\naccelerations of the ground are inferred to have ex-\nerage value (as based on the figures of the Los Ange-\nceeded 40 percent of g (Structural Engineers Asso-\nles County Assessor) Steinbrugge et al. (1971, fig.\nciation of Southern California 1971, Slosson 1971,\n24) also found that 25 percent of their sample had\nand Frazier et al. 1971, pp. 175-180) The San Fer-\nlosses exceeding 5 percent of the preearthquake mar-\nnando Veterans Administration Hospital complex is\nket value, 14 percent had losses exceeding 10 percent\nlocated in the mountain-front belt about 1 mile\nof their value, and about 2 percent (217) had losses\nsouthwest of Pacoima Dam; the complex includes a\nexceeding 50 percent. The Small Business Adminis-\nnumber of both pre-1933 and post-1933 buildings.\ntration reported in June 1971 (U.S. Congress 1971,\nThe older buildings collapsed or were damaged se-\np. 418) that more than 1,200 homes were damaged\nverely, whereas the post-1933 buildings suffered no\nin excess of $17,000-more than the average value of\nsevere structural damage (Frazier et al. 1971).\ndwellings in the area.\nSeveral tracts of new wood frame dwellings, one\nstory, one and two story, or two story, are located in\nDistribution of Damage.-Severe damage to modern\nthe mountain-front belt east of the Olive View medi-\nstructures was restricted to the Sylmar-San Fernando-\ncal facility. One of the most severely damaged was a\nPacoima area-that part of northern San Fernando\ntract of uncompleted one-story houses just east of the\nValley north of the rupture zone. Within that area,\nVeterans Administration facility, near the mouth of\nit was particularly intense along the rupture zone\nPacoima Canyon. In this tract, a number of houses\nin the city of San Fernando and along the mountain-\nthat were framed, but not completely walled, col-\nfront belt of severe shaking north of Sylmar (fig. 8)\nlapsed. In tracts between the Olive View and Veter-\nAlthough the zone of tectonic ruptures is as much as\nans Administration facilities, the most severe damage\n660 feet wide in the city of San Fernando, the most","152\nSan Fernando Earthquake of 1971\nwas sustained by combination one- and two-story\ntures of all types and ages along the mountain-front\nhouses in which the lower story of the two-story part\nbelt north of Sylmar where the intensity of shaking\ncollapsed because of inadequate lateral bracing. In\nlocally exceeded 40 percent of g. Accelerations were\nnone of these cases was ground failure a significant\nnot measured along the mountain front between Pa-\ncause of damage.\ncoima Dam and Pasadena, but horizontal accelera-\ntions as high as 24 percent of g were measured at\nEffects of Deformation.- effects of surface defor-\nSierra Madre, 25 miles southeast of the epicenter\nmation include the following: Vertical displacements\n(fig. 4) Although the alluvium is very thin in the\ncaused tilting and fracturing of floors, foundations,\nSylmar area (fig. 3), that area overlies the fault sur-\nand pavements; and lateral displacements caused\nface and was intensely shaken, with accelerations of\nshearing, buckling, and stretching of pipelines, pave-\n30 percent of g and greater. The intensity of shaking\nments, and foundations SO that a pipeline or side-\nwas somewhat diminished in the main part of San\nwalk that was buckled in compression at one point\nFernando Valley south of the rupture zone, where al-\nwas commonly broken in tension at another. The\nluvium is relatively thick, and in the northern part\nshortening component caused buckling of founda-\nof the Los Angeles Basin. These effects emphasize\ntions, pavements, and pipelines. In other instances,\nthe conclusion of Steinbrugge et al. (1971, p. 11)\nthe shortening was expressed as slippage between the\nthat mountain-front zones, known to be associated\nstructure and the adjoining ground SO that pipelines\nwith geologically young faults such as the Sierra\nwere thrust over curbs and buildings seemingly slid\nMadre, are especially hazardous areas in terms of\nover the ground surface. In one instance, a building\nseismic shaking and potential surface faulting.\nwas jammed into an adjacent building formerly sepa-\nrated by a 6-inch gap; after the earthquake, the two\nbuildings overlapped about 1 foot (Frazier et al.\nPREDICTING THE FAULTING\n1971, pp. 233-235) Those structures that were in-\nBarrows et al. (1971) report the results of shallow\ntersected by the ruptures were subjected to vertical\ntrenching across the rupture zone at a number of dif-\nand lateral displacements of more than 3 feet and\nferent localities. In only one of eight trenches dug\ncompressive horizontal shortening of as much as 2\nacross the tectonic ruptures in alluvial deposits could\nfeet. These displacements may have been imposed at\nthe causative fault be recognized in unconsolidated\nrates of 3 fps (feet per second) or greater.1\ngravels; this result supports the judgment of Jen-\nCorrelation and Implications.-The distribution of\nnings and Housner (1971, p. 491) that the location\ndamage shows a strong correlation with: 1) the rela-\nof individual surface ruptures could not, in general,\ntively narrow zone of tectonic ruptures in the San\nhave been predicted precisely enough SO that occu-\nFernando area; 2) the south-facing mountain front\npants of specific buildings could be warned of the\nof the San Gabriel Mountains north of Sylmar, ex-\nhazard. (Where the ruptures involved consolidated\ntending southeastward from San Fernando to Pasa-\nmaterials, the fault surface was identified readily in\ndena; and 3) the boundaries of alluviated areas (Q1\nthe trench walls.) However, the zone of surface rup-\nand Q2, figs. 8 and 9) On a relative basis, the\ntures coincides, in general, with a preexisting topo-\namount of damage caused by the zone of tectonic\ngraphic scarp and a ground water impediment, both\nruptures was small, but the degree of damage was\nof which indicate geologically young, recurring fault-\nlarge.\ning along this part of the valley floor. Thus, the gen-\nThe most severe damage was sustained by struc-\neral position of the 1971 rupture zone could have\nbeen determined had a specific study been made.\nI The peak velocity of horizontal ground movement derived from\nanalysis of the Pacoima Dam accelerogram, recorded on jointed\nThe 1971 tectonic ruptures have been mapped at\ncrystalline basement rocks, was 3.77 fps; the peak rate of vertical\nscales suitable for future identification of their loca-\nmovement was about one-half of that amount (Trifunac and Hud-\ntion to within 50 feet, the width of small city lot\nson 1971) The velocity of displacement of alluvium during normal\n(Barrows et al. 1971; Kamb et al. 1971, fig. 3; and\nfaulting associated with buried nuclear explosions in Nevada ranged\nupward from about the same value, 3.3 fps. In contrast to these\nthe U.S. Geological Survey Staff 1971, fig. 2) This\nrates are the velocities of propagation of ruptures along the ground\nrecord should surely serve as sufficient warning of fu-\nsurface during the nuclear tests, more than 2 km (6,560 ft) per\nture risk to those occupying buildings within the\nsecond, comparable to expected shear-wave velocities in alluvium\n(McKeown and Dickey 1969).\nzone, even if more detailed mapping is not available.","Effects of Earthquake as Related to Geology\n153\nDamaging effects of the earthquake can be corre-\nThe distribution of the greatest deformation across a\nlated with the narrow zone of tectonic ruptures, with\nzone about 200 feet wide suggests that the precise lo-\nthe area of relatively intense shaking between the\ncation of individual ruptures may not be as signifi-\nrupture zone and the epicenter of the main shock,\ncant for engineering purposes as identification and\nand with boundaries between unconsolidated al-\nproper land-use zoning of the area within which rup-\nluvial materials and harder rocks. Although evidence\nturing may recur.\nof geologically young movement along the San Fer-\nThere is little doubt that the fault along which\nnando fault was available, it had not been recog-\nthe February 1971 tectonic ruptures occurred could\nnized or appreciated. Faults not now recognized as\nhave been recognized beforehand had sufficiently de-\nactive in this area (south and southeast of the \"great\ntailed studies been made. However, no study specifi-\nbend\" of the San Andreas) should be examined for\ncally directed toward locating the fault or its degree\nsuch evidence.\nof activity had been made; this is not surprising be-\ncause in only very recent years have geologists begun\nREFERENCES\nto evaluate the potential activity of faults that have\nno record of historic rupture. However, preexisting\nAllen, Clarence R., Engen, G.R., Hanks, Thomas C., Nord-\nevidence, such as the ground water impediment and\nquist, J.M., and Thatcher, W.R., \"Main Shock and Larger\ntopographic scarps, could have led to specific investi-\nAftershocks of the San Fernando Earthquake, February 9\nThrough March 1, 1971,\" The San Fernando, California,\ngation and to a reasonable assessment of the degree\nEarthquake of February 9, 1971, Geological Survey Profes-\nof activity (e.g., Wentworth et al. 1970) In addition,\nsional Paper 733, U.S. Geological Survey and the National\nanalysis of topographic expression of the faults and\nOceanic and Atmospheric Administration, U.S. Department\nrelevant literature (Oakeshott 1958, Hill 1954, Meri-\nof the Interior and U.S. Department of Commerce, Wash-\nfield 1958, and Proctor 1970) could have led to pre-\nington, D.C., 1971, pp. 17-20.\ndiction of the type of movement to be expected on\nBarrows, A.G., Kahle, J.E., Weber, F.H., Jr., and Saul, R.B.,\nMap of Surface Breaks Resulting From the San Fernando,\nthe fault.\nCalifornia, Earthquake of February 9, 1971, Preliminary Re-\nport II, Plate I, California Division of Mines and Geology,\nCONCLUSIONS\nSacramento, 1971, scale 1:24,000.\nCalifornia Division of Safety of Dams, \"Effects of the San\nThe San Fernando earthquake was unique in sev-\nFernando Earthquake on the Van Norman Reservoir Com-\neral respects: It was the first in historic time to form\nplex,\" California Department of Water Resources Interim\nReport, Sacramento, May 1971, 27 pp. and 5 pl.\ntectonic ruptures in the Los Angeles metropolitan\nCalifornia State Water Rights Board, \"City of Los Angeles VS.\narea; the geometry of the causative fault is such that\nCity of San Fernando, et al.,\" San Fernando Valley Refer-\nit underlies part of the urbanized area at shallow\nence Report of Referee No. 650079, Vols. I and II, Superior\ndepths, thus accounting, in part, for the relatively in-\nCourt, Los Angeles County, Calif., July 1962.\ntense effects in that area; and these effects included\nCorbató, Charles E., \"Bouguer Gravity Anomalies of the San\nFernando Valley, California,\" California University Publi-\nthe strongest ground motions ever recorded and were\ncations in Geological Sciences, Vol. 46, No. 1, University of\nrelatively well recorded over a large part of the\nCalifornia Press, Berkeley, Nov. 1963, pp. 1-32.\nnorthern Los Angeles Basin.\nFallgren, Richard B., and Smith, Jay L., \"Geologic and Soil\nAt magnitude 6.4, the earthquake was significantly\nInvestigation, San Fernando Valley Juvenile Hall, Sylmar,\nsmaller than the 1857 Fort Tejon earthquake (mag-\nCalifornia,\" for the Los Angeles County Engineer by\nFUGRO, Inc., Long Beach, Calif., Sept. 20, 1971, 45 pp.\nnitude 8+), caused by right-lateral strike slip and\nand 2 pl. (unpublished report).\nsurface rupturing on the San Andreas fault just\nFrazier, G.A., Wood, J.H., and Housner, G.W., \"Earthquake\nnorth of the San Gabriel Mountains, as well as the\nDamage to Buildings,\" Earthquake Engineering Research\n1952 Kern County earthquake (magnitude 7.7),\nLaboratory Report EERL 71-02, California Institute of\ncaused by left-oblique reverse slip and surface rup-\nTechnology, Pasadena, June 1971, pp. 140-298.\nHill, M.L., \"Tectonics of Faulting in Southern California,\"\nturing on the White Wolf fault. These much larger\nCalifornia Division of Mines Bulletin 170, Sept. 1954, pp.\nearthquakes and much longer rupture zones resulted\n5-14.\nfrom the same stress system that produced the San\nHudson, Donald E., \"Strong-Motion Accelerogram Processing,\"\nFernando earthquake, which thus should be viewed\nStrong-Motion Instrumental Data on the San Fernando\nas only the lower limit to be expected from this sys-\nEarthquake of February 9, 1971, Division of Engineering\nand Applied Science, Earthquake Engineering Research\ntem.","154\nSan Fernando Earthquake of 1971\nLaboratory, California Institute of Technology, Pasadena,\nvoir Complex, California Division of Safety of Dams, Sacra-\nSept. 1971, pp. 157-204 (see table I, pp. 165-181).\nmento, May 1971, 13 pp. and 15 pl.\nJennings, P.C., and Housner, G.W., \"Conclusions and Recom-\nSlosson, James E., \"Engineering Geology Review of San Fer-\nmendations,\" Earthquake Engineering Research Laboratory\nnando Valley Juvenile Hall, Exhibit D,\" Report on Olive\nReport EERL 71-02, California Institute of Technology,\nView Hospital, Structural Engineers Association of Southern\nPasadena, June 1971, pp. 471-499.\nCalifornia, Los Angeles, May 25, 1971, 4 pp.\nJennings, C.W., and Strand, R.G., Geologic Map of California,\nSteinbrugge, Karl V., Schader, E.E., Bigglestone, H.C., and\nOlaf P. Jenkins Edition, Los Angeles Sheet, California\nWeers, C.A., San Fernando Earthquake, February 9, 1971,\nDivision of Mines and Geology, Sacramento, 1969, scale\nPacific Fire Rating Bureau, San Francisco, Calif., 1971, 93 pp.\n1:250,000.\nStructural Engineers Association of Southern California, Report\nKamb, Barclay, Silver, L.T., Abrams, M.J., Carter, B.A., Jor-\non Olive View Hospital, Los Angeles, May 25, 1971, 40 pp.\ndan, Thomas H., and Minster, J. Bernard, \"Pattern of Fault-\nTrifunac, Mihailo D., and Hudson, Donald E., \"Analysis of\ning and Nature of Fault Movement in the San Fernando\nthe Pacoima Dam Accelerogram-San Fernando, California,\nEarthquake,\" The San Fernando, California, Earthquake of\nEarthquake of 1971,\" Bulletin of the Seismological Society\nFebruary 9, 1971, Geological Survey Professional Paper 733,\nof America, Vol. 61, No. 5, Oct. 1971, pp. 1393-1411.\nU.S. Geological Survey and the National Oceanic and At-\nU.S. Congress, Senate Committee on Public Works, Govern-\nmospheric Administration, U.S. Department of the Interior\nmental Response to the California Earthquake Disaster of\nand U.S. Department of Commerce, Washington, D.C.,\nFebruary 1971, Serial No. 92-H22, U.S. 92d Congress, 1st\n1971, pp. 41-54.\nSession, Washington, D.C., 1971, 985 pp.\nMcKeown, F.A., and Dickey, D.D., \"Fault Displacements and\nU.S. Geological Survey Staff, \"Surface Faulting,\" The San Fer-\nMotion Related to Nuclear Explosions,\" Bulletin of the\nnando, California, Earthquake of February 9, 1971, Geologi-\nSeismological Society of America, Vol. 59, No. 6, Dec. 1969,\ncal Survey Professional Paper 733, U.S. Geological Survey\npp. 2253-2270.\nand the National Oceanic and Atmospheric Administration,\nMerifield, P.M., \"Geology of a Portion of the Southwestern\nU.S. Department of the Interior and U.S. Department of\nSan Gabriel Mountains, San Fernando and Oat Mountain\nCommerce, Washington, D.C., 1971, pp. 55-76.\nQuadrangles, Los Angeles County, California,\" M.A. thesis,\nWentworth, Carl M., Yerkes, R.F., and Allen, Clarence R.,\nUniversity of California, Los Angeles, 1958, 61 pp.\n\"Geologic Setting and Activity of Faults in the San Fer-\nOakeshott, Gordon B., \"Geology and Mineral Deposits of San\nnando Area, California,\" The San Fernando, California,\nFernando Quadrangle, Los Angeles County, California,\"\nEarthquake of February 9, 1971, Geological Survey Pro-\nCalifornia Division of Mines Bulletin 172, Feb. 1958, 147\nfessional Paper 733, U.S. Geological Survey and the Na-\npp. (see plate 1, scale 1:62,500, in back pocket).\ntional Oceanic and Atmospheric Administration, U.S. De-\nOliver, H.W., Robbins, S.L., Grannell, R.B., Alewine, R.W.,\npartment of the Interior and U.S. Department of Com-\nand Biehler, Shawn, \"Surface and Subsurface Movements\nmerce, Washington, D.C., 1971, pp. 6-16.\nDetermined by Measuring Gravity,\" California Division of\nWentworth, Carl M., Ziony, J.I., and Buchanan, J.M., \"Pre-\nMines and Geology Bulletin 196, Ch. 10, 1973? (to be pub-\nliminary Geologic Environmental Map of the Greater Los\nlished).\nAngeles Area, California, Plate 1,\" U.S. Atomic Energy Com-\nProctor, R.J. (Compiler), \"Geologic Map and Sections Along\nmission TID-25363, Technical Information Division, Oak\nthe 4.4-Mile Sunland Tunnel,\" B-20262, Metropolitan\nRidge, Tenn., 1970, scale 1:250,000.\nWater District of Southern California, Los Angeles, July\nWesson, R.L., Lee, W.H.K., and Gibbs, J.F., \"Aftershocks\n1970 (unpublished map, scale 1:12,000)\nof the Earthquake,\" The San Fernando, California, Earth-\nScott, Nina H., \"Preliminary Report on Felt Area and In-\nquake of February 9, 1971, Geological Survey Profes-\ntensity,\" The San Fernando, California, Earthquake of Feb-\nsional Paper 733, U.S. Geological Survey and the National\nruary 9, 1971, Geological Survey Professional Paper 733, U.S.\nOceanic and Atmospheric Administration, U.S. Department\nGeological Survey and the National Oceanic and Atmos-\nof the Interior and U.S. Department of Commerce, Wash-\npheric Administration, U.S. Department of the Interior and\nington, D.C., 1971, pp. 24-29.\nU.S. Department of Commerce, Washington, D.C., 1971,\nYoud, T. Leslie, \"Landsliding in the Vicinity of the Van\npp. 153-154.\nNorman Lakes,\" The San Fernando, California, Earthquake\nScott, R.F., \"Preliminary Soil Engineering Report,\" Engineer-\nof February 9, 1971, Geological Survey Professional Paper\ning Features of the San Fernando Earthquake of February 9,\n733, U.S. Geological Survey and the National Oceanic\n1971, Earthquake Engineering Research Laboratory Report\nand Atmospheric Administration, U.S. Department of the\nEERL 71-02, California Institute of Technology, Pasadena,\nInterior and U.S. Department of Commerce, Washington,\nJune 1971, pp. 299-331.\nD.C., 1971, pp. 105-109.\nSeed, H.B., Lee, K.L., and Idriss, I.M., \"Appendix B-Pre-\nYoud, T. Leslie, and Castle, R.O., \"Borrego Mountain Earth-\nliminary Report on Lower San Fernando Dam Slide During\nquake of April 8, 1968,\" Proceedings Paper 7396, Journal of\nthe San Fernando Earthquake of February 9, 1971,\" Effects\nSoil Mechanics and Foundations Division, Vol. 96, No.\nof the San Fernando Earthquake on the Van Norman Reser-\nSM 4, July 1970, pp. 1201-1219.","Subsurface Geology of\nPortions of San Fernando Valley\nand Los Angeles Basin\nINTRODUCTION\nThe regional geologic setting of the San Fernando\nValley area and the Los Angeles Basin and a detailed\nrepresentation of subsurface geological conditions at\nselected locations of instruments which recorded the\nmain shock and certain aftershocks of the San Fer-\nnando earthquake are presented in this paper. Fig-\nCONTENTS\nure 1 is a generalized geologic map showing the loca-\nPage\ntions of geologic cross sections A-A' (fig. 2) and\n155 INTRODUCTION\nREGIONAL GEOLOGY\nB-B' and C-C' (fig. 3) Tables 1 and 2 are general-\n155\nGeneral Geology of San Fernando\n155\nized geologic columns for the San Fernando Valley\nValley Area\nand Los Angeles Basin, respectively.\nGeneral Geology of Los Angeles\n159\nThe general geologic map was designed to give a\nBasin\nSTRATIGRAPHY OF SAN FERNANDO VALLEY\nsurvey of the major rock types in the area studied\n161\nAREA\n(basement rocks, sedimentary rocks, and recent al-\nSTRATIGRAPHY OF Los ANGELES BASIN\n162\nluvial materials) and their relationship to topo-\n163 REFERENCES\ngraphic and geologic features. The three geologic\n164 BIBLIOGRAPHY\ncross sections are of interest for studies of earthquake\nground motion. See the paper by Duke et al.,\n\"Subsurface Site Conditions in the San Fernando\nEarthquake Area,\" in the section on Soils and Foun-\ndations, Volume I, for the engineering aspects of the\nDeep Subsurface Models identified in figures 2 and\n3. Areas of little information are interpretive, and\nthe conventional symbols were used to indicate the\nreliability of the information.\nREGIONAL GEOLOGY\nGeneral Geology of San Fernando Valley Area\nThe San Fernando Valley is a broad, fairly flat\nJ. A. JOHNSON\nplain bounded on the north by the San Gabriel and\nGeologist\nSanta Susana Mountains, on the west by the Simi\nC. M. DUKE\nHills, on the south by the Santa Monica Mountains,\nProfessor of Engineering\nand on the east by the Verdugo Mountains. See gen-\nUniversity of California at Los Angeles\neralized geologic map (fig. 1) .\nLos Angeles, Calif.\n155","San Fernando Earthquake of 1971\n156\nBc\nBe\nBc\nB c\nQal\nQal\nLAKE\nBc\n38\nPIRU\nBc\nBc\nBc\nBc\nQal\n14\nBc\nBc\nBc\nBc\n26\nQal\nQal\nit\nEPICENTER\nB\nQat\nBc.\nS\nan\nof\nc\nD\nBc\n=\nQal\nVAN NORMAN\nRESERVOIRS\nB c\nBc\n5\nthis\nCO\nGABRIEL\nQal\nFAULT\nQal\nEO\nBc\nBc\n170\nQal\n405\nBc\nBGA\nB c\n10\nBc\nQal\no\nQai\nthe\nBc\nsonto\nBc\nBc\nQal\nTUT\nLos Angeles\nQal\nSANTA\nHOLLYWOOD\n<001\nSanta Monica\nQal\n10\nQal\nLEGEND:\nQal\nQal\nAlluvium\n11\n5\nSedimentary Rocks, Pleistocene and older\nQal\nBc\nBasement Complex\nContact\nFault, dashed where approximately\nlocated or concealed\nThrust Fault, barbs on upper plate;\ndashed where approximately located\nboal\nLong Beach\nSurface Break, February 9, 1971\nQal\no4\nDeep Subsurface Models\nA\nA'\n405\nCross Section Line\nGeology modified from California Division\n0\n2\n4\n6\n8\n10\nof Mines and Geology map sheets of Los\nAngeles, San Bernardino, Long Beach,\nScale in miles\nand Santa Ana by J.A. Johnson\nFigure 1.-Generalized geologic map of Los Angeles area. Lines A-A', B-B', and C-C'\nare locations of geologic cross sections shown in figures 2 and 3.","Location of Deep Subsurface Model\nFault Questioned (?) where inferred\nRocks of the Basement Complex\nContact (Formation Boundary)\nQuestioned (?) where inferred\nRE-CAMBRIAN\nVertical Exaggeration 2:1\nGeology by J.A. Johnson\n10000\n--12000\nAll Elevations are in feet\n--14000\nHorizontal Scale in miles\n2000\n--2000\n--4000\n--6000\n--8000\nRecent Alluvial Deposits\nIntraformational Bedding\nArrows indicate relative\n4000\n- 0\nEXPLANATION\nDiorite\nDecember 1971\nA'\nB.C.\nGrano-\nB.C\nSaugus Fm.\n-22,000 ft. ?\nBASE OF\nB.C.\nOlive View San Gabriel\nmovement E\n2al\nMountains\nLOWER PLEISTOCENE\n5\nSaugus Fm.\nHospital\n-10000\n12000\n2000\n2000\n--4000\n-6000\n--8000\nOal\nFAULT\n0\nMatch Line\nMIDDLE MIOCENE\nZone\nTopanga Fm\nSection\nBend\nLOWER PLEISTOCENE\nFaul\nPLIOCENE\nUPPER PLIOCENE\nLOWER PLIOCENE\nwells\nUPPER MIOCENE\nRepetto Fm.\nPuente Fm.\nB.C.\nQal\nPico Fm.\nMIDDLE MIOCENE\nRinaldi St.\nTopanga Fm.\nUPPER MIOCENE\nMIOCENE\nUPPER\nModelo Fm.\n/\nFigure 2.-Geologic cross section A-A'. Palos Verdes-San Gabriel Mountains.\nUPPER MIOCENEO\nUPPER PLIOCENE\nLOWER PLIOCENE\nRepetto Fm.\nPuente Fm.\nDal\nPico Fm.\nB.C.\nB.C\nCatalina Schist\nLOWER PLIOCENE\nMESOZOIC\nRepetto Fm.\nSection Bend\nHoliday Inn\n8244 Orion\nMIDDLE MIOCENE\nE\nTopanga Fm.\n2al\n15107 Van Owen\nUPPER MIOCENE\nHospital\nUPPER PLIOCENE\nModelo Fm.\nF\nB.C.\nPico Fm.\nQal\nB.C.\nLOWER PLEISTOCENE San Pedro Fm\n15433 Ventura Blvd.\nUPPER MIOCENE\nHoward Johnson's\nModelo Fm.\nTopanga Fm.\nG\nMIOCENE\nMIDDLE\nSanta Monica Mountains\nUPPER MIOCENE\nPuente Fm.\nB.C.\nSanta Monica\nB.C\nPacific\nTRIASSIC?\nSlate\nSection Bend\nIal\nSection Bend\nB.C.\nBlvd.\nMIDDLE\nMIOCENE\nMonterey Shale\nMIOCENE\nTopanga\nPalos Verdes Hills\nwhening\nUPPER\nTopanga Fm.\nB.C.\nMIOCENE\nB.C.\nMIDDLE\nMIOCENE\nModelo\nFm\nFm.\nCatalina Schist\nMIOCENE\nUPPER\nModelo\nMESOZOIC\nSection\nUPPER Bend\nPLEISTOCENE\nTerrace\nUPPER PLIOCENE\nSan Pedro Fm.\nTopanga\nRepetto Fm.\nFm.\n-4000- PLIOCENE\nPico Fm.\nLOWER\nModelo\nMatch Line\nFm.\n-6000-?\nA\n-6000-\n-8000-\n2000-\n-2000-\n-4000-\n-2000-\n-8000-\n-10000-\n-12000-\n-14000-\n2000-\n0.\n0","--10000\n--12000\n--2000\n--4000\n--6000\n--8000\n3000\n2000\n1000\n--2000\n--4000\n4000\n2000\n--0\n- 0\nB'\nC'\nBlvd.\nRocks\nB.C.\nB.C.\nPLEISTOCENE\nGabbroic\nPacoima Fm\nCAMBRIAN\nFoothin,\nB.C.\nPRE-\nQal\nB.C.\n2al\nSan Gabriel Mountains\nGranitic Rocks\nB.C.\nVerdugo Mountains\nMESOZOIC\nCRETACEOUS?\nJURASSIC ?or\nLOWER\nB.C.\nB.C.\nBASE OF Saugus Fm.\nDiorite\nGneiss\nUPPER\n-22,000 ft. ?\nSYLMAR SECTION\nFigure 3.-Geologic cross sections. B-B', Sylmar section, and C-C', Elysian Park Hills section.\nSECURITY\nLOWER PLEISTOCENE\nSECURITY\nMIDDLE\nPLEISTOCENE\nPacoima Fm\nSaugus Fm.\nB.C.\n,2al\nPLIOCENE\nRepetto\nLOWER\nFm.\nMIDDLE MIOCENE\nTopanga Fm.\nB.C.?\n-2al\nUPPER MIOCENE\nModelo Fm.\nMIDDLE MIOCENE\nIi\nUPPER MIOCENE\nSanta Monica Slate B.C.\nTopanga Fm.\nFwy,\nB.C.\nOax\nIal\nElysian Park Hills\nJURASSIC?\nB.C.\nMIOCENE\nPuente Fm.\nB\n4000-\n-4000-\n-10000-\n-12000-\n2000-\n0-\n-2000-\n-6000-\n-8000-\nUPPER\nFault Questioned (?) where inferred\n,2al\nArrows indicate relative movement\nRocks of the Basement Complex\nQuestioned (?) where inferred\nMIOCENE\nRecent Alluvial Deposits\nVertical Exaggeration 2:1\nTopanga\nIntraformational Bedding\nAll Elevations are in feet\nLOWER\nHorizontal scale in miles\nGeology by J.A. Johnson\n(Formation Boundary)\n1\nEXPLANATION\nDecember 1971\nFm.\nUPPER MIOCENE\nContact\nPuente Fm.\nQal\nB.C.\n2al\n0\nB.C.\n.5\nFernando Fm\nPLIOCENE\nELYSIAN PARK HILLS SECTION\nSt.\nPLIOCENE\nJurassic\nPlutonic\nQal\nUPPER MIOCENE\nRocks ?\nPuente Fm.\nLOWER MIOCENE\nSan Pedro Fm.\nTopanga Fm.\nPLEISTOCENE\nRiver\nUPPER PLIOCENE\nLOWER PLIOCENE\nRepetto Fm.\nB.C.\nPico Fm.\nC\n-18000-\n-4000-\n-6000-\n-8000-\n-10000-\n-12000-\n-14000-\n-16000-\n-20000-\n0-\n-2000-","Subsurface Geology of Earthquake Area\n159\nThe extreme eastern end of the valley is bounded\nStructurally, the valley is a faulted series of folds\nby an uplifted block of metamorphic and granitic\n(Bailey and Jahns 1954, cross section A-A') that\nrocks. This block, known as the Verdugo Mountains,\nbroadens and deepens to the east where it is trun-\nis separated from the valley by the Verdugo fault\ncated by the upfaulted southwest front of the Ver-\nand from the La Crescenta area, to the east, by the\ndugo Mountains. To the north is a smaller fold,\nLa Crescenta Valley fault.\nknown as the Little Tujunga syncline (Oakeshott\n1958), that extends along the southern margin of the\nGeneral Geology of Los Angeles Basin\nSan Gabriel Mountains. The northern limb of this\nfold is truncated by the San Gabriel Mountains\nThe Los Angeles Basin, as described in this report,\n(cross section B-B') The southern border of the\nis a structurally complex region bounded on the\nvalley is underlain by the north-dipping sedimentary\nnorth by the Santa Monica Mountains and the Ely-\nformations that cap the Santa Monica Mountains\nsian, Repetto, and Puente Hills. The southern\n(cross section A-A')\nboundary is made up of the Palos Verdes Hills and\nThe sediments underlying the valley at their deep-\nthe Pacific Ocean. Although the basin extends be-\nest point include some 15,000 feet (Corbató 1963)\nneath the Pacific Ocean, this part will not be in-\nof broadly folded and faulted Cenozoic and Mesozoic\ncluded in the discussion.\n(?) rocks that unconformably rest on basement com-\nThe present topography of the basin is a low-lying\nplex (table 1) Quaternary materials in the form of\nsurface which, except for a series of hills along the\nstream-deposited, coalescing alluvial fans and terrace\nNewport-Inglewood uplift and the Palos Verdes\ndeposits blanket most of the floor of the valley.\nHills, slopes gently toward the ocean. The subsurface\nThe southern margin of the valley is bounded by\ngeology is not as simple as the topography and,\nthe east-west trending Santa Monica Mountains.\ntherefore, has been broken up into several subbasins\nStructurally, the mountainous area east of Topanga\nor \"blocks\" on the bases of rock type (table 2) and\nCanyon is a large, complexly faulted anticline which\na series of major faults that cross the region (Yerkes\nplunges to the west with basement rocks exposed to\net al. 1965) This report is concerned only with\nthe east (cross section A-A') Rocks of the area in-\nYerkes' \"Southwestern Block,\" the northwestern part\nclude a wide variety of coarsely crystalline plutonic\nof the \"Central Block,\" and the westernmost portion\nrocks, other intrusives and pyroclastic rocks, meta-\nof the \"Northeastern Block\" (Yerkes et al. 1965, fig.\nmorphic schists and slates, and a sequence of sedi-\n3, p. A5) See general geologic map in figure 1.\nmentary rocks (Hoots 1931)\nThe surface of the \"Southwestern Block\" is a low\nThe San Gabriel Mountains, which border the val-\nflat plain that extends from the Santa Monica-\nley to the north, are bounded on all sides by major\nHollywood fault zone (cross section A-A') south to\nfaults. The series of faults, along the northern mar-\nLong Beach, with little topographic relief except for\ngin of the valley or the southern margin of the San\nthe Palos Verdes Hills. The area to the east is\nGabriel Mountains, are north-dipping thrust faults\nbounded by the Newport-Inglewood fault zone.\nwhich offset rocks as young as Quaternary and in-\nBased on oil well information and exposure in the\nclude the fault that broke the surface on February 9,\nPalos Verdes Hills, the basement complex of the\n1971 (cross section B-B')\n\"Southwestern Block\" probably is composed entirely\nThe rocks within the San Gabriel Mountains con-\nof Catalina schist (Schoellhamer and Woodford\nsist of late Mesozoic plutonic rocks and a complex\n1951). The overlying rocks are a thick section of\nseries of older plutonic, metasedimentary, and meta-\nmiddle Miocene to Recent marine sediments, which\nvolcanic rocks.\nlocally includes Miocene intrusives.\nThe Simi Hills are a faulted and elevated block of\nStructurally, this block consists of two major\nmassive Upper Cretaceous sandstones and thinly bed-\nnorthwest-trending anticlinal arches (Yerkes et al.\nded shales, overlain by lesser amounts of Eocene and\n1965) in basement rocks north of the Palos Verdes\nMiocene marine sandstones and conglomerates. To\nHills. To the south and underlying the Palos Verdes\nthe north and east of the Simi Hills are the Santa\nHills is a doubly plunging anticline paralleling these\nSusana Mountains, a complexly folded and faulted\nmajor structures.\nseries of Miocene marine sandstones, conglomerates,\nThe area studied in the \"Central\" and \"Northeast-\nern\" Blocks is south of the Hollywood and Raymond\nand diatomaceous shales.","160\nSan Fernando Earthquake of 1971\nTable 1.-Generalized geologic column-San Fernando Valley\nAge\nFormation name\nLithologic description\nRecent\nAlluvium\nClay, silt, and sand to the west end of the valley; coarser\nmaterial (sand, gravel, and boulders) toward the eastern\nportion of the valley.\nUpper Pleistocene\nOlder alluvium and terrace\nWell-graded, poorly consolidated, angular-to-subangular\ndeposits\nfanglomerate and terrace gravels.\nQuater-\nMiddle Pleistocene\nPacoima Formation\nReddish-brown, well-graded, and slightly folded conglomerate\nnary\nand fanglomerate.\nLower Pleistocene\nSaugus Formation\nWell-graded, loosely consolidated, nonmarine conglomerate\nand coarse-grained sandstone beds, with generally finer\ninterbedded marine sediments toward the west end of the\nvalley.\nUpper\nPico Formation\nNonmarine sandstone, mudstone, and conglomerate which\nFernando\n(Sunshine\ngrade into older sediments, consisting of marine sandstone,\nTertiary\nPliocene\nMiddle\nForma-\nRanch)\nsiltstone, and conglomerate.\ntion (?)\nLower\nRepetto Forma-\nMarine sandstone, conglomerate, siltstone, and shale.\ntion (Towsley)\nUpper Miocene\nModelo Formation\nMarine fine-to-coarse-grained sandstone and conglomerate,\ninterbedded with diatomaceous shales.\nMiddle to lower Miocene\nTopanga Formation\nCoarse-grained continental and marine sandstone and con-\nglomerate beds, interbedded with basaltic lava flows.\nMiddle Eocene\nDomengine Formation\nMassive marine sandstone and conglomerates.\nLower Eocene to Paleocene\nMartinez Formation\nCoarse sandstone, interbedded with dark shales and pebble\n(?)\nconglomerate.\nUpper Cretaceous\nChico Formation\nMassive marine sandstones, coarse conglomerates, and inter-\nmixed shale beds.\nGranitic and metamorphic rocks.\nPre-Cretaceous\nBasement\nto Precambrian\nSanta Monica\nBlack slates with schist facies.\ncom-\nplex\nSlate, Jurassic(?)\nMendenhall\nQuartz-feldspar gneiss intruded by gabbroic rocks.\nGneiss\nHill fault zones, east of the Newport-Inglewood\n\"Northeastern\" Blocks, which consists of Mesozoic\nuplift, and west of the San Gabriel River (fig. 1 and\nmetasedimentary rocks, is overlain by up to 32,000\ncross section C-C') .\nfeet of Late Cretaceous to Pleistocene marine-nonma-\nTopographically, the region includes the Elysian\nrine sediments interbedded with middle Miocene vol-\nand Repetto Hills, a low-lying plain to the south,\ncanics (Yerkes et al. 1965) Locally, the area is blan-\nand the northwest-trending hills that extend south\nketed by a thin layer of alluvial and older alluvial\nfrom Beverly Hills along the Newport-Inglewood\nmaterials.\nfault zone.\nStructurally, this area is dominated by an asym-\nThe basement complex of the \"Central\" and metrical, doubly plunging, synclinal trough that","Subsurface Geology of Earthquake Area\n161\nTable 2.-Generalized geologic column-Los Angeles Basin\nAge\nFormation name\nLithologic description\nSand, silt, gravels, and dune sand.\nRecent\nAlluvium\nTerrace and older alluvium\nMarine and nonmarine silt, sand, and gravel-forming terrace\nQuater-\nUpper Pleistocene\ndeposits.\nnary\nLower Pleistocene\nSan Pedro Formation\nSilt, sand, gravel, and clay.\nUpper Pliocene\nPico Formation\nTan-to-brown conglomerate, sandstone, and siltstone.\nPliocene\nFernando\nForma-\nLower Pliocene\ntion (?)\nRepetto Forma-\ntion\nTertiary\nUpper Miocene\nPuente, Monterey (Palos\nSiltstone and shale, well-bedded; coarse-grained sandstone\nVerdes Hills), and Modelo\nand conglomerate.\nMiocene\nFormation\nPalos Verdes Hills-mudstone and diatomaceous shale with\nsiltstone, sandstone, limestone, and conglomerate.\nMiddle and\nTopanga Formation\nCoarse-grained, well-bedded sandstone; massive conglomerate\nlower(?) Miocene\nand siltstone with interbedded sandstone.\nOligocene\nVaqueros, Sespe, Santiago,\nNot present in area of study.\nEocene\nand Silverado Formations\nPaleocene\nFine-grained chlorite quartz schist and blue glaucophane-\nWest-\nCatalina\nSchist,\nbearing schist.\nern\nJurassic\ncom-\nBase-\nplex\n(?)\nment\ncom-\nUpper Cretaceous\nplex\nGranitic intrusives.\nEast-\nern\nUpper Jurassic\nVolcanics.\ncom-\nplex\nTriassic\nMetasedimentary schists.\ntrends northwest. The structural relief of the base-\nFernando Valley area is a group of pre-Cretaceous\nment rocks between the ends and central portion of\ncrystalline and metamorphic rocks, exposed in and\nthe trough varies vertically between 15,000 and\ncomprising the main mass of the San Gabriel and\nVerdugo Mountains to the north of the valley and\n18,000 feet.\nthe eastern portion of the Santa Monica Mountains\nThe Elysian-Repetto Hills area is very complex\nto the south. The subsurface distribution of pre-Cre-\nbecause of its location at the intersection of the east-\ntaceous basement rocks below the San Fernando Val-\nwest-trending Hollywood fault system and the north-\nley is unknown as to type and extent.\nwest-trending faults which may be a part of the\nWhittier fault system (Lamar 1970) This complex\nBasement rocks within the central portion of the\nSanta Monica Mountains consist of Late Jurassic (?)\nfault pattern has caused rapid local changes in the\nslates of the Santa Monica Formation (Hoots 1931)\nlithology and thickness of Miocene formations in the\nTo the east, including large portions of the Verdugo\narea (cross section C-C').\nMountains, the basement rocks consist of intrusive\nplutonic rocks of quartz dioritic or granodioritic\nSTRATIGRAPHY OF SAN FERNANDO\ncomposition similar to rocks of Late Cretaceous age\nVALLEY AREA\nfound in the San Gabriel Mountains (Lamar 1961)\nBasement Rocks.-The basement complex of the San\nThe San Gabriel Mountains south of the San Ga-","San Fernando Earthquake of 1971\n162\nwell-graded and poorly consolidated conglomerate\nbriel fault contain basement rocks that include\nand coarse-grained sandstone beds (Oakeshott 1958).\nschists, and quartzites, which are associated with and\nThe formation is mainly of continental origin, but\nintruded by quartz diorite (Oakeshott 1958) These\nmay grade into older and generally finer marine sedi-\nrocks are all intruded by Upper Jurassic to Lower\nCretaceous granitics. North of the fault, the base-\nments.\nment rocks contain Mesozoic syenite, hornblende\nThe Pacoima Formation (middle Pleistocene)\ndiorite, and Precambrian gneiss and gabbros that are\nconsists of well-graded reddish-brown fanglomerate\nalso intruded by Upper Jurassic to Lower Cretaceous\nand conglomerate lying on Saugus Formation gravels\ngranitic rocks.\nand underneath terrace deposits around the southern\nmargin of the San Gabriel Mountains.\nUpper Cretaceous (Chico Formation).- The oldest\nUpper Pleistocene to Recent \"older alluvium\"\nsedimentary rocks of the San Fernando Valley area\nconsists of uplifted, poorly consolidated, unsorted,\n(Chico Formation) are exposed at the surface in the\nangular-to-subangular fanglomerate and terrace grav-\nSimi Hills. They consist of massive marine sandstones\nels.\nand coarse conglomerates, interbedded with shale.\nRecent.-The alluvial materials of the San Fernando\nEocene (Martinez and Domengine Formations).-\nValley vary from location to location, depending on\nThe Eocene is represented by the Martinez and Do-\nthe source rock. In the western and extreme south-\nmengine Formations (California State Water Rights\nern portions of the valley (generally south of the Los\nBoard 1962). The Martinez, older of the two forma-\nAngeles River) the alluvial materials consist of clay,\ntions, is exposed along the San Gabriel fault and\nsilt, and sand-size particles derived from sedimentary\nconsists of a series of coarse marine shales, sand-\nrocks which make up large portions of the Simi Hills\nstones, and conglomerates. The Domengine Forma-\nand the Santa Susana and Santa Monica Mountains\ntion is composed of massive marine standstones and\n(fig. 1) In the northernmost portion of the valley\nconglomerates that are exposed along the northwest-\n(Sylmar-San Fernando area) and the east valley area\nern margin of the valley.\nsouth to the Los Angeles River, the deposits are\nMiocene (Topanga and Modelo Formations).- The\nmuch coarser; they range from boulder size near\nTopanga Formation makes up the lower to middle\nthe San Gabriel Mountains to sand, silt, and gravels\nportion of the Miocene and is composed of coarse\nnear the Los Angeles River (California State Water\nmarine and continental sandstone and conglomerate\nRights Board 1962)\nbeds, interbedded with andesite and basalt flows.\nThe upper Miocene is made up of a series of marine\nSTRATIGRAPHY OF LOS ANGELES BASIN\nconglomerate and fine-to-coarse-grained sandstones,\ninterbedded with diatomaceous shales (Modelo For-\nBasement Rocks.-The basement rocks of the Los\nmation) The Modelo may underlie the whole valley\nAngeles Basin have been divided into two groups by\n(California State Water Rights Board 1962)\nYerkes et al. (1965) on the basis of lithology. The\nPliocene (Repetto and Pico Formations).-The\ngroups, known as the \"eastern\" and \"western\" com-\nlower portion of the Pliocene is composed of the Re-\nplexes, are separated by the Newport-Inglewood and\npetto (Towsley) Formation, which consists of ma-\nSanta Monica fault zones.\nrine siltstones and mudstones combined with lesser\nThe western complex (west of the Newport-\namounts of sandstone and conglomerate. The middle\nInglewood fault), composed of Catalina schist, is\nand upper Pliocene Pico Formation is mainly com-\nexposed in the Los Angeles Basin (cross section\nposed of marine siltstones, sandstones, and conglom\nA-A') only in the Palos Verdes Hills. This complex\nerates, which grade into younger nonmarine sand-\nconsists of fine-grained chlorite-quartz schist and\nstone, mudstone, and conglomerate. Both formations\nblue glaucophane-bearing schist of unknown, unde-\nmay be included under one name, Fernando, as\ntermined, or not definitely known age or strati-\nsuggested by Lamar (1970).\ngraphic position (Woodring et al. 1946).\nPleistocene (Saugus and Pacoima Formations).-\nThe basement rocks of the eastern complex are\nThe lower Pleistocene Saugus Formation consists of\ncomposed of Late Cretaceous granitic intrusives,","Subsurface Geology of Earthquake Area\n163\nTriassic metasedimentary schists, and a series of vol-\nREFERENCES\ncanics of probable Late Jurassic age (cross section\nBailey, T., and Jahns, R., \"Geology of the Transverse Range\nC-C').\nProvince,\" California Division of Mines Bulletin 170, Ch. II,\nPaleocene, Eocene, and Oligocene.-Rocks of Paleo-\nNo. 6, Sept. 1954, pp. 83-106.\nCalifornia State Water Rights Board, \"City of Los Angeles vs.\ncene, Eocene, and Oligocene age do exist in the Los\nCity of San Fernando, et al.,\" San Fernando Valley Refer-\nAngeles Basin (Vaqueros, Sespe, Santiago, and Sil-\nence Report of Referee No. 650079, Vols. I and II, Superior\nverado Formations), but are not considered in this\nCourt, Los Angeles County, Calif., July 1962.\nreport because they are not included in the cross sec-\nCorbató, Charles E., \"Bouguer Gravity Anomalies of the San\ntions or site model studies.\nFernando Valley, California,\" California University Publica-\ntions in Geological Sciences, Vol. 46, No. 1, University of\nMiocene (Topanga, Modelo, Monterey, and Puente\nCalifornia Press, Berkeley, Nov. 1963, pp. 1-32.\nFormations).-Rocks of the Los Angeles Basin area\nEldridge, G.H., and Arnold, Ralph, \"The Santa Clara Valley,\nof middle to lower Miocene are, for the most part,\nPuente Hills, and the Los Angeles Oil Districts, Southern\nincluded in the Topanga Formation which consists\nCalifornia,\" Geological Survey Bulletin 309, U.S. Department\nof the Interior, Washington, D.C., 1907, 266 pp.\nof marine well-bedded sandstones, siltstones, and\nHoots, Harold W., \"Geology of the Eastern Part of the Santa\nmassive conglomerates. Late Miocene rocks are in-\nMonica Mountains, Los Angeles County, California,\" Geo-\ncluded in the equivalent, or nearly equivalent, Mo-\nlogical Survey Professional Paper 165-C, U.S. Department of\ndelo, Monterey, and Puente Formations. Lithologi-\nthe Interior, Washington, D.C., 1931, 134 pp.\ncally, these formations include marine shales of\nJennings, C.W., Geologic Map of California, Long Beach\nSheet, California Division of Mines and Geology, Sacra-\nvarious types, sandstone, conglomerate, and, in the\nmento, 1962, scale 1:250,000.\nPalos Verdes Hills (Monterey Formation), mud-\nJennings, C.W., and Strand, R.G., Geologic Map of Cali-\nstone, diatomaceous shale, and interbedded siltstone,\nfornia, Los Angeles Sheet, California Division of Mines and\nsandstone, limestone, and conglomerate beds\nGeology, Sacramento, 1969, scale 1:250,000.\n(Woodring et al. 1946).\nLamar, Donald L., \"Structural Evolution of the Northern Mar-\ngin of the Los Angeles Basin,\" Ph. D. thesis, University of\nPliocene (Repetto and Pico Formations).-Rocks of\nCalifornia, Los Angeles, 1961, 142 pp.\nPliocene age have been divided into two formations\nLamar, Donald L., \"Geology of the Elysian Park-Repetto Hills\n-Repetto (lower Pliocene) and Pico (upper Pli-\nArea, Los Angeles County, California,\" California Division\nocene) -by many authors. Recently, Lamar (1970)\nof Mines and Geology Special Report 101, Sacramento, 1970,\n45 pp.\nhas combined the two formations and used the name\nMerifield, P.M., \"Geology of a Portion of the Southwestern\nFernando Formation, as was mentioned earlier in\nSan Gabriel Mountains, San Fernando and Oat Mountain\nthe section on the Stratigraphy of San Fernando Val-\nQuadrangles, Los Angeles County, California,\" M. A. thesis,\nley Area. The name Fernando was first used by Eld-\nUniversity of California, Los Angeles, 1958, 61 pp.\nridge and Arnold in 1907. Lamar's Fernando Forma-\nOakeshott, Gordon B., \"Geology and Mineral Deposits of San\ntion includes \"rocks lying between the Puente\nFernando Quadrangle, Los Angeles County, California,\"\nCalifornia Division of Mines Bulletin 172, Feb. 1958, 147 pp.\nFormation and the younger alluvial and terrace de-\nPoland, Joseph F., Garrett, A.A., and Sinnott, Allen, \"Geology,\nposits,\" and consists of marine tan-to-brown siltstone,\nHydrology and Chemical Character of Ground Waters in\nsandstone, shale, and conglomerate beds.\nthe Torrance-Santa Monica Area, California,\" Geological\nSurvey Water-Supply Paper 1461, U.S. Department of the\nPleistocene (San Pedro Formation and Terrace De-\nInterior, Washington, D.C., 1959, 425 pp.\nposits).-Lower Pleistocene rocks (San Pedro For-\nProctor, R.J., \"La Crescenta Tunnel Route,\" Metropolitan\nmation) include marine silt, sand, and gravels and\nWater District of Southern California, Los Angeles, June\nare overlain, at various localities, by upper Pleisto-\n1964, scale 1:12,000 (unpublished geologic map and section)\ncene marine and nonmarine terrace deposits. These\nProctor, R.J., \"Flint Ridge Tunnel Route,\" Metropolitan\nWater District of Southern California, Los Angeles, May\nterrace deposits include, respectively, marine and\n1965, scale 1:12,000 (unpublished geologic map and section)\nnonmarine sand, gravel, and silt.\nProctor, R.J., \"Sepulveda Tunnel Route,\" Metropolitan Water\nRecent.-Recent deposits include dune sand (south\nDistrict of Southern California, Los Angeles, June 1967,\nscale 1:12,000 (unpublished geologic map and section)\nof Ballona Creek and near the present-day coastline)\nProctor, R.J., \"Verdugo Tunnel Route,\" Metropolitan Water\nand alluvial materials that consist of sand, gravel,\nDistrict of Southern California, Los Angeles, Nov. 1970,\nand silt in the stream channels and beneath the flood\nscale 1:12,000 (unpublished geologic map and section).\nplains (Poland et al. 1959).\nRogers, T.H., Geologic Map of California, Santa Ana Sheet,","San Fernando Earthquake of 1971\n164\nDosch, M.W., and Hunter, W.J., \"Bandini Oil Field,\" Sum-\nCalifornia Division of Mines and Geology, Sacramento, 1965,\nmary of Operations, California Oil Fields, Vol. 44, No. 1,\nscale 1:250,000.\nState of California Division of Oil and Gas, Sacramento,\nRogers, T.H., Geologic Map of California, San Bernardino\nJan.-June 1958, pp. 5-12.\nSheet, California Division of Mines and Geology, Sacra-\nDuke, C. Martin, and Leeds, David J., \"Site Characteristics of\nmento, 1967, scale 1:250,000.\nSouthern California Strong-Motion Earthquake Stations,\"\nSchoellhamer, J.E., and Woodford, A.O., \"The Floor of the\nUniversity of California, Los Angeles, Report 62-55, 1962,\nLos Angeles Basin, Los Angeles, Orange and San Bernar-\ndino Counties, California,\" Geological Survey Oil and Gas\n33 pp. and an appendix.\nDurrell, C., \"Geology of the Santa Monica Mountains, Los\nDivision Map OM-117, U.S. Department of the Interior,\nAngeles and Ventura Counties, Map Sheet 8,\" California\nWashington, D.C., 1951, scale 1:500,000.\nDivision of Mines Bulletin 170, Sept. 1954, scale 1:126,720.\nU.S. Geological Survey and the National Oceanic and Atmos-\nEckis, Rollin, \"Geology and Ground Water Storage Capacity\npheric Administration (Publishers), The San Fernando, Cali-\nof Valley Fill,\" California Division of Water Resources Bul-\nfornia, Earthquake of February 9, 1971, Geological Survey\nletin 45, Department of Water Resources, Sacramento, 1934,\nProfessional Paper 733, U.S. Department of the Interior and\nU.S. Department of Commerce, Washington, D.C., 1971,\n279 pp.\nHolmes, L.C., Soil Survey of the San Fernando Valley Area,\n254 pp.\nCalifornia, U.S. Department of Agriculture, Washington,\nWoodring, W.P., Bramlette, M.N., and Kew, W.S.W., \"Geol-\nogy and Paleontology of the Palos Verdes Hills, California,\"\nD.C., 1916, 63 pp.\nGeological Survey Professional Paper 207, U.S. Department\nJenkins, O.P. (Editor), \"Geologic Formations and Economic\nof the Interior, Washington, D.C., 1946, 145 pp.\nDevelopment of the Oil and Gas Fields of California,\"\nYerkes, R.F., McCulloh, T.H., Schoellhamer, J.E., and Ved-\nCalifornia Division of Mines Bulletin 118, San Francisco,\nder, J.G., \"Geology of the Los Angeles Basin, California\nApr. 1943, 773 pp.\n-An Introduction,\" Geological Survey Professional Paper\nJennings, C., and Hart, E., \"Exploratory Wells Drilled Outside\n420-A, U.S. Department of the Interior, Washington, D.C.,\nof Oil and Gas Fields in California to December 1953,\"\n1965, 57 pp.\nCalifornia Division of Mines Special Report 45, San Fran-\ncisco, 1956, 104 pp.\nJohnson, R.A., \"Boyle Heights Oil Field,\" Summary of Opera-\nBIBLIOGRAPHY\ntions, California Oil Fields, Vol. 52, No. 1, State of Cali-\nfornia Division of Oil and Gas, Sacramento, 1966, pp. 69-72.\nUsed to construct general geologic map and cross sec-\nLastrico, R.M., \"Effects of Site and Propagation Path on Re-\ntions\ncorded Strong Earthquake Motions,\" Ph. D. thesis, School of\nEngineering and Applied Science, University of California,\nBarrows, A.G., Kahle, J.E., Weber, F.H., Jr., and Saul, R.B.,\nLos Angeles, 1970, 205 pp.\nMap of Surface Breaks Resulting From the San Fernando,\nLos Angeles County Flood Control District, Coastal Plain\nCalifornia, Earthquake of February 9, 1971, Preliminary Re-\nGround-Water Contours Shallow Aquifers Map, Los Angeles,\nport II, Plate I, California Division of Mines and Geology,\nCalif., Apr. 1969a, scale 1:63,360.\nSacramento, 1971, scale 1:24,000.\nLos Angeles County Flood Control District, San Fernando\nCalifornia Department of Water Resources, \"Planned Utiliza-\nValley Ground-Water Contour Map, Los Angeles, Calif.,\ntion of the Ground Water Basins of the Coastal Plain of\nApr. 1969b, scale 1:63,360.\nLos Angeles County, Appendix A, Ground Water Geology,\"\nMcCulloh, T.H., \"Gravity Variations and the Geology of the\nBulletin 104, Sacramento, 1961, 181 pp.\nLos Angeles Basin of California,\" Geological Survey Profes-\nCalifornia Department of Water Resources, \"Crustal Strain and\nsional Paper 400-B, U.S. Department of the Interior, Wash-\nFault Movement Investigation, Faults and Earthquake Epi-\nington, D.C., 1960, pp. 320-325.\ncenters in California,\" Bulletin 116-2, Sacramento, Mar. 5,\nMerifield, P.M., \"Geology of a Portion of the Southwestern\n1964, 96 pp.\nSan Gabriel Mountains, San Fernando and Oat Mountain\nCalifornia State Division of Oil and Gas, California Oil and\nQuadrangles, Los Angeles County, California,\" M.A. thesis,\nGas Fields Supplemental Maps and Data Sheets, Dept. of\nUniversity of California, Los Angeles, 1958, 61 pp.\nConservation, Sacramento, Sept. 1969, 183 pp.\nSmith, M., Geological Survey Oil and Gas Investigation Map,\nCordova, Simon, \"El Segundo Oil Field,\" Summary of Opera-\nON-215, Sheet 2, U.S. Department of the Interior, Wash-\ntions, California Oil Fields, Vol. 49, No. 2, State of Cali-\nington, D.C., 1969, scale 1:500,000.\nfornia Division of Oil and Gas, Sacramento, 1963, pp. 45-52.\nWinterer, E.L., and Durham, D.L., \"Geology of Southeastern\nCrowder, R.E., \"Los Angeles City Oil Field,\" Summary of\nVentura Basin, Los Angeles County, California,\" Geological\nOperations, California Oil Fields, Vol. 47, No. 1, State of\nSurvey Professional Paper 334-H, U.S. Department of the\nCalifornia Division of Oil and Gas, Sacramento, Jan.-June\nInterior, Washington, D.C., 1962, 366 pp.\n1961, pp. 67-78.\nWoodford, A.O., Schoellhamer, J.E., Vedder, J.G., and Yerkes,\nCrowder, R.E., \"Cheviot Hills Oil Field,\" Summary of Opera-\nR.F., \"Geology of the Los Angeles Basin,\" California Divi-\ntions, California Oil Fields, Vol. 54, No. 1, State of Cali-\nsion of Mines Bulletin 170, Ch. II, No. 5, Sept. 1954, pp.\nfornia Division of Oil and Gas, Sacramento, 1968, pp. 17-21.\n65-81.","Subsurface Investigation of\nGround Rupturing\nDuring San Fernando Earthquake\nINTRODUCTION\nAfter the San Fernando earthquake of February 9,\n1971, geologic mapping of the numerous cracks,\nscarps, and other evidence of ground rupturing that\noccurred throughout the Sylmar-San Fernando area\nwas begun. Reconnaissance mapping showed that\nCONTENTS\nmost ground ruptures were concentrated along two\nPage\nmain tectonic alignments now referred to as the Syl-\n165 INTRODUCTION\nmar and Tujunga segments of the San Fernando\n165\nTUJUNGA SEGMENT OF SAN FERNANDO\nfault. Because neither of these fault segments had\nFAULT\n166\nSYLMAR SEGMENT OF SAN FERNANDO\nbeen mapped by geologists before the February 9\nFAULT\nevent, two questions immediately arose: \"Could\n171 CONCLUSIONS\nthese faults have been discovered and mapped before\nthe earthquake?\" and \"What kind of data would be\nrequired to determine if preexisting and potentially\nactive faults did exist in these locations?\"\nTo help answer these questions, a subsurface geo-\nlogic investigation utilizing largely backhoe trenches\nwas organized in cooperation with the California Di-\nvision of Mines and Geology (CDMG). Fourteen\ntrenches were excavated to depths ranging from 6 to\n14 feet and were logged generally at a scale of 1:60.\nSelection of trench locations was determined by: (1)\npatterns of recent ground breakage; (2) known rela-\ntion of overburden, alluvium, and alluvium in con-\ntact with bedrock; and (3) accessibility and authori-\nzation to excavate.\nTUJUNGA SEGMENT OF SAN FERNANDO\nFAULT\nEDWARD G. HEATH\nSeven of the 14 trenches were excavated along the\nF. BEACH LEIGHTON\nTujunga segment and related faults farther to the\nF. Beach Leighton & Associates\nnorth. Logs 1, 2, 3, 6, and 8 are included herein be-\nEngineering Geologists\ncause they are most significant.\nLa Habra, Calif.\n165","166\nSan Fernando Earthquake of 1971\nTrenches 1 and 2 were excavated in Lopez Can-\nistence of a Quaternary or younger fault at this lo-\nyon across a recent fault branch located approxi-\ncation, and the fault could have been classified as\nmately 1/2 mile north of the main trace of the fault\npotentially active had a trench been excavated and\nsegment near the canyon mouth (fig. 1) The fault\nproperly logged before the February 9, 1971, event.\nis parallel, and apparently related, to the Tujunga\nTrench 6 (fig. 5) was excavated where the Tu-\nfault segment. Trench 1 (fig. 2) was located where\njunga fault segment crosses Big Tujunga Wash. At\nthe faulting produced a nearly vertical 3-foot-high\nthis location, the fault scarp ranged from 11/2 to 2\nscarp. Examination of the test trench showed that re-\nfeet high. The excavation exposed loose alluvial sand\ncent alluvial sands had been offset approximately 32\nand gravel that limited the trench depth to 7 to\n8\ninches by one fault trace and that these alluvial\nfeet because of sidewall sloughing. The fault zone\nsands rest on different bedrock on both sides of the\nin the coarse sediment was a jumbled zone that cut\nfault. A second fault, showing offset of the bedrock\nacross the stratified units. There was, however, no in-\nand bedrock in fault contact with alluvial sands, is\ndication of prior earth movement in the area; it is,\nalso exposed in the test trench. Therefore, this trench\ntherefore, presumed that the faulting observed in the\nexposed evidence that the faulting of February 9,\ntrench was entirely caused by the February 9 move-\n1971, occurred along previously existing faults which\nment. This trench, however, does illustrate that care-\ncould have been detected by trenching before the\nful and detailed trench examination can reveal fault-\nFebruary 9 event.\ning in loose and unconsolidated sand and gravel\nTrench 2 (fig. 3) was located 85 feet east of\ndeposits.\nTrench 1, along the same fault trend where the fault\nTrench 8 (fig. 6) was excavated across the Tu-\nis expressed at the surface by a 3-foot-high flexure\njunga segment at the mouth of Lopez Canyon. The\napproximately 60 feet in width. No ground breakage\ntrench was entirely in the upper Miocene Modelo\nwas observed at the surface in the immediate area of\nsiltstones and sandstones. Near the fault zone, these\nthe test trench. The trench itself revealed approxi-\nunits were highly sheared and contorted, giving evi-\nmately 3 feet of very recent stream deposits overlying\ndence of substantial prior faulting and ground move-\n3 to 4 feet of old fill which, in turn, overlies recent\nment. Because of the exceptional folding and fault-\nsands and gravels. There was no indication of tec-\ning in this trench, the trench was mapped at the\ntonic disturbance of any of these units other than\nscale of 1:12 by CDMG personnel. Holocene sedi-\nthe same gentle warp that was evident at the surface.\nments were not exposed in the trench; therefore, the\nTrench depth was limited to approximately 8 feet by\nmost recent age of faulting before February 9, 1971,\ncaving of the loose sand and gravel near the bottom.\ncould not be determined at this location.\nComparison of Trenches 1 and 2 reveals the extreme\nvariation that can occur along the strike of a fault in\nSYLMAR SEGMENT OF SAN FERNANDO\na distance of only 85 feet. It also illustrates the need\nFAULT\nfor more than one test trench along a particular fea-\nture to define accurately the nature of the geologic\nThree test trenches (logs 5, 12, and 13) were exca-\nconditions.\nvated across the eastern end of the Sylmar segment\nTrench 3 (fig. 4) was located approximately 3,000\nand are included here because they represent the\nfeet east of the mouth of Lopez Canyon across a 3- to\nvariations in usable data that can be obtained from\n6-inch surface scarp of the Tujunga fault segment.\ntest trenches and also illustrate some typical trench-\ning problems.\nAt this location, an 8-foot-deep test trench revealed a\nsection of Modelo siltstone and shale that had been\nTrench 5 (fig. 7) was located adjacent to Newton\nthrust at an angle of approximately 45° over a Qua-\nStreet where the Sylmar fault segment crosses Pa-\nternary fanglomerate. Approximately 12 feet of re-\ncoima Wash. The excavation cut across a 1-foot-high\nverse dip-slip movement could be seen in the trench.\nfault scarp produced by the February 9 event and ex-\nThis movement far exceeds the 3 to 6 inches of\nposed an extremely coarse boulder gravel of recent\nmovement caused by the February 9 event, indicat-\nalluvial sediments of the wash. The ground rupture\ning that this fault has been active in recent time.\ncould be traced no more than 1 foot below the sur-\nTherefore, this trench clearly revealed the prior ex-\nface into these coarse materials. Severe sloughing of","Water\n922\nSan Fernando & Sunland Quadrangles\nWater\nTank\n6\nSylmar and Tujunga Segments\nBig Tujunga Wash\n1400\nTEST PIT LOCATIONS\nSan Fernando Fault\nBase map from USGS\n510\nScale: 1\"=2000'\nINDEX MAP\nSanitacium\nLakeview Terrac\nSpring\n10\nto\n1800-\nFigure 1.-Index map to test pit locations along Sylmar and Tujunga segments of San Fernando fault.\nTujunga\n2023\nWI\nwater\nTank\n#1180\n-\nBranch\neservoire\n800\nENA\nins\nCONT\nFenton\n1845\n-\nHANSEN\nForest Station\n1280\nLopez Caryou\n3\n(BM\\1093\nGun\nClub\nPicoro\nArea\nOak Hill\nTujunga Segment\nSch\n66\n2\n-4\nBM 157\nTrailer\nWater\nPank\nJr.High Sch\n8\n1\n36\n1880\nPa\nMaclay\nTrailer\nPark\n588\nBurns\nRanch,\nSan ernando\nRange Station\n20\n44\nStation\nNorth Pâcoima\nPark\nGag\nFilmore St\nSch\nBM\n1151\nBM 1061\nLopez\nDam\nAVE\nHistorical Monument\n125\nP152 Griffith Ranch\n080\n5\n\"\n173\nDOROE\nHighland\nSanitarium\n8\niSy1mar Segment\n1054\n12\n1050\nHarding\nSch\nEire\n/68\n1.194\nSan Fernando\nBMX1100\nVaughn St\n13\nAirport\n8\nSch\n118","168\nSan Fernando Earthquake of 1971\nLogged by Heath\nNorthern Trace Lopez Canyon\nTract Lopez Canyon\nPit location\nType of rig 24\" backhoe\nDate 3-30-71\nPHYSICAL\nATTITUDES\nENGINEERING GEOLOGY DESCRIPTION\nCOMMENTS\nCONDITION\nQal Sw,\nAlluvium and slope wash, silty sand with angular clast of Slt + Ss and well rounded\nNone\npebbles. Well bedded sand at base, stream deposits with some pebbles and\nSoft-friable\n1 Bedding\ncobbles at base.\nN77W, 74N\nSlt,\nSiltstone, medium gray, iron stain-mass.-highly fractured\nFirm\n2\nBedding plane fault\nN80W, 75N\nSs Slt,\nSandstone with thin siltstone interbeds well bedded, beds up to 4' thick.\nFirm-hard\n3 Fault\nNATURAL\nN75W, 62N\nSLOPE\nNone\nCg Ss,\nConglomerate and sandstone matrix - white, clean, ig. and meta. clast up to 3\"\nFirm-hard\nGRAPHIC REPRESENTATION\nPit trend North\nSs\nRecent scarp\nSs\nQal+Sw\nSs\nSand\nQal+Sw\nSlt\nSs\nSs\nCg+Ss\nSlt\nSlt\nFault\nSlt\n0\n1\n2\n4\nScale in feet\nFigure 2.-Geologic pit log for Trench 1.\n85'E of trench 1, Northern Trace Lopez Canyon\nLogged by Heath\nTract Lopez Canyon\nPit location\nType of rig backhoe\nDate 4-12-71\nATTITUDES\nPHYSICAL\nENGINEERING GEOLOGY DESCRIPTION\nCOMMENTS\nCONDITION\nNone\nQal,\nAlluvium, light gray sand and some gravel, deposited on fill, as late as\nNo faulting\nspring floods of 1969, crudely bedded.\nSoft and friable\nin trench\n36\"-42\" uplift\nFill,\nDark gray brown, mass to poorly laminated, sandy\nSoft\non north side\nby warping only\nSoil,\nDark brown-black, carbonaceous, buried grass and roots.\nSoft\nQalo,\nLight gray, older alluvium, gravel and boulders in sand.\nSoft-firm\nNATURAL\nSLOPE\nGraded flat\nGRAPHIC REPRESENTATION\nPit trend= N3E\nProjected line of\nQal\nmain scarp to the west\nPresent\nsurface\nQal\nx\nSilty bed\nTrench\nSoil\ncaved\nFill\nQalo (gravel with boulders)\nBottom of\nSoil\ntrench excavation\nQalo\n0\n1\n2\n4\nScale in feet\nFigure 3.-Geologic pit log for Trench 2.","Subsurface Investigation of Ground Rupturing\n169\nRidge north of Carl Street east of Van Nuys Boulevard\nDate 4-12-71\nLogged by Heath\nPit location\nPHYSICAL\nCOMMENTS\nENGINEERING GEOLOGY DESCRIPTION\nATTITUDES\nCONDITION\nConglomerate, light yellow brown, pebbles to cobbles in coarse sand matrix,\nFirm-hard\nWell defined\nFault E-W, 44N\nCg,\n1\nangular to well rounded clasts, some caliche along joints and root tubes,\nNo open fracturing\nsingle fault\napparent dip 37\nlocally silty, minor clay content, possibly alluvial fanglomerate.\nplane\nBedding N85E, 44N\n2\nSiltstone and shale, buff to rust brown, thinly bedded alternately cemented beds,\nSoft, firm to hard\nSlt Sh,\nhighly fractured some dragfolds and contorted bedding.\n3\nBedding N80E, 55N\nBedding N81E, 28N\nNATURAL\n4\nSLOPE\nGRAPHIC REPRESENTATION\nPit trend= N6E\nSoil\nSoil\nSlt+Sh\nCaliche\n0\n2\n4\nScale in feet\nFigure 4.-Geologic pit log for Trench 3.\nBig Tujunga Wash, North Side\nTract Big Tujunga\nLogged by Dickey\nPit location\nDate 4-15-71\nType of rig 24\" backhoe\nPHYSICAL\nENGINEERING GEOLOGY DESCRIPTION\nCOMMENTS\nATTITUDES\nCONDITION\nFine to coarse sand with roots and plants\nLoose\nDifficult to\nFlat lying bedding\nSand soil,\nconclude active\nBoulders with sand and pebbles\nLoose\nfault without\nBldrs,\nsurface offset.\nPebbles and medium to coarse sand\nLoose\nCorrelation is\nPbls Sd,\ntentative.\nFine micaceous sand, to to 2\" thick bed\nDamp, loose\nSd,\nNATURAL\nBldrs Cbls, Boulders and cobbles with sand matrix\nLoose\nSLOPE\nFlat lying\nNote: Fault zone marked by boulders on end, generally not flat lying, as above.\nSurface offset\nof 18-22\"\nGRAPHIC REPRESENTATION\nVertical offset 50-60 cm (22+\")\nSpoil\nSand\nsoil\nBldrs\nSand soil\nBldrs\nPbls+Sd\nSd\nJumbled\nRock zone\nBldrs+Cbls\nPbls+Sd\nBldrs+Cbl\n0\n1\n2\n4\nScale in feet\nFigure 5.-Geologic pit log for Trench 6.","170\nSan Fernando Earthquake of 1971\nLogged by Dickey\nLopez Canyon, Lower Trailer Park, Spaces 322 & 323\nDate 4-15-71\nNotes by Dickey\nPit location\nType of rig backhoe (DWR)\nPHYSICAL\nATTITUDES\nENGINEERING GEOLOGY DESCRIPTION\nCOMMENTS\nCONDITION\nN88E, 48N\nSs Slt,\nInterbedded, laminated siltstone and fine-medium sandstone well bedded\nHard\nBedrock\nH 20-30%\nfeatures\nN77, 36N\nShr'd Slt,\nSiltstone with claystone interbeds and gypsum layers between beds. Sheared\nSoft to firm\nreflect active\nalong gouge zones parallel to bedding. Some gypsum beds folded and contorted.\nH20 15-40%\nfaulting\nN80E, 27N\nSs lenses,\nSandstone lenses with contorted siltstone and claystone interbedded.\nFirm\nN80W, 33N\nH,0 15-30%\nContorted\nSheared and contorted siltstone and claystone with sandstone interbeds and\nFirm-hard\nNATURAL\nSlt, Clay, Ss, cemented zones.\nSLOPE\nH20 25-35%\nFlat,\ngraded\nGRAPHIC REPRESENTATION\nPit trend= N27'E\nSs lenses\nSs+Slt\nContorted\nShr'd Slt\nSlt, Clay & Ss\n0\n2\n4\nScale in feet\nFigure 6.-Geologic pit log for Trench 8.\nLogged by Heath\nNewton Street and Sylmar Fault Segment\nTract Newton Street\nPit location\nDate 4-13-71\nType of rig backhoe\nPHYSICAL\nATTITUDES\nENGINEERING GEOLOGY DESCRIPTION\nCOMMENTS\nCONDITION\nalluvial gravels, cobbles and boulders up to 2' across, average 2\"-6\" in very\nQal,\nLoose\nFault line could\ncoarse sand matrix. Sand 30+ %, pebbles, cobbles and boulders 70+%.\nCaves easily\nnot be traced\nSome crude bedding where sandy.\nin gravels.\nTrench caved\nbadly.\nNATURAL\nSLOPE\nNote: Trench caved badly, could not expose face over 4' high.\nGRAPHIC REPRESENTATION\nPit trend= N42E\nSoil rich zone\nFault scarp\n0\n1\n2\n4\nScale in feet\nFigure 7.-Geologic pit log for Trench 5.","Subsurface Investigation of Ground Rupturing\n171\ngreater than the 3 to 4 inches of vertical movement\nthe trench walls limited the depth of the trench to\nobservable at the surface. It can be concluded that\napproximately 6 feet and prevented the exposure of\nfaulting had taken place at this location before the\na sufficient section of coarse sediments SO as to be di-\nFebruary 9 event.\nagnostic. This trench emphasizes that, even with a\nknown fault that has at least 1 foot of displacement,\ncoarse unconsolidated gravel having boulders up to 2\nCONCLUSIONS\nfeet across and averaging 2 to 6 inches can defy fault\nTrenching along the Tujunga segment revealed\ndefinition.\nthe following tectonic events: (1) preexisting bed-\nTrench 12 (fig. 8) was excavated approximately\nrock faulting that had contorted and sheared units\n1,000 feet west of Trench 5 across a gentle topo-\nof the Modelo Formation of late Miocene age; (2)\ngraphic warp. There was no evidence of actual\nthrusting of Modelo units over Quaternary fanglom-\nground breakage at the trenching site, though ground\nerate; (3) alluvium in preearthquake fault contact\nrupturing had occurred through residences on both\nwith the Repetto Formation; and (4) displacement\nsides of the site. The excavation exposed terrace\nof both Holocene alluvial sediments and bedrock\nsands and gravels that conformed to the surface\nduring the February 9 earthquake. Trenching along\nwarping and, though slight fracturing was observed,\nthe Sylmar segment clearly shows that Quaternary\noffset of bedding surface was not evident. The only\nterrace deposits had been offset by faulting before\nindication of deeper breaks was the relatively narrow\nthe February 9 event.\n(approximately 50 ft wide) zone of warping.\nThe subsurface trenching program demonstrated\nTrench 13 (fig. 9) was excavated next to the Foot-\nthat faults readily can be observed and mapped in\nhill Freeway at a location approximately 1,000 feet\ntest trenches, 6 to 15 feet deep, whether these are\nwest of Trench 12. Here, the north side of the free-\ndug in youthful alluvial sands, Quaternary fanglom-\nway shows a 3- to 4-inch vertical scarp, with 7 to 8\nerates, terrace deposits, or bedrock units. However,\ninches of left-lateral movement. The test trench was\ncommonly two or three trenches must be located\nin terrace sand and gravel, and the fault trace could\nalong a suspected fault zone to establish with cer-\nreadily be followed in the trench. The total offset of\ntainty the presence or absence of faulting.\nthe bedding could not be established, but it was\nAdjacent to 12670 Gladstone\nLogged by Heath\nDate 6-30-71\nPit location\nType of rig backhoe\nPHYSICAL\nCOMMENTS\nENGINEERING GEOLOGY DESCRIPTION\nATTITUDES\nCONDITION\nTrench shows\nGravel, soil and debris\nOld fill,\nNone\nLoose, uncon-\nno significant\nsolidated,\nbreaks, bedded\nConglomerate, alluvial, light-medium brown, subangular to well rounded pebbles,\nCg,\nslightly damp\ncobbles, and boulders up to 2', average 3\"-6\", sandy matrix\nstrata bend to\nconform to\nLoose, friable\nSand, medium-dark brown, fine-medium sand, silty and clayey with common\nsurface warp\nSd,\ndamp\npebbles up to 3\"\nor scarp\nNATURAL\nSLOPE\nPit trend N5E\nGRAPHIC REPRESENTATION\nSlight\nfracturing\nAsphalt tile\nCg\nOld\n012\nScale in feet\nFigure 8.-Geologic pit log for Trench 12.","172\nSan Fernando Earthquake of 1971\nDetection of faulting in test trenches excavated in optimum trenching conditions are those in which re-\nloose, coarse alluvium is difficult, but detailed map- cent alluvial and older alluvial sediments are in con-\nping can help to identify jumbled fault zones. The tact with bedrock units.\nLogged by Dickey\nMaclay Street on-ramp, northbound Foothill Freeway\nTract Maclay, O.C.\nNotes by Dickey\nPit location\nType of rig 24\" backhoe\nDate 7-1-71\nPHYSICAL\nATTITUDES\nENGINEERING GEOLOGY DESCRIPTION\nCOMMENTS\nCONDITION\nPeb. dep,\nSilty sandy pebble deposits\nFirm damp\nLithology\nchanges across\nNone\nSdy.bldrs\nBoulders with sand and pebbles\nFirm damp\n2-9-71 quake\ndep.\ntrace (3-4\")\nBldrs,\nBoulders with sand and pebbles\nFirm damp\nwith 6+' offset\nin rock type\nNATURAL\nSLOPE\nGraded\n4:1+ slope\nGRAPHIC REPRESENTATION\nNE Side\nPit trend= N42W\nSurface trace\n(3-4\" vertical\n7-8\" left lateral)\nSdy bldrs dep.\nPeb dep.\n0.10.0\nBldrs\n0\n2\n4\nScale in feet\nFigure 9.-Geologic pit log for Trench 13.","Trench Exposures Across\nSurface Fault Ruptures\nAssociated With San Fernando Earthquake\nINTRODUCTION\nThis report gives the principal results of the exam-\nination of several exploratory trenches excavated\nacross the February 9, 1971, surface fault ruptures.\nThe trenches, some dug for the U.S. Geological Sur-\nvey and some for other organizations, were exposed\nCONTENTS\nat various times from April through August 1971.\nPage\nResults of detailed study of four trenches are pre-\n173 INTRODUCTION\nsented, followed by generalizations based on investi-\nBARTHOLOMAUS RANCH TRENCHES\n173\ngation of those trenches, seven trenches examined in\nSurface Evidence of Faulting\n174\nreconnaissance, and trench data reported by others.\nSubsurface Evidence of Faulting,\n175\nTrench A\nSpecial thanks are due C. T. Brown, Ellen Dubois,\nEvidence of Faulting Prior to 1971,\n176\nand W. D. Bartholomaus for permission to trench on\nTrench A\ntheir property; G. J. Lensen of the New Zealand\nSubsurface Evidence of Faulting,\n177\nGeological Survey, and J. B. Pinkerton, J. Schlocker,\nTrench B\nEvidence of Faulting Prior to 1971,\n178\nand J. N. Alt of the U.S. Geological Survey for col-\nTrench B\nlaboration in the mapping of various trenches; the\n178\nBROWN TRENCH\nCalifornia Division of Mines and Geology and F.\nSurface Evidence of Faulting\n178\nSubsurface Evidence of Faulting\nBeach Leighton & Associates for inviting the author\n179\nEvidence of Faulting Prior to 1971\n179\nto examine their trenches; and the U.S. Atomic En-\n179 OAK HILL TRENCH\nergy Commission, Division of Reactor Development\n181 DISCUSSION AND CONCLUSIONS\nand Technology, for partial support of the work.\n182 REFERENCES\nPublication authorized by Director,\nBARTHOLOMAUS RANCH TRENCHES\nU.S. Geological Survey.\nTwo trenches were excavated across the February\n9 surface ruptures about 0.3 km north of the Pacoima\nMemorial Lutheran Hospital on the Bartholomaus\nRanch (Trenches 3, 4, fig. 1) Each trench was 0.9 m\nwide and 3.7 m deep. The western trench (A, fig. 2)\nwas 46 m long and the eastern trench (B, fig. 2) was\n38 m long. Trench A was located in alluvial deposits\nat the mouth of a small canyon with the expectation\nthat bedded sediments would be found; Trench B\nM. G. BONILLA\nwas located SO as to expose the contact between the\nU.S. Geological Survey\nbedrock (Modelo Formation) composing the hills\nMenlo Park, Calif.\n173","174\nSan Fernando Earthquake of 1971\n1\n2\nSAN\nFERNANDO\n3\n4\no\nMi\no\n1 Km\nFigure 1.-Index map showing location of trenches and generalized trace of surface faulting. Numbers identify trenches: 1, Brown Trench;\n2, Oak Hill Trench; 3, Bartholomaus Ranch Trench A; 4, Bartholomaus Ranch Trench B. Fault traces modified from U.S. Geological\nSurvey Staff (1971, fig. 2).\nSurface Evidence of Faulting\nThe faulting in this area was expressed at the sur-\nface by a series of small furrowlike ruptures of the\nsoil in a zone some 30 m wide, accompanied by var-\nious differences in elevation across the zone. The\nruptures appear in figure 2 as a series of subparallel,\nirregular white lines and light-colored zones. A dif-\nference in elevation across the zone, north side up,\nA\nwas visible on aerial photographs and on the ground\nalong most of the rupture zone. A view of the rup-\n30M\nture zone, where it crossed the road west of Trench\nB\nA, is shown in figure 3. The vertical component of\ndisplacement was about 30 cm on the rupture in the\nforeground and about 80 cm across the whole zone.\nTrench A was about 10 m east of the road where the\nprominent rupture shown in figure 3 had split into\nFigure 2.-Vertical aerial photograph (taken Feb. 12, 1971) of part\ntwo branches and where the vertical component\nof Bartholomaus Ranch, showing surface ruptures and locations\nof trenches A and B.\nacross it was less than at the road. Cultivation of the\nsurface prevented direct measurement of the fault\nand the surficial deposits at the base of the hills.\ndisplacement, and the ground surface profile (fig. 4)\nDetails of the surface ruptures were destroyed by\ndoes not show any clear-cut scarp. The ground sur-\ncultivation before the trench sites were selected, but\nface profile of Trench B (fig. 6) indicates that the\naerial photographs taken February 12 were used to\nvertical component of displacement there was about\ninsure that the trenches crossed the ruptures.\n60 cm and that most of this displacement occurred","Trench Exposures Across Surface Fault Ruptures\n175\nlight olive gray and contains calcium carbonate in\nthe form of white spots and coatings on the pebbles.\nThus, the entire exposed thickness of unit A is in\nthe soil profile. Neither clay coatings nor develop-\nment of soil structure was observed. The upper sur-\nface of this unit was partially eroded before deposi-\ntion of the overlying unit, producing the gully\nshown near point E (fig. 4) and other irregularities\nin the surface. The next younger unit (B, fig. 4) is\nmore varied in grain size and development of bed-\nding than unit A. It consists of obscurely bedded\nsilty sand containing scattered angular gravel and\ncobbles; short lenses of laminated sand and silt or of\nbedded silty gravel and sand; and unbedded mix-\ntures of silty sand, gravel, and cobbles. In the lower\npart, it locally contains irregular areas of olive-gray\nFigure 3.-View northward across zone of surface ruptures from a\nslightly organic soil, apparently reworked material\npoint near south end of Bartholomaus Ranch Trench A. Marks\nfrom the buried soil below; some of these areas are\non stick are at 1-foot (0.3-m) intervals. Bottom of stick is on sur-\nface of road in foreground. R. F. Yerkes photograph (date Feb.\nshown above unit A (fig. 4) The surface soil is\n10, 1971).\nsandy silt and silty sand, slightly organic, slightly cal-\ncareous in the lower 5 cm or so, and 30 to 50 cm\nin the northern one-third of the 19-m-wide zone of\nthick. A subdivision of unit B was mapped in the\nvisible surface ruptures.\nsouthern part of the trench (C, fig. 4). Unit C could\nbe traced by its slightly darker color (light olive\nSubsurface Evidence of Faulting, Trench A\ngray, 5Y 5/2 in the Munsell system) than by the\noverlying material (yellowish gray, 5Y 7/2) It ap-\nIn Trench A, one definite fault and several proba-\npeared to be slightly organic and was somewhat cal-\nble faults were found in the poorly bedded alluvial\ncareous 30 to 45 cm below its top; it probably repre-\nmaterials revealed in the trench. A description of the\nsents a surface soil slightly older than the modern\nsediments is given below, followed by a description\nsoil. The youngest material recognized in the trench\nof the faults.\nis artificial fill (D, fig. 4) above two buried pipe-\nThe oldest sediment unit in the trench (A, fig.\nlines.\n4) is friable-to-firm silty fine sand containing scat-\nThe fault at E (fig. 4) was clearly expressed in\ntered angular pebbles; no bedding was visible. A soil\nwell-bedded sand and fine gravel (fig. 5) but ob-\nprofile had developed in this unit before its burial\nscure in unbedded mixtures of silty sand and gravel.\nby the overlying unit. The upper 0.8 m of the bur-\nThe apparent dip was 37°S., and the apparent re-\nied soil is olive gray, slightly organic (judging from\nverse displacement was 2.5 to 5 cm. Its lower end\nits color), and noncalcareous; the lower 1.2 m is\nN\nS\n8\n6\nC\n4\nBottom of trench\n2-\n0-\n44\n48\n32\n36\n40\n24\n28\n12\n16\n20\n4\n8\n0\nMETERS\nFigure 4.-Geologic section of west wall of Bartholomaus Ranch Trench A, showing approximate locations of surface ruptures (short\nvertical lines such as H) and ruptures exposed in trench (E, F, G). Surveyed points on ground surface indicated by dots. Dashes\nindicate approximate position of top of unit C and of boundary of unit D. See text for further explanation.","176\nSan Fernando Earthquake of 1971\nlaminated silt about 4 cm in a reverse sense. Unfor-\ntunately, the silt deposit is neither uniform in thick-\nness, in expression of upper and lower contacts, nor\nin general appearance; therefore a firm statement\ncannot be made about its former continuity. Simi-\nlarly, where the fracture intersects unit C, the unit\nboundary-especially south of the fracture-is not\nsufficiently sharp to permit a firm conclusion as to\nwhether or not the boundary is offset. A difference\nin altitude and inclination of this boundary near the\nfracture is, however, visible in figure 4 and is dis-\ncussed in a following paragraph.\nThe fault and probable faults shown in figure 4\nare believed to have formed (or to have been reacti-\nvated) in February 1971. The soft zones, which were\nFigure 5.-Fault (E, fig. 4) in well-bedded sediments in west wall of\nthe principal evidence for the fractures, probably re-\nBartholomaus Ranch Trench A. Scale in centimeters.\nsulted from intergranular movements that destroyed\nweak intergranular bonds along narrow zones. These\nwas concealed by the timber supports, but possible\nbonds probably are formed within a few tens of\noffset of the upper contact of unit A probably would\nyears by seasonal wetting and partial desiccation.\nnot have been visible because the contact is not\nThe absence of the bonds thus suggests that the\nsharp. The fault could not be traced farther north;\nmovements were very recent, as do the open cracks.\nit either terminated there or was invisible in the\nunbedded sediments. The fault was not found in the\nEvidence of Faulting Prior to 1971, Trench A\neast wall of the trench, apparently because it did not\nintersect well-bedded sediments.\nTwo different soil features in the trench suggest,\nA group of fractures, probably faults, found in the\nbut do not prove, pre-1971 faulting. The top of unit\ntrench below the southern part of the zone of surface\nA, although irregular, defines in gross aspect a mod-\nruptures is represented by fine lines near F on figure\nerately even surface. The sharp change in elevation\n4. The south-dipping fractures appeared as soft zones\nof this surface below F on figure 4 suggests deforma-\na few centimeters thick whose prominence could be\ntion of both the surface and the buried soil after\nenhanced by careful brushing with a paint brush.\nthey formed, or after the formation of the soil on the\nOpen cracks about 1 mm wide were visible along\nupper part of a modified fault scarp. The trench was\nthem in a few places, but these are not unequivo-\ndeepened at this point in a search for offset of the\ncally diagnostic of faulting, because irregular desicca-\nsoil surface, but none was found. The inflection of\ntion cracks of similar width also developed in the\nthe top of unit A does not appear in unit C, nor in\ntrench walls. The north-dipping fracture zone indi-\nthe ground surface, and therefore is older. The con-\ncated directly above F on figure 4 was first called to\nfiguration of unit C also may indicate pre-1971 fault-\nmy attention by J. L. Smith (FUGRO, Inc.). This\ning. The top of unit C consists essentially of three\nzone was more obscure than the south-dipping frac-\nstraight-line segments separated at fill D and fracture\ntures, but also consisted of narrow soft zones accom-\nG. The southern segment apparently is rotated with\npanied, in places, by very narrow open cracks. No\nrespect to the other two, and the middle segment is\noffset beds or consistently rotated pebbles were found,\nvertically offset downward with respect to the north-\nand neither the amount nor sense of displacement on\nern segment. These can be seen by looking at figure\nthese fractures could be ascertained.\n4 almost edgewise from the south end. The ground\nThe north-dipping fracture indicated at G (fig. 4)\nsurface does not show the same apparent rotation\nwas first seen on enlargements of photos of the\nand offset as unit C. Thus, the apparent rotation and\ntrench walls and later confirmed in the field. It ap-\noffset, which presumably resulted from faulting and\npeared primarily as a discontinuous open crack, but\nwarping, occurred before the formation of the pres-\nat one point seemingly displaced a thin deposit of\nent ground profile. The ground profile very proba-","Trench Exposures Across Surface Fault Ruptures\n177\ncia at least 6 cm thick; the other is adjacent to the\nbly was considerably modified for agricultural uses\nvery steep, probably faulted contact between the bed-\nin past decades, but not since February 9.\nrock and the ancient stream deposit (unit B). This\ncontact, exposed in the west wall of the trench, is\nSubsurface Evidence of Faulting, Trench B\nvertical to slightly overhanging (fig. 7) Because the\nEvidence suggestive of faulting was found in the\nrock at that point is highly fractured, it is very un-\nbedrock, at the contact between bedrock and an an-\nlikely that a vertical-to-overhanging face could have\ncient stream deposit, and at the contact between bed-\nremained stable long enough for the stream gravel to\nrock and colluvium. Clear evidence of the February\nhave been deposited against it. A more reasonable\n9 faulting was not found in the trench. The evidence\ninterpretation is that the bedrock was faulted against\nis summarized below, following a brief description of\nthe already deposited stream gravel. The vertical sep-\nthe material revealed in the trench.\naration at the contact is more than 0.35 m. The\nThe bedrock exposed in Trench B (unit A, fig. 6)\nstony colluvium above this contact is in a rather\nis friable-to-firm sandstone, siltstone, and shale of the\nloose state, suggesting that a small amount of differ-\nModelo Formation. Unit B consists of loose to very\nential movement occurred along the contact on Feb-\nhard, poorly sorted, moderately clean to silty sand,\nruary 9.\ngravel, cobbles, and boulders that are interpreted as\nA shear surface in the bedrock (at A, fig. 6) was\nthe deposit of an old torrential stream. Unit C is un-\ntraced to the contact with the colluvium, where bed-\nstratified yellowish-gray colluvium, consisting of fri-\nrock extended 0.4 m over a tongue of colluvium. Al-\nable silty fine sand that contains scattered angular to\nthough the shear surface was not seen in the collu-\nsubangular fragments of the bedrock and rare round-\nvium, the relations strongly suggest that the bedrock\ned-to-subangular granitic cobbles and boulders. Unit\nwas displaced locally over the colluvium. The shear\nD is light olive gray (darker than the colluvium)\nsurface strikes N.20°E and dips 50° SE. Because this\nand consists of slightly organic friable-to-firm silty\nstrike direction makes a moderately large angle with\nsand that contains scattered granules and rare angu-\nthe front of the hill, faulting is a more likely cause\nlar to subangular gravel. This unit is massive, except\nof the bedrock displacement than landsliding.\nfor a few ill-defined zones containing a high concen-\nNumerous slightly open cracks dipping in various\ntration of organic matter or gravel and some layers\ndirections could be seen near the top of unit D after\nof silty sand and gravel shown near point E of figure\nthe trench walls had dried out; some of these may\nhave been the locus of shearing on February 9, but\n6.\nthe lack of distinct stratification prevented any defi-\nAt two places, the bedding in the bedrock (unit\nnite conclusion regarding shearing along the cracks.\nA) steepens abruptly, suggestive of reverse-fault\nMapping of a zone of discontinuous pockets and\ndrag. One of these sharp flexures is associated with a\nstreaks of black, possibly manganese-stained or or-\nsteep north-dipping fault accompanied by fault brec-\nS\nN\nI\n-\n10\nF\n8\n6\nD\nB\nE\n4\nBottom of trench\n2\n0\n40\n32\n36\n28\n16\n20\n24\n0\n4\n8\n12\nMETERS\nFigure 6.-Geologic section of east wall of Bartholomaus Ranch Trench B. Approximate locations of surface ruptures indicated by short\nvertical lines, such as F. Dashed lines indicate indefinite contacts. See text for further explanation.","178\nSan Fernando Earthquake of 1971\n1.4\nthan 0.35 m) would have left some clear evidence if\nit had all occurred on February 9; therefore, most of\n1.2\nthat faulting must have occurred before 1971 also.\nColluvium\n1.0\nC\nBROWN TRENCH\n1.8\nThis trench was located in San Fernando near the\nwest end of the Sylmar segment of the San Fernando\n0.6\nfault zone (1, fig. 1) . The trench was excavated in\nBedrock\nthe equipment yard of general contractor C. T.\nA\n1.4\nBrown, one of the very few open areas in the city\nStream deposit\ncrossed by the fault. The trench was 29.6 m long, 1.2\nB\n0.2\nto 1.5 m wide, as much as 6.4 m deep, and was ori-\nented N.18° W.-nearly perpendicular to the trend\n0\nof the fault zone.\no\n0.2\n0.4\n0.6\n0.8\n1.0\n1.2\n1.4\n1.6\nMETERS\nSurface Evidence of Faulting\nFigure 7.-Detail of contact between bedrock (A) on right and\nThe trench crossed at least one surface rupture\nstream deposit (B) on left. Lines in bedrock indicate bedding.\nWest wall of Bartholomaus Ranch Trench B.\nand perhaps two others that were faintly visible on\naerial photographs, but surface expression of the\nganic material near the ground surface in the vicin-\nrupture was lost before the trenching. One rupture\nity of point D (fig. 6) did not show any obvious\nappeared as a moletrack about 5 cm high and 1 m\noffsets; however, the zone is SO irregular and discon-\nwide, combined with a vertical displacement of\ntinuous that no positive statement regarding offset is\nabout 8 cm, north side up, along a dirt road 5 m\njustified.\nwest of the trench. The moletrack scarp, which inter-\nsected the trench near point A (fig. 8) was less\nEvidence of Faulting Prior to 1971, Trench B\nconspicuous eastward, and its dimensions were per-\nThe step and locally overhanging contact be-\nhaps 10 percent smaller at the trench than at the\ntween the bedrock and the colluvium is, as discussed\nroad.\npreviously, suggestive of faulting. This faulting is\nAlthough the whole zone of 1971 surface faulting\nnot reflected in the contact between the colluvium\nin this area was about 200 m wide (U.S. Geological\nand unit D and must have occurred long before\nSurvey Staff 1971, fig. 2) the principal surface dis-\n1971, prior to formation of that contact. The proba-\nplacements were in the southern part of the zone\nble faulting at the contact between bedrock and the\nnear the trench site. About 30 m north of the trench,\nold stream deposit (with vertical separation of more\na rise in the land surface is suggestive of an old fault\nS\nN\n8\nA\nB\n4\nD\nBottom of trench\no\n0\n4\n8\n12\n16\n20\n24\n28\n32\nMETERS\nFigure 8.-Geologic section of west wall of Brown Trench, showing locations of ruptures (near A, C, D, and E) and sedimentary units.","179\nTrench Exposures Across Surface Fault Ruptures\ntraced for 0.6 m. Open fractures, voids, and cementa-\nscarp; if so, the principal displacements in the past\ntion were not observed.\nwere probably north of the principal displacement\nzone of 1971 and were not intersected by the trench.\nEvidence of Faulting Prior to 1971\nSubsurface Evidence of Faulting\nAt least two of the three faults recognized in the\nBrown Trench had moved before 1971, but the dis-\nNo large fault displacements have affected the geo-\nlogic units mapped in the Brown Trench, but three\nplacements were very small and inconsistent in sense.\nIt seems likely that these were minor subsidiary rup-\nvery small ruptures dipping northwest were found.\ntures and that a trench farther north across the topo-\nNo clear evidence of the 1971 surface ruptures was\ngraphic rise would reveal a better defined and more\nfound in the trench. A brief description of the sedi-\nments exposed in the trench is given below, followed\nimportant fault zone.\nby a description of the faults.\nMost of the sediments exposed in the trench con-\nOAK HILL TRENCH\nsist of firm silty sand and clayey sandy silt (B, fig.\nA trench dug across the Oak Hill fault by F.\n8) Although zones showing minor differences in\nBeach Leighton & Associates in cooperation with the\ngrain size and sorting could be detected by detailed\nCalifornia Division of Mines and Geology (Trench 1\nexamination with a lens and by other field tests, bed-\nof the report by Heath and Leighton, \"Subsur-\nding generally was not visible. The only readily\nface Investigation of Ground Rupturing During San\nmappable units were a gravelly silty sand at a depth\nFernando Earthquake\" in Volume III) also was ex-\nof about 3 to 3.5 m (C, fig. 8) and a friable silty\namined by Gerald J. Lensen of the New Zealand\nsand (E, fig. 8) at a depth of about 4.5 to 5 m below\nGeological Survey and the author. The trench\nthe surface, underlain by friable-to-loose clean sand\ncrossed the Oak Hill fault at the transition from\nand gravel.\nscarp to monoclinal warp (fig. 9) The formerly\nA barely visible fault surface was found near point\nsmooth, artificially graded surface was disrupted by\nC (fig. 8). The fault, whose attitude is about\nthe 1971 fault which, about 40 m west of the trench\nN.50°E. 25°NW., shows less than 5 cm of apparent\nsite, had 1.05-m reverse-slip and 0.80-m left-slip com-\nreverse displacement of the upper boundary of the\nponents of displacement (U.S. Geological Survey\ngravelly silty sand. The fault could not be followed\nStaff 1971, pp. 68-69)\nacross the lower boundary of the gravelly sand and\nits total visible length was only 1 m. Cementation\nalong parts of the fault and lack of open fractures in-\ndicate that the displacement occurred before 1971.\nA fracture near point D (fig. 8) at a depth of 3.5\nto 4 m could be traced for 1.2 m. This fracture,\nwhose attitude is about N.15°E., 40°NW., appeared\nas a discontinuous series of thin, shallow, lenticular\nopenings in the wall of the trench, locally showing a\nfresh-looking hairline crack. The fracture penetrates\nthe lower poorly defined boundary of the gravelly\nsand, but no offset was detected. No cementation was\nnoted. The open crack suggests that some movement\noccurred on February 9, but a direct connection\nwith the surface ruptures of February 9 could not be\nestablished.\nThe third rupture was found 5.5 m below ground\nFigure 9.-Oblique aerial photograph of Oak Hill fault scarp,\nsurface near point E. Its attitude is approximately\nshowing location of Oak Hill Trench (heavy black line). Scarp\nN.65°E., 52° NW., and normal separations of 4.5 and\nappears as dark ragged line extending from trench to road\n6 cm were measured in the wall of the trench. The\n(upper left center). View to west. V. A. Frizzell photograph\nfault, developed in sand and silty sand, could be\n(date Feb. 19, 1971).","180\nSan Fernando Earthquake of 1971\nThe trench revealed two distinct ruptures (A and\nat least 1 m to move these beds out of the section ex-\nB, fig. 10), the southernmost of which is believed to\nposed in the trench. Thus, the fault displacement\nbe the locus of the 1971 displacement, although the\nthat occurred about 200 years ago and probably the\nnorthernmost also may have moved a small amount\nearthquake that almost certainly accompanied it\nat that time. A distinctive sand bed (C, fig. 10) is\nwere both greater than that of February 9, 1971.\noverlain by a wedge-shaped mixture of poorly sorted,\nAlthough the relations observed in the trench can\nloosely compacted angular fragments of sandstone,\nbe interpreted as above, some rather special circum-\nrounded gravel, and fines (D, fig. 10) This wedge,\nstances are assumed, and the given interpretation\nbecause of its shape, composition, compaction, sort-\nmay not be the correct one. One problem is the ap-\ning, and position in relation to the northern fault\nparent absence of conglomerate immediately north\nand the rock adjacent to it, is interpreted as col-\nof fault B to supply some of the rounded gravel\nluvium and collapsed bedrock that accumulated\nfound in the supposed collapse-rubble. This may be\nadjacent to, and shortly after the formation of, a\nexplained by postulating a thin lens of conglomerate\nscarp produced by pre-1971 movement of the north-\nimmediately north of the fault to supply part of the\nern fault. A piece of wood was found among the\nrubble; conglomerate beds are exposed in the forma-\nangular pieces of rock believed to have fallen during\ntion north of the fault at other nearby points. An-\nthe formation of the old scarp. The wood was age-\nother problem is to explain the apparent erosion of\ndated as less than 200 years old by Rubin (1971)\nsome of the sandstone immediately north of fault B\nThe wood is possibly as much as 300 years old, but\nnear sand bed C, while only a bit of the soft sand\nmay be as young as 100 years old (Rubin 1972)\nbed was eroded. A clay seam 1 to 3 cm thick was\nThe sand bed (C, fig. 10) and the clayey silt that\nnoted along fault B in the lower part of the trench.\nunderlies it almost certainly extended a few meters\nThe clay and sandstone, which could have been\nnorthward across the northern fault, but the part\nsheared and fractured adjacent to the fault, were ap-\nnorth of the fault was moved upward by the dis-\nparently more easily eroded than the sand bed pro-\nplacement that produced the pre-1971 scarp. The\ntected by a capping of rubble. The erosion itself\nvertical component of displacement must have been\ncould have resulted from local concentration of run-\nN\nS\n4m\nSlope wash and artificial fill\nWeathered S S ?\n(stony clay)\nGravelly sand\nWood\n3\nGray sand\n-\n(Probably artificial fill)\nC\nB\nA\nGravelly sand\n2\n-\nSS\nE\nClayey silt\nCgl\nFine grained SS\nClay seam 1-3 cm thick\nI\n-\nBottom of trench\no\nI\nI\nI\n1\nI\nI\nI\n2\n3\n4\n5\n6\n7\n8\n9m\nFigure 10.-Geologic section of east wall of Oak Hill Trench. Abbreviations used: cl, clay; ss, sandstone; and cgl, conglomerate. The gray\nsand probably includes spoil from 1971 trenching operation which conceals upward continuation of fault A. See text for further\nexplanation.","181\nTrench Exposures Across Surface Fault Ruptures\nThis inference is not contradicted by the fact that\noff between the collapse-rubble and the fault scarp.\ntopographic evidence of young faulting is not ob-\nDuring our field examination, Gerald Lensen and\nvious, as it is along the San Andreas fault. Topo-\nthe author tentatively concluded that, essentially the\ngraphic evidence of young faulting is less likely to be\nentire wedge of material above the sand bed was\npreserved on a reverse fault than on a strike-slip fault\nrubble formed by collapse of a former fault scarp;\nbecause: (1) Active reverse faults are usually at the\nhowever, calculation shows that insufficient volume\nbase of steep mountain fronts where vigorous chan-\nof rubble would be produced by collapse, even as-\nneled and sheetflood runoff and landsliding can\nsuming 25-percent voids in the rubble and a vertical\nquickly eradicate fault topography, and (2) the re-\ndisplacement twice as great as that which occurred\nverse faulting itself produces instability both on a\non February 9. Thus, a composite origin by collapse,\nsmall scale at the overhanging fault scarp and on a\nslope wash, and downhill creep must be postulated\nlarge scale by oversteepening the mountain front,\nfor the wedge of material overlying the sand bed.\ncausing small and large landslides that are very effec-\nThe age of the wood thus gives a minimum, but\ntive in obscuring fault topography.\nprobably close, approximation of the time of forma-\nThe radiocarbon date from the Oak Hill fault\ntion of the scarp.\nsuggests the possibility that pre-1971 surface faulting\noccurred on the San Fernando fault zone between\nDISCUSSION AND CONCLUSIONS\n100 and 300 years ago and may have been associated\nwith one of the recorded strong earthquakes such as\nThe following observations and conclusions re-\nthat of July 28, 1769. Thus, the Holocene strati-\ngarding trenching and the activity of the San Fer-\ngraphic record along the San Fernando fault zone in-\nnando fault system are based primarily on detailed\ndicates that substantial surface faulting and damag-\nexamination of the four trenches described above, re-\ning earthquakes may occur rather frequently on the\nconnaissance examination of seven other trenches\nfault.\nacross ruptures in the San Fernando area, and trench\nTen out of 16 trenches across 1971 surface rup-\ninformation reported by others (Barrows et al. 1971\ntures clearly revealed the ruptures, but six trenches\nand Heath and Leighton, \"Subsurface Investigation\nyielded no or very equivocal evidence of the rup-\nof Ground Rupturing During San Fernando Earth-\ntures. Fault ruptures can be extremely difficult or\nquake\" in Volume III).\nimpossible to see in massive unbedded material rang-\nThe trenches show that the San Fernando fault\ning from silt and clay to coarse bouldery sand and\nsystem could have been identified as active by appro-\ngravel. The type of material exposed thus needs to\npriate investigations before 1971. The majority (9\nbe considered in drawing conclusions based on the\nout of 11) of the trenches that extended below the\napparent absence of faulting in trench exposures.\nmodern stream alluvium and artificial fill showed ev-\nTo promote recognition of faulting, trench exami-\nidence of faulting involving Quaternary deposits. In-\nnations should be detailed and the walls should be\ndeed, a pre-1971 unpublished report includes a cross\ncleaned by a technique (such as scraping, brushing,\nsection, based on surface evidence and drilling, that\nor picking) that is appropriate to the material en-\nshows bedrock faulted over alluvium just east of the\ncountered. Geologists from several different organiza-\nmouth of Lopez Canyon (Geotechnical Consultants,\ntions at first agreed that no evidence of 1971 rup-\nInc. 1965) The radiocarbon date on the Oak Hill\ntures was present in one of the trenches, but\nfault indicates very recent movement there. This\nadditional cleaning and close examination eventu-\nmovement history can be applied to the rest of the\nally did reveal such evidence. Careful mapping of\nSan Fernando fault system because the Oak Hill\nthe walls can show relations not readily apparent by\nfault is either part of the main fault or, if a subsidi-\nvisual examination alone.\nTrenches that are too short or too shallow may\nary fault, it is not likely to have moved without an\nmiss important information. A trench at the mouth\nequal or greater movement on the main fault. The\nof Lopez Canyon, when it was less than 9 m long,\npossible pre-1971 faulting of a young, near-surface\nmissed the fault contact between bedrock and allu-\nsoil horizon in Trench A on the Bartholomaus Ranch\nvium that was revealed several days later when the\nstrengthens the inference from the Oak Hill data\ntrench was extended to a length of 12 m. The\nthat the San Fernando fault system is very active.","182\nSan Fernando Earthquake of 1971\nBrown Trench would have intersected no faults if it\nport II, Plate I, California Division of Mines and Geology,\nhad been only 3 m deep.\nSacramento, 1971, scale 1:24,000.\nTrenching confined to a particular project site\nGeotechnical Consultants, Inc., Burbank, Calif., \"Geotechnical\nInvestigation of Tract 28201, City of Los Angeles, Cali-\nmay not reveal diagnostic relations despite use of the\nfornia,\" for McIntyre and Quiros, Inc., Monterey Park,\nbest judgment in locating the trench within the proj-\nCalif., Apr. 8, 1965, 26 pp. (unpublished report)\nect. For example, two of the trenches across the San\nRubin, Meyer, \"Sample W-2624,\" U.S. Geological Survey Ra-\nFernando fault system showed no evidence of pre-\ndiocarbon Laboratory, Washington, D.C., 1971 (written\n1971 faulting of Quaternary deposits, but nine oth-\ncommunication)\ners did. Realistic evaluation of the activity of a fault\nRubin, Meyer, \"Sample W-2624,\" U.S. Geological Survey Ra-\nusually requires consideration of data obtained well\ndiocarbon Laboratory, Washington, D.C., 1972 (personal\noutside the confines of a particular site.\ncommunication)\nU.S. Geological Survey Staff, \"Surface Faulting,\" The San Fer-\nREFERENCES\nnando, California, Earthquake of February 9, 1971, Geologi-\ncal Survey Professional Paper 733, U.S. Geological Survey\nBarrows, A.G., Kahle, J.E., Weber, F.H., Jr., and Saul, R.B.,\nand the National Oceanic and Atmospheric Administration,\nMap of Surface Breaks Resulting From the San Fernando,\nU.S. Department of the Interior and U.S. Department of\nCalifornia, Earthquake of February 9, 1971, Preliminary Re-\nCommerce, Washington, D.C., 1971, pp. 55-76.","Planetable Survey\nof Parking Lot Damaged\nby San Fernando Earthquake\nThe Hubbard-Glenoaks Shopping Center, situated\nat the south corner of the intersection of Glenoaks\nBoulevard and Hubbard Street in San Fernando, was\ndamaged severely during the earthquake of February\n9, 1971. The shopping center stood at the west end\nof the Sylmar segment of the San Fernando fault\nzone (U.S. Geological Survey Staff 1971, p. 57) As\nCONTENTS\npart of the preliminary work to determine the\nPage\namount and direction of displacement across this\nPLANETABLE SURVEY\n183\nzone, a planetable survey of part of the parking lot\nDISPLACEMENT ALONG FAULT ZONE\n184\nat the shopping center was made on February 15-16,\n184 REFERENCES\n1971.\nPublication authorized by Director,\nU.S. Geological Survey.\nPLANETABLE SURVEY\nThe survey consisted of two parts: measurement\nof elevations of selected points (table 1) and con-\nstruction of a contour map (fig. 1) , and preparation\nof a sketch map (fig. 2) showing pavement cracks of\nprobable tectonic origin. These pavement cracks\ncould be matched to presumed tectonic ruptures in\nthe ground beneath the pavement and were clearly\nnot the result of sliding, buckling, and breaking of\npavement sheets during the earthquake.\nElevations in the parking lot were first computed\nwith respect to an arbitrary datum of 100 feet. Later,\na postearthquake spot elevation for the top of the\nsidewalk at the north corner of the Boys Market\nwas obtained from the B. S. Fischer Engineering\nCompany of Encino, Calif. This spot elevation was\nbased on the preearthquake elevation of a bench\nmark on the northeast curb of Glenoaks Boulevard,\n73.5 feet northwest of the centerline of Hubbard\nStreet. Postearthquake leveling by surveyors for Los\nAngeles city showed that the bench mark had been\nJAMES B. PINKERTON\nuplifted 4.8 feet (Church 1971), and this amount\nJANE M. BUCHANAN\nwas added to the computed elevations before the\nU.S. Geological Survey\ncontours were drawn.\nMenlo Park, Calif.\n183","184\nSan Fernando Earthquake of 1971\nTable 1.-Postearthquake elevations of points in Hubbard-Glenoaks\nby a wide band of extension on the north. Vertical\nShopping Center parking lot, San Fernando\ndisplacement occurred in both bands, but about\nStation\nElevation\none-half of the vertical and virtually all of the hori-\nzonal displacements were confined to the narrow\nFeet*\n1\n1,166.2\nshear-thrust zone on the south.\n2\n1,166.8\nThe results of our survey agree with these general\n3\n1,163.9\n4\nobservations. Comparison of the postearthquake and\n1,165.3\n5\n1,164.5\npreearthquake maps of the parking lot (figs. 1 and\n6\n1,164.1\n3) shows that despite the number and complexity of\n7\n1,163.7\n8\nthe cracks, the parking lot surface was not deformed\n1,163.5\n9\n1,163.2\nsignificantly. Profiles drawn along the axis of the\n10\n1,163.1\ndrainage trough and along the sidewalk (fig. 4) indi-\n11\n1,162.8\n12\ncate that the surface was uplifted and tilted south-\n1,162.6\n13\n1,162.2\nward. The cracks show a stepwise northward increase\n14\n1,161.9\nin vertical displacement (fig. 2) and figure 5, on\n15\n1,168.3\n16\nwhich points of equal uplift are plotted, clearly\n1,163.9\n17\n1,164.1\nindicates that the amount of vertical displacement\n18\n1,163.3\nincreased northward and was spread across the entire\n19\n1,162.1\nfault zone. Most of the cracks showed no lateral\n20\n1,161.5\n21\n**1,164.9\noffset, but those that did generally showed a small\n22\n1,162.7\nright-lateral component. Differences between the pre-\n23\n1,160.8\nearthquake and postearthquake positions of the\n24\n1,159.7\n25\n1,161.3\nbuildings and sidewalks on figures 1 and 3 may stem\n26\n1,156.3\nfrom lateral displacement, but it is more likely that\n27\n1,160.6\nthese differences reflect errors in horizontal measure-\n28\n1,161.1\n29\n1,164.6\nment. More than 1 m of left-lateral displacement\n30\n1,165.4\nwas measured on the main shear-thrust zone in this\n31\n1,162.9\narea (Clark 1971) , but this displacement is not\n* The elevations are based on postearthquake preliminary releveling\nreflected in our survey because no stations were\n(by Los Angeles city) of bench mark on northeast curb of Glenoaks\npicked south of the shear zone.\nBoulevard, 73.5 feet northwest of centerline of Hubbard Street. Spike\nis in curb. Preearthquake elevation was 1,170.804 feet; postearth-\nquake elevation is 1,175.604 feet (+4.8 feet). All elevations are\nrounded to nearest one-tenth of a foot.\nREFERENCES\nThe computed elevation of station 21 is anomalously high and\nwas disregarded when the contour map (fig. 1) was drawn.\nChurch, J.P., U.S. Geological Survey, 1971 (personal com-\nmunication)\nDISPLACEMENT ALONG FAULT ZONE\nClark, M.M., U.S. Geological Survey, 1971 (written communi-\nAccording to earlier reports (U.S. Geological Sur-\ncation)\nvey Staff 1971, p. 57) displacement along the Sylmar\nU.S. Geological Survey Staff, \"Surface Faulting,\" The San\nFernando, California, Earthquake of February 9, 1971, Geo-\nsegment of the San Fernando fault zone consisted of\nlogical Survey Professional Paper 733, U.S. Geological Sur-\nuplift and horizontal (primarily left-lateral) offset\nvey and the National Oceanic and Atmospheric Adminis-\nalong a steep, north-dipping plane. A narrow band\ntration, U.S. Department of the Interior and U.S. Depart-\nof shearing and thrusting on the south was flanked\nment of Commerce, Washington, D.C., 1971, pp. 55-76.","185\n2\n1168\n1167\n1166\n.30\n1165\n.5\n.29\n.9\n1164\n1163\n12\n.21\n13\n18\n22\n1162\n14\n20\n28\n1161\n23\n24\nSHOPS\n25\n1157\nN\n.26\n27\n50Feet\no","San Fernando Earthquake of 1971\n186\n1Vs\n2\nCrack at base of curb\n40E\nCURB\n15\nApproximate OXIS\n60-65V\nof drainage low\n40E\n40V 30 V\nHairline\n4\n3\nX in cement on curb\n30\n07\nI.P.\n8\nMost collapse and subsidence in this band apparently associated\n29\nwith buried utilities (storm drain? sewer?)\n09\n9\n10\n95E,120R\nO\n100 V,\n16\n65 L\nII\n30-40E\n-,\n45V\nO\n80E\n031\n25V\n100V\n-\n50V\n12\n65V\nJUNIPER\nWorped but not broken\n75v0\n21\n13\nN\n18\n22\n100E,40R\n14\n60V\n95V07\n20\n50v\n28\n0\n50 FEET\nLight pole\n19\n20V\n60V\nApporently mislocated\n23\n25V\nShould be at SE edge of the\n50V\nWarped but\ncollapsed zone in low part\n65E\nunbroken 25mm\nO\nof drainage trough. Elevation\n24\ndown on SE\nprobably OK\n30V\nEXPLANATION\n80E 025\nZONE\n80R,40E\n.\nSHEAR\nPovement rupture\nMain zone of\nShowing amount and direction of displacement, in millimeters\nleft-lateral horizontal\n026\nV, vertical; R, right lateral; L, left lateral; E, gope or\nRS\noffset\nextension across rupture. Bar and ball on downthrown\nReconstructed outline of\nside\n2\nplanter and stairs\nApproximate oxis of\ndrainage low\n##############\nCollapse feature\nShattered povement\nCompressional feature\nArrow points in apparent direction of\noverthrust of upper plate\no21\nL.P.\nRod station\nInstrument point for\nentire survey\nCracks mapped by J.B. Pinkerton,\nFebruary 15 -16, 1971\nFigure 2.-Sketch map showing ruptures in the northeastern part of Hubbard-Glenoaks Shopping Center parking lot.","Planetable Survey of Parking Lot\n187\nSOUTHEAST\nSIDEWALK\nNORTHWEST\n1170\n15\nPostearthquake\nprofile\nRod station\n1165\n22\n(projected to plane\nof profile)\n28\n1160\nPreearthquake profile\n1155\n60\n1150\n200\n250\n300\n50\n100\n150\no\nSOUTHEAST\nDRAINAGE TROUGH\nBOYS\nNORTHWEST\n50 Feet\n1170\no\nWARKET\nRod stations\n1159\nTigh\nprojected plane\n3\n10\n1165\nof profile)\nPostearthquake\n13\n2\n23\nprofile\n1158\n1160\n1157\n26\nPreearthquake profile\n1155\n1155\n1150\n350\n200\n250\n300\n100\n150\n50\no\nHorizontal distance, in feet\nRedrown from map (site plan) prepared by\nFigure 4.-Preearthquake and postearthquake profiles of sidewalk\nRobert H. Peterson, architect. December 4,\nALLEY\n1961, for the Hubbard-Gienoaks Shopping\nand drainage trough, Hubbard-Glenoaks Shopping Center.\nCenter Job No 61-126, Sheet A-1\nFigure 3.-Contour map of preearthquake surface,\nHubbard-Glenoaks Shopping Center parking lot.\no5\no5\no5\no5\no5\n04\n04\no3\n03\nO3\nN\no2\no2\no2\n50Feet\no\nEXPLANATION\no5\nPoint of intersection of pre- and\npostearthquoke contours, showing\namount of uplift. in feet\nFigure 5.-Map showing points of equal uplift in\nHubbard-Glenoaks Shopping Center parking lot.","","Ground Displacement\nat San Fernando Valley Juvenile Hall\nDuring San Fernando Earthquake\nINTRODUCTION\nThe San Fernando Valley Juvenile Hall was dam-\naged severely during the earthquake of February 9,\n1971. Although located in a region of moderate to\nheavy damage (Modified Mercalli intensity VIII+)\nthe destruction at the Juvenile Hall was unusually\nCONTENTS\nsevere because of the ground displacement through-\nPage\nout the facility. An investigation conducted for Los\n189 INTRODUCTION\nAngeles County has determined that local soil and\n190\nZONE OF DISPLACEMENT\ngeologic conditions were responsible for the displace-\n191\nGEOLOGIC AND SOIL CONDITIONS\n194\nCONCLUSIONS\nments and the concentration of damage to structures\n196 REFERENCES\nat this facility (Fallgren and Smith 1971)\nThe Juvenile Hall is a Los Angeles County juve-\nnile-detention facility located in the Sylmar district\nnorth of San Fernando Road (fig. 1) The site is ap-\nproximately 71/2 miles south of the epicenter of the\nFebruary 9 earthquake and 21/2 miles northwest of\nthe known surface ruptures along the Sylmar seg-\nment of the San Fernando fault. The facility was\nconstructed in 1962 on the 30-acre site and involved\nthe removal of an existing olive grove, with subse-\nquent grading to produce a multilevel site using cuts\nand fills as much as 15 feet deep.\nStructures on the site include numerous one- and\ntwo-story school and dormitory buildings, with con-\ncrete frame or reinforced masonry bearing walls and\nconcrete floors and roofs. Foundations consist of shal-\nlow spread footings supported on at least 2 feet of\ncompacted fill. Most of the buildings are around the\nperimeter of the site, and many split-level buildings\nare connected. Interior areas of the site are devoted\nto athletic fields and landscaping, and the facility is\nRICHARD B. FALLGREN\nenclosed entirely by a 10-foot-high concrete block\nJAY L. SMITH\nwall.\nFUGRO, Inc.\nDamage to the facility occurred as the result of se-\nConsulting Engineers and Geologists\nvere shaking and differential ground movement.\nLong Beach, Calif.\n189","San Fernando Earthquake of 1971\n190\nBOULEVARD\nFOOTHILL\nnile Hall site, crossing the facility through the\nkitchen, medical, and court buildings (fig. 3).\nGround ruptures along this boundary indicate right-\nSAN FERNANDO JUVENILE HALL\nlateral slip, and the trend of major cracks is gener-\nSYLMAR\nally parallel to the direction of movement of the dis-\nCONVERTER\nplaced zone. The south boundary of the\nSTATION\ndisplacement zone crosses the southeast corner of the\nJuvenile Hall site through the maintenance and sup-\nply building. Ground ruptures along this boundary\nare characterized by left-lateral slip, and the larger\ncracks generally trend nearly north-south in en eche-\nUPPER\nlon pattern, approximately 45° to the direction of\nVAN NORMAN\ngross movement.\nThe amount of relative lateral movement within\nRESERVOIR\nthe zone is shown in figure 3. The lateral movement\nLOWER\nshown represents offsets of curbs and property lines\nVAN NORMAN\ncrossing the zone, as measured by the California Di-\nRESERVOIR\nvision of Highways, the Los Angeles Department of\nWater and Power, and the Los Angeles County Engi-\nneer. This survey information indicates that as much\nas 5 feet of relative lateral movement has occurred\nMILE\non the Juvenile Hall site. The same magnitude of\nrelative movement has occurred to the southwest as\nFigure 1.-Vicinity map-San Fernando Valley Juvenile Hall.\nfar as Sepulveda Boulevard, adjacent to the converter\nstation. However, beyond the drainage channel\nHeaviest damage to buildings occurred in the vicin-\nwhich separates the converter station from Sepulveda\nity of the permanent ground displacements. The\nBoulevard, the lateral movements measured were no\nground displacements across the Juvenile Hall site\ngreater than about 2 feet.\nwere first identified and described by Youd (1971a).\nExploratory trenches across the boundaries of the\nPreliminary studies indicated that ground movement\nzone of displacement within Juvenile Hall and\non the site was related to a larger zone of ground dis-\nsouthwest of San Fernando Road allowed examina-\nplacement extending southwestward to the shore of\ntion of the cracks at depth. In general, the cracks\nUpper Van Norman Reservoir.\nwere found to die out and to curve inward with\ndepth toward the interior of the zone of displace-\nment. The diagram of the trench shown in figure 4\nZONE OF DISPLACEMENT\nrepresents the conditions encountered in a nearly\nThe limits of the zone of displacement are indi-\nnorth-south trench excavated across the north bound-\ncated approximately by the pattern of ground sur-\nary of the zone of displacement on the Juvenile Hall\nface ruptures shown in figure 2. The zone is approx-\nsite. The largest crack coincides with a 7-inch verti-\nimately 4,000 feet long and about 900 feet wide (at\ncal displacement of the ground surface, with under-\nits maximum width). It extends from a point 500\nlying soil contacts being similarly displaced. Near the\nfeet northeast of the Juvenile Hall to within the Syl-\nbottom of the trench, however, the crack is\nmar Converter Station site at the edge of Upper Van\ncoincident with a displaced soil-contact that has al-\nNorman Reservoir. The ground surface descends ap-\nmost twice the amount of offset of higher strata. In\nproximately 40 feet in elevation along the length of\nview of the lateral continuity of the boundaries of\nthe zone, resulting in an average slope of about 1\nthe involved soil horizons, such a difference must\npercent from the northeast. Major lateral movement\nrepresent evidence of prior displacement. Narrow\nwithin the zone was downslope in a southwest direc-\nvertical zones of soft soil, truncated by upper hori-\ntion.\nzons of alluvium and fill soil, also were disclosed in\nThe north boundary of the zone bisects the Juve-\nthe trenches. Because vertical displacements of the","Ground Displacement at San Fernando Valley Juvenile Hall\n191\nSAN FERNANDO VALLEY\nDEBRIS\nJUVENILE HALL\nUPPER\nVAN\nEvidence of\nNORMAN\nSand Boils\nSYLMAR\nRESERVOIR\nCONVERTER\nSTATION\nLocation of Major\nSurface Ruptures\nOLIVE SWITCHING\nSTATION\nA\nFigure 2.-Location of ground surface ruptures in zone of displacement.\nhorizons are not apparent, these zones most likely\nposed of siltstone, sandstone, and conglomerate of\nrepresent loosely filled tension cracks produced by\nthe Saugus Formation. The location and maximum\nepisodes of displacement before 1971.\ndepth to bedrock beneath the Juvenile Hall site and\nin the central part of the depression are unknown,\nbut are at least 100 feet beneath the Juvenile Hall,\nGEOLOGIC AND SOIL CONDITIONS\nand the depression undoubtedly bottoms in the Sau-\nThe Juvenile Hall site is near the mouth of Grape-\ngus Formation.\nvine Canyon, a south-draining valley of the San\nThe alluvium beneath the Juvenile Hall site exists\nGabriel Mountains (fig. 5) This valley and others\nas fans, developed during late Pleistocene and Holo-\nimmediately to the east and west have been eroded\ncene time, at the mouth of Grapevine Canyon and of\ninto sedimentary rocks to produce steep-flanking\nsmaller valleys immediately east. This material was\nridges and gently sloping alluvial fans. The alluvial\ndeposited chiefly by torrential streamflow with occa-\nmaterial has accumulated in a depression between\nsional deposition by mudflow. Large composite fans\nthe San Gabriel Mountains and the Mission Hills.\nhave also developed below Sombrero and Weldon\nThis depression has a northeast-southwest trend and\nCanyons, and below other smaller tributaries. As\na\ngenerally follows the projected trend of the Mission\nconsequence of the merging of several fans, a low-\nHills syncline (Merifield 1958)\nland has developed at their intersection with the\nThe east-flanking ridge of Grapevine Canyon ex-\nMission Hills and occupies the area between Juve-\ntends into the northwest corner of the Juvenile Hall\nnile Hall and Upper Van Norman Reservoir.\nsite and descends beneath the alluvium that fills the\nTwo northeast-trending faults have been recog-\nnortheast-trending depression. The ridge is com-\nnized in the San Gabriel Mountains immediately","San Fernando Earthquake of 1971\n192\nWest Edge of Pavement\nof\nJuvenile Facility\nEast Curb of\nSan Fernando Road\nSAN FERNANDO VALLEY\nDEBRIS\nEast Security Wall\nCenterline of\nframes\nBASIN\nof Juvenile Facility\nJUVENILE HALL\nConverter Station\non\nUPPER\nVAN\nNORMAN\nSYLMAR\nRESERVOIR\nCONVERTER\nFEET\n200\n400\nSTATION\nMAP SCALE\nFEET\n1250\nSCALE OF OFFSETS\nAPPROXIMATE BOUNDARY OF\nOLIVE SWITCHING\nZONE OF DISPLACEMENT\nSTATION\nWest Curb of\nWest Property Line of\nSepulveda Boulevard\nConverter Station\nFigure 3.-Relative lateral ground movement in zone of displacement.\n35\n55\n60\n65\n20\n25\n30\n40\n45\n50\nO\n5\n10\n15\nI\nI\nT\nI\nI Feet\nI\nI\nI\nGround surface\nN55E\nTrend of crack N40E\nVery narrow cracks\n7\"\n3\"\n0\nFill\n0\nSandy Silt,\ndry, hard\nSandy Silt, porous,\n5\nvery stiff, dry\nSoft soil filling\n5\nSilty Sand, brown w/scat.\nstreaks sand, sl. porous\n|3/4\nSand & Gravel, grey\nSoft zone\nSandy Silt, light brown,\n10\n10\nfirm, slightly moist\nSandy Silt, grey-brown, firm,\nmoist, slightly porous\nSandy Silt, dark brown, moist, porous\n15\n15\nFeet\nSilty Sand, very dark brown with some gravel\nTRENCH 1\nWest Wall\nFigure 4.-Exploratory trench across ground ruptures on Juvenile Hall site.\nabove the Olive View Hospital. These are the Olive 1971) . A careful examination was made of the hill-\nView and North Olive View faults (Merifield 1958 side exposure of these faults after the earthquake\nof\nand Proctor 1968) . Projections of these faults to the February 9. Although irregular and discontinuous\nsouthwest through the Juvenile Hall site have been cracks associated with slumping on steep slopes exist\nmade by Merifield (1958) and Proctor (1968 and in many nearby places, no evidence was observed of","Ground Displacement at San Fernando Valley Juvenile Hall\n193\n(600)\nSambrero\nSANATORIUM\nOlive\nBoulevard\nView\n153\nRes\nM\n(306\nSan\n1:\n1280\nSYLMAR\nUpper San\nFernando\nReservoir\n187\n6\nNote: Shading denotes approximate areas of alluvial fans\nFigure 5.-Topography as shown on 1935 Sylmar Quadrangle.\nSan Fernando Earthquake\" in Volume III) . This\nslip on the Olive View and North Olive View faults\nmovement may be related to displacements across\nduring the San Fernando earthquake. Trenches\nfaults in the underlying rock during the earthquake\nacross the zone of displacement within and outside\nof February 9. Detailed postearthquake mapping (by\nthe Juvenile Hall site disclosed no evidence in the\nthe California Division of Mines and Geology) of\nupper 15 feet of alluvium of an offset lithology at-\nthe hills immediately above Olive View Hospital has\ntributable to slip on a fault. Survey data, obtained\ndisclosed an approximately 1-inch vertical displace-\nfrom the U.S. Geological Survey at the time of our\nment of the ground surface, with a thrust-sense of\ninvestigation, indicated that there has been no net\nslip that developed across a shear in bedrock that\nrelative displacement in the vicinity of the Juvenile\ncould be interpreted as evidence of faulting (Weber\nHall and Sylmar Converter Station outside the dis-\n1971). At this date, it is our opinion that tectonic\nplacement zone (Youd 1971b)\nslip, if any, on the Olive View and North Olive\nBecause evidence of fault movement had not been\nView faults was minor and did not influence the dis-\nfound on the surface exposures or in shallow\nplacement of the ground at Juvenile Hall.\ntrenches, it was our opinion that tectonic slip did\nThe properties of alluvial soils in the vicinity of\nnot occur on the Olive View and North Olive View\nthe Juvenile Hall were investigated by means of\nfaults. The U.S. Geological Survey has, however, re-\nbucket-auger borings up to 80 feet deep. The\ncently reported finding a small right-lateral displace-\nsoil profile along a section line crossing the Juvenile\nment across the zone of displacement based on re-\nHall site from northwest to southeast is shown in\nsurvey data (see the paper by Youd, \"Ground\nfigure 6. This section is taken along a line transverse\nMovements in Van Norman Lake Vicinity During","San Fernando Earthquake of 1971\n194\nSan Fernando Valley Juvenile Hall\nA\nZone of Displacement\nOriginal ground surface\n1320\nOlive Switching Station\nExisting ground surface\nFill\n1300\nA'\n1280\n1280\nSaugus formation\nMedium dense\nSilty sand\nFill\nFill\n1260\n-1260\nDense silty sand\nIX\nFirm clayey silt\nLoose silty sand\nSaugus\n1240\n-1240\nformation\nDense sand and silty sand\n1220\nAlluvium\n-1220\n1200\n1200\nElevations in feet\nSECTION A A'\nFigure 6.-Geologic and soil profile across Juvenile Hall site.\nto the direction of movement within the zone of dis-\nCONCLUSIONS\nplacement. The sand and silt soils indicated are typi-\nThe permanent ground displacements in the vicin-\ncal of soils to be expected near the terminus of al-\nity of the Juvenile Hall are the result of settlement\nluvial fans merging in a lowland. The significant soil\nand gradual migration of soft soils downslope in a\nfeature, however, is the existence of a zone of soft,\nzone of narrow lateral extent during the earthquake.\nsaturated soil underlying the dense, dry upper soils.\nThe zone exists here as the combined effects of: (1)\nSoils in the soft zone consist of sandy silt and uni-\nselective deposition of soft soils in a lowland or\nform fine sand. A similar profile of soil consistency\ntrough formed by coalescing alluvial fans in a bed-\nwas disclosed as a result of a penetrometer survey by\nrock depression; (2) near-surface ground water; and\nthe California Division of Highways (Marek 1971)\nalong the Golden State Freeway (fig. 7) .\n(3) past displacements of similar nature in the same\narea. The Olive View and North Olive View faults\nThe depth to ground water in the vicinity of the\npass through or near the displacement zone, but tec-\nJuvenile Hall is shown in figure 8. The contours in-\ndicated are based on data from the recent bucket-au-\ntonic slip on them probably did not occur on Febru-\nger borings and from nearby wells. The ground-wa-\nary 9. The presence of the faults, and their past dis-\nter surface generally conforms to the topography,\nplacement of the ground surface during late\nbeing nearest to the ground surface in the low area\nPleistocene and Holocene time, may have contrib-\nsouth of the Juvenile Hall.\nuted to the formation of the depression containing\nD'\nB-6\n(Proj.)\nA-1\n1300\n-1300\n(Proj.)\nB-1\nA-5\n1280\n-1280\nB-2\nA-4\nB-3\nA-3\nB-4\nA-2\nB-5\n1260\n1260\nApproximate limits of soft soil zone\nExisting ground surface\n1240\n-1240\n1220\n-1220\n1200\n1200\n1180\n1180\nSECTION D - D'\nFigure 7.-Soil profile along Golden State Freeway as indicated by penetrometer survey.","Ground Displacement at San Fernando Valley Juvenile Hall\n195\nMWD\nbc\nMWD\nD-25F\n107\nQTs\nEASTERN PORTION SYLMAR\nGROUND WATER BASIN\nQal\nQTs\nQTs\n08.5\nLEGEND\nJUVENILE HALL FACILITY\n014.7\n19.2\n014.2\n22\nQal\nQUATERNARY ALLUVIUM\nQal\nQTs\nSAUGUS FORMATION\nWESTERN PORTION SYLMAR\nBASEMENT COMPLEX\nbc\nGROUND WATER BASIN\nWELL SHOWING DEPTH TO WATER\nQTs\nSOIL BORING SHOWING DEPTH\nWELL 5929\nTO WATER\n70\nPORTION OF\nUPPER\nQal\nMISSION\nHILLS\nVAN NORMAN\nRESERVOIR\nWELL 5939\nQTs\n99\nFigure 8.-Depth-to-water contours (by Glenn A. Brown & Associates, Sept. 1971).\nof movement were less, depending on the thickness\nthe soft soils, but in the Juvenile Hall area it is not\nand consistency of the soft layer. The net lateral dis-\nlikely that the past tectonic slip on the faults signifi-\ncantly changed the strength characteristics of the soft\nplacement in the direction of Upper Van Norman\nReservoir was caused, in part, by the slight topo-\nsoil.\ngraphic slope in that direction and, in part, by the\nA generalized soil profile near the center of the\nlesser degree of lateral support in that direction at\ndisplaced zone, based on the borings, consists of 20\nthe drainage channel.\nfeet of medium dense and moist soil overlying a 10-\nThe location and size of ground ruptures along\nfoot-thick layer of soft and saturated soil. The re-\nsponse of this soil model to lateral forces generated\nthe boundaries of the zone of displacement are re-\nlated to the existence of relatively brittle surface\nby the earthquake would result in large, nonelastic\nsoils, both natural and fill. The natural surface soils,\nshearing strains throughout the depth of the soft soil\nwhere exposed on the Juvenile Hall site, consist of\nlayer. It is estimated that shear strain in this layer\nhard, dry, and slightly cemented clayey sand to a\nduring the San Fernando earthquake resulted in a\ndepth of several feet. An exposure of this condition\nmaximum net downslope lateral displacement of the\nis shown in figure 9 where the underlying softer soils\nground surface of the order of 3 inches during each\nhave been consolidated by the blast from a small dy-\ncycle of strong shaking. The San Fernando earth-\nnamite charge during a seismic refraction survey.\nquake produced about 20 cycles of strong shaking.\nTherefore, a total ground-surface displacement of\nThe fill soils are also brittle compared to the moist\ndeeper soils. Long and relatively continuous ground\nabout 5 feet can be accounted for by this explana-\nruptures along the north boundary of the displace-\ntion. Displacements away from the center of the zone","196\nSan Fernando Earthquake of 1971\nplacements under seismic conditions can be expected\nto remain confined to the zone of displacement that\ndeveloped during the San Fernando earthquake.\nThis conclusion is based on the lateral extent of the\nsoft soils responsible for the movement and on geo-\nlogic evidence that past displacements have occurred\nalong this same zone. The evidence indicates that an\nearthquake with characteristics similar to those of the\nFebruary 9, 1971, earthquake could be expected to\nproduce ground displacements across the Juvenile\nHall site, following the same path and pattern and\nof about the same magnitude as those caused by\nthat earthquake.\nFigure 9.-Crater resulting from consolidation of soft soil\nby small dynamite blast during seismic refraction survey.\nREFERENCES\nFallgren, Richard B., and Smith, Jay L., \"Geologic and Soil\nment zone are generally found in the crustlike soils\nInvestigation, San Fernando Juvenile Hall, Sylmar, Cali-\ndescribed above. Surface ruptures along the south\nfornia,\" for the Los Angeles County Engineer by FUGRO,\nboundary are shorter and less well-developed, tend-\nInc., Long Beach, Calif., Sept. 20, 1971, 45 pp. and 2 pl.\ning toward an en echelon pattern because of the lack\n(unpublished report)\nMarek, C.E., California Division of Highways, Sacramento,\nof brittle surface soils.\nSept. 1971 (written communication)\nSome saturated soils in the zone of displacement\nMerifield, P.M., \"Geology of a Portion of the Southwestern\nconsist of uniform fine sand which has a potential\nSan Gabriel Mountains, San Fernando and Oat Mountain\nfor liquefaction during strong shaking. It is quite\nQuadrangles, Los Angeles County, California,\" M. A. thesis,\nlikely that local liquefaction of these soils during\nUniversity of California, Los Angeles, 1958, 61 pp.\nthe earthquake contributed to ground instability and\nProctor, R.J., \"Geologic Map and Section Along the 5.5-Mile\nSan Fernando Tunnel,\" No. L-1078, Metropolitan Water\nsubsequent displacement. The existence of sand boils\nDistrict of Southern California, Los Angeles, 1968, scale\nin the high ground-water area southeast of Juvenile\n1:12,000 (unpublished).\nHall (fig. 2) is evidence of this local liquefaction.\nProctor, R.J., \"Geologic Map and Section Along the 5.5-Mile\nHowever, soils with liquefaction potential are not\nSan Fernando Tunnel,\" No. L-1078 (revised), Metropolitan\nsufficiently widespread throughout the zone of dis-\nWater District of Southern California, Los Angeles, Feb. 26,\n1971, scale 1:12,000 (unpublished)\nplacement to account for the lack of stability of the\nWeber, H., California Division of Mines and Geology, Sacra-\narea during the earthquake. The soft and loose satu-\nmento, Sept. 1971 (personal communication).\nrated soils have sufficiently low strength under static\nYoud, T. Leslie, \"Landsliding in the Vicinity of the Van Nor-\nconditions to account for the lateral and downslope\nman Lakes,\" The San Fernando, California, Earthquake of\nground movement during strong shaking. Large-scale\nFebruary 9, 1971, Geological Survey Professional Paper 733,\nliquefaction would have resulted in much greater\nU.S. Geological Survey and the National Oceanic and At-\nmospheric Administration, U.S. Department of the Interior\ndisplacements. It may be concluded, therefore, that\nand U.S. Department of Commerce, Washington, D.C.,\nliquefaction played a minor role in the performance\n1971a, pp. 105-109.\nof the site during the earthquake.\nYoud, T. Leslie, U.S. Geological Survey, Menlo Park, Calif.,\nOur investigation indicates that future ground dis-\nAug. 1971b (personal communication)","Ground Movements in\nVan Norman Lake Vicinity\nDuring San Fernando Earthquake\nINTRODUCTION\nRupturing and shifting of the earth's surface OC-\ncurred at several locations on very gentle slopes in\nthe vicinity of Van Norman Lake (commonly called\nUpper Van Norman Reservoir) during the 1971 San\nFernando earthquake. The precise origin of these\nCONTENTS\nruptures and displacements has been the subject of\nPage\nsome controversy. A landslide origin has been pro-\n197 INTRODUCTION\nposed by Youd (1971) who recognized, nonetheless,\n198\nSURFICIAL FEATURES\nthat some differential tectonic displacements could\n198\nSURVEY RESULTS\n203\nSUBSURFACE CONDITIONS\nhave occurred. This view is also generally shared by\n205 ORIGIN OF RUPTURE ZONES\nthe Metropolitan Water District of Southern Cali-\n205 ACKNOWLEDGMENTS\nfornia (MWD) staff (see paper, \"Geology, Earth-\n206 REFERENCES\nquake Damage, and Water Table Fluctuations-\nPublication authorized by Director,\nMetropolitan Water District Facilities, Sylmar Area\"\nU.S. Geological Survey.\nin Volume III), but others (Crandall 1971 and\nSlosson 1971) have suggested that the ruptures, at\nleast those northeast of the lake, were probably\nthe result of deep-seated fault movements. Still oth-\ners, while agreeing that the features northeast of the\nlake were nontectonic, concluded that they were\nformed as the result of compaction of subsurface sed-\niments (Scott 1971) or downslope migration (Fall-\ngren and Smith 1971) rather than by landsliding.\nThis study was made to determine the origin of\nthe ruptures and displacements in the Van Norman\nLake vicinity and to obtain more information about\nthe phenomena that occurred there. Surficial features\nwere mapped, points with known preearthquake lo-\ncations surveyed, and subsurface data gathered. The\nresults show that differential displacements were\nsmaller outside rupture zones than inside and that\nrelative horizontal displacements within rupture\nzones were downslope and generally several times\nT. LESLIE YOUD\ngreater than corresponding vertical displacements.\nU.S. Geological Survey\nSoft soil layers or potentially liquefiable layers were\nMenlo Park, Calif.\n197","198\nSan Fernando Earthquake of 1971\nfound at relatively shallow depths beneath the dis-\neast of the lake; a single boil was found 200 feet east\nturbed zones. It is concluded that landsliding, pre-\nof the freeway near the southern margin of the zone;\ndominantly of the lateral spreading type (Varnes\napproximately 50 boils erupted on the rupture zone\n1958), was the immediate cause of the ruptures and\nin the field between San Fernando Road and the un-\ndifferential displacements that occurred near Van\ncompleted freeway access ramp; another group was\nNorman Lake.\nfound at the base of the railroad embankment south\nof the Juvenile Hall.\nWest of the lake, the rupture zone extended 3,000\nSURFICIAL FEATURES\nfeet from the lake to the Van Gogh School. The av-\nThe ruptures were confined to a northeast-trend-\nerage slope between these two locations is about 2.5\ning band which extended from the Van Gogh Street\npercent. The rupture zone was as much as 3,000 feet\nElementary School on the southwest to the olive\nwide on the eastern segment of the Joseph Jensen Fil-\ngroves east of the San Fernando Valley Juvenile Hall\ntration Plant fill. Displacements on these ruptures\non the northeast. The more significant ruptures are\nwere mainly vertical or extensional in a downslope\nplotted on figure 1. Van Norman Lake effectively\ndirection.\ndivides this band into two zones, one on each side of\nThe partly completed filtration plant suffered con-\nthe lake. In each zone, the ruptures formed in allu-\nsiderable damage from rupturing and displacements\nvium or in fill overlying alluvium.\n(Duke 1971) Other damage included disrupted\nNortheast of the Van Norman Lake, the ruptures\npipelines and pavements at several locations, a frac-\nbounded a tongue-shaped area that extended about\ntured and offset floor slab in a house, and fractured\n4,000 feet upslope from the lake. The zone was as\nfoundations and floor slabs at the Van Gogh School.\nmuch as 1,300 feet wide southwest of San Fernando\nRuptures, lateral and vertical displacements, and\nRoad, but was only about 900 feet wide farther\nsand boils also occurred in recent alluvium in and\ndownslope at the Golden State Freeway. The average\nnear the upper reaches of Lower Van Norman Lake.\nslope between the lake (1,220-ft elevation) and the\nThese disturbances caused no significant damage.\nupper margin of the zone (1,280-ft elevation) is 1.5\npercent. Near the lake and near the upper margin,\nSURVEY RESULTS\nthe slope is locally greater; through the midsection,\nthe slope is only about 0.9 percent.\nThe magnitudes and locations of displacements as-\nRuptures with right-lateral displacement formed\nsociated with the earthquake in the area surrounding\non the north margin of this zone; ruptures with left-\nthe rupture zones were determined by comparing\nlateral displacement formed on the south margin;\npostearthquake coordinates and elevations of survey\nand extensional ruptures formed at the northeast\nmonuments within the subject area to those estab-\nmargin. These ruptures and displacements were re-\nlished before the event. The preearthquake positions\nsponsible in large part for the considerable damage\nof the monuments are plotted on figure 1. The\nto constructed works located within this zone\npreearthquake elevations and coordinates were estab-\n(Moran 1971, Thompson 1971, Youd 1971, and\nlished, or rechecked, in nearly all cases since 1963 by\nYoud and Olsen 1971).\nother agencies, including the National Geodetic\nSand boils erupted at several locations on or near\nSurvey (NGS) of the NOAA National Ocean Sur-\nthe disturbed zones (fig. 1). Two groups of sand\nvey,1 the Los Angeles City Bureau of Engineering\nboils were exposed on the lake bottom after the\n(LABE) and the Los Angeles Department of Water\nand Power (LADWP) Postearthquake elevations\nwater was drawn down, one in the eastern lobe of\nthe lake generally on line with the southern part of\nare from releveling by LABE (February to March\n1971) using a point at the intersection of Van Nuys\nthe rupture zone and the other in a band through\nand Foothill Boulevards, one-half mile south of the\nthe north and northwest sectors of the lake. Sand\nboils also erupted on the Joseph Jensen Filtration\nSan Fernando fault zone, for reference. Postearth-\nPlant fill near the southern margin of the rupture\nquake coordinates are based on surveys by LADWP\n(February to April 1971) and the U.S. Geological\nzone and along the base of the fill about 500 feet\nwest of the lake. Other sand boils erupted at the base\nSurvey-USGS- (June 1971) and were later unoffi-\nof the Sylmar Converter Station fill about 200 feet\n1 Formerly U.S. Coast and Geodetic Survey.","Ground Movements in Van Norman Lake Vicinity\n199\nTanis\nGRAPEVINE\n(0.73 N, 0,43 E)\nSchoolhouse\nDebris Basic\nFOOTHISL\nBOUNDARY\nBM\n1280\n(0.56 up)\nMACK\nA\n(0.36 N.0.72 E)\nVI\n3.1 R\nSYLBHC\n0.77 up)\nHerrick\nSYLB118\n<(0.79 up)\n(Q.13N,0.59E,0.92\n149\nSubstat\n(OJON,0,34 E)\nPower\nCSN\nSYLCHC\n(0.20 N, 0,23 E)\n(Held, 1,97 up)\nPOL\n1/9,\n(0.18 N, 0,41 E)\n240.\nOil Tanks\n1299\n24\nTraiter\nA\nPARK\n(2.22 up)\nPark\n(0.03 N,0,02 E, 1,59)\n1240\nSYL D12 B\nA SYL A 12 B\n(0.27 S, 0.18E, 2,23 up)\n(1.93 S, 2.63 E)\nVan\nNorman\nWP3\nGogh\nSchool\n(0.01 N, OHE) Debris\nLahe\nPO\nBasin\nBENDIX\nSPILLWAY ELEV\n(0,04 N\nSYLA12A\n1219\ns\n(0:15 N, 0.74 E, 0.57 up)\nIntake\nTower\nSYL A 12 RM1\n(0.07 N, 0,72 E)\nSYL A 12, NO. 2\n0\n(0.20 N, 0.87 E)\nil\nEXPLANATION\nEldorado Ave\nSeh\nSurface rupture\n2.3V\nWP6\n(0.18 N, 0.34 E)\nVertical displacement in feet\n(down on hachured side)\no\nSand boil\nDebris\n0.5V\n1.7 L\nBasin\nLeft-lateral displacement in feet\nto\nVAD\n(0.46 9, 0.67 E)\n0.8 R\nRight-lateral displacement, in feet\nA\nSurvey point\nReservair\n10.15.N.0.511\n(0.21 S, 1.07 E. 2.22\nDisplacement vector and components\nof displacement in feet\nWpo\n2000 FEET\nPacoimo E2\n(0,25 N,1,07E)\n(0.42.5.2.27 E)\n0\n5 FEET\nMAP SCALE\n405\nDISPLACEMENT SCALE\n39\nWp.10\n(0.38 N 1.48 E)\nPAC C2\n(0.60 N,1,79 E)\nFigure 1.-Map of Van Norman Lake vicinity, showing locations of ruptures generated by earthquake and survey monument locations.\nHorizontal displacements shown are in relation to SYL C11C, and elevation changes are in relation to external LABE reference point.\n(Revised and updated version of fig. 1, Youd 1971.)\ncially adjusted by the author to the constrained ad- C11C moved north 0.54 foot, moved west 1.34 feet,\njustment of coordinates established by NGS. and rose 1.97 feet. To show more clearly the differ-\nA comparison of preearthquake and postearth- ential horizontal displacements in the area, the hori-\nquake data shows tentatively that monument SYL zontal displacements relative to monument\nSYL","San Fernando Earthquake of 1971\n200\nC11C, rather than absolute horizontal displacements,\nmovement (SYL B11C) from those displacements of\nwere plotted on figure 1. (To obtain the tentative\nnearby stations located outside the disturbed zones.\nabsolute movement, one need only add algebraically\nFurther data on movements within the rupture zones\nthe components given above for SYL C11C to the\nwere obtained by resurveying other previously set\ncomponents given in parentheses for each station on\npoints, such as nails set on highway stations, con-\nfig. 1.)\nstruction control points, and points on property\nMonument SYL B11B may have been disturbed\nlines. Data from the converter station were supplied\nafter the earthquake. It was located beneath a badly\nby LADWP, while the other points were surveyed by\ndamaged freeway overpass that was dismantled and\nUSGS using a radial-line traverse procedure.\nreplaced before the resurvey was made. Because the\nAdditional displacement data came from offset\nstability of SYL B11B is questionable, two other\nmeasurements of the east and west fences at the\npoints, a lead and tack at the northeast entrance to\nconverter station by LADWP, the curb line of San\nthe converter station (CSN) and a nail at station\nFernando Road by LABE, and the north-south axis\n149+00 on San Fernando Road (149), were used to\nof the filtration plant by MWD. The displacement\ngive additional control for that area. Also, station\nvectors on the extension of Yarnell Street between\nPOL, a spike and tin on Balboa Boulevard, was\nBradley Avenue and San Fernando Road are from\nadded to provide a control point for that area.\ndirect-distance measurements between a set of nails\nOutside the rupture zones, the displacement vec-\nplaced before the earthquake by LABE and a similar\ntors appear to define at least two separate units or\nset placed after the event.\ncrustal blocks that moved relative to each other dur-\nDisplacement vectors (adjusted to nullify the in-\ning the earthquake. The first block, south of the Ju-\nfluence of the displacements in the area surrounding\nvenile Hall, remaining essentially fixed with respect\nthe rupture zones) and offset measurements are plot-\nto SYL C11C, includes SYL C11C, Park, WP3,\nted in figure 2 for the area northeast of the lake and\nBendix, and SYL D12B. The second block, west of\nin figure 3 for the area west of the lake. Northeast of\nthe Juvenile Hall, contains stations CSN, SYL B11B,\nthe lake, the horizontal displacements form a well-de-\n149, and possibly POL, Mack, and Grapevine. This\nfined pattern in which the margins of the displace-\nblock appears to have moved northeast or right later-\nment zone correspond closely to those of the rupture\nally with respect to the first block, possibly across the\nzone. In every instance, displacement was downslope,\nOlive View fault (Merifield 1958 and paper by\nalthough in some local areas a component of cross-\nMWD, \"Geology, Earthquake Damage, and Water\nslope displacement also occurred.\nTable Fluctuations-Metropolitan Water District\nHorizontal displacement within the zone of failure\nFacilities, Sylmar Area\" in Volume III), which is\nincreased downslope from zero at the upper margin\ninferred to trend northeastward approximately be-\nof the zone to a maximum of 5.7 feet at San Fer-\nneath the rupture zone (fig. 1) At the Juvenile\nnando Road. At the extension of Yarnell Street, the\nHall, the relative displacement across the inferred\nmaximum was 1.8 feet. Between San Fernando Road\nfault is about 0.4 foot (between stations WP3, Park,\nand the east fence of the converter station, the maxi-\nand SYL C11C on the southeast and stations CSN\nmum displacement appears to have been essentially\nand 149 on the northwest), SO that the distance be-\nconstant: 5.1 feet at the freeway and 5.0 feet at the\ntween 149 and SYL C11C was shortened by 0.32\neast fence.\nfoot. This compression probably caused the spectacu-\nA discontinuity in the horizontal displacement\nlar bowing and buckling of the railroad tracks that\npattern occurred across the approximately 8-foot-\noccurred between these two points during the earth-\ndeep flood control channel between the east fence of\nquake (Scott 1971, fig. 4.15) It is of interest to note\nthe converter station and a group of A-frames and\nthat the approximately 0.31 foot of rail removed in\ntransformer pads west of the channel, whose maxi-\nrepairing the tracks (Clark 1971) was almost equiva-\nmum measured displacement was about 0.7 foot.\nlent to the shortening of distance between 149 and\nThus, more than 4 feet of horizontal displacement\nSYL C11C.\nwas absorbed by the channel. This compression se-\nThe vector displacements of SYL B11C and SYL\nAn offset is the perpendicular distance from the relative pre-\nA12B, located within the rupture zones, clearly differ\nearthquake position of a linear feature, such as a curb or fence, to\neither in magnitude (SYL A12B) or direction of\nthe postearthquake position of a point on that feature.","Ground Movements in Van Norman Lake Vicinity\n201\nBRADLEY\nSYL BIIB\n149\nO\nSAN\nFER\\NANDO\nSYL BII\nCSN\nA\nSta 1554\nPARK\nEXPLANATION\nVector displacement\nFlood\nchannel\nOffset displaceme...\nSurface rupture\n0\n5\n10 Feet\nDISPLACEMENT SCALE\n0\n1000 FEET\nWP 3\nMAP SCALE\nFigure 2.-Rupture zone northeast of Van Norman Lake, with horizontal displacements superimposed.\nverely disrupted the concrete lining and visibly offset\nplan elevations and postearthquake level data ob-\nthe east bank of the channel (Youd and Olsen 1971,\ntained from the California Division of Highways.\nfig. 2) . The invert of the channel also heaved as\nSecondary vertical displacements were separated\nmuch as 2 feet across this section (Pitzer 1972) .\nfrom tectonic elevation changes across the section as\nThe magnitude of the horizontal movement in-\nfollows. South to the rupture zone, the uplift, which\ncreased downslope from the flood control channel to\nis assumed to be of tectonic origin, increased almost\nthe lake. For example, at the west fence of the con-\nlinearly with distance southward. At San Fernando\nverter station, the maximum offset was 2.4 feet com-\nRoad, north of the rupture zone, the tectonic uplift\npared to 0.7 foot just west of the channel.\nwas about 0.8 foot (based on BM 1273 rather than\nVertical and horizontal displacements on a section\nSYL B11B, whose stability is questionable) . The rel-\nacross the rupture zone at the Golden State Freeway\native uplift at San Fernando Road is consistent with\nare plotted on figures 4a and 4b, respectively. The\na linear extrapolation of the data south of the rup-\nvertical displacements are the differences between\nture zone. Therefore, it is assumed that the linear","202\nSan Fernando Earthquake of 1971\n8 + 00 N St\n1,000 FEET\nMAP SCALE\nPOL\nJENSEN\nFILTRATION\nSYL A12B\nPLANT\nVan Gogh\nEXPLANATION\nSchool\nVector splacement\nOffset displacement\n-\nSurface rupture\n0\n5 Feet\nSYL A12A\nDI SPLACEME NT SCALE\nFigure 3.-Rupture zone west of Van Norman Lake, with horizontal displacements superimposed.\nextrapolation on figure 4a represents tectonic eleva-\nOn the west side of the lake (fig. 3) , horizontal\ntion change and that deviations from this line are\ndisplacement increased with distance downslope.\nthe result of secondary effects.\nThe maximum secondary displacement at Balboa\nBased on the above assumption, differential sub-\nBoulevard was about 0.8 foot. At the north-south\nsidence as great as 0.5 foot occurred across the rup-\naxis of the filtration plant, the maximum displace-\nture zone. Immediately north of the zone, an anoma-\nment was 1.8 feet; and at SYL A12B, the displace-\nlous rise of 0.2 foot was measured; and from there to\nment was about 3 feet. The margins of the displace-\nthe bridge over San Fernando Road, subsidence up\nment zone corresponded to the margins of the\nto 0.5 foot occurred. A bridge-approach fill underlies\nrupture zone.\nthe latter section of freeway, and the subsidence\nPoints along the north-south axis of the filtration\nthere most likely resulted from compaction of the\nplant were releveled periodically by MWD after the\nfill.\nearthquake. Elevation changes recorded on February","Ground Movements in Van Norman Lake Vicinity\n203\n+2.0\n(a)\nVertical displacements\nEstimated tectonic uplift\nElevation change at BM1273\n+1.0\n0\nHighway fill\nBridge\nRupture zone\nHighway stations\nSouth\nNorth\n6,0\n(b)\nSecondary horizontal\ndisplacements\n4.0\n500 FEET\n0\n250\n2.0\nNails not set on highway stations\nin this section\n0\nFigure 4.-Vertical (a) and horizontal (b) displacements along Golden State Freeway at latitude of the rupture zone.\nElevation data from California Division of Highways.\nbeen done by others (Fallgren and Smith 1971; Fall-\n10, 16, and 27 (1, 7, and 18 days after the earth-\nquake, respectively) are plotted in figure 5a. These\ngren and Smith, \"Ground Displacement at San Fer-\nchanges are with respect to station 8+ 00 north\nnando Valley Juvenile Hall During San Fernando\nwhich was held fixed (see fig. 3 for location) Hori-\nEarthquake\" in Volume III; and MWD, \"Geology,\nzontal offsets at the corresponding stations, relative\nEarthquake Damage, and Water Table Fluctuations\nto points on the upland hills (Saugus Formation) at\n-Metropolitan Water District Facilities, Sylmar\neither end of the axis, are plotted in figure 5b. Sub-\nArea\" in Volume III) Within and along the north\nsidence occurred across the main rupture zone; the\nboundary of the displacement zone northeast of the\nmaximum was about 0.4 foot. To the north of the\nlake, Fallgren and Smith (1971) report the following:\nmain zone, both uplift and subsidence were re-\nThe soils were dense to medium dense and dry near the\ncorded. It is also interesting to note that additional\nground surface. However, soil consistency (firmness) gen-\nrelative elevation changes (both positive and nega-\nerally decreased with depth until a 5- to 15-foot-thick zone\ntive) occurred at many points after the earthquake.\nof saturated and soft, or loose, soils was encountered at\nSimilarly, minor horizontal movements occurred\ndepths of 10 to 25 feet. Soils in the soft or loose zone con-\nafter the main earthquake; these movements were\nsisted of sandy silt or uniform fine sand. Below the soft\ngenerally downslope, but some upslope movements\nzone, soil consistency increased and varied from medium\ndense to dense.\nalso were recorded. No attempt was made to estimate\nthe influence of local tectonic movements on these\nOutside the rupture zone, the soft, saturated soils\ndata.\nwere absent or the soil was of firmer consistency.\nFallgren and Smith (1971) concluded that slippage\nSUBSURFACE CONDITIONS\noccurred within the soft, saturated layer, most likely\nas a discontinuous deformation of the layer rather\nIt was beyond the scope of this study to perform\npostearthquake subsurface investigations; work has\nthan along a single continuous failure surface.","San Fernando Earthquake of 1971\n204\n+0.50\n(a) Profile\n0\nFeb. 10, 1971\nFeb. 16, 1971\n-0.50\nFeb. 27,1971\n0\n500\n1000 FEET\n-1.00\nSouth\nStations\nNorth\n0\n(b) Plan view\n1.0\n2.0\nFigure 5.-Vertical (a) and horizontal (b) displacements along north-south axis of Joseph Jensen Filtration Plant.\nData from Metropolitan Water District of Southern California.\nPreearthquake subsurface investigations were con-\ninterest to note that during both the original con-\nducted at the Juvenile Hall by LeRoy Crandall &\nstruction and the postearthquake repairs to the chan-\nAssociates (1961) and at the Sylmar Converter Sta-\nnel, work was hampered by high ground water and\ntion by Converse Foundation Engineers (1966)\nsoft, saturated soils (Pitzer 1972)\nThese reports show the soft layer of silts and sands\nA brief summary of soil conditions beneath the Jo-\nidentified by Fallgren and Smith (1971) . Preearth-\nseph Jensen Filtration Plant, west of the lake, has\nquake densities measured in this layer ranged from\nbeen given in a paper by MWD, \"Geology, Earth-\n80 to 110 pcf. Of particular interest to this study\nquake Damage, and Water Table Fluctuations-\nwere two borings along the east boundary of the con-\nMetropolitan Water District Facilities, Sylmar Area\"\nverter station property near the disrupted flood con-\nin Volume III. They report that a saturated layer of\ntrol channel. In each boring, a soft, wet, or saturated\nfine sand was found in several postearthquake bor-\nlayer of silt or sandy silt was found at depths of 9\nings at depths ranging from 6 to 9 feet below the\nand 11 feet, respectively. The depth of the channel\noriginal ground surface. They infer that slippage\nin this area is about 8 feet, but was excavated to at\noccurred within this layer, possibly because of lique-\nleast a 10-foot depth during construction. It is also of\nfaction.","Ground Movements in Van Norman Lake Vicinity\n205\nORIGIN OF RUPTURE ZONES\nhave diminished with distance to the northeast. A re-\nlated objection is the absence of a sizable landslide\nThe survey data show that, although the earth's\ntoe in the lake bottom (paper by MWD, \"Geology,\ncrust was uplifted, tilted, and horizontally displaced\nEarthquake Damage, and Water Table Fluctuations\nbeneath the Van Norman Lake area, differential dis-\n-Metropolitan Water District Facilities, Sylmar\nplacements outside the rupture zones were small\nArea\" in Volume III). Both variances from normal\ncompared with differential displacements within the\nlandslide behavior are explained by survey data that\nzones. If the differential displacements outside the\nshow that the flood control channel east of the con-\nrupture zones are a reflection of tectonic movements\nverter station acted as a free face or toe. Essentially,\nin the underlying bedrock, as is generally accepted,\nall of the displacement from upslope was absorbed\nthen it would be mechanically impossible for the\nat that point. Thus, the slide can be divided into two\nlarger and, in many instances, oppositely directed\nsegments, one extending from the lake to the flood\ndisplacements within the rupture zones to be also of\ncontrol channel and the other extending from the\ntectonic origin; thus, they must be surficial move-\nchannel to the upper margin of the rupture zone.\nments of secondary origin-that is, in some way the\nOver both of these segments, displacement generally\nresult of seismic shaking.\ndecreased upslope.\nThe evidence indicates that landslides, predomi-\nFallgren and Smith (1971) objected to calling the\nnantly of the lateral spreading type (Varnes 1958),\nfeature a slide because relative movement apparently\nwith some rotational slumping on the steeper slopes\noccurred across a zone of considerable thickness\nnear the shore of the lake, were the causes of the\nrather than along a single, continuous failure surface\nrupturing and displacements. Even though the lat-\nand because the feature is stable under static condi-\neral spreading slides were not as well developed as\ntions. The first of these objections is eliminated by\nsome failures reported in the literature, they meet\nthe definition of lateral spreading (Varnes 1958)\nthe criteria for this type of failure.\nthat allows for a thick mobile zone. Indeed, if the\nNortheast of the lake, evidence of lateral spreading\nfailure zone had been along a thin layer, the slide\nincludes: (1) The feature is tongue-shaped in plan,\nwould have been more properly classified as a block-\nwith right-lateral displacements across the northwest\nglide. With respect to the second objection, slides\nmargin, left-lateral displacements across the southeast\nthat are mobile only during periods of seismic shak-\nmargin, and extensional displacements at the upper\ning have long been recognized in what would other-\nmargin. (2) Displacements were downslope, with\nwise be considered stable ground.\nmaximum horizontal components being several times\nThe rupture and displacement patterns on the\nlarger than the corresponding vertical components.\nwest side of the lake were more typical of normal\n(The latter factor cannot be accommodated by sim-\nlandslide behavior. The magnitude of the displace-\nple compaction of subsurface sediments, an explana-\nments decreased with distance upslope from the lake,\ntion suggested by Scott 1971.) (3) The surface layer\nand the surface layer was ruptured along lines more\nfractured into large-sized blocks, particularly that\nor less perpendicular to the direction of movement.\narea north of San Fernando Road. These blocks\nThe blocks between ruptures generally moved later-\nmoved downslope with very little tilting, a mode\nally downslope; however, some blocks rotated\ncharacteristic of lateral spreading (Varnes 1958)\nslightly. Again, it is concluded that the origins of\n(4) The soil profile beneath the rupture zone con-\nthese ruptures and displacements were low-angle\nsists of a firm surface layer overlying a soft saturated\nlandslides, predominantly of the lateral spreading or\nlayer, which is in turn underlain by firm soils to\npossibly blockglide types, with rotational slumping\ndepth. This profile is consistent with the three-layer\nat the free face near the shore of the lake.\nprofile given by Varnes (1958) for lateral spreading\nfailures.\nACKNOWLEDGMENTS\nSeveral objections have been raised against calling\nthe rupture zone northeast of the lake a landslide.\nMany of the data used in this study were supplied\nScott (1971) noted that if it were a landslide the\nby other agencies. Their cooperation and the assist-\ngreatest displacements should have occurred at the\nance of their staff members are gratefully acknowl-\nunrestrained face along the lake margin and should\nedged: A. G. Keene and R. J. Mitchell, Los Angeles","San Fernando Earthquake of 1971\n206\nCounty Engineer's Office; I. E. Shinkle, Los Angeles\nMoran, D.F., \"Damage to Energy and Communication Sys-\nitems,\" The San Fernando, California, Earthquake of Febru-\nFlood Control District; W. N. Meslow and L. D.\nary 9, 1971, Geological Survey Professional Paper 733, U.S.\nPaulsen, Los Angeles City Bureau of Engineering; L.\nGeological Survey and the National Oceanic and Atmos-\nJ. Vadasz and C. P. Pistole, Los Angeles Department\npheric Administration, U.S. Department of the Interior and\nof Water and Power; E. A. Varon, California Divi-\nU.S. Department of Commerce, Washington, D.C., 1971,\nsion of Highways; W. J. Edwards, Metropolitan\npp. 245-250.\nPitzer, A.G., Los Angeles Department of Water and Power,\nWater District of Southern California; and R. B.\nLos Angeles, Calif., 1972 (written communication)\nFallgren and J. L. Smith, FUGRO, Inc.\nScott, R.F., \"Preliminary Soil Engineering Report,\" Engineer-\ning Features of the San Fernando Earthquake of February 9,\nREFERENCES\n1971, Earthquake Engineering Research Laboratory Report\nEERL 71-02, California Institute of Technology, Pasadena,\nClark, M.M., U.S. Geological Survey, Menlo Park, Calif., 1971\nJune 1971, pp. 299-331.\n(personal communication).\nSlosson, James E., \"Engineering Geology Review of San Fer-\nConverse Foundation Engineers, Pasadena, Calif., \"Foundation\nnando Valley Juvenile Hall, Exhibit D,\" Report on Olive\nInvestigation, Proposed Sylmar Converter Station, City of\nView Hospital, Structural Engineers Association of Southern\nLos Angeles, California,\" for the Bechtel Corporation,\nCalifornia, Los Angeles, May 25, 1971, 4 pp.\nVernon, Calif., Oct. 24, 1966, 14 pp. and 31 figs. (unpub-\nThompson, James H., \"Damage to the Los Angeles County\nlished report)\nJuvenile Facilities, Sylmar,\" The San Fernando, California,\nCrandall, LeRoy, \"Opinions on Foundation Behavior During\nEarthquake of February 9, 1971, Geological Survey Profes-\nSan Fernando Earthquake, Exhibit C,\" Report on Olive\nsional Paper 733, U.S. Geological Survey and the National\nView Hospital, Structural Engineers Association of Southern\nOceanic and Atmospheric Administration, U.S. Department\nCalifornia, Los Angeles, May 25, 1971, 2 pp.\nof the Interior and U.S. Department of Commerce, Wash-\nCrandall, LeRoy, & Associates, Los Angeles, Calif., \"Report\nington, D.C., 1971, pp. 191-192.\nof Foundation Investigation, Proposed San Fernando Branch\nVarnes, D.J., \"Landslide Types and Processes,\" Landslides\nJuvenile Hall, San Fernando Road and Yarnell Street, Los\nand Engineering Practice, Highway Research Board Special\nAngeles,\" for County of Los Angeles, Calif., Sept. 27, 1961,\nReport 29, Washington, D.C., 1958, pp. 20-47.\n10 pp. and 26 figs. (unpublished report).\nDuke, C. Martin, \"Damage to Water Supply Systems,\" The\nYoud, T. Leslie, \"Landsliding in the Vicinity of the Van Nor-\nSan Fernando, California, Earthquake of February 9, 1971,\nman Lakes,\" The San Fernando, California, Earthquake of\nGeological Survey Professional Paper 733, U.S. Geological\nFebruary 9, 1971, Geological Survey Professional Paper 733,\nSurvey and the National Oceanic and Atmospheric Adminis-\nU.S. Geological Survey and the National Oceanic and At-\ntration, U.S. Department of the Interior and U.S. Depart-\nmospheric Administration, U.S. Department of the Interior\nment of Commerce, Washington, D.C., 1971, pp. 225-240.\nand U.S. Department of Commerce, Washington, D.C., 1971,\nFallgren, Richard B., and Smith, Jay L., \"Geologic and Soil\npp. 105-109.\nInvestigation, San Fernando Valley Juvenile Hall, Sylmar,\nYoud, T. Leslie, and Olsen, H.W., \"Damage to Constructed\nCalifornia,\" for the Los Angeles County Engineer by\nWorks, Associated With Soil Movements and Foundation\nFUGRO, Inc., Long Beach, Calif., Sept. 20, 1971, 45 pp.\nFailures,\" The San Fernando, California, Earthquake of\nand 2 pl. (unpublished report)\nFebruary 9, 1971, Geological Survey Professional Paper 733,\nMerifield, P.M., \"Geology of a Portion of the Southwestern\nU.S. Geological Survey and the National Oceanic and At-\nSan Gabriel Mountains, San Fernando and Oat Mountain\nmospheric Administration, U.S. Department of the Interior\nQuadrangles, Los Angeles County, California,\" M.A. thesis,\nand U.S. Department of Commerce, Washington, D.C., 1971,\nUniversity of California, Los Angeles, 1958, 61 pp.\npp. 126-132.","Earth Rupture and Structural Damage\nby San Fernando Earthquake\nin North Sylmar Housing Development\nINTRODUCTION\nThis report summarizes the results of an investiga-\ntion of the geological aspects of earthquake damage\nin a housing development in northern Sylmar. This\nwas one of the areas hardest hit by the San Fernando\nearthquake of February 9, 1971. This investigation\nCONTENTS\nwas undertaken at the request of the developer and\nPage\nincluded both developed and undeveloped properties\n207\nINTRODUCTION\nin the damaged area.\n207\nScope of Investigation\nThe results of the investigation are significant to\n208\nGeologic Setting\nthe overall problem of earthquake hazard because of\n208\nSeismic Setting\n208\nRESULTS OF INVESTIGATION\nthe wide range of engineering geologic conditions in\n208\nActive Faulting\nthe housing development including movement along\n208\nDamage to Construction From\nan active fault, structures in various stages of con-\nGround Rupture\n208\nDamage to Fills\nstruction, and earth foundation materials, ranging\n211\nDamage to Houses Not Associated\nfrom firm bedrock, to moderately firm to soft terrace\nWith Ground Failure\ngravels, to manmade fill. Also, geologic conditions in\n212 CONCLUSIONS\nthe development bear on the evaluation of condi-\n212\nREFERENCES\ntions and events at the Veterans Administration\nPublished with permission of PBS Corporation.\nHospital, located immediately northwest of the de-\nvelopment.\nScope of Investigation\nThe investigation consisted of two phases: first a\nsurface mapping phase, followed by a subsurface ex-\nploration phase. The surface phase included mapping\nof geologic units and structure at a scale of 1 inch\nequals 60 feet (1:720), with emphasis on the line of\nrecent fault movement and on cracks and ruptures of\nthe ground and structures. The boundary between\nDONALD O. ASQUITH\ncut and fill areas was determined from maps of to-\nEnvicom Corp.\npography and designed grades and was modified as\nEncino, Calif.\nnecessary in the field.\nF. BEACH LEIGHTON\nThe subsurface exploration phase consisted of\nF. Beach Leighton & Associates\nbackhoe pits and borings located on the basis of the\nEngineering Geologists\nsurface investigation. Pits were placed transverse to\nLa Habra, Calif.\n207","San Fernando Earthquake of 1971\n208\nfaults and cracks in order that three-dimensional re-\nings excavated during the investigation, are sum-\nlationships could be viewed and mapped.\nmarized in table 1.\nDamage to Construction From Ground Rupture\nGeologic Setting\nThe Veterans fault had not been recognized in\nThe area of investigation is located at the base of\nthe development before the earthquake or during\nthe San Gabriel Mountains (fig. 1) in an area of sed-\nthe time homebuilding was in progress. Fortunately,\nimentary rocks and alluvial sediments defined by\nonly one house had been built over the trace of the\nOakeshott (1958) as Plio-Pleistocene Saugus Forma-\nfault, and it was not occupied at the time of the\ntion, late Pleistocene terrace gravels, and Recent al-\nearthquake. That house and the two adjacent houses\nluvium. The Saugus Formation in the area is com-\nwere still under construction, but were completed to\nposed of brown-to-light-brown sandy siltstone, with\nthe extent that stucco had been applied to the outer\napproximately 25-percent interbedded arkosic sand-\nwalls and drywall to the inside. Damage to the house\nstone and pebbly arkose. It is medium to thin bedded\non the trace of the fault included rupture and offset\nand well indurated. The terrace gravels consist of\nof the garage-floor slab overlying the fault, tilting of\ngranitic detritus, with cobbles and boulders to 2 feet\nthe house slab, and severe cracking of the walls in\nin diameter in a matrix of pebbly, coarse sands. It is\nthe raised northwest-corner bedroom. While the\npoorly sorted and moderately indurated.\nhouse was a total loss because of the foundation dam-\nThe principal structural features in the area are\nage, the limited extent of the damage to the upper\nthe Hospital fault and the Little Tujunga syncline\nparts of the structure indicates that severe injury\n(fig. 1) Rocks of the Saugus Formation strike N.80°\nprobably would not have occurred had the house\nto 90°E. and dip northward toward the axis of the\nbeen occupied.\nsyncline at angles of 60° to 80°. The terrace gravels\nDamage to the two adjacent houses was limited to\nunconformably overlie the Saugus Formation and\nminor cracking between footings and floor slabs and\nare relatively flat.\nto some small cracks at the joints between sheets of\ndrywall. The house to the west is approximately 5\nSeismic Setting\nfeet from the fault, and the house to the east is ap-\nThe area of investigation is located approximately\nproximately 10 feet from the fault.\n1.5 miles north of the Sylmar segment of the San\nFernando fault zone and 5 miles south of the epicen-\nDamage to Fills\nter of the February 9, 1971, earthquake. Maximum\nThe most significant damage in the housing devel-\nground accelerations of 0.5 to 0.75g, with high-fre-\nopment was related to settlements at the boundary\nquency peaks to 1.0g (Maley and Cloud 1971) were\nbetween natural and fill materials and to failures of\nrecorded at Pacoima Dam approximately 0.9 mile to\nfill slopes.\nthe northeast.\nThe largest failure of a fill occurred at the north-\neast corner of the development (near B' on fig. 4)\nRESULTS OF INVESTIGATION\nHere fill was placed on a northeast- to east-facing\nslope composed of Saugus Formation, with alluvial\nActive Faulting\nsand at the toe (northeast end of cross section B-B',\nfig. 4) Vertical settlement at the cut-fill boundary\nAn active fault extends diagonally across the hous-\ning development (fig. 2) This fault has been named\nTable 1.-Principal characteristics of Veterans fault\nthe Veterans fault because of its close proximity to\nthe Veterans Administration Hospital. However, it\nTrend\nN.80° to 85°E. turning to N.60°E. near its\nshould be emphasized that it has not been possible to\nwesternmost exposure.\nDip\n60° to 70°N. (approximately parallel to\ntrace the fault westward to the grounds of the hos-\nbedding in Saugus Formation), decreasing\nto 35° to 40° at west end.\npital and that a westward extension of its trend does\nMovement (February\n6 to 8 in., decreasing to 2 to 3 in. near loca-\n9, 1971).\ntion where fault is beneath fill at east and\nnot pass through or near the hospital wing that\nwest end of exposure.\ncollapsed in the earthquake (fig. 2).\nMovement (pre-\n70 ft (fig. 6).\n1971).\nThe principal characteristics of the fault, as ex-\nFormations faulted\nSaugus Formation (Plio-Pleistocene) and\nterrace gravel (late Pleistocene).\nposed on lot pads, in cut slopes between pads (figs. 3\nWidth of rupture\n1/2 to 2 in.\nand 4), in backhoe trenches (e.g., fig. 5) and bor-\nzone.","Earth Rupture and Structural Damage\n209\n30\nEpicenter of\nFebruary 9, 1971,\nearthquake\n232\n2:20\n34\n35\n33\n36\n2284\nLEGEND\nQal-Alluvium (Recent)\nCanyo\nQt-Terrace deposits (Late Pleistocene)\nQT-Sediments (Tertiary and Quaternary)\nA\nFault\nE S12\nFault along which displacement\noccurred February 9, 1971\nPacoima Dam\n15\n18\n13\nbc\nMicoinos\nbc\nHospital\nfault\nQT\n21\nbc\n19\n20\nQT\n2250\n3262\nBM\nQal\n-N-\n1535\nQt\nFOOTHILL\nQT\nOlive fley\nArea of\ninvestigation\nQt\nQal\n25\n30\n1\"\n= approx. 5200'\no\nN\nM\nI\nS\nS\nLittle Tujunga\nQT\nsyncline\n7\nBM\n31\n86\nVan\nNormal\nSylmar segment of\nSan Fernando fault zone\nSan\n118\nFernando\nReservoir\nE\nN\nD\no\nS\nA\nSant Fernando\nQal\nSan Fernando\nMission\nuters\nFigure 1.-Geologic index map.","210\nSan Fernando Earthquake of 1971\nCollapsed wing of\nA'\nVeteran's Hospital\nB'\nTs\nTs\nQt\nSC\nQt\nft\nTs\n0\n200\n400\n800\nA\nScale in feet\nLEGEND\nQt\nTerrace deposits\nTs\nSaugus formation\nVeteran's fault\nCut-fill boundary\nAssignment of geologic units\nafter Oakeshott (1958)\nFigure 2.-Geologic map of housing development.\nwas approximately 12 inches, and the slope at the uted to settlement of the alluvial sand at the toe of\nboundary ranges from approximately 1.5 to 1 to 2 to\nthe slope. Settlement of alluvial sand and gravel was\n1. A downslope movement of 18 to 24 inches is indi-\ncommon in the canyons in the area. No houses had\ncated. The large magnitude of this failure is attrib-\nbeen built on the lots in this part of the develop-\nA\nA'\nLurching\nGavina\nGraber Ave.\nTucker Ave.\nTopography\nWallaby Ave.\nAve\nprior to grading\n1720\n1720\nGv\n1660\n1660\nGv\n1600\n1600\nAk\n1540\n1540\no\n60\n120\nscale\nfeet\nFigure 3.-Cross section A-A'.","Earth Rupture and Structural Damage\n211\nB\nB'\non the fill was generally moderate, but was locally se-\nvere where one house had been built over or near\nthe boundary between cut and fill.\nIn addition to general cracking along the cut-fill\nAlluvium\nboundary, failures occurred at the corners of some\nTopography\nWallaby\nTucker Ave\nPit 3\nfill embankments. These failures were particularly\nprior to grading\nAve.\nsevere where heavy watering of lawns and shrubbery\n1500\n-1500\nhad preceded the earthquake. Much of the heavy\ndamage to the model homes, watered regularly each\n1440\nIti440\nnight by an electrically timed sprinkling system, can\nbe attributed to excessive moisture content of the\n1380\n-1380\nsoil. Extensive failures of embankments as low as 2\n60\n120\nto 3 feet in height occurred between some of the\nmodels.\nFigure 4.-Cross section B-B'.\nDamage to Houses Not Associated With Ground\nment, and damage was limited to rupture of streets,\nFailure\nsidewalks, and utility lines.\nSettlement of the fill in the central part of the de-\nIncomplete houses, all of similar construction, sus-\nvelopment (near A and B of cross sections A-A' and\ntained some of the most spectacular damage in the\nB-B', figs. 3 and 4) was much less severe. Tension\ndevelopment. All were located on Saugus Formation\ncracking and settlement in the range of 1 to 3 inches\nor terrace gravel and were of one-story frame and\nwere common along the cut-fill boundary and near\nstucco construction, with trussed roofs and slab\nthe base of some fill slopes. Damage to houses built\nfloors. The extent of damage followed a regular pat-\nLot 25\nDate 3-16-71\nPit location\nPHYSICAL\nENGINEERING GEOLOGY DESCRIPTION\nCOMMENTS\nATTITUDES\nCONDITION\nTerrace gravel with pebbles and cobbles to 8\" principally of weathered granite\nSlightly damp,\nBedding\nGv,\nN75W, 63N\nrocks in matrix of coarse sand, silty.\nsoft\nSlightly damp\nto dry, firm\n3\nN50W, 66N\nSlt Cstn,\nSiltstone, red-brown with 10-20% claystone, red-brown, medium plastic\nSaugus fm.\nSlightly damp\nN85W, 55N\nSs,\nSandstone, light gray, medium to fine grain, arkosic\nto dry, medium\nfirm\nFault\nNATURAL\nN85E, 61N\nSLOPE\nFlat\nCut-fill\ngraded\n5 N45W, 29NE\nlot pad)\nGRAPHIC REPRESENTATION\nPit trend= N27E\nFaulting\nSurface cracking parallel\n2-9-71\nto cut-fill boundary\nLoose\n\\fill\nWeathered\nFill\nGv\nsiltstone\nSlt+Cstn\n\\Sit+Cstn\nSlt+Cstn\n(weathered)\n0\n1\n2\n4\nScale in feet\nFigure 5.-Geologic pit log No. 2.","212\nSan Fernando Earthquake of 1971\nactive Veterans fault and to ground shaking with\nC'\nC\nmaximum accelerations of at least 0.5g.\n2 The one house built over the trace of the Vet-\nerans fault in bedrock was damaged beyond repair,\n1590\n1590\nbut the two adjacent houses, also on bedrock and lo-\ncated approximately 5 and 10 feet from the trace of\n1560\n1560\n70'\nthe fault, were essentially undamaged. Apparently,\n1530\n1530\nsetback from active or potentially active fault traces\nfor normal residential construction need not be large\n/\n1500\nAk\n1500\nwhere the zone of movement is narrow and the\namount of anticipated displacement is small.\n1470\n1470\n3 Fills located over the active Veterans fault\n3C\n60\nwere not cut by the fault, but moved as independ-\nent, cohesive units. Consequently, damage was much\nFigure 6.-Cross section C-C'.\nmore extensive in areas of fill and along the cut-fill\nboundary than in areas of bedrock. This suggests\ntern. Many of the houses that had been framed and\nthat houses should not be constructed on any part of\nroofed, but which were without either interior or ex-\na cohesive fill placed over an active or potentially ac-\nterior walls, collapsed. The trussed roofs remained\ntive fault, and that reexamination of grading and\nessentially intact, but the wall frames failed as a re-\nconstruction procedures along the cut-fill boundary\nsult of breaking of the diagonal bracing and the\nin seismically prone areas is needed.\nstuds. The houses that had been papered and wired\n4 Sidehill fills, toed into alluvial sand, settled by\nfor stucco failed in a similar manner, but did not\nabnormally large amounts because of compaction of\ncollapse completely. The wire held them in leaning\nthe sand during ground shaking. The compaction\npositions at angles of approximately 30° from the\ncharacteristics of some natural materials (e.g., loose\nvertical. The houses that had been stuccoed on the\nalluvial sand) under conditions of seismic shaking\noutside and had the drywall installed on the inside\nneed additional attention of the soils engineer.\nsustained very little damage.\nDamage to completed houses was similar to the\ndamage to houses in other parts of Sylmar and San\nREFERENCES\nFernando. Two weak points stand out: the un-\nMaley, R.P., and Cloud, W.K., \"Preliminary Strong-Motion\nbraced door-wall of the garage and the independent\nResults From the San Fernando Earthquake of February 9,\nconstruction of the two levels of two-story houses.\n1971,\" The San Fernando, California, Earthquake of Febru-\nWhere the upper level of the house was built over\nary 9, 1971, Geological Survey Professional Paper 733, U.S.\nthe garage, the damage was often particularly severe.\nGeological Survey and the National Oceanic and Atmos-\npheric Administration, U.S. Department of the Interior and\nU.S. Department of Commerce, Washington, D.C., 1971,\nCONCLUSIONS\npp. 163-176.\nOakeshott, Gordon B., \"Geology and Mineral Deposits of San\n1 The housing development was subjected to\nFernando Quadrangle, Los Angeles County, California,\"\nground rupture of up to 8 inches vertically along the\nCalifornia Division of Mines Bulletin 172, Feb. 1958, 147 pp.","Geology, Earthquake Damage,\nand Water Table Fluctuations\nMetropolitan Water District\nFacilities, Sylmar Area\nINTRODUCTION\nThe Metropolitan Water District of Southern Cal-\nifornia (MWD) is involved in major construction in\nthe Sylmar-San Fernando area for the distribution\nsystem for State Project (\"Feather River\") water.\nThis construction involves large-diameter tunnels,\nCONTENTS\npipelines, and a 400-million-gallon-per-day-capacity\nPage\nwater treatment plant located at the northwest end\n213 INTRODUCTION\nof upper San Fernando Valley.\n214\nSURVEY DATA\n214\nDAMAGE TO BALBOA INLET TUNNEL\nThe Engineering Geology Branch of MWD has\n214\nMOVEMENT OF SAN FERNANDO TUNNEL\nbeen investigating this area for tunnel routes since\n214\nNORTH OLIVE VIEW FAULT\n1962 (Proctor et al. 1966) Geologic maps prepared\n215\nJUVENILE HALL LANDSLIDE\n217\nMOVEMENT AT JOSEPH JENSEN\nby MWD were provided to all interested governmen-\nFILTRATION PLANT\ntal and private agencies some years before and were\n218\nPATTERN OF CRACKS AND RELATION TO\nfurnished immediately after the February 9, 1971,\nDAMAGE\nearthquake. These maps relate to the San Fernando\n220\nFLUCTUATIONS OF GROUND-WATER\nLEVELS\nTunnel (now under construction) and the two Sun-\n222 REFERENCES\nland Tunnels (now in the proposal stage) Preearth-\nquake knowledge of the geology and faults in this\nFrom material provided by Richard J. Proctor\nand William J. Edwards.\narea was surprisingly complete, but much of the in-\nformation was in the form of in-house reports and\nmaps (fig. 1) . Most faults, along which movement\ntook place, were known previously; but some of\nthese were not the faults that appear on published\nmaps.\nA program of 54 test borings was initiated to ex-\namine subsurface lithology and to locate faults along\nproposed tunnel alignments. Cores of fault zone ma-\nterials were studied in detail, and perforated casing\nwas installed in many borings to obtain hydrologic\ndata. Results from programs of investigation were re-\nMETROPOLITAN WATER DISTRICT\nported on geologic maps and in descriptions of condi-\nOF SOUTHERN CALIFORNIA\ntions, including potential hazards pertinent to tun-\nEngineering Geology and Survey Branches\nneling in the area. Among the most important\nLos Angeles, Calif.\n213","214\nSan Fernando Earthquake of 1971\nengineering considerations were faults that could be\ncm relative to that in the damaged area. The tunnel\nintersected during tunneling. These faults were stud-\nremains on grade north of the damaged area.\nied to define position, thickness of zones of crushed\nSome surface cracks appear along the upper\nrock and gouge, amount of displacement, and when\nbranch of the Santa Susana fault in an area 460 m\nmovement occurred.\nnorth of the intersection of the lower branch with\nthe Balboa Inlet Tunnel. As much as 11 cm of left-\nlateral displacement occurred across the Golden State\nSURVEY DATA\nFreeway and Foothill Boulevard, but damage to the\nPreliminary route surveying for State Project\ntunnel lining was not observed directly beneath\nwater distribution lines began in the early 1960s\nthese cracks.\nand, fortunately, involved establishing bench marks\nand triangulation points. The surveys taken in the\nMOVEMENT OF SAN FERNANDO TUNNEL\nweeks after the major shock provided precise meas-\nurements of ground distortion in many localities.\nThe cumulative total vertical displacement result-\nThese surveys are discussed under the sections on in-\ning from the earthquake is at least 2.3 m, as mea-\ndividual MWD facilities that were damaged.\nsured along the 9-km-long San Fernando Tunnel.\nThe maximum measurement of ground displace-\nThe east portal of this pressure tunnel is just north\nment from recent MWD trilateration surveys was 2.5\nof the Sylmar fault, and it will terminate in the west\nm. This appears as shortening between north-south\nat a 48-foot-diameter (about 15-m) construction\noriented points 6.6 km apart (Pacoima-2 on the hill\nshaft located in Magazine Canyon (fig. 1) Survey\nwest of Hansen Dam, south of the known surface\nleveling extending eastward from the shaft has\nbreaks; Washington-2 on Sugarloaf Peak in upper\nshown a 1-foot ground rise from the shaft to a point\nLopez Canyon, east of fig. 1) Washington-2 moved\nwest of the large bend in alignment near the middle\nwestward and southward, as did most points north of\nof the tunnel. From this bend to the east portal, the\nthe surface ruptures, and also moved upward 1.3 m,\nsurvey indicates a gradual rise in tunnel elevation to\nas averaged between U.S. Geological Survey (USGS)\nthe maximum of 2.3 m. The absence of recognizable\nelevation stations (USGS and NOAA 1971, p. 82,\nshear surfaces in the tunnel is consonant with re-\nfigs. 1 and 2) on either side of Sugarloaf Peak. The\nports from miners present in the tunnel at the time\nMWD trilateration was by electrotape on a network\nof the earthquake. The miners were excavating with\npreviously surveyed in 1969.\na 22-foot-diameter (6.7-m) mechanical boring ma-\nchine at the working heading, then 6 km in from the\neast portal. The material at the face was soft, water-\nDAMAGE TO BALBOA INLET TUNNEL\nsaturated silt, sand, and gravel (old alluvium). The\nIn the 1-mile-long Balboa Inlet Tunnel, the zone\nearthquake was accompanied by an outage of electri-\nof damage occurred in an area 26 m long that is ap-\ncal power that caused the water pumps to stop. Amid\nproximately 46 m south of the lower branch of the\nthe attendant confusion and anxiety, the miners\nSanta Susana fault, as mapped during tunnel excava-\nmade their way to the locomotive and drove out of\ntion. The damage to the tunnel consisted of severe\nthe tunnel; this means that the rails were not suffi-\nspalling and breaking of the concrete lining and of\nciently distorted to cause a derailment.\ndeformation of the reinforcing steel bars (figs. 2 and\n3) The zone of damage occurs in an area where the\nNORTH OLIVE VIEW FAULT\ntunnel lies below a canyon. The damage itself is lon-\ngitudinal in relation to the tunnel alignment, and,\nDuring exploratory drilling for the San Fernando\nhence, it is not parallel to bedding or mapped fault\nTunnel in 1965, anomalous water levels were ob-\ntraces. Because of this relation and the discordance\nserved between auger borings A-3 and A-4 along\nin location of the damage relative to the mapped\nFoothill Boulevard near the intersection of Glenoaks\nfault, we believe that the zone of damage is a result\nBoulevard (fig. 1) Measurements in these and other\nof strong ground shaking in the tunnel under local\nnearby borings showed water-level differences (north\nshallow cover. A resurvey of the Balboa Inlet Tun-\nside higher) of more than 21 m. Subsequent ground\nnel showed that the invert at the south portal rose 8\nexamination in the adjacent foothills disclosed a","<\"Oal\nHOSPITAL\nFAULT\n118°26'\nEXPLANATION\nQTs\n221\nQTs\nPACOIMA\nFORMATION\nOAKESHOTT\n(1958\n-LANDS\nREMNANT\nLANDSLIDE DEPOSITS Majority of slides existed before Feb 9th earthquake (Qls section)\nQTs\nQool\nQTs\n\"OTs\nOTs\nQal\nALLUVIUM Stream laid debris of silt, sand and boulders\nQal\ntest\nQal\nQTs\nUSA\nLOPEZ-FAULT\nX25':QTs\nHOSPITAL\nOal\nSevere damage new\nOpal\nCQTs\nQool\nHOSPITAL\nQoal\nOLD ALLUVIUM Tan, silty sand coarse conglomerate soil formation on surface\nhomes in this area.\nQgl\nA-2SF\nCRACKS\nQool\nSTETSON SOMBRERO\nQal\nVIEW\nQal\nHOSPITAL\nVIEW\nTERRACE DEPOSITS Older alluvial debris higher levels\n=-\nLOS WATER WELLS8\nQal\nbc\nOLIVE\nVIEW\nUS\nOLIVE\nSevere damage to new\nEXPLORATORY SHAFT\n0b-8\nSAUGUS FORMATION Brown and tan. poorly cemented sandstone and conglomerate, greenish-gray\nhomes area.\nEXPLORATORY SHAFT N&\n4SF\nTERANS FAULT\nQoal\nQTs\nQal\nQal\nsandstone and reddish -brown siltstone. Mainly non -marine origin\nQal\nQal\n12430\nA-USE\nSUNSHINE RANCH FORMATION Pnle green, mostly soft sandy siltstone with minor amounts of sand-\nHEADING OF TUNNELAT TIME\nSAN FERNANDO TUNNEL\nD-3SF\nM.W.D.\nQoal\nQoal\nQoal\nstone and conglomerate Shallow marine origin\nQgl\nQo\nQg\non\nQal\nQal\nPICO FORMATION Yellow-brown soft to very hard sandstone and conglomerate, with minor amounts\nFAUL\nA-6SF\nQgl\nA-15SF\nof greenish- gray siltstone Locally, the conglomerate beds hardest sedimentary rocks\n\"\nQal\nEXPLORATORY SHAFT N°3\nthe region The upper part interfingers with the SAUGUS FORMATION: the lower part with the\nQT:\nWASH\nQgl\nQoo\nTOWSLEY FORMATION Marine origin\nQal\nQoal\nOTs:\non -3SF\nOgl\nQal\nGoal\nQal\nQal\nQoal\nPICO and/or TOWSLEY FORMATION ( (s) Mostly light brown and gray sandstone with some\nQa\nQoal\nQa\nUVENILE\n>TOTs\nQTs\ngenerally soft siltstone and mudstone; local lenses and beds of conglomerate Marine origin\n11/14\nD-6SF\nQg\nTOWSLEY FORMATION Brown. mostly soft siltstone and mudstone light brown and gray sand\nQoal\nQal\nQgl\nQal\n0g\nQal\nstone and conglomerate The upper end interfingers with the PICO FORMATION Marine origin\nQal\nQo\nQoal\nQoal\nA-13SF\nQal\nQoal\nQgt\nCOMPRESSION RIDGES\nQoal\nQal\nACROSS FREEWAY\nbc\nPACIFIC\nBASEMENT COMPLEX Gneiss, quartz diorite, granite\nQoal\nINTERTIE\nQai\nQal\nQal\nQal\nTEST HOLE\nQg\nQTs\nCONVERTER\nQoal\nQoo\nM.W.D.\nQTs:\nQTs\nOgl\nSTATION\nJOSEPH JENSEN\nQal\nOf\nQoal\nFILTRATION/\nQal\nQTs\nPLANT\nSYMBOLS\nQg\nQTs\nSylmar\nQal\nOf\nQal\nQg\nQg\nQal\nQTs\nQg\n*QTs\nQt\nCONTACT\nAXIS SYNCLINE Dashed where approximately\nQool\nQoa\nlocated, dotted where concealed o inferred\nA-14SF\nQoal\nOT\nQTs\nCONGLOMERATE BED LENS\nV-6SF\nOFFI\nCreek\nAXIS OVERTURNED SYNCLINE Dashed where\nQgl\nQgl\nSYLMAR\nQTs\nOal\n40;\n:OTs\nHIGH SCHOO\nFAULT Dashed where approximately located, dotted\nQoi\napproximately located dotted where concealed\nUpper\nQoal\nQoal\nHIGHLAND\nQal\nA-18SP\nconcealed U: up. thrown side; down\nor inferred\nSANITARIUM\nVan Norman\nthrown\nQoal\nQTs\nQg\n40Y\nSTRIKE AND REDS\nN\nSANITARIUM\nSHEARS\nReservoir\nSURFACE FAULTING (2-9-71) Showing dip. U:\nOTs\nofs\nSTRIKE VERTICAL BEDS\nSHEAR\n50\nup-thrown side; down thrown side arrows\nQal\nSECONDARY\nevan /VAN GOGH STREET\nQoal\n70x STRIKE OF OVERTURNED BEDS\nQal\n:OTs\nOg\nindicate\nmovement\n7044\nA-17SF\nSTREE\nSCHOOL CRACKS\n--\nQg\nM.W.D. TEST HOLE\nOT\nQoal\nSURFACE CRACKS SECONDARY SHEARS(2-9-71)\nA-5SF\n:OTs*\nOTs Severe damage to new\nLOPEZ\n11\ne TEST HOLE Post -earthquoke\nQTs\nDAM\nup-thrown Down thrown thrown side arrows\nQal\nQgl\nhomes this area\nQal\nQoal\nindicate relative movement\nQg\nWATER WELL\nQgi\nQTs\nQal\nQal\nQal\nOogl\nof\nSYLMAR\nM.W.D. EXPLORATORY SHAFT\nI'\nFAULT\nAXIS ANTICLINE Dashed where approximately\nOSE\nQTs\nRD\nOTs\nlocated. dotted where concealed inferred\n-&\nABANDONED EXPLORATORY OIL WELL\nQTs\n-34°18'\nSYLMAR NOTCH\nTpts\n'60\nQal\nQal\nQg\nOal\nQal\nQal\nQgl\nQal\nTpts\nQTs\n*OTs\nQal\nGEOLOGY MOSTLY FROM UNPUBLISHED MAP BY P.M. MERIFIELD (1958), M.A. THESIS(U.C.L.A)\nMWD SAN FERNANDO TUNNEL\nOF FEB OF TUNNEL AT TIME\nQal a Qoal\nQoal\n1000\n2000\nQal & Qoai\n1 gal\nMETERS\n-\n.......\nFHH 1000\n2000\n4000\n5000\n6000\n3000\nSECTION ALONG M.W.D SAN FERNANDO TUNNEL\nFEET\nSANDSTONE\nSILTSTONE\nSANDSTONE CONGLOMERATE\nFigure 1.-Geologic map and section along the 5.5-mile San Fernando Tunnel This drawing is similar to those furnished prospective tunnel contractors by Metropolitan Water District of Southern California.","Geology, Earthquake Damage, and Water Table Fluctuations\n215\nA 3-m-deep postearthquake exploratory trench was\nexcavated across the northern boundary crack (strik-\ning N.52°E.) of the Juvenile Hall landslide. The\ntrench revealed dark humus-rich soil, smelling of hy-\ndrogen sulfide, which was cut by the crack that was\nnearly vertical; almost 30 cm of vertical displacement\nhad occurred.\nA southwestward projection of this crack goes\nthrough the earthquake-damaged Van Gogh Street\nElementary School. Partly because the school was\nbuilt on alluvium, the damage and surface cracks\nhere were more abundant than on the adjacent\nsandstone bedrock; thus, the cracks cannot definitely\nbe attributed to fault movement. However, a dis-\ncontinuous zone of cracks can be traced for several\nblocks farther southwest in streets and curbs directly\nFigure 2.-Balboa Inlet Tunnel earthquake damage consisting\noverlying the Saugus Formation bedrock. An oil\nmainly of spalled concrete in longitudinal cracks.\nexploration map prepared for a major oil company\nshows a buried fault essentially in the same position\nas is shown for the North Olive View fault.\nJUVENILE HALL LANDSLIDE\nAn alluvial slide, 1.2 km long on a surface slope of\nonly 11/2°, occurred through the San Fernando Val-\nley Juvenile Hall (Los Angeles County-owned facil-\nity) and Sylmar Converter Station (owned by the Los\nAngeles Department of Water and Power) of the Pa-\ncific Intertie. The slide features included: (1)\nsand boils; (2) movement with south side down\n(maximum 28 cm or 11 in.) and right-lateral dis-\nplacement along the northern boundary cracks; (3)\nmovement with north side down and left-lateral dis-\nplacement along the southern boundary cracks; and\nFigure 3.-Balboa Inlet Tunnel earthquake damage\n(4) northeast closure of these boundary fractures in\nshowing deformed bars.\na zone of tension cracks 90 m wide (Youd 1971).\nThe slide moved southwestward at least 1.5 m. The\nfault in bedrock trending toward this ground-water\nfollowing evidence indicates that this feature proba-\nbarrier in the alluvium (fig. 4) Differences in\nbly resulted from a combination of sliding and set-\nground-water levels indicate that this fault extends\ntlement caused by seismic compaction of poorly con-\nsouthwestward into the alluvium; this particular\nsolidated alluvium, with the north boundary\nfault has been named the North Olive View fault by\ncoincident with the North Olive View fault.\nMWD geologists. A linear contrast in vegetation\nThe margins of the slide can be traced southwest-\ntone is clearly shown on a 1929 vertical aerial photo-\nward to the converter station where they become less\ngraph. This feature strikes N.55°E., coincides with\ndistinct. No typical landslide toe has been observed.\nthe projected fault trace, and extends to the San Fer-\nA large area where a toe could form is in or near\nnando Valley Juvenile Hall. We cannot definitely as-\nUpper Van Norman Reservoir. Examination of the\nreservoir (while almost drained) disclosed no toelike\nsign recent tectonic activity to this fault, but differ-\nfeature attributable to more than minor bank fail-\nential movement by shaking may have occurred\nures. Saturation of alluvium in this area may have\nalong it in February 1971.","Figure 4.-Diagrammatic cross section A-A' showing location of oil well log and diffusion of Sylmar fault into thick alluvium at Sylmar notch.\nA'\nTt\nNOTCH\nSYLMAR\nTt\nNo vertical exaggeration. See figure 1 for location.\nQal\nTsr\nTt\nQTs\nMERRICK SYNCLINE\nBase of Saugus Formation\nQTs\nTsr\nQTs\nT.D.12,027'\nQTs\nWater table\nTsr\nTsr\nTsr\nTt\nTt\nTt\nbc\nA\nbc\n2000\n-2000\n-3000'\n-12,000'\n1000\n-1000'\n-4000'\n-5000\n-6000'\n-7000\n-8000'\n-10,000'\n-9000\n-11,000'\no","Geology, Earthquake Damage, and Water Table Fluctuations\n217\nhad to be cut and removed to make the lines straight\nresulted from a rise in water table accompanying res-\nervoir filling in 1921. However, the water table\nagain.\nThe depth to water in a postearthquake test hole\nnorth of the fault (Grapevine Canyon drainage)\nin sandy alluvium south of the Juvenile Hall was 4.3\nmay have been very close to the ground surface. The\nm on April 20, 1971. Thus, the conditions are met\ngeneral saturation of the alluvium may well have\nfor both seismic consolidation causing subsidence in\ncontributed to the local sliding and settlement along\nthis area and for the low-slope landsliding possibly\nthe fault boundary.\naided by liquefaction.\nFences that mark the east and west property lines\nof the converter station were resurveyed by the Los\nAngeles Department of Water and Power (Dunlap\nMOVEMENT AT JOSEPH JENSEN\n1971) with the following results: The central part of\nFILTRATION PLANT\nthe eastern fence moved a maximum of 1.5 m west-\nThis $25 million water-treatment facility was\nward in relation to \"zero points\" at the north and\nunder construction, and portions, such as the fin-\nsouth ends of the property. The central part of the\nished water reservoir, sustained extensive damage\nwestern fence moved westward only 0.7 m. The east-\nmainly from severe shaking of wet foundation mate-\nern fence is adjacent to and east of a drainage canal\nrials (fig. 6) (See also discussion in Jennings 1971,\n(Youd and Olsen 1971, p. 127), which was severely\npp. 434-449.) A 100-foot-diameter (30.5-m) 30-foot-\nbuckled. The canal, therefore, probably absorbed 0.8\nhigh (9-m) steel water tank on sandstone bedrock\nm of the slide movement, with the remainder of the\nsuffered atypical damage (figs. 7 and 8) Surveys in-\ntoe dissipated around Upper Van Norman Reservoir\ndicate some uplift and left-lateral movement of the\nwhere most of the sand boils occurred. The maxi-\nplant in relation to an established point on bedrock\nmum relative subsidence within the converter station\nwas 23 cm.\nNorthwest-southeast shortening also occurred\nacross the slide area, as evidenced by the compression\nof curbs and of the Southern Pacific Railroad tracks\nwhich cross the slide. The tracks were compressed\ninto tight curves both downslope and upslope to the\ndirection of sliding (fig. 5) Tension features and\nbowing of the tracks downslope should have OC\ncurred if only sliding was involved. Lengths of track\nFigure 5.-Southern Pacific Railroad tracks, looking west across\neastern boundary of Juvenile Hall landslide. Note contortion of\nFigure 6.-Landslide tension cracks in fill at Joseph Jensen\nrails both downslope and upslope to direction of sliding (to the\nFiltration Plant.\nleft). Rails at left were sheared.","218\nSan Fernando Earthquake of 1971\nnear the north portal of the Balboa Outlet Tunnel\nwhich underlies the plant site, has been compressed.\nat the south end of the plant site. In addition, there\nThe base or sole of sliding at the plant and at the\nhas been some north-south shortening, which indi-\nJuvenile Hall probably occurred along a liquefied\ncates that the Mission Hills (Merrick) syncline,\nlayer caused by seismic shaking of the subsoils.\n(These are two separate slides.) It was estimated by\nSeed (1971) that liquefaction beneath the Joseph\nJensen Filtration Plant did not occur until after\nabout 10 seconds of shaking (major shear-wave dura-\ntion was about 12 seconds) Several postearthquake\nborings at the plant revealed a saturated fine-sand\nlayer 2 to 3 m below the original ground surface.\nTwo accelerometers were installed for MWD at\nthe filtration plant by Converse, Davis & Associates\nafter the main shock of February 9, one on fill 35\nfeet (11 m) thick and one on soft sandstone of the\nSaugus Formation. The records of two aftershocks\nhave interesting implications in relation to seismic\ndesign and the acceleration of gravity:\nAfter-\nPeak ground\nFigure 7.-Water tank at Joseph Jensen Filtration Plant. Tank was\nAftershock\nshock\nacceleration\nDistance from\nabout one-half full at time of earthquake, and rocking caused\ndate\nmagni-\nepicenter\nanchor bolts to be pulled out. Well-trussed roof resisted initial\ntude\nFill\nBedrock\naccelerations more than upper shell wall.\n3-30-71\n3.7\n0.12g\n0.06g\n3.2 miles (5. 1 km)\n3-31-71\n4.9\n0.15g\n0.10g\n4.5 miles (7.2 km)\nPATTERN OF CRACKS AND RELATION\nTO DAMAGE\nMany surficial cracks appeared throughout the Syl-\nmar area during the earthquake. These are nontec-\ntonic and can be attributed to lurching effects, com-\npression ridges, tension cracks, subsidence, and\ninsipient landslides. Cracks representing these fea-\ntures were not significant at MWD facilities, except\nfor the landslide cracks at the Joseph Jensen Filtra-\ntion Plant. Other significant cracks should be men-\ntioned, however, because overlying structures were\nselectively damaged. Some examples follow.\nSurficial cracks at Olive View Hospital (fig. 9)\nwhich are compressional, cannot be traced very far\nand are nontectonic. Thus, it should be stressed that,\nin our opinion, the spectacular damage to the new\n$27 million Olive View Hospital and damage at the\nVeterans Administration Hospital resulted entirely\nfrom the effects of ground shaking. That the intensity\nof ground shaking was SO great here (Modified Mer-\ncalli intensity VIII-XI, Scott 1971, p. 153) should\nnot be surprising considering: (1) The Sylmar basin\nis on the upper plate of a thrust-fault wedge; thus,\nthe rupturing along the fault planes passed closer to\nFigure -Anchor bolt pulled out 13 inches at base of\nJoseph Jensen Filtration Plant water tank.\nthe surface over the basin than at the hypocentral","Geology, Earthquake Damage, and Water Table Fluctuations\n219\nFigure 10.-Typical split-level home with collapsed two-car garage;\nAlmetz Street, Sylmar.\nSome types of highway bridges and overpasses dis-\nplayed unacceptable performance when subjected to\nground shaking (figs. 11 and 12). No faults underlie\nthe 42 bridges damaged; five suffered complete col-\nlapse (Jennings 1971, p. 366).\nSmall but continuous cracks south of Astoria\nStreet are associated with selective damage to the Syl-\nmar High School buildings. In two places, sidewalk\nslabs were thrust under the building as much as 4\ninches (10 cm). One ground crack at the school\nFigure 9.-Water tank at Olive View Hospital. The belling at\ntrends toward two compression ridges that buckled\nbottom of tank occurred during the earthquake by sloshing water,\nthe newly opened Foothill Freeway (Interstate 210)\ncausing the tank to rock back and forth and thus \"walk\" off its\non both sides of the Astoria Street pedestrian cross-\nfoundation. Note lack of anchor bolts.\ndepth of 12 km. (2) The northern end of San Fer-\nnando Valley is the interface between high-velocity\ncrystalline basement rocks and low-velocity alluvium\nand sedimentary rocks. (3) The buried sedimentary-\ngranitic interface or bottom of the basin may also be\ndirectly beneath the northern end of the valley, be-\ntween the faulting and the epicenter. Housner (1966,\np. III-105) states: \"The intensity of ground shaking\nimmediately adjacent to a fault is not especially se-\nvere but is, in general, somewhat less than at a dis-\ntance of several miles from the fault.\"\nExtensive damage to new homes in the tract east\nof Olive View Hospital appears to reflect a lack of\nadequate internal bracing rather than fault lines.\nFigure 11.-Crane was crushed by 140-ft tall column, similar to\nMost one-story houses in this area withstood shaking\none in background, which sheared near ground surface, causing\nbetter than the split-level houses which have the mas-\nspan of bridge to fall on freeway and railroad tracks. Construc-\ntion similar to this design is currently underway for San\nter bedroom over a two-car garage. Such garages have\nBernardino-Barstow Freeway interchange in Colton where the\na single large door and are without internal cross\nfoundation is adjacent to San Jacinto fault in Santa Ana River\nbracing; many of them collapsed (fig. 10).\nsand.","220\nSan Fernando Earthquake of 1971\nFigure 12.-Collapsed highway overpasses at northwest end of Sylmar area.\ning (fig. 13) At one compression ridge, the north\nslab overrode the south one by 18 inches (about 45\ncm). The freeway pavement was sawed and most\nslabs displayed separation, in places amounting to\n11/2 inches (4 cm), suggesting local extension be-\ntween the compression ridges. North-south compres-\nsion (shortening) is thus well expressed on the free-\nway here and farther south at the Sylmar fault trace\nacross and west of the freeway. Total shortening may\namount to as much as 2.3 m, as revealed by surveys\nof Southern California Edison Company transmis-\nsion tower bases from points north of the valley to\nHansen Dam (McNey 1971).\nFLUCTUATIONS OF GROUND-WATER\nLEVELS\nMWD routinely measures the ground-water levels\nin 33 wells and observation holes between Grape-\nvine Canyon in northwest Sylmar and Big Tujunga\nWash. The purposes of these measurements are to\npredict the limits in which ground water will be\nencountered during tunnel excavation and to have a\nprior record for ground water in the event that tun-\nnel construction may damage water production by\nlowering the water table severely. Most measure-\nments began in the mid-1960s and are on a monthly\nFigure 13.-Compression ridges across freeway pavement near\nbasis.\nAstoria Street pedestrian crossing.","Geology, Earthquake Damage, and Water Table Fluctuations\n221\nOB-8 SF Sylmar\nA\n122.0\n2-10-71\n3:15\nD/W 122.40 meas.\nRLB/DHK\nM=3.0\n3-11-71\n.2\n9:55\nD/W 129.98 meas.\nA\nRLB/DHK\n.4\nM=3.8\nM=3.3\nA\nA\n.6\nA\nM=3.2\nM=3.0\nA\nM=3.0\n.8\nn\nA\nA\nM=3.4\nA\n123.0\nM=3.3\nA\n2\nA\nM=4.0\n.4\nA\nA\nM=3.2\n6\nA\nA\nA\nM=3. 4\n10,11,12,13\n15\n16,17 18,19,20,21\n24,25 26,27,28 1\n234\n5\n67\n8\nFebruary\nMarch\nDays\nLEGEND:\nM = Earthquake Magnitude\nA = Aftershock (16 in total). Length of line\nassociated with A corresponds to length\nof aftershock jiggle on recorder chart.\nFigure 14.-Hydrograph of MWD observation hole No. 8 in northwest Sylmar area. At least 16 aftershocks are recorded here because\ntheir epicenters were close to the recorder; some of the larger magnitude aftershocks, more than a few miles distant, were not\nrecorded.","222\nSan Fernando Earthquake of 1971\nMost of the wells and observation holes were meas-\nneering Research Laboratory Report EERL 71-02, Cali-\nfornia Institute of Technology, Pasadena, June 1971, 512 pp.\nured 3 days after the earthquake of February 9; the\nKamb, Barclay, Silver, L.T., Abrams, M.J., Carter, B.A.,\nfollowing summarizes the results: The water levels\nJordan, Thomas H., and Minster, J. Bernard, \"Pattern of\nin 18 wells (55 percent) dropped, rose in six wells\nFaulting and Nature of Fault Movement in the San Fer-\n(18 percent) and was essentially unchanged in nine\nnando Earthquake,\" The San Fernando, California, Earth-\nwells (27 percent) Most water levels in wells in the\nquake of February 9, 1971, Geological Survey Professional\nSylmar basin rose, while the levels in the foothills\nPaper 733, U.S. Geological Survey and the National Oceanic\nand Atmospheric Administration, U.S. Department of the\neast of Pacoima Wash dropped. The average change\nInterior and U.S. Department of Commerce, Washington,\nwas of the order of 2 feet (60 cm). The most dra-\nD.C., 1971, pp. 41-54.\nmatic drop occurred in Kagel Canyon, north of the\nMcNey, Jerrold L., Southern California Edison Company,\nKagel fault, where the water levels in five wells\nRosemead, Calif., 1971 (personal communication)\ndropped 28, 32, 45, 86, and 100 feet (8.5, 10, 14, 26,\nProctor, R.J., Brooks, D.C., and Pentegoff, V.P., \"Explora-\nand 30.5 m) from their preearthquake levels. This\ntion for 52 Miles of Tunnels for the Foothill Feeder,\" Engi-\nneering Geology in Southern California, Association of En-\nmay result from dilatancy or expansion of the aqui-\ngineering Geologists, Arcadia, Calif., 1966, pp. 81-87.\nfers, causing more pore space. Conversely, the rise in\nProctor, R.J., Crook, R., McKeown, M.H., and Moresco,\nsome wells may be the result of local compression of\nR.L., \"Relationship of Known Faults to Surface Ruptures,\nthe aquifers. Most wells recovered slowly, but some\n1971 San Fernando Earthquake, Southern California,\" Bulle-\nhave only partially recovered.\ntin of the Geological Society of America, Vol. 83, No. 6,\nJune 1972, pp. 1601-1618.\nThe earthquake and some aftershocks were perma-\nScott, Nina H., \"Preliminary Report on Felt Area and Inten-\nnently recorded on several local water-level recorders\nsity,\" The San Fernando, California, Earthquake of Febru-\nand in San Jacinto Valley 90 miles (145 km) south-\nary 9, 1971, Geological Survey Professional Paper 733, U.S.\neast of the epicenter (fig. 14)\nGeological Survey and the National Oceanic and Atmos-\npheric Administration, U.S. Department of the Interior and\nU.S. Department of Commerce, Washington, D.C., 1971,\npp. 153-154.\nREFERENCES\nSeed, H. Bolton, University of California, Berkeley, Calif.,\n1971 (personal communication)\nAlbee, A.L., and Smith, J.L., \"Earthquake Characteristics\nU.S. Geological Survey and the National Oceanic and Atmos-\nand Fault Activity in Southern California,\" Engineering\npheric Administration (Publishers), The San Fernando,\nGeology in Southern California, Association of Engineering\nCalifornia, Earthquake of February 9, 1971, Geological Sur-\nGeologists, Arcadia, Calif., 1966, pp. 9-33.\nvey Professional Paper 733, U.S. Department of the Interior\nAnderson, M.M. (Metropolitan Water District of Southern\nand U.S. Department of Commerce, Washington, D.C., 1971,\nCalifornia, Los Angeles), \"Construction of a Two-Million\n254 pp.\nGallon per Day Water Distribution System,\" paper pre-\nYoud, T. Leslie, \"Landsliding in the Vicinity of the Van Nor-\nsented at the meeting of the American Society of Civil Engi-\nman Lakes,\" The San Fernando, California, Earthquake of\nneers, Memphis, Tenn., Jan. 28, 1970.\nFebruary 9, 1971, Geological Survey Professional Paper\nBonilla, M.G., \"Surface Faulting and Related Effects,\" Earth-\n733, U.S. Geological Survey and the National Oceanic and\nquake Engineering, Prentice-Hall, Inc., New York, N.Y.,\nAtmospheric Administration, U.S. Department of the Inte-\n1970, pp. 47-74.\nrior and U.S. Department of Commerce, Washington, D.C.,\nDunlap, John T., Los Angeles Department of Water and\n1971, pp. 105-109.\nPower, Los Angeles, Calif., 1971 (personal communication)\nYoud, T. Leslie, and Olsen, H.W., \"Damage to Constructed\nHousner, G.W., \"Intensity of Earthquake Shaking Near the\nWorks, Associated With Soil Movements and Foundation\nCausative Fault,\" Proceedings of the Third World Confer-\nFailures,\" The San Fernando, California, Earthquake of\nence on Earthquake Engineering, Wellington, New Zealand,\nFebruary 9, 1971, Geological Survey Professional Paper 733,\n1965, Vol. I, New Zealand Institution of Engineers, Welling-\nU.S. Geological Survey and the National Oceanic and At-\nton, 1966, pp. III-94-III-115.\nmospheric Administration, U.S. Department of the Interior\nJennings, P.C. (Editor) \"Engineering Features of the San\nand U.S. Department of Commerce, Washington, D.C., 1971,\nFernando Earthquake, February 9, 1971,\" Earthquake Engi\npp. 126-132.","Land Movement Studies\nRelated to\nSan Fernando Earthquake\nINTRODUCTION\nGeneral\nThe February 9, 1971, San Fernando earthquake\naffected a metropolitan area (fig. 1) in which active\ngeodetic programs were in effect by several organiza-\ntions and in which there were many first-order hori-\nCONTENTS\nzontal (fig. 2) and vertical (fig. 3) control stations\nPage\nwithin the area of maximum damage. Thus, redeter-\n223 INTRODUCTION\nmination of horizontal positions and elevations\n223\nGeneral\nthroughout the region will provide a large volume of\n226\nDefinitions\nquantitative data as to the direction and magnitude\n226\nContents of Report\n228\nPART I-WORK RÉSUMÉ OF AGENCIES\nof land movements resulting from the earthquake.\n230 PART II-DETERMINATION OF\nThe implications of this information to the\nHORIZONTAL EARTH MOVEMENTS\ngeodesist, topographer, and civil engineer are fairly\n230\nInitial Surveys\nclear, but the structural engineer, geologist, soils en-\n234\nEvaluation of Apparent Movement\ngineer, and others engaged in determinations of site\n235\nSupplementary Surveys\n235\nPART III-DETERMINATION OF VERTICAL\nsafety and stability should likewise benefit. The im-\nEARTH MOVEMENTS\nplications to the land surveyor and property owner\n240\nPART IV-FINDINGS\nare discussed in the report of the Subcommittee\n240 Conclusions\non Sociological Aspects (in Volume II)\n241\nGeneral Recommendations\n242\nSpecific Recommendations\n242 ACKNOWLEDGMENTS\n242 REFERENCES\nLOS ANGELES COUNTY\nNewhall\nEarthquake Area\nSylmar\nSan Fernando\nGranada\nHills\nLos Angeles\nLos Angeles\nLong Beach\nLong Beach\nDEPARTMENT OF COUNTY ENGINEER\nCOUNTY OF LOS ANGELES\nGeodetic Section-Survey Division\nFigure 1.-Maps of San Fernando earthquake area.\nLos Angeles, Calif.\n223","Lopez Dam\nLEGEND\nnet\nOlive\nBoundary\nAngeles\nLos\nNational\n2.--Existing\n(MWD)\nJoseph\nFigure","4\n(Movements shown in feet)\nScale in miles\n2\n11\n1\n+.14\n0\nBURBANK\nFigure 3.-Selected vertical movements resulting from February 9, 1971, earthquake (preliminary).\n+.11\nSUNLAND\n+.07\nVeterans Hospital\n07\nFERNANDO\n+.47\n+1.05\nSAN\nRoad\n0+.97\n8+.94\nd+.93\n+4.72\n$+.97\nVAN NUYS\n2+.85\nPlacerita Canyon Road\nOlive View\n+2.68\nHospital\n--08\n0+.25\nCanyon\nQ+1.19\n0+1.87\nMISSION\nHILLS\n+2.19\n6+1.74\n37\nHighway\nFreeway\nSoledad\n.89\nVentura\n+.120\n+.74\n+.300\n+.56C\nGRANADA HILLS\nCanyon\nNEWHALL\n+.30\n26\n51\n+.41\nAvenue\n+.21\nLyons\nMayo\n+.23\nDevonshire Street\nSherman Way\nCANOGA PARK\nSanta Susana\nPass Road\nPotrero","226\nSan Fernando Earthquake of 1971\nLess than 2 hours after the major tremor occurred\nposition may be transformed into a unique grid co-\nat 6:01 a.m., a map reconnaissance of available sur-\nordinate. Coordinates, where used in this report,\nvey control was instituted with reliance being placed\nrefer to the California Coordinate System, zone VII\non fragmentary reports of damage being broadcast by\n(U.S. Coast and Geodetic Survey 1948 and 1951).\nlocal radio stations as to the location of the area of\nReference will be made in the body of this report\ngreatest damage (Los Angeles County Earthquake\nto the \"Coop Net\" and to \"Coop Lines.\" Where this\nCommission 1971) Within 4 hours, the National\nis done, the reference is to the Southern California\nGeodetic Survey (NGS) of the National Oceanic\nCooperative Leveling Program (Franceschini and\nand Atmospheric Administration (NOAA) and Los\nMitchell 1969) Field work for this Coop Net was\nAngeles County Engineer (LACO) had established\nexecuted by Los Angeles, Orange, Riverside, San\ncontact and agreed on a tentative plan to evaluate\nBernardino, San Diego, and Ventura Counties, by\nhorizontal movements. An NGS party was immedi-\nLos Angeles city, and by the U.S. Coast and Geo-\nately assigned to reobserve two of the existing\ndetic Survey (USC&GS) The final adjustment was\nfaultline-crossing networks on the San Andreas rift.¹\ncompleted by the USC&GS in 1970. Precise leveling\nBy February 11, the primary objectives of major local\nof 1,575 miles was included in the completed adjust-\nagencies had been established and field observations\nment. Those portions relating to the San Fernando\nhad begun. By February 17, a fully coordinated pro-\nearthquake area are shown in figure 4.\ngram involving all interested local agencies with sur-\nThe vertical positions (or elevations) of points\nvey capabilities had been effected. At this time,\nare given with respect to the Mean Sea Level Datum\nLACO was designated as the coordinating agency.\nof 1929, as established and maintained by NGS of\nOn March 3, 1971, I. H. Alexander, LACO, was\nthe National Ocean Survey (formerly the USC&GS)\ninvited to chair this Subcommittee on Geodesy.\nBecause southern California is an area of known\nThe first surveys had two primary objectives: to\ngeodetic instability, dates will accompany adjust-\ndetermine the gross differential movement within or\nments, observations, and positions of various monu-\nat the visual boundaries of the area apparently dis-\nments in many instances.\nplaced; and to determine the stability of damaged,\nGeodetic work is performed at various levels of\nbut still standing, structures under aftershock\npredefined results called \"orders of accuracy,\" and an\nstresses. Some of the data obtained under the first\nattempt will be made to append the appropriate\nobjective will be adapted and included in this re-\norder applying to a particular result. In all cases,\nport. Most of the data obtained under the second\nthe standards acceptable for that order will be as de-\nobjective will be included in the structural engineer-\nfined by the NGS (U.S. Coast and Geodetic Survey\ning sections.\n1950)\nWhat monuments to hold as \"fixed\" or \"stable\" in\nDefinitions\ndetermining resulting movements was a primary\nIt is presumed that not all readers of this report\nquestion. Part II of this report discusses the prob-\nwill be trained in geodesy; hence, certain basic con-\nlems encountered and methods of solution.\ncepts will be detailed.\nContents of Report\nGeodesy, as defined for this paper, refers to all sur-\nveys falling within NGS specifications for first- and\nPart I of the report will discuss the contribution\nsecond-order work and to such secondary and lower\nof each local and national agency to the geodetic\norder surveys as required to give a clear picture of\nprogram. Parts II and III will discuss the problems\nthe major earth movements resulting from the earth-\nassociated with the respective determinations of hori-\nquake.\nzontal and vertical movements, while Part IV will re-\nReference in this report to the horizontal position\nport the findings.\nof a point is in terms of its geodetic coordinates, lat-\nIn evaluating the findings reported in Part IV, it\nitude, and longitude. These are given with respect to\nmust be stressed that all movements are in relation\nthe North American Datum of 1927 (U.S. Coast and\nto some established point or datum of reference. A\nGeodetic Survey 1936) For mapping purposes, this\nmajor element of the geodetic program was, and re-\nmains, the determination of an adequate base of ref-\n1 National Geodetic Survey periodic reports are published when\nerence. This topic is developed in greater detail in\nreobservation data have been analyzed. These are available from\nNOAA/NGS, Rockville, Md. 20852.\nParts II and III of this report.","Old Woman Springs\n603\nSAN DIEGO COUNTY\nRIVERSIDE COUNTY\nWhite Water\nSAN BERNARDINO COUNTY\n50\n603\nBarstow\n705\nPala\n600\nSan Bernardino\nRiverside\nVictorville\nColton\nFigure 4.-Southern California Cooperative Leveling Program, September 1970.\n7.\n600&601\nSan Onofre\n700\n601\n704\nCOUNTY\nOntario\nUpland\nORANGE\n202\nSanta Ana\n205\n403\nSan Dimas\nLOS ANGELES COUNTY\nLittle Rock\n401\n404\nAlamitos\nSeal Beach\nPalmdale\nRosamond\nPasadena\nLos\n202\n200\n300B\nSan Fernando\n303\n205\n300A\n208\nSylmar\n303\nCastaic Junction\nKERN COUNTY\nNewhall\nLos Angeles\nRedondo Beach\nChatsworth\nTopanga\n40\nSanta Monica\nSandberg\n208\nPrecise Level Line (along railroad) **********\nPACIFIC OCEAN\nGorman\n102\nScale in miles\nGrapevine\n205\n20\nFillmore\nUSC&GS\n200\nVENTURA COUNTY\nMoorpark\nPrecise Level Line\n102\n10\nCounty Line\nOxnard\nLEGEND:\nRailroad\n10\n100\nOjai\n0\nPort Hueneme\nBARBARA\nCOUNTY\nSANTA","228\nSan Fernando Earthquake of 1971\nA related problem concerns the inability of indicate a maximum variance of 0.04 foot between\ngeodesists to distinguish between long-term strain ac-\n1969 preearthquake and 1971 postearthquake field\ncumulation and the sudden release of that accumula-\nwork.\ntion at the time of an earthquake. The recent advent\nCalifornia Division of Highways, District VII\nof electronic distance-measurement equipment now\n(CDH-VII). Extensive losses occurred to the State\nprovides tools far superior to any in existence before\nhighway network adjacent to the Sylmar-San Fer-\n1955. It still remains, however, for the scientific com-\nnando area. Realizing that major demolition, rede-\nmunity to obtain sufficient funds to make the needed\nsign, and reconstruction would be required, the Dis-\nmeasurements in the quantity and with the fre-\ntrict VII survey forces completed secondary\nquency needed. This limitation will be apparent as\ntriangulation from Castaic into the San Fernando\nthis report is considered.\narea (fig. 6) Directly affected were Interstate High-\nways 5, 210, and 405 and California Highway Route\nPART I-WORK RÉSUMÉ OF AGENCIES\n14.\nCity of Los Angeles, Bureau of Engineering\nA minimum of duplication of survey work OC-\n(LABE). Extensive surveys were undertaken to assist\ncurred as a result of close cooperation between the\nin determining amounts and locations of land move-\nmany participating agencies.\nment. (Geodetic surveying consisted of releveling\nEach of the following listed agencies undertook\nfrom Tidal Bench Mark No. 8 at Los Angeles Harbor\nthe survey work required to determine in the best\ninto the San Fernando area along Coop Lines 301,\nmanner the effect the earthquake had on its facili-\n305, 307, and 308 as shown in figure 4. Triangula-\nties, improvements, or public responsibilities.\ntion and traverse surveys were completed and will be\nAlphabetically, the agencies contributing to the\nconnected to the primary control net as shown in\ngeodetic study were:\nfigure 7. Movement data of selected stations within\nCalifornia Department of Water Resources\nthe shaded area in figure 7 are tabulated in table 3.\nCalifornia Division of Highways, District VII\nAdditional surveys are continuing and, while not a\nCity of Los Angeles, Bureau of Engineering\npart of the geodetic program, will assist in defining\nCity of Los Angeles, Department of Water and\nthe area of movement and will indicate movements\nPower\naffecting owners of property in the area. Control sur-\nPower Systems\nveys were performed by the LABE Central Office,\nWater Systems\nwhile other surveys were done by the Van Nuys\nLos Angeles County Engineer\nDistrict Office.\nLos Angeles County Flood Control District\nCity of Los Angeles, Department of Water and\nMetropolitan Water District of Southern Cali-\nPower (LADWP).\nfornia\nNational Geodetic Survey, NOAA\nPower Systems (LADWP-P) A traverse was\nSouthern California Edison Company\nrun along transmission lines from Sylmar to Haskell\nU.S. Army Corps of Engineers\nCanyon before the earthquake. This same traverse\nU.S. Geological Survey\nwas rerun after the earthquake. For coordinate con-\nThe specific contribution of each of these agencies\ntrol, triangulation stations View and Haskell were\nis summarized in the following paragraphs. The in-\nheld fixed.\nterrelation between the work of the various agencies\nWater Systems (LADWP-W) Major damage\nis explained more fully in Parts II and III of this re-\nat the Van Norman Reservoir focused the activities\nport.\nof this agency on the horizontal and vertical control\nin the vicinity of the reservoir as shown in figures 2\nCalifornia Department of Water Resources\nand 8. The reservoir area has been remapped using\n(CDWR). Leveling was completed along the CDWR\nAqueduct from San Bernardino County through\nphotogrammetric methods, based upon postearth-\nPalmdale in Los Angeles County northwesterly into\nquake local ground control (fig. 8) Because the pri-\nKern County. This line is shown as the \"CDWR\nmary control net was not complete, it was not possi-\nAqueduct\" in figure 5. Many NGS and LACO pre-\nble to relate this mapping to the national net as\ncise bench marks were used. Elevation differences\nwould have been desirable.","Land Movement Studies Related to Earthquake\n229\nMojave\nKERN COUNTY\nRosamond\nGrapevine\nGorman\n205\nNGS\nPalmdale\nVENTURA COUNTY\nPearblossom\n205\nCastaic\nFillmore\nLOS ANGELES COUNTY\nSylmar\n0000000\nMontalvo\n100\nAzusa\nLos Angeles\n200\nTidal 4A\nCivic Center\nPooooooooo!\n12 & 16 (L.A. Co.)\nPACIFIC OCEAN\nORANGE COUNTY\nTidal 8\nLEGEND:\nNational Geodetic Survey\nL.A. County Engineer\n0000000\n40\n0\n10\n20\nL.A. City Bureau of Engineering\n000000\nScale in miles\nFigure 5.-Precise postearthquake leveling nets, southern California, December 1971.\nLos Angeles County Engineer (LACO). Field earthquake-related, activity has included work at the\ncounty's damaged Olive View Hospital to check the\nreconnaissance started immediately after the earth-\neffects of aftershock activity on building stability. As-\nquake. The primary triangulation net (fig. 9) was\nsistance was given to the NGS in its precise leveling\ndeveloped and observed cooperatively with NGS.\nand gravity measurement activities. Close coordina-\nThe LACO Llano Base Line in Antelope Valley was\ntion between LACO and NGS greatly facilitated the\nretaped to provide a length standard for all elec-\nobservations and adjustments of the primary control\ntronic distance-measuring equipment. Precise level-\ning was delayed until major aftershock activity had\nnet.\nLos Angeles County Flood Control District\ndiminished. Early in March 1971, the leveling shown\non figure 5 was started. Other nongeodetic, but (LACFCD). Immediately after the earthquake,","230\nSan Fernando Earthquake of 1971\nFebruary 9, 1971, earthquake. Two geodetic parties\nwere assigned to work cooperatively with LACO.\nAngeles National Forest\nReleveling was completed along Coop Lines 102,\n200, 206, 207, and along portions of Coop Lines 100\nand 205 (fig. 5) Again, this was a cooperative project\nwith LABE and LACO assisting. A gravimetric party\nwas assigned to make gravity determinations along\nthe lines of precise leveling. The extent of the pri-\nmary horizontal control net is shown in figure 9.\nLake Piru\nSouthern California Edison Company (SCE).\nSaugus Ventura Rd\nData have been compiled showing differential move-\nment along the Sylmar-Gould 220-kv and the Sylmar\nTap Transmission Lines. This was a Tellurometer\nand Wild T-2 Theodolite traverse survey performed\n'San\nby SCE. LACO has located each end of this traverse\nFernando\nSimi Valley\nFreeway\nwith respect to stations of the primary control net,\nFoothill\nBlvd\nenabling movement data to be determined whenever\nGolden\nthe primary control net data became available.\n0\n2\n4\n8\nScale in miles\nU.S. Army Corps of Engineers (USCE). Survey\nVentura\nFreeway\nactivities have consisted of leveling in the Wilson-\nMansfield Channel and of damage surveys of im-\nprovements in the vicinity of Lopez Canyon and the\nFigure 6.-Earthquake study area (shaded).\nSan Fernando Reservoir.\nCalifornia Division of Highways District VII.\nU.S. Geological Survey (USGS). The National\nLACFCD reran levels along the District's channels in\nCenter for Earthquake Research in Menlo Park,\nthe San Fernando-Sylmar area to determine major\nCalif., took an active role in determining land move-\nelevation changes. Later, they ran precise levels\nments in the 2 weeks immediately following the\nalong these channels and made ties to LABE and\nearthquake. The Topographic Section dispatched\nLACO bench marks where available. Deformation\nleveling parties to the Sylmar-San Fernando area\nstudies, both horizontal and vertical, using first-order\nand performed leveling from February 11 to April\nobserving methods and equipment were undertaken\n11, 1971. Portions of this leveling supplement the\nat Pacoima and Big Tujunga Dams and are discussed\ngeodetic leveling.\nin the section on Water and Sewerage Systems (in\nThe following additional agencies-California Di-\nVolume II) Direct survey connection of these study\nvision of Mines and Geology, Los Angeles County\nsites to the primary control net was not considered\nRoad Department, and U.S. Forest Service-were\nnecessary.\ncontacted regarding involvement in the geodetic sur-\nMetropolitan Water District of Southern Cali-\nvey program. No precise work is contemplated by\nfornia (MWD). The primary concern of MWD was\nthem as a result of the earthquake.\nto determine the effect of the earthquake on the\nJoseph Jensen Filtration Plant, west of Interstate 5\nPART II-DETERMINATION OF HORIZON-\nand north of the Van Norman Reservoirs (fig. 2)\nTAL EARTH MOVEMENTS\nHorizontal and vertical work was completed based\nupon a local datum. Survey work was continued at\nInitial Surveys\nthe filtration plant site to monitor the effects of the\naftershock activity. Length changes of record survey\nReconnaissance was started immediately after it be-\nlines were noted by MWD, but were not directly\ncame apparent that major surface displacements had\nconnected to the national net.\noccurred as a result of the February 9 earthquake.\nNational Geodetic Survey (NGS). A high prior-\nAn abundance of existing control permitted a high\nity has been given to all work associated with the\ndegree of freedom in selecting and planning an ob-","OAK GROVE\nARROYO\nANGELES\nCREST STA\nR.S.C.\nASOAKWILDE\n134\nNIRO\nLa Canada\n11\nFlastridge\n2290\nEagle Rock\nEagle\nFlint\nBIG TUJUNGA\nCondor\nMontrose\nPk\nIron Mtn\nLa Crescenta\nLukens\n2\nBY\nTOM LUCAS\nMr\nVerdugo City\nCondo\nname\nGLENDALE\nHighlands\nHighway\nNo Shooting\nIron Mtr\nFigure 7.-Earthquake study area (shaded), December 1971. Los Angeles City Bureau of Engineering.\nYerha Buena\nTujunga\nSpr\n$1.0\nSouth\nGold C\n00\nPATTE\n5\nBURBANK\nSunland\nMendenhall PK.C\nSpr\nGRILLITH\nTCenter\nLOOKOUT\nescination\nPARK\nCanuenga PK\n118\nUniversal\nDUTCH LOUIE\nalley\nCity\n134\nRes\nSun\nMAGNOLIA\nHONEY\nCan\nNorth Hollywood\nDIVIDE\nStudio City\nBEAR\nANTERNANDO\nSTA\nPacoiran\nSan Fernando\nSherman Oaks\nNUYS\nPanorama\nCity\nFINE STA\nVAN\nScale in miles\nSylman\nCBM1243\n5\n2\nSepulveda\n405\nFLOOD CONTROL\nSEPULVEDA\nSTATE Fernando\n1\nVICTORY\nReservour\nUppur\nFERNAND\n0\nEncino\nNorthridge\n\"NEWHALL\nR.S.\nEncino\nRes\nReseda\nMission\nGranada Hills\nVALLEY\nTarzana\n118\nNS\nHorse\nRes\nCan","232\nSan Fernando Earthquake of 1971\nPac E2 ECC1\nSan Fernando Valley\nJuvenile Hall\nBendix\nLOWER\nVAN NORMAN\nLAKE\n12\nGrapevine\nH.V.D.C.\nConverter Station\nVAN\nPac C-2\nNORMAN\nLAKE\nSyl A-12\nRm 1A\n+.04\nMack\n0\n1000\n2000\n4000\nScale in feet\nNote: Length changes in feet\nFigure 8.-Typical example of line-length changes for determination of earthquake differential movement data.\nWater Systems, Los Angeles City Department of Water and Power.\nservation program. This survey résumé will relate to\nan attempt here to make the corresponding compari-\nthe work of the four primary agencies; namely,\nson with preearthquake-published versus postearth-\nUSGS, NGS, LABE, and LACO.\nquake-published lengths or with preearthquake-\nWhile major aftershocks were still occurring, the\nunconstrained versus postearthquake-unconstrained\nUSGS obtained line-length changes on 18 lines\nlengths.\nwithin the area of major damage and on seven lines\nThe measurements shown in table 1 were made\nto points outside the area. These changes resulted\nusing a Geodolite. The atmospheric corrections ap-\nfrom a comparison of line lengths determined from\nplied were based on observations taken in a helicop-\npreearthquake-published positions and from post-\nter flying along the line of sight at the time of meas-\nearthquake direct measurements (table 1) . Figure 9\nurement. Additional measurements had been planned,\nshows the location of these stations.\nbut were curtailed when a change in weather condi-\nThe postearthquake observations initially were re-\ntions prevented further helicopter flights.\nduced using incomplete vertical data. They were\nMany surface failures (upheavals or cracks) were\npublished less than 3 weeks after the earthquake. In\nvisible for examination by geophysicists and geolo-\nsubsequent months, these reductions were refined\ngists. The first data to be released regarding land\nand are those now shown in Savage et al. (1972)\nmovements appeared in a preliminary USGS report\nBoth postearthquake values are shown in table 1 and\ndated March 3, 1971. Close cooperation between\nillustrate the magnitude of uncertainty that may be\nUSGS and LACO was accomplished.\nintroduced using incomplete data, There will not be\nThe LABE also undertook distance measuring be-","Land Movement Studies Related to Earthquake\n233\n+\n+ 34°45'\n118°15'\n118°30'\n118°45'\n44\n35\n9\n5\n3\n31\nLake Hughes\n13 A 14\n47\n29\n28\n6\n24\n12\n54\n60\n34°35'\n34°35'\n55\n44\n49\n33\n4\n-58\nNo scale\n45\n35\n50\n7\n10\n57\nINSERT MAP\n53\n8\n59\n9\n5/6\n52\n/61\n51\n39\n5\n38\n43\n31 x 32\n841\n37\n14/0\n36\n-34°25'\n- 34°25'\n42\n20\n18\n15\n14\n13\n1\nNewhall\n21\n17\n47\n123\n46\n29\n65\n30\n19\n64\nOlive\nView\n22/\nSylmar\nb\n48\nSee Fig. 2\n62\nfor detail\nSan\n26\n27\nFernando\n12\n28\no\nGranada\n- 34°15'\n6\n63\nSunland\n34°15'\nHills\nO\n24\n16\n11\nMt. Wilson\n2\nVan Nuys\n7\n4\n34\n+ 34°5'\n0\n1\n2\n4\n+ 34°5'\n118°0'\n118°15'\n118°30'\nScale in miles\n118°45'\nNot used in Triangulation Net\nNOTE:\nThe numbering of stations shown\nrelates to main net and insert map\nFigure 9.-San Fernando earthquake primary triangulation net. See index of triangulation stations in table 5.\nLos Angeles City Bureau of Engineering, National Geodetic Survey, and Los Angeles County Engineer.\ntween certain existing control monuments to deter- shown at reduced scale as an insert in figure 9. Ob-\nservations were initiated at stations Hauser and Pe-\nmine differential movement data.\nA primary net extending from the crest of the lona by NGS and at stations Cahuenga and Calabasas\nSanta Monica Mountains northward to the vicinity\nby LACO.\nPreliminary checks on the position of station Sister\nof Gorman was devised by LACO and submitted to\nNGS for review and comment. This first net is Elsie prompted the addition of stations in the vi-","234\nSan Fernando Earthquake of 1971\nTable 1.-Line length changes\n[Determined by U.S. Geological Survey; measured in m]\n(1)\n(2)\n(3)\n(4)\n(5)\n(6)\nLines and limiting points\nPreliminary\nLine\nFinal\nAdjusted\nMagnitude\nPreearthquake postearthquake\nlength\npostearthquake\nline length\nof\ndistance 1\ndistance 2\nchange\ndistance 3\nchange\nuncertainty 4\n(2)-(1)\n(4)-(1)\n(3)-(5)\nPacoima L-1 to:\nMays 2\n4511.72\n4510.47\n-1.25\n4510.475\n-1.24\n+0.01\nSylmar F-8\n6708.68\n6707.11\n-1.57\n6707.098\n-1.58\n-0.01\nPAC E-2 ECC 1\n5141.72\n5139.66\n-2.06\n5139.665\n-2.06\n0.00\nPacoima No. 2\n3229.33\n3229.27\n-0.06\n3229.226\n-0.10\n-0.04\nMay\n6951.26\n6949.82\n-1.44\n6949.936\n-1.32\n+0.12\nMesa\n5444.05\n5442.77\n-1.28\n5442.820\n-1.23\n+0.05\nPAC E-2 ECC 1 to:\nMays 2\n5454.10\n5453.75\n-0.35\n5453.719\n-0.38\n-0.03\nPacoima No. 2\n5728.76\n5728.57\n-0.19\n5728.552\n-0.21\n-0.02\nSylmar I-12\n3150.74\n3149.94\n-0.80\n3149.946\n-0.79\n+0.01\nReservoir\n2420.21\n2420.62\n+0.41\n2420.592\n+0.38\n-0.03\nMay\n7572.70\n7572.35\n-0.35\n7572.334\n-0.37\n-0.02\nEast\n8116.16\n8116.46\n+0.30\n8116.452\n+0.29\n-0.01\nMission Point\n7048.57\n7048.97\n+0.40\n7048.978\n+0.41\n+0.01\nBluff\n7256.39\n7256.74\n+0.35\n7256.707\n+0.32\n-0.03\nCalabasas\n23689.20\n23689.42\n+0.22\nSylmar F-8 to:\nSylmar I-12\n4063.59\n4063.04\n-0.55\n4063.147\n-0.44\n+0.11\nReservoir\n5918.50\n5918.58\n+0.08\n5918.542\n+0.04\n-0.04\nPAC E-2 ECC 1\n5354.90\n5354.95\n+0.05\n5354.932\n+0.03\n-0.02\nPacoima No. 2\n9268.57\n9268.37\n-0.20\n9268.301\n-0.27\n-0.07\nBluff\n9643.56\n9643.52\n-0.04\n9643.450\n-0.11\n-0.07\nMays 2\n2719.77\n2719.60\n-0.17\n2719.620\n-0.15\n+0.02\nMesa\n4406.76\n4406.23\n-0.53\n4406.161\n-0.60\n-0.07\nMay\n2874.85\n2874.95\n+0.10\n2874.638\n-0.21\n-0.31\nMission Point\n7776.93\n7776.93\n0.00\n7776.907\n-0.02\n-0.02\n1 Calculated from published positions.\n3 Later refined reductions.\n2 Reduced using incomplete vertical data.\n4 Uncertainty that can be introduced by using incomplete data.\ncinity of Mt. Wilson, Mt. Gleason, and Pacifico\nGeodetic Service of the USGS immediately following\nMountain. Stations Flint and Verdugo were added at\nthe earthquake (Anonymous 1971) The precision\nthis time to provide connections needed by LABE in\nnow obtainable by analytical methods suggests that\nits connection to the primary net.\nmuch data desired in the early stages of the investiga-\nThe arc of smaller figures extending northward\ntion could have been obtained by this method and\nfrom station Corner was added by NGS to\nlater refined as the geodetic survey was completed.\nstrengthen the net and to provide information on\ncrustal movements in the Newhall-Saugus area.\nEvaluation of Apparent Movement\nOther modifications were made as the work pro-\nTo evaluate the significance of movement vectors\ngressed, and the final net is shown in figure 9.\nderived from postearthquake observations, it is neces-\nThese additions added greatly to the value of the\nsary to make a detailed examination of the signifi-\ncompleted net, but, at the same time, increased the\ncance of the published preearthquake positions of\namount of field time required for the survey. The\nfield work was greatly expedited by a cooperative in-\nthe affected stations.\nterchange of personnel and equipment between NGS\nThe primary geodetic control in the Los Angeles\nand LACO. This interchange was accomplished at\nBasin was based on field work performed in 1934.\nthe survey party level, thereby permitting the maxi-\nThirty-eight stations were included in the first local\nmum freedom to cope with the ever-changing re-\nestablishment of geodetic control. In this classic ad-\nquirements of field operations.\njustment, the following NGS stations were held\nThe only large-scale photography known to have\nfixed: Castro, 1898; San Fernando, 1898; San Pedro,\nbeen taken immediately after the earthquake was\n1853; Los Angeles Northwest Base, 1889; and Wilson\ntaken for news purposes and for damage assessment\nPeak, 1890. The resulting positions of stations in this\nin particular areas. High-altitude photogrammetric\nnet were published by the U.S. Coast and Geodetic\ncoverage was taken by the Aerospace Charting and\nSurvey (1936)","Land Movement Studies Related to Earthquake\n235\ntion. The magnitude of these length changes, except\nAs new surveys were established throughout Los\nAngeles County, USC&GS was forced to fit the posi-\nfor the extreme northern part of the area, is on the\ntions of stations previously determined. This resulted\norder of one part in 75,000.\nThe positions obtained from these constrained ad-\nin some distortions, and, in recent years, some prob-\njustments of the preearthquake and postearthquake\nlems were encountered in obtaining satisfactory clo-\nsurveys will, however, be adopted by local agencies\nsures between positions determined previously. To\nresolve these problems, a simultaneous adjustment of\nfor engineering purposes and will be used for con-\ntrol to determine shifts of property lines, street cen-\nthe primary network of stations was performed by\nterlines, and other works of man both public and\nNGS in 1970. This readjustment included the pri-\nmary geodetic control stations north of the San Ga-\nprivate.\nTo obtain the best possible data for horizontal\nbriel Mountains in Los Angeles County and some\nearth movement studies, it is necessary to eliminate\nstations in adjacent counties. Results of this readjust-\nthe adjustment uncertainties from the results. This\nment were adopted by LACO, and these values will\nis done by making free adjustments of the preearth-\nsupersede the previously adjusted positions in NGS\nquake and postearthquake surveys. In a free adjust-\nfiles.\nment, there are no constraints to force the observa-\nThe network of stations observed in the postearth-\ntional data to fit previously determined positions.\nquake surveys is shown in figure 9. After a careful\nFree adjustments have been performed by geodesists\nreview of the observational data by NGS, it was\nof NGS, and the results are discussed in Volume III\nfound that observed angles at the exterior stations\nin the paper, \"Horizontal Crustal Movements De-\n(fig. 9) were in very close agreement with the\ntermined From Surveys After San Fernando Earth-\npreearthquake values. An adjustment of this net was\nthen made by NGS, holding positions of the exterior\nquake\" by Meade and Miller.\nstations fixed. The adjusted positions of the interior\nstations will be added to the files of NGS, and these\nSupplementary Surveys\ndata will carry the note: \"This position to be used\nWithin the framework of the primary nets de-\nin surveys performed after the earthquake of Febru-\nscribed above, LABE has executed first-order control\nary 9, 1971.\"\nsurveys within the area indicated by shading in\nThe vectors shown in figure 10 indicate the shift\nfigure 7. LABE will continue first-order traverse\nfrom preearthquake positions of 1970 to postearth-\nand second- and third-order traverses along all city\nquake-constrained positions for the various stations.\nstreets in the earthquake area. Even with the com-\nThe vectors are based on position data for these and\nmitment of five or more survey parties to this work,\nother stations shown in table 2. The reader is cau-\nthe traverse work is expected to continue into 1973.\ntioned that these positions and vectors reflect not\nSecond-order surveys were made by CDH-VII in\nonly earthquake movement, but also reflect any of the\nthe Santa Clara River area. The location of these\nadjustment uncertainties of both the preearthquake\nsurveys is indicated by the shaded portion of figure 6.\nand postearthquake data. These adjustment uncer-\nResults of these local agency control surveys will\ntainties are introduced when the survey networks are\nbe available from the agency or from LACO and\nmade consistent with previously determined posi-\nwill be consistent with the data shown in tables 2\ntions on the North American Datum of 1927. In the\nand 3.\n1970 readjustment of the Los Angeles County net-\nwork, stations which were held fixed along the north-\nPART III-DETERMINATION OF VERTICAL\nern extremity were about 20 miles north of the\nEARTH MOVEMENTS\ncounty boundary. Using the selected control stations\nalong the southern part of the network, the computa-\nIn June 1970, the results of the Southern Califor-\ntions showed a closure of 8 feet (about one part in\nnia Cooperative Leveling Program-Coop Net-\n50,000) south to north across the area. There was no\n(U.S. Coast and Geodetic Survey 1970) 2 were made\nsignificant closure in the east-west direction.\navailable (fig. 4) The Coop Net was the result of a\nTo absorb the 8-foot closure in latitude, the\n2 Data are available from National Geodetic Survey, National\npreearthquake- and postearthquake-constrained ad-\nOcean Survey, National Oceanic and Atmospheric Administration,\njusted distances increased in the north-south direc-\nRockville, Md. 20852.","San Fernando Earthquake of 1971\n236\n34°45'\n-34°45'\n118°45'\n118 30'\n118°15'\n118°0'\nA\n3\n0\nLake Hughes\nA\n54\nA\n-34°35'\n-34°35'\n60\no\n49\n44\n55\nPalmdale\nA\nA\n50\nA\n58\n45\n53\n57\n10\n28\nA\n9\na\n59\n8\n35\n45\n28\n24\no\n52\n.26\n56\n9\na\no\n:33\n51\n34\n61\n1\n44\nA\no\n52\n35\no\n5\n39\n43\n38\n.61\n72\n31\n37\n41\n32\n93\n94\n36\n-34°25'\n42\n-34°25'\n1.04\n00\no\n20\n38\n14\n22\n18\nNewhall\n-O\n88\n13 1.28\n15\n1\n21\n66\no\n48\n34\n17\n65\n223\n47\n29\n3.18\no\n46\nA\n6.35\n0\nOlive View\n30\n40\n48\n22\nSYLMAR\n61\n88\n67\no\nSan\n27\n2.54\n25\n26\n62\nFernando\n.03\n1.17\n0\n12\nA\n28\nGranada Hills 63\n-34°15'\n6\nSunland\n-34°15'\n1.42\nA\n16\n11\nA\n2\nVan Nuys\nA\n7\nA\n4\n34\n+34°5'\n+34°5'\n118°45'\n118°30'\n118°15'\n118°0'\nLEGEND\nA Held Fixed in Position\n8 Movement Vector\n0\n1\n2\n4\nOnly movements greater than 0. 20 foot shown\nScale in miles\nVector movement in feet\nFigure 10.-Apparent horizontal movement at survey control stations resulting from\nconstrained adjustment by National Geodetic Survey.","Land Movement Studies Related to Earthquake\n237\nTable 2.-California Zone 7 coordinates and coordinate change data resulting from National Geodetic Survey constrained adjustment,\nregarding San Fernando earthquake\nDeterminations made by Los Angeles County Engineer]\nCalifornia Zone 7 coordinates\nDate\nLACO\nPopular name\nNGS\nStation name\nno.\nno.\n1970 N 4,251,503.65\nE $4,277,110.25\n212\n01 Pacifico\nACR H-3\nN 4,251,503.65\nE 4,277,110.25\n724\n1971\n01 Pacifico\nACR H-3\nPosition held fixed\n1968 N 4,171,957.93\nE € 4,228,288.79\n02 Flint\nALT A-5\n1971 N N 4,171,957.93\nE 14,228,288.79\n719\n02 Flint\nALT A-5\nPosition held fixed\nN 4,364,741.93\nE 4,118,406.66\n112\n1970\n03 Sawmill\nBPK H-7\n£4,118,406.66\n768\n1971\nN 4,364,741.93\n03 Sawmill\nBPK H-7\nPosition held fixed\nE 4,189,241.55\n1915\nN 4,162,250.30\n04 Cahuenga 2\nBUR J-8\nN 14,162,250.30\nE 4,189,241.55\n717\n1971\n04 Cahuenga 2\nBUR J-8\nPosition held fixed\nN T 4,293,191.50\nE 4,085,929.87\n05 Loma Verde\n080\n1970\nCAS D-1\nE 4,085,929.87\n764\n1971\nN 4,293,191.50\n05 Loma Verde\nCAS D-1\nPosition held fixed\n1967\nN 4,206,090.37\nE 4,094,114.20\n06 Chatsworth\nCHA H-6\nE 4,094,114.20\n06 Chatsworth\n703\n1971\nN 4,206,090.37\nCHA H-6\nPosition held fixed\nE 4,092,459.23\n1965\n14,163,510.85\n07 Calabasas\nDC G-8\n$ 4,163,510.85\nE 4,092,459.23\n701\n1971\n07 Calabasas\nDC G-8\nPosition held fixed\n1970 N 4,310,995.34\nE 4,136,775.88\n021\n08 Brushy\nGV A-10\n1971 N 4,310,995.26\nE 4,136,775.61\n754\n08 Brushy\nGV A-10\nCoordinate change 0.28 ft S73-30W\n1970 N 4,306,232.96\nE 4,143,192.56\n102\n09 Deer\nGV C-12\n1971 14,306,232.97\nE 4,143,193.01\n752\n09 Deer\nGV C-12\nCoordinate change 0.45 N88-44E\nE 4,145,558.02\n1970 T 4,315,051.68\n022\n10 House\nGV D-9\n1971 14,315,051.68\nE 4,145,558.02\n753\n10 House\nGV D-9\nPosition held fixed\n€ 4,202,675.88\n1967 N N 4,190,541.68\nVerdugo AUX\nLCR C-11 AUX 1\n11\n1971 N 4,190,542.08\nE 4,202,676.01\n11 Verdugo AUX\n718\nLCR C-11 AUX 1\nCoordinate change 0.42 N18-00E\n1970 14,210,310.05\nE 4,215,472.08\n12 Sister Elsie\n903\nLCR H-4\nE 4,215,472.67\n721\n1971 4,210,310.89\n12 Sister Elsie\nLCR H-4\nCoordinate change 1.03 ft N35-05E\n1970 N 4,253,006.80\nE 4,188,052.07\n187\n13\nPort\nLT I-2\n1971 N 4,253,006.75\nE 4,188,051.69\n732\n13\nPort\nLT I-2\nCoordinate change 0.38 ft S82-30W\n1970 N 4,252,946.57\nE 4,191,495.82\n14 Magic\n188\nLT J-2\n1971 N 4,252,946.29\nE 4,191,495.83\n731\n14 Magic\nLT J-2\nCoordinate change 0.28 ft S02-03E\n1961 N 4,253,220.48\nE 4,231,803.77\n15\nMTG B-2\n1971 N 4,253,220.44\n€ 4,231,803.55\n727\n15\nMTG B-2\nCoordinate change 0.22 S79-42W\n1970 14,193,514.03\nE 4,268,814.78\n16\nMTW E-10A\n1971 N 4,193,514.03\n€ 4,268,814.78\n720\n16\nMTW E-10A\nPosition held fixed\n1970 N 4,242,086.22\nE 4,109,216.52\n17 Towsley\n008\nNH B-6\n1971 N 14,242,086.88\nE 4,109,216.58\n740\n17 Towsley\nNH B-6\nCoordinate change 0.66 ft N05-12E\nE 4,111,592.27\n1970 N 4,255,886.93\n010\n18 Lock\nNH C-1\n1971 N 4,255,887.96\n€ 4,111,592.16\n742\n18 Lock\nNH C-1\nCoordinate change 1.04 ft N06-06W\n1971 N 4,229,019.62\nE 4,116,958.28\n713\n19 Ridge 2\nNH E-10B\nNew station\n1970 N 4,255,938.76\nE 4,125,944.80\n20 Newhall\n009\nNH H-1\n1971 N 4,255,939.67\nE 4,125,944.39\n741\n20 Newhall\nNH H-1\nCoordinate change 1.00 ft N24-15W\n1970 N 4,249,031.45\nE 4,125,755.46\n007\n21\nEdison No. 2\nNH H-3\n1971 N 4,249,032.29\nE 4,125,755.20\n739\n21\nEdison No. 2\nNH H-3\nCoordinate change 0.88 ft N17-12W\n1970 N 4,225,899.79\n€ 4,126,424.10\n22 Mission Point\n004\nNH I-11\n1971 N 4,225,900.19\nE 4,126,424.10\n712\n22 Mission Point\nNH I-11\nCoordinate change 0.40 ft N00-00\n1970 N 4,237,725.46\n€ 4,130,426.39\n273\n23\nEast\nNH J-8\n1971 N 4,237,725.79\n€ 4,130,426.31\n735\n23\nEast\nNH J-8\nCoordinate change 0.34 ft N13-38W\n1954 T4,201,820.88\nE 4,139,949.50\n24 Darling\nPAC B-7\nStation not recovered\nE 4,140,181.12\n25 Reservoir 1932\n001\n1970 N [4,218,584.73\nPAC C-1\n1971 N 4,218,585.11\nE 4,140,180.64\n25 Reservoir 1932\n709\nPAC C-1\nCoordinate change 0.61 N51-38W\n1961 N 4,217,792.36\nE 4,148,081.52\n26\nPAC E-2 ECC 1\n1971 N 4,217,792.54\nE 4,148,082.38\n706\nPAC E-2 ECC 1\n26\nCoordinate change 0.88 ft N78-11E","238\nSan Fernando Earthquake of 1971\nTable 2.-California Zone 7 coordinates and coordinate change data resulting from National Geodetic Survey constrained adjustment,\nregarding San Fernando earthquake-Continued\n[Determinations made by Los Angeles County Engineer]\nStation name\nLACO\nPopular name\nNGS\nDate\nCalifornia Zone 7 coordinates\nno.\nno.\nPAC L-1\n27\n1969 N 4,218,895.60\nE 4,164,914.44\nPAC L-1\n27\n705\n1971 4,218,897.84\nE 4,164,908.50\nCoordinate change 6.35 N69-20W\nPAC L-5\n28\nPacoima No. 2\n1933 N 4,208,317.74\nE 4,164,313.73\nPAC L-5\n28\nPacoima No. 2\n715\n1971 N 4,208,320.03\nE 4,164,314.83\nCoordinate change 2.54 ft N25-39E\nPIC L-9 AUX 2 ECC 1\n29 San Fernando AUX 2 ECC 1\n1970 N 4,232,769.66\nE 4,106,131.58\nPIC L-9 AUX 2 ECC 1\n29 San Fernando AUX 2 ECC 1\n737\n1971 N 4,232,769.66\n€ 4,106,131.58\nPosition held fixed\nPIC L-9A\n30\n1970 N 4,232,409.17\nE 4,106,258.33\nPIC L-9A\n30\n736\n1971 N 4,232,409.17\nE 4,106,258.33\nPosition held fixed\nRAV J-5\n31 Parker\n189\n1970 N 4,279,758.18\nE 4,221,497.61\nRAV J-5\n31 Parker\n730\n1971\n4,279,757.99\nE 4,221,497.58\nCoordinate change 0.19 S08-58W\nRAV J-5 AUX 2\n32 Parker AUX 2\n1970 N 14,279,740.19\nE 4,221,517.92\nRAV J-5 AUX 2\n32 Parker AUX 2\n726\n1971 N 4,279,740.00\nE 4,221,517.89\nCoordinate change 0.19 ft S08-58W\nRES K-9\n33 San Vicente\n1955 N 4,159,284.17\nE 4,132,638.00\nStation not recovered\nRES K-9A\n34\n1969 N 4,159,320.44\nE 4,132,635.09\nRES K-9A\n34\n702\n1971 N 4,159,320.44\nE 4,132,635.09\nPosition held fixed\nRR E-10\n35 Hauser\n186\n1970 14,311,746.41\nE 4,222,442.44\nRR E-10\n35 Hauser\n729\n1971\nN 14,311,746.41\n€ 4,222,442.44\nPosition held fixed\nSAU C-9\n36 Yucca\n012\n1970 N 4,268,855.59\nE 4,112,354.55\nSAU C-9\n36 Yucca\n744\n1971\n4,268,856.52\n€4,112,354.52\nCoordinate change 0.93 N01-51W\nSAU D-5\n37 Long\n014\n1970 4,281,370.55\nE 4,114,563.99\nSAU D-5\n37 Long\n746\n1971 N 4,281,371.16\n£4,114,564.00\nCoordinate change 0.61 ft N00-56E\nSAU E-3\n38 Bum\n016\n1970 N 4,286,877.45\nE 4,116,652.49\nSAU E-3\n38 Bum\n748\n1971 N 4,286,878.09\nE 4,116,652.54\nCoordinate change 0.64 ft N04-28E\nSAU F-1\n39 Steer\n018\n1970 N 4,293,645.47\nE 4,121,322.44\nSAU F-1\n39 Steer\n750\n1971 14,293,645.91\nE 4,121,322.49\nCoordinate change 0.44 N06-29E\nSAU G-8A\n40 Foot 2\n745\n1971 N 4,272,169.10\nE 4,123,913.82\nNew station\nSAU H-5\n41\nDry\n015\n1970 N 4,280,838.80\nE $4,124,414.35\nSAU H-5\n41\nDry\n747\n1971 N 4,280,839.50\nE £4,124,414.17\nCoordinate change 0.72 N14-25W\nSAU H-11\n42 Saugus\n011\n1970 N 4,263,991.35\nE 4,124,576.91\nSAU H-11\n42 Saugus\n743\n1971 N 4,263,992.21\nE 4,124,576.54\nCoordinate change 0.94 N23-17W\nSAU J-2\n43 View\n017\n1970 N 4,291,300.57\nE 4,131,118.19\nSAU J-2\n43 View\n749\n1971 N 4,291,301.02\nE 4,131,117.93\nCoordinate change 0.52 N30-01W\nSV C-8\n44 Pelona\n179\n1970 N 4,316,559.11\n£4,180,130.88\nSV C-8\n44 Pelona\n734\n1971 N 4,316,559.11\n14,180,130.88\nPosition held fixed\nSV C-8 ECC 2\n45\nPelona ECC 2\n1970\nN 4,316,398.53\n€ 4,180,148.43\nSV C-8 ECC 2\n45\nPelona ECC 2\n733\n1971\nN 4,316,398.53\n€ 4,180,148.43\nPosition held fixed\nSYL F-8\n46\n1935\nN 4,235,236.24\n€ 4,150,169.27\nSYL F-8\n46\n704\n1971\nN T4,235,236.82\n4,150,168.97\nCoordinate change 0.65 ft N27-21W\nSYL I-6\n47 May\n902\n1970 N 4,240,603.85\n€ 4,157,924.81\nSYL I-6\n47 May\n738\n1971\nN 4,240,603.59\nE 4,157,924.41\nCoordinate change 0.48 ft S56-59W\nSYL I-12\n48\n1936 N 4,223,582.55\nE 4,156,644.61\nSYL I-12\n48\n707\n1971\nN 4,223,583.71\n€ 4,156,641.65\nCoordinate change 3.18 ft N68-36W\nWPK A-7A\n49 Whitaker\n103\n1970 N 4,319,196.91\n4,063,679.77\nWPK A-7A\n49 Whitaker\n765\n1971 N 4,319,196.91\n€ 4,063,679.77\nPosition held fixed\nWPK A-7A AUX 1\n50 Whitaker AUX 1\n1970 N 4,319,156.73\n$4,063,699.51\nWPK A-7A AUX 1\n50 Whitaker AUX 1\n766\n1971 N 4,319,156.73\nE 4,063,699.51\nPosition held fixed\nWPK N-15\n51\nCast C\n082\n1970\nN ₦ 4,295,178.04\nE 4,095,671.70\nWPK N-15\n51\nCast C\n760\n1971\nN 14,295,177.83\nE 4,095,671.42\nCoordinate change 0.35 ft S53-08W\nWSM B-13\n52 Fork\n084\n1970 N 4,302,594.09\nE 4,101,663.43\nWSM B-13\n52 Fork\n761\n1971\nN 4,302,593.86\nE 4,101,663.19\nCoordinate change 0.33 ft S46-13W","Land Movement Studies Related to Earthquake\n239\nTable 2.-California Zone 7 coordinates and coordinate change data resulting from National Geodetic Survey constrained adjustment,\nregarding San Fernando earthquake-Continued\n[Determinations made by Los Angeles County Engineer]\nStation name\nLACO\nPopular name\nNGS\nDate\nCalifornia Zone 7 coordinates\nno.\nno.\nWSM C-10\n53 Daires\n085\n1970 N ,310,377.60\nE 4,106,280.94\nWSM C-10\n53 Daires\n762\n1971 N 4,310,377.44\nE 4,106,280.76\nCoordinate change 0.24 ft S48-22W\nWSM F-4\n54 Warm Springs\n101\n1970 4,329,228.22\nE 4,112,794.68\nWSM F-4\n54 Warm Springs\n767\n1971 N 4,329,228.22\nE 4,112,794.68\nPosition held fixed\nWSM F-6\n55 Necktie\n087\n1970 N 4, 322,858.33\nE 4,112,110.37\nWSM F-6\n55 Necktie\n763\n1971 N 4, ,322, 858.25\nE 4,112,110.30\nCoordinate change 0.11 ft S41-11W\nWSM F-13A\n56 Charlie\n083\n1970 N 300,655.75\nE 4,111,562.11\nWSM F-13A\n56 Charlie\n757\n1971 N 4,300,655.52\n€ 4,111,561.86\nCoordinate change 0.34 ft S47-23W\nWSM H-10\n57 Taylor\n086\n1970 N 4,310,195.22\n€4,118,327.56\nWSM H-10\n57 Taylor\n758\n1971 4,310,194.98\nE 4,118,327.41\nCoordinate change 0.28 ft S32-00W\nWSM J-8\n58 Elizabeth\n088\n1970 N 4,317,298.91\nE 4,122,400.01\nWSM J-8\n58 Elizabeth\n759\n1971 4,317,298.81\nE 4,122,399.92\nCoordinate change 0.13 ft S41-59W\nWSM K-11\n59 Powerhouse\n020\n1970 N 4,306,630.96\nE 4,125,020.15\nWSM K-11\n59 Powerhouse\n756\n1971 N 4,306,630.98\nE 4,125,020.14\nCoordinate change 0.02 ft N26-34W\nWSM M-5\n60 Red 1932\n081\n1970 N 4,325,929.75\nE 4,129,659.76\nWSM M-5\n60 Red 1932\n755\n1971\n4,325,929.75\nE 4,129,659.76\nPosition held fixed\nWSM N-13\n61 Rock\n019\n1970 N 4,300,769.89\nE 4,132,104.62\nWSM N-13\n61 Rock\n751\n1971\nN 4,300,770.03\nE 4,132,104.40\nCoordinate change 0.26 ft N57-32W\nZEL H-2\n62 Bluff\n003\n1970 N 4,217,040.36\nE 4,124,286.54\nZEL H-2\n62 Bluff\n711\n1971 N 4,217,040.98\nE 4,124,286.80\nCoordinate change 0.67 ft N22-45E\nZEL I-6D\n63 Corner 2\n002\n1970 N 4,206,243.59\nE 4,130,385.05\nZEL I-6D\n63 Corner 2\n710\n1971 N 14,206,244.41\nE 4,130,385.88\nCoordinate change 1.17 ft N45-21E\n64\nMays 2\nNot a part of the primary net\n65 Mesa\nNot a part of the primary net\nTable 3.-California Zone 7 coordinates and coordinate change data resulting from National Geodetic Survey constrained adjustment,\nregarding San Fernando earthquake\n[Determinations made by Los Angeles City Bureau of Engineering]\nStation name\nDate\nCalifornia Zone 7 coordinates\nLCR A-7\n1958 N 4,202,553.62\nE 4,196,772.91\nLCR A-7\n1971 N 4,202,554.50\nE 4,196,772.91\nCoordinate change 0.88 ft North\nLCR B-10A\n1957 N 4,192,884.00\n€ 4,200,850.22\nLCR B-10A\n1971 N 4,192,884.35\nE 4,200,850.15\nCoordinate change 0.36 6 ft N11-19W\nPAC C-2\n1966 N 14,216,724.94\n€ 4,141,566.89\nPAC C-2\n1971 N 4,216,726.11\nE 4,141,567.46\nCoordinate change 1.30 ft N25-58E\nSYL A-12B\n1962 N 14,224,243.46\nE 4,138,271.47\nSYL A-12B\n1971 N 14,224,242.13\nE 4,138,272.94\nCoordinate change 1.98 ft S47-52E\nSUN B-2\n1964 N 4,217,897.65\nE 4,169,538.46\nSUN B-2\n1971 N 4,217,896.01\n€ 4,169,533.31\nCoordinate change 5.40 ft S72-20W\nSUN C-3\n1940 N 4,213,826.36\nE 4,172,364.82\nSUN C-3\n1971 N 4,213,829.12\nE 4,172,366.09\nCoordinate change 3.04 ft N24-43E\nSUN H-3\n1940 N 4,213,275.40\nE 4,185,871.12\nSUN H-3\n1971 N 4,213,271.28\nE 4,185,871.96\nCoordinate change 4.20 ft S11-31E\nZEL L-2\n1938 N 4,216,446.85\nE 4,134,280.83\nZEL L-2\n1971 N 4,216,447.58\nE 4,134,281.41\nCoordinate change 0.93 ft N38-28E","San Fernando Earthquake of 1971\n240\nThe field data obtained were compiled and sent\nconstrained adjustment, based on elevations of tidal\nto NGS for study and adjustment. All information\nbench marks Tidal 8 at Los Angeles Outer Harbor,\non vertical movement shown in this report is pre-\nTidal 6 at La Jolla, and Tidal 4A at Point Mugu, as\nliminary. Figure 3 shows selected vertical move-\nwell as on six bedrock marks in Ventura, Kern, San\nments derived from a comparison of preearthquake-\nBernardino, Riverside, and San Diego Counties, and\nconstrained 1970 elevations with postearthquake-\na mark at the County Hall of Justice in the Los An-\nunadjusted preliminary field elevations. It should be\ngeles Civic Center. For scientific purposes, a free ad-\nnoted that only first-order bench mark locations are\njustment also was completed and is available upon\nshown; several areas of much greater movement are\nrequest. In this latter adjustment, only Tidal 8 was\nheld fixed. Several lines of the Coop Net run\nknown to exist.\nthrough the area of major earthquake land move-\nment.\nPART IV-FINDINGS\nFollowing the February 9 earthquake, it was\nConclusions\nagreed that primary vertical control would be rerun\nby the agency that did the work in the Coop Net,\n1 The preearthquake existence of well-monu-\nwith LABE being assigned a major role. This con-\nmented first-order geodetic control, both horizontal\ncept was modified when NGS elected to level south-\nand vertical, has made possible the collection of a\nward from Grapevine through Castaic to Pearblos-\nsignificant body of scientific data that will be of\nsom along Line 205 and leveled Line 207 from\ngreat value to earth scientists and the engineering\nPalmdale to Rosamond.\ncommunity.\nPostearthquake precise leveling was completed as\n2 Published positions of geodetic control stations\nshown in figure 5.\nmay not form an adequate basis for the scientific\nIn fully evaluating the results of the releveling as\nstudy of movements resulting from earthquakes.\nthey pertain to the San Fernando earthquake, it is\nLine lengths and directions computed from pub-\nnecessary to take into account subsidence that has\nlished positions contain both the accidental errors in-\nbeen occurring in the Los Angeles Basin (including\nherent in direct measurement and the additional un-\nthe San Fernando Valley) during the past 20-year pe-\ncertainties introduced when the observed data are\nriod in which precise leveling data have been avail-\nconstrained to fit the existing network.\nable. The apparent movement at BM 5-46C in the\n3 Although both preearthquake- and postearth-\nWilmington area, showing a continuing history of\nquake-published positions contain restraints, both\nprogressive subsidence (table 4), would not appear\ndata sets will be adequate for determining the rela-\nto be significant with respect to the earthquake;\ntive positions of points before and after the earth-\nhowever, the movement at BM 60-40, showing an\nquake and for demonstrating to the courts the dis-\nuplift after 8 years of downtrend, would appear sig-\nplacements that appear to have occurred. In this\nnificant.\napplication of the postearthquake geodetic survey,\nconsistency can be expected to be of greater impor-\nTable 4.-Comparison of elevation changes-subsidence effects\ntance than ultimate accuracy.\nversus earthquake effects\n4 The Southern California Cooperative Leveling\nStations\nProgram provided an excellent base for the evalua-\nBM 5-46C\nBM 60-40\ntion of vertical movements resulting from the earth-\nLocations\nquake.\nNear intersection of Lomita Boule-\nSan Fernando Road, 0.8 mile\n5 A local agency coordinated the field\nvard and Avalon Boulevard in\nsouth of Saugus\nWilmington\nobservation programs of all agencies, resulting in a\nElevations\nmaximum accumulation of data with a minimum of\nYear\nElevation\nYear\nElevation\nduplication of effort.\nFeet\nFeet\n6 The availability of electronic distance-measure-\n1960\n43.395\n1960\n1191.899\nment equipment greatly increased the certainty of\n1964\n43.192\n1966\n1191.710\n1968\n43.071\n1968\n1191.654\npostearthquake positions of the horizontal control\n1971\n*43.008\n1971\n*1192.06\nstations.\n*Preliminary only.","Land Movement Studies Related to Farthquake\n241\nIncreased funds should be provided for geo-\n7\nFailure to make use of large-scale photogram-\n5\nmetric mapping and failure to separate primary hori-\ndetic programs at all levels in earthquake-prone areas\nSO that stress accumulations can be assessed and eval-\nzontal control from secondary control has delayed\nthe publication of final positions and movement data\nuated later if an earthquake should occur.\n6 The publication of constrained-adjustment\nby several months.\n8 The delay in publication of final results has, in\nturn, been detrimental to redevelopment of civil\nTable 5.-Index of triangulation stations used with\nworks in the area. Redevelopment has gone ahead on\nfigures 9 and 10\nless than the best possible data base.\nLACO no.\nStation quad name\nPopular name\n9 The low density of control in the San Gabriel\n1\nACR H-3\nPacifico\nMountains area north of San Fernando constituted a\n2\nALT A-5\nFlint\n3\nBPK H-7\nSawmill\nlimitation on the possible movement analysis.\n4\nBUR J-8\nCahuenga 2\n10 Based on the comparison of preearthquake-\n5\nCAS D-1\nLoma Verde\nChatsworth\n6\nCHA H-6\nand postearthquake-constrained values, the greatest\n7\nDC G-8\nCalabasas\n8\nGV A-10\nBrushy\nmovement of a first-order horizontal control station\n9\nGV C-12\nDeer\noccurred at station Pacoima L-1, with a movement of\n10\nGV D-9\nHouse\n11\nLCR C-11 AUX 1\nVerdugo AUX\n6.35 feet N.69°W.\n12\nLCR H-4\nSister Elsie\n13\nLT I-2\nPort\n11 Based on the preearthquake-constrained ad-\n14\nLT J-2\nMagic\njustment of the Coop Net and the postearthquake-\n15\nMTG B-2\n16\nMTW E-10A\nunadjusted preliminary values, the greatest elevation\n17\nNH B-6\nTowsley\n18\nNH C-1\nLock\nchange of a precise bench mark was + 4.72 feet at\n19\nNH E-10B\nRidge 2\nBM 03-00820-located near the intersection of Foot-\n20\nNH H-1\nNewhall\n21\nNH H-3\nEdison No. 2\nhill Boulevard and Hubbard Street.\n22\nNH I-11\nMission Point\n23\nNH J-8\nEast\n12 No significant change appeared in the eleva-\n24\nPAC B-7\nDarling\ntion of any bench mark along the CDWR line,\nReservoir 1932\n25\nPAC C-1\n26\nPAC E-2 ECC 1\nwhich generally parallels the San Andreas rift zone;\n27\nPAC L-1\nPacoima No. 2\n28\nPAC L-5\nhence, it appears that the San Fernando earthquake\nPIC L-9 AUX 2 ECC 1\nSan Fernando\n29\nhad insignificant, if any, effect in that zone.\nAUX 2 ECC 1\n30\nPIC L-9A\n31\nRAV J-5\nParker\nParker AUX 2\n32\nRAV J-5 AUX 2\nGeneral Recommendations\nRES K-9\n33\nSan Vicente\n34\nRES K-9A\n35\nRR E-10\nHauser\n1\nAs future earthquakes occur, a strong local sur-\n36\nSAU C-9\nYucca\nvey agency should be selected to coordinate all field\n37\nSAU D-5\nLong\n38\nSAU E-3\nBum\nobservation programs and to serve as repository for\n39\nSAU F-1\nSteer\n40\nSAU G-8A\nFoot 2\nearthquake-related observations and data.\n41\nSAU H-5\nDry\n2 Each governing body should provide emer-\n42\nSAU H-11\nSaugus\n43\nSAU J-2\nView\ngency funds for surveying activities and should au-\n44\nSV C-8\nPelona\n45\nSV C-8 ECC 2\nPelona ECC 2\nthorize its commitment at the lowest responsible\n46\nSYL F-8\nlevel in the event of an earthquake. Such funds\n47\nSYL I-6\nMay\n48\nSYL I-12\nshould be available for both direct measurement and\n49\nWPK A-7A\nWhitaker\nWhitaker AUX 1\n50\nWPK A-7A AUX 1\nfor photogrammetric mapping.\n51\nWPK N-15\nCast C\n3 Local governments should actively encourage\n52\nWSM B-13\nFord\n53\nWSM C-10\nDaires\nlateral cooperative surveys SO that in time of emer-\n54\nWSM F-4\nWarm Springs\n55\nWSM F-6\nNecktie\ngency the facilities and skills of all technical branches\n56\nWSM F-13 A\nCharlie\ncan be brought to bear on the problem.\n57\nWSM H-10\nTaylor\n58\nWSM J-8\nElizabeth\n4 The Federal Government should be encour-\n59\nWSM K-11\nPowerhouse\n60\nWSM M-5\nRed 1932\naged to provide NGS and USGS with additional\n61\nWSM N-13\nRock\nhigh-accuracy devices and personnel to expedite the\n62\nZEL H-2\nBluff\n63\nZEL I-6D\nCorner 2\nacquisition and dissemination of geodetic data fol-\n64\nMays 2\n65\nMesa\nlowing an earthquake.","242\nSan Fernando Earthquake of 1971\npositions should be continued for engineering usage,\nOrganizations and agencies that were most helpful\nbut all such data should be dated and be considered\nin providing data, and field and other assistance, are\nincomplete without such a date.\nlisted in Part I-Work Résumé of Agencies. The\nsubcommittee gratefully acknowledges the counsel\nand assistance given them by Charles Whitten, Leon-\nSpecific Recommendations\nard Baker, Buford Meade, Roy Williamson, and Jo-\nRelative to the 1971 San Fernando earthquake, it\nseph Dracup of the National Geodetic Survey.\nis recommended that:\n1 All survey data developed by local agencies\nREFERENCES\npertinent to the event should continue to be submit-\nted to LACO for filing and general access.\nAnonymous, \"Aerospace Charting and Geodetic Service-Cali-\nfornia Earthquake Area,\" The Military Engineer, Vol. 63,\n2 Planning meetings should be scheduled to\nNo. 415, Sept.-Oct. 1971, p. 353.\nprepare the releveling needs for the Southern Cali-\nFranceschini, G. J., and Mitchell, R. J. (Survey Division, Dept.\nfornia Cooperative Leveling Program in keeping\nof Los Angeles County Engineer, Los Angeles, Calif.),\nwith the 1968 plan.\n\"Southern California Cooperative Leveling Program,\" paper\npresented at the 29th annual meeting of the American\nCongress on Surveying and Mapping, Washington, D.C.,\nACKNOWLEDGMENTS\nMar. 9-14, 1969.\nLos Angeles County Earthquake Commission, San Fernando\nThis report was prepared for the NOAA/EERI\nEarthquake, February 9, 1971, Los Angeles, Calif., Nov. 1971,\nSubcommittee on Geodesy. Members of the commit-\n45 pp.\ntee were:\nSavage, James C., Burford, R. O., and Kinoshita, W. T.,\nEarth Movements From Geodetic Measurements, U.S. Geo-\nChairman\nlogical Survey, National Center for Earthquake Research,\nIra H. Alexander, Assistant Chief Deputy County Engi-\nMenlo Park, Calif., Jan. 1972, 41 pp. (unpublished manu-\nneer, Department of County Engineer, County of Los\nscript)\nAngeles.\nU.S. Coast and Geodetic Survey, \"First and Second Order Tri-\nangulation in California (1927 Datum), Special Publication\nJohn A. Lambie, County Engineer, Department of County\n202, U.S. Department of Commerce, Washington, D.C., 1936,\nEngineer, County of Los Angeles (until March 31,\n548 pp.\n1971)\nU.S. Coast and Geodetic Survey, \"The State Coordinate System\nHarvey T. Brandt, County Engineer, Department of\n(a Manual for Surveyors),\" Special Publication 235, U.S.\nCounty Engineer, County of Los Angeles.\nDepartment of Commerce, Washington, D.C., 1945, 62 pp.\nGeorge J. Franceschini, Division Engineer, Survey Divi-\nU.S. Coast and Geodetic Survey, \"Definitions of Terms Used\nsion, Department of County Engineer, County of Los\nin Geodetic and Other Surveys,\" Special Publication 242,\nAngeles.\nU.S. Department of Commerce, Washington, D.C., 1948,\nRichard J. Mitchell, Assistant Division Engineer, Survey\n87 pp.\nDivision, Department of County Engineer, County of\nU.S. Coast and Geodetic Survey, \"Manual of Geodetic Trian-\nLos Angeles.\ngulation,\" Special Publication 247, U.S. Department of Com-\nJohn F. McMillan, Head, Geodetic Section-Survey Divi-\nmerce, Washington, D.C., 1950, 344 pp.\nsion, Department of County Engineer, County of Los\nU.S. Coast and Geodetic Survey, \"Plane Coordinate Projection\nAngeles.\nTables-California (Lambert),\" Special Publication 253,\nHenry Beitler, Chief of Surveys, Los Angeles City Bureau\nU.S. Department of Commerce, Washington, D.C., 1951,\nof Engineering.\n70 pp.","Horizontal Crustal Movements\nDetermined From Surveys\nAfter San Fernando Earthquake\nINTRODUCTION\nHorizontal control surveys from 1922 to 1967 were\ncombined into a single composite network for use as\na preearthquake survey and compared with the re-\nsults of surveys made soon after the February 9,\n1971, earthquake. This net in Los Angeles County is\nCONTENTS\nbounded approximately by latitude 34°08' to 34°42'\nPage\nN. and longitude 118°02' to 118°45' W. Tables 1A\n243 INTRODUCTION\nand 1B list the stations and their respective code\n243\nPREARTHQUAKE TRIANGULATION\nnumbers used in the preearthquake and postearth-\n244\nPOSTEARTHQUAKE TRIANGULATION AND\nTRILATERATION\nquake survey solutions.\n247\nADJUSTMENTS AND RESULTS\nBefore the earthquake, a field party from the Na-\n248\nAdjustment 1\ntional Oceanic and Atmospheric Administration's\n251\nAdjustment 2\n(NOAA) National Ocean Survey was engaged in a\n251\nAdjustment 3\n251\nCONCLUSIONS\nresurvey of Barrel, a small triangulation net, which\n254\nREFERENCES\nhad been established along the route of the Califor-\nnia Aqueduct. After the earthquake, two sites-Bar-\nrel (35 km northeast of the epicenter) and Cast (25\nkm northwest of the epicenter) -were resurveyed to\ndetect possible fault slippage. At the Barrel site, the\nresults of surveys just before and following the earth-\nquake did not show any significant differences. Also,\nthese results were in close agreement with previous\nsurveys of 1964, 1965, 1966, and 1967. At the Cast\nsite, the overall change from 1964 to 1971 indicates\npossible right-lateral movement of a few millimeters,\nalthough in 1971 it was determined that this net-\nwork did not straddle the San Gabriel fault.\nPREEARTHQUAKE TRIANGULATION\nSome of the triangulation stations used in the\nBUFORD K. MEADE\npreearthquake composite network had been used in\nROBERT W. MILLER\nprevious crustal movement studies. The stations used\nNational Geodetic Survey\nin this investigation are listed in table 1C, together\nNational Ocean Survey, NOAA\n243","244\nSan Fernando Earthquake of 1971\nSUMMARY KEY TO TABLES\nwith the dates the stations were established and the\ndates of the survey observations used in the adjust-\nPage\nHORIZONTAL CONTROL STATIONS\nment. This network is shown in figure 1A.\nPREEARTHQUAKE STATION INDEXES: Table 1A\n245\nThe combined first-order horizontal directions\nPOSTEARTHQUAKE STATION INDEXES: Table 1B\n246\nused in the preearthquake adjustment are listed in\nCOMMON PREEARTHQUAKE AND POSTEARTHQUAKE\ntable 2A.\nSTATIONS: Table 1C\n247\nSix of the lines in the preearthquake network had\nPREEARTHQUAKE TRIANGULATION\nbeen measured with the Geodimeter. Two other dis-\nOBSERVED HORIZONTAL DIRECTIONS: Table 2A\n249\ntances, previously determined in an adjustment of\nMEASURED LENGTHS: Table 2B\n250\nthe Los Angeles City (LAC) net, were used with the\nsix Geodimeter distances to provide length control.\nPOSTEARTHQUAKE TRIANGULATION AND\nThese values are listed in table 2B.\nTRILATERATION\nOBSERVED HORIZONTAL DIRECTIONS: Table 3A\n253\nMEASURED LENGTHS: Table 3B\n255\nPOSTEARTHQUAKE TRIANGULATION AND\nAZIMUTH CONTROL: Table 4A\n256\nTRILATERATION\nTRIANGLE CLOSURES: Table 4B\n256\nELEVATIONS OF STATIONS: Table 4C\n256\nShortly after the earthquake, a resurvey was made\nADJUSTMENTS AND RESULTS\nto measure earth movement. It was a cooperative ef-\nADJUSTMENT I\nfort by personnel of the National Ocean Survey\nCorrections to directions:\n(NOS) the Los Angeles County Engineer (LACE)\nPreearthquake: Table 5A\n257\nand the Los Angeles City Bureau of Engineering\nPostearthquake: Table 5B\n259\n(LACBE) using first-order class-I specifications.\nCorrections to lengths:\nThis network of stations is shown in figure 1B.\nPreearthquake: Table 6A\n260\nPostearthquake: Table 6B\n261\nObservations made by LACE and LACBE and in-\nAdjusted geographic positions:\ncorporated in the postearthquake adjustments are as\nPreearthquake: Table 7A\n263\nfollows:\nPostearthquake: Table 7B\n264\nPosition shifts: Table 8A\n265\nError ellipses: Table 9A\n266\nLACE\nLACBE\nParameters of strain: Table 10\n268\nstation numbers\nstation\nnumbers\nADJUSTMENT 2\nCorrections to directions:\n701\n717\n729\n746\n706\n702\n720\n732\n747\n718\nPreearthquake: Table 5C\n273\n703\n724\n736\n752\n719\nPostearthquake: Table 5D\n275\n707\n726\n737\n766\n721\nCorrections to lengths:\n715\n727\n738\nPreearthquake: Table 6C\n276\nPostearthquake: Table 6D\n277\nFour stations that could not be recovered or found\nAdjusted geographic positions:\nwere replaced by the following stations: Foot 2, Pa-\nPreearthquake: Table 7C\n279\ncoima E-2 ECC 1, Ridge 2, and Verdugo AUX.\nPostearthquake: Table 7D\n280\nPosition shifts: Table 8B\n281\nAll observations used in these adjustments were\nmade after the February 9, 1971, earthquake except\nADJUSTMENT 3\nfor station Rock (751), observed in July 1963, and\nCorrections to directions:\nPreearthquake: Table 5E\n283\nstations Cast (760), Fork (761) and Necktie (763),\nPostearthquake: Table 5F\n285\nobserved in July 1964. These four stations, near the\nCorrections to lengths:\nnorthern edge of the project, were included to\nPreearthquake: Table 6E\n286\nstrengthen the net. Postearthquake observations at\nPostearthquake: Table 6F\n287\nadjacent stations were in very close agreement with\nAdjusted geographic positions:\nPreearthquake: Table 7E\n289\nthe preearthquake values, and these observational\nPostearthquake: Table 7F\n290\nchecks indicated there were no significant move-\nPosition shifts: Table 8C\n291\nments in this area.\nError ellipses: Table 9B\n292","Horizontal Crustal Movements\n245\nStation name\nThe following seven auxiliary new stations were\nStation number\nPico L-9A\ntied to previously established stations by distance\n736\nPico L-9 AUX 2 ECC 1 (San Fernando\n737\nand direction:\nAUX 2 ECC 1).\nWPK A-7A AUX 1\n766\nStation number\nStation name\nThe postearthquake horizontal directions are\nPacoima E-2 ECC 1 (Aqueduct #1 ECC 1)\n706\nlisted in table 3A. At the following eight stations,\n720\nMTW E-10A\nParker AUX 2\n726\nhorizontal directions observed by NOS and LAC\n733\nPelona ECC 2\nTable 1A.-Numerical and alphabetical indexes of stations used in preearthquake survey\nAlphabetical station name\nNumerical station name\nStation no.\nStation no.\nAqueduct No. 1 Pacoima E-2 LAC\nCalabasas USGS LAC&C\n006\n001\nSan Vicente No. 1 LAWD LAC&C\n036\nBee\n002\nChatsworth USGS LAC&C\n011\nBluff\n003\nBrushy\nSylmar F-8 LAC\n040\n004\nPacoima L-1 LAC\n045\nBum\n005\nCahuenga 2 LAC\nAqueduct No. 1 Pacoima E-2 LAC\n017\n006\nCalabasas USGS LAC&C\n001\n007\nSylmar I-12 LAC\nChatsworth USGS LAC&C\n008\nSylmar I-9 LAC\n003\n010\nCorner 2\n009\nReservoir\nDarling USGS LAC&C\n014\n010\nCorner 2\nDeer USGS Green Valley C-12 LAC\n059\n011\nBluff\n046\nDry\n012\nMission Pt.\n054\nEast\n013\nRidge\nEdison\nDarling USGS LAC&C\n055\n014\nFernando 2 USGS LAC&C\nPacoima No. 2 LAC&C\n016\n015\nFlint LAWD LAC&C\nFernando 2 USGS LAC&C\n019\n016\nFoot\nCahuenga 2 LAC\n048\n017\nGleason\nVerdugo USGS LAC&C\n023\n018\nFlint LAWD LAC&C\n029\nHauser\n019\n038\nHouse\nWilson Peak\n020\nSister Elsie USGS LAC&C\n022\nIron\n021\nJupiter Mt. USGS\n035\n022\nIron\n051\nLock\n023\nGleason\nLoma Verde USGS LAC\n060\n024\nPacifico\n047\nLong\n025\nPacifico\n031\nMagic\n026\nVince\nMay\nMt. Gleason LAC\n056\n027\n012\nMission Pt.\n028\nTenhi\nMt. Gleason LAC\n027\n029\nHauser\n052\nNewhall\n030\nParker\n024\nPacifico\n031\nMagic\nPacifico\nPort Little Tujunga I-2 LAC\n025\n032\nPacoima L-1 LAC\nPelona ECC 2 LAC\n005\n033\nPacoima No. 2 LAC&C\n015\n034\nPelona\nParker\n035\nJupiter Mt. USGS\n030\n034\nPelona\n036\nBee\nPelona ECC 2 LAC\n033\n037\nSurge\nPico L-9 AUX 2 ECC 1 S F AUX 2 ECC 1 LAC\n058\n038\nHouse\nPort Little Tujunga I-2 LAC\n032\n039\nRed\n041\nPowerhouse\n040\nBrushy\n039\nRed\n041\nPowerhouse\n009\nReservoir\n042\nRock\n013\nRidge\n043\nSteer\n042\nRock\n044\nView\n057\nSan Fernando\n045\nBum\nSan Vicente No. 1 LAWD LAC&C\n002\n046\nDry\n050\nSaugus\n047\nLong\n064\nSawmill\n048\nFoot\nSister Elsie USGS LAC&C\n021\n049\nYucca\n043\nSteer\n050\nSaugus\n037\nSurge\n051\nLock\nSylmar F-8 LAC\n004\n052\nNewhall\nSylmar I-9 LAC\n008\n053\nTowsley\nSylmar I-12 LAC\n007\n054\nEast\n028\nTenhi\n055\nEdison\n053\nTowsley\n056\nMay\nVerdugo USGS LAC&C\n018\n057\nSan Fernando\nPico L-9 AUX 2 ECC 1 SF AUX 2 ECC 1 LAC\n044\nView\n058\nVince\nDeer USGS Green Valley C-12 LAC\n026\n059\n063\nWarm Springs\n060\nLoma Verde USGS LAC\nWPK A-7A AUX 1 Whitaker LOT AUX 1 LAC\n062\nWhitaker\n061\n020\nWilson Peak\n062\nWhitaker\nWhitaker LOT AUX 1 LAC\nWPK A-7A AUX 1\n061\n063\nWarm Springs\n049\nYucca\n064\nSawmill","246\nSan Fernando Earthquake of 1971\nTable 1B.-Numerical and alphabetical indexes of stations used in postearthquake survey\nStation no.\nNumerical station name\nStation no.\nAlphabetical station name\n701\nCalabasas USGS LAC&C\n711\nBluff\n702\nRES K-9A LAC\n754\nBrushy\n703\nChatsworth USGS LAC&C\n748\nBum\n704\nSylmar F-8 LAC\n717\nCahuenga 2 LAC\n705\nPacoima L-1 LAC\n701\nCalabasas USGS LAC&C\n706\nPAC E-2 ECC 1 LAC\n760\nCast C\n707\nSylmar I-12 LAC\n757\nCharlie\n709\nReservoir\n703\nChatsworth USGS LAC&C\n710\nCorner 2\n710\nCorner 2\n711\nBluff\n762\nDaires\n712\nMission Pt.\n752\nDeer USGS Green Valley C-12 LAC\n713\nRidge 2\n747\nDry\n715\nPacoima No. 2 LAC&C\n735\nEast\n717\nCahuenga 2 LAC\n739\nEdison\n718\nVerdugo AUX LAC\n759\nElizabeth\n719\nFlint LAWD LAC&C\n719\nFlint LAWD LAC&C\n720\nMTW E-10A LAC\n745\nFoot 2\n721\nSister Elsie USGS LAC&C\n761\nFork CDWR\n724\nPacifico\n729\nHauser\n726\nParker AUX 2 LAC\n753\nHouse\n727\nMt. Gleason LAC\n742\nLock\n729\nHauser\n764\nLoma Verde USGS LAC\n730\nParker\n746\nLong\n731\nMagic\n731\nMagic\n732\nPort Little Tujunga I-2 LAC\n738\nMay\n733\nPelona ECC 2 LAC\n712\nMission Pt.\n734\nPelona\n727\nMt. Gleason LAC\n735\nEast\n720\nMTW E-10A LAC\n736\nPico L-9A LAC\n763\nNecktie\n737\nPico L-9 AUX 2 ECC\n1\nSF AUX 2 ECC 1 LAC\n741\nNewhall\n738\nMay\n706\nPAC E-2 ECC 1 LAC\n739\nEdison\n724\nPacifico\n740\nTowsley\n705\nPacoima L-1 LAC\n741\nNewhall\n715\nPacoima No. 2 LAC&C\n742\nLock\n730\nParker\n743\nSaugus\n726\nParker AUX 2 LAC\n744\nYucca\n734\nPelona\n745\nFoot 2\n733\nPelona ECC 2 LAC\n746\nLong\n737\nPico L-9 AUX 2 ECC 1 S F AUX 2 ECC 1 LAC\n747\nDry\n736\nPico L-9A LAC\n748\nBum\n732\nPort Little Tujunga I-2 LAC\n749\nView\n756\nPowerhouse\n750\nSteer\n755\nRed\n751\nRock\n702\nRES K-9A LAC\n752\nDeer USGS Green Valley C-12 LAC\n709\nReservoir\n753\nHouse\n713\nRidge 2\n754\nBrushy\n751\nRock\n755\nRed\n743\nSaugus\n756\nPowerhouse\n768\nSawmill\n757\nCharlie\n721\nSister Elsie USGS LAC&C\n758\nTaylor\n750\nSteer\n759\nElizabeth\n704\nSylmar F-8 LAC\n760\nCast C\n707\nSylmar I-12 LAC\n761\nFork CDWR\n758\nTaylor\n762\nDaires\n740\nTowsley\n763\nNecktie\n718\nVerdugo AUX LAC\n764\nLoma Verde USGS LAC\n749\nView\n765\nWhitaker\n767\nWarm Springs\n766\nWPK A-7A AUX 1\nWhitaker LOT AUX 1 LAC\n765\nWhitaker\n767\nWarm Springs\n766\nWPK A-7A AUX 1\nWhitaker LOT AUX 1 LAC\n768\nSawmill\n744\nYucca\nwere combined and used in the adjustments: Hauser\nGeodimeter. Twenty-two of the distances were meas-\n(729), Port (732), Pico L-9 AUX 2 ECC 1 (737)\nured by LAC and two by the U.S. Geological Survey\nMay (738), Long (746), Dry (747), Deer (752)\n(USGS) The two USGS distances were taken from\nand WPK A-7A AUX 1 (766)\na preliminary report (Savage 1971) These were in-\nA very large percentage of the lines in the post-\ncluded to obtain a postearthquake position for sta-\nearthquake survey was measured with the Geodime-\ntion Sylmar I-12 (707) All of the measured dis-\nter. Most of these distances were measured by NOS,\ntances are listed in table 3B.\nwith some assistance by LACE, using a laser-type\nOther observational and statistical data used in the","Horizontal Crustal Movements\n247\nTable 1C.-Preearthquake network of stations used in\ninvestigation are listed in tables 4A, 4B, and 4C, as\npostearthquake investigation\nfollows:\nStation\nYear\nYear of\nTable 4A-lines used for azimuth control;\nnumber\nStation name\nestablished\nsurvey\nTable 4B-average and maximum triangle closures of the pre-\nused\nearthquake and postearthquake surveys; and\n1\n*Calabasas\n1933\n1934\nTable 4C-elevations of stations used in reduction of Geodimeter\n2\n*San Vicente No. 1\n1933\n1934\n3\n*Chatsworth\n1933\n1934\ndistances.\n4\n*Sylmar F-8\n1935\n1936\n5\n*Pacoima L-1\n1935\n1936\nADJUSTMENTS AND RESULTS\n6\n*Aqueduct No. 1\n1924\n1936, 1955\n7\n*Sylmar I-12\n1936\n1936\nIn an attempt to obtain a geometrical representa-\n8\n*Sylmar I-9\n1936\n1936\n9\nReservoir\n1932\n1932-63\ntion of horizontal crustal movement in the region,\n10\nCorner 2\n1963\n1963\nseveral hypotheses based on physical and geological\n11\nBluff\n1932\n1963\n12\nMission Pt\n1932\n1963\nevidence may be assumed. In this study, three as-\n13\nRidge\n1932\n1963\nsumptions were made and tested with the same ob-\n14\n*Darling\n1933\n1934, 1936\n15\n*Pacoima No. 2\n1933\n1934-55\nservational data. The first assumption (adjustment\n16\n*Fernando 2\n1933\n1934, 1955\n1) provided for the possibility that all stations, ex-\n17\n*Cahuenga 2\n1933\n1934\ncept one station used for position control, may shift.\n18\n*Verdugo\n1933\n1934, 1958\n19\n*Flint\n1933\n1934\nThe second assumption (adjustment 2) hypothesized\n20\nWilson Peak\n1890\n1934, 1958\nthat stations along the outer rim of the net have not\n21\n*Sister Elsie\n1933\n1934, 1958\n22\nIron\n1958\n1958\nmoved between surveys. The third assumption (ad-\n23\nGleason\n1958\n1958\njustment 3) relaxed the condition of no movement\n24\nPacifico\n1958\n1958\n25\nPacifico\n1958\n1964\nalong the western side of the project at stations Chats-\n26\nVince\n1938\n1940, 1958\nworth, San Fernando, Pico L-9 AUX 2 ECC 1, and\n27\n*Mt. Gleason\n1965\n1965\n28\nTenhi\n1938\n1938-64\nPico L-9A. The same observational data were used\n29\nHauser\n1938\n1938-65\nfor each of the three adjustments. The only varia-\n30\nParker\n1940\n1940-65\ntions were the constraints on positions. All adjust-\n31\nMagic\n1958\n1958\n32\n*Port\n1964\n1964\nments were referenced to the North American\n33\n*Pelona ECC 2\n1961\n1965\nDatum of 1927.\n34\nPelona\n1932\n1932-67\n35\nJupiter Mt\n1932\n1963\nUnit weight, based on a standard error of 0.\"5, was\n36\nBee\n1932\n1963\nassigned to each direction and azimuth observation.\n37\nSurge\n1932\n1963\n38\nHouse\n1932\n1963\nWeights for the Geodimeter measurements were\n39\nRed\n1932\n1932-64\nbased on the following equation for standard error,\n40\nBrushy\n1932\n1963\n41\nPowerhouse\n1932\n1963\nstandarderror=0.006m+1ppm+5/3HX105, =\n42\nRock\n1932\n1963\n43\nSteer\n1932\n1963\nwhere AH is the difference in elevation between ter-\n44\nView\n1932\n1963\n45\nBum\n1932\n1963\nminals of the line.\n46\nDry\n1932\n1963\nUnit weight for the distance observations, equiva-\n47\nLong\n1932\n1963\n48\nFoot\n1932\n1963\nlent to 0.\"5 for the direction observations, is then a\n49\nYucca\n1932\n1963\nstandard error of one part in 412,000 of the distance.\n50\nSaugus\n1932\n1963\nIn the adjustment procedure used, that is, by vari-\n51\nLock\n1932\n1963\nation of geographic coordinates, observation equa-\n52\nNewhall\n1932\n1963\n53\nTowsley\n1932\n1963\ntions were formed for each direction, azimuth, and\n54\nEast\n1932\n1963\n55\nEdison\n1932\n1963\nlength observation. These observation equations\nwere then multiplied by a factor proportional to the\n56\nMay\n1932\n1932-64\n57\nSan Fernando\n1898\n1922-65\na priori value of the standard error of unit weight.\n*Pico L-9 AUX 2 ECC 1\n58\n1961\n1964-65\n59\n*Deer\n1964\n1964-65\nIn some of the tabulated results, these multipliers\n60\nLoma Verde\n1932\n1932-67\nare identified as weight factors.\n61\n*WPK A-7A AUX 1\n1964\n1964\nThe standard error of an observation of unit\n62\nWhitaker\n1941\n1941-65\n63\nWarm Springs\n1941\n1941-65\nweight, as obtained from the adjustments, was in\n64\nSawmill\n1932\n1932-67\nvery close agreement with the a priori value assigned.\nStation established by LAC.","San Fernando Earthquake of 1971\n248\nSAN FERNANDO EARTHQUAKE AREA\nPRE EARTHQUAKE ADJUSTMENT\nSTATIONS ARE NOT NECESSARILY PLOTTED\nIN TRUE LOCATIONS IN CONGESTED AREAS\n39\n41\n43\n*****\nthe 45\n47\n46\n49\n51\n27 1.\n..........\nFigure 1A.-Preearthquake - triangulation net (1922-1967).\nAdjustment 1\nfixed. Variance-covariance matrices were computed\nto determine error ellipses for stations common to\nA free adjustment (the network is not constrained\nthe two surveys.\nto fit previously adjusted geographic positions) was\nmade using the least-squares variation of geographic\nResults\ncoordinates method and all of the combined\npreearthquake observations. Another free adjustment\nThe corrections applied to the horizontal direc-\nwas made using the postearthquake observations.\ntions are given in table 5A for the preearthquake\nOnly one position, station Cahuenga 2, was held\nsurvey and in table 5B for the postearthquake sur-","Horizontal Crustal Movements\n249\nTable 2A.-Preearthquake observed horizontal directions-Continued\nTable 2A.-Preearthquake observed horizontal directions\nObserved\nStation\nObserved\nStation\nObserved\nStation\nObserved\nStation\ndirection\ndirection\ndirection\ndirection\nFrom\nTo\nFrom\nTo\nFrom\nTo\nFrom\nTo\no\no\no\no\n020\n032\n001\n012\n017\n341 09 59.64\n056\n000 00 00.00\n003\n000 00 00.00\n010\n103 37 44.08\n059\n072 15 00.46\n057\n009 00 15.80\n011\n128 35 14.18\n021\n033\n105 16 03.75\n014\n048 52 51.96\n013\n222 55 50.33\n018\n359 59 59.66\n029\n142 43 21.28\n313 43 12.75\n002\n093 46 46.23\n054\n015\n055 30 56.65\n030\n163 43 14.40\n002\n013\n056\n085 30 31.39\n027\n202 05 41.92\n359 38 19.63\n001\n000 00 00.00\n057\n016\n087 24 31.63\n031\n203 22 49.23\n003\n044 32 19.54\n054\n128 47 34.72\n031\n118 23 37.07\n033\n012\n179 16 20.54\n153 31 29.11\n057\n064 07 11.78\n022\n029\n000 00 00.00\n014\n093 44 51.68\n011\n219 18 28.08\n023\n173 58 30.28\n030\n035 16 03.13\n016\n103 32 45.31\n014\n020\n254 43 08.62\n027\n044 27 08.73\n015\n116 51 26.86\n057\n000 00 00.00\n019\n309 16 00.75\n032\n076 36 57.79\n018\n149 57 51.64\n006\n074 39 49.14\n017\n356 22 16.27\n056\n100 03 53.66\n076 44 07.99\n017\n170 59 43.51\n016\n022\n059\n158 20 36.08\n005\n103 22 08.58\n003\n023\n000 00 00.00\n034\n122 48 30.00\n057\n000 00 00.00\n015\n021\n126 55 03.80\n026\n062 21 59.16\n016\n038 10 59.29\n017\n176 29 45.86\n031\n237 58 28.76\n030\n088 21 20.75\n014\n070 49 05.72\n002\n237 29 32.20\n023\n031\n126 34 11.65\n002\n116 02 26.78\n001\n278 50 48.31\n022\n000 00 00.00\n056\n152 59 46.02\n001\n157 43 22.02\n003\n323 03 40.59\n031\n036 14 05.91\n060\n212 46 06.92\n004\n015\n030\n098 01 03.55\n036\n234 04 38.10\n008\n000 00 00.00\n016\n359 59 59.79\n026\n146 54 00.71\n039\n237 13 02.76\n005\n015 11 34.25\n005\n007 55 24.28\n024\n207 54 26.94\n064\n264 40 31.46\n007\n028 11 46.00\n021\n092 26 32.89\n020\n269 06 16.08\n035\n274 50 40.28\n015\n029 32 05.45\n018\n119 06 15.73\n021\n327 22 05.24\n035\n006\n064 12 02.77\n017\n156 15 16.05\n024\n036\n000 00 00.00\n005\n002\n217 32 08.07\n020\n000 00 00.00\n038\n034 04 14.97\n015\n000 00 00.00\n014\n259 44 32.29\n023\n078 50 47.92\n039\n062 22 15.18\n014\n052 22 46.86\n057\n297 16 19.94\n026\n147 02 31.61\n037\n068 02 30.38\n006\n082 51 46.45\n009\n297 43 09.19\n025\n064\n104 15 51.66\n007\n116 17 32.28\n006\n304 45 55.69\n027\n000 00 00.00\n034\n297 38 21.94\n004\n134 41 16.31\n004\n336 57 11.75\n029\n045 36 24.97\n036\n008\n143 39 30.46\n056\n353 28 46.25\n028\n055 22 36.63\n038\n000 00 00.00\n006\n016\n026\n037\n055 11 23.39\n004\n000 00 00.00\n021\n000 00 00.00\n023\n042 55 39.31\n035\n122 30 17.75\n020 49 38.78\n056\n016 26 42.22\n018\n030\n083 42 20.08\n034\n199 22 36.54\n016\n023 25 33.60\n017\n041 01 03.77\n034\n122 49 59.40\n037\n008\n028 23 16.13\n015\n055 39 52.49\n024\n352 07 51.08\n039\n000 00 00.00\n079 53 19.91\n007\n048 55 20.10\n002\n027\n035\n190 02 26.70\n005\n079 10 01.69\n014\n089 20 03.85\n032\n000 00 00.00\n036\n234 41 01.21\n090 42 35.08\n015\n113 08 46.69\n006\n033\n051 00 32.71\n038\n300 40 29.20\n014\n199 58 42.72\n009\n104 08 19.07\n030\n069 03 14.31\n040\n317 39 32.72\n123 01 27.55\n009\n269 07 22.81\n003\n029\n081 11 27.90\n038\n141 41 06.99\n007\n057\n028\n102 04 14.50\n039\n000 00 00.00\n004\n000 00 00.00\n056\n144 46 35.82\n025\n182 26 54.95\n037\n074 48 02.35\n008\n033 41 13.54\n017\n035\n110 11 44.10\n005\n148 36 02.53\n002\n000 00 00.00\n028\n006\n264 55 34.59\n014\n041 45 24.00\n027\n155 01 10.59\n036\n133 37 09.30\n040\n300 49 39.85\n182 40 30.20\n008\n015\n064 34 53.69\n030\n039\n005\n000 00 00.00\n016\n073 40 48.81\n029\n250 10 09.04\n064\n000 00 00.00\n007\n037 43 13.25\n018\n118 58 01.01\n029\n037\n094 40 32.57\n006\n068 25 30.48\n021\n121 37 31.54\n028\n176 55 10.43\n035\n099 02 43.10\n004\n155 50 11.61\n020\n161 21 15.56\n025\n207 45 19.59\n034\n116 41 11.48\n009\n019\n169 02 19.43\n027\n240 53 26.67\n038\n140 32 59.48\n012\n000 00 00.00\n018\n030\n251 40 12.40\n040\n170 41 29.86\n056\n100 51 42.26\n021\n000 00 00.00\n032\n280 19 37.34\n056\n177 50 25.32\n010\n280 26 26.50\n020\n054 55 59.30\n033\n346 15 21.00\n042\n190 37 08.86\n011\n326 26 57.38\n019\n094 23 35.89\n030\n041\n209 41 12.52\n016\n105 47 59.00\n017\n173 42 45.12\n026\n000 00 00.00\n060\n249 20 58.04\n006\n158 04 04.37\n002\n213 42 56.14\n023\n090 20 20.03\n063\n297 14 06.92\n015\n175 02 41.87\n015\n262 10 38.87\n027\n092 14 05.02\n040\n285 35 44.25\n010\n056\n031\n161 40 27.28\n042\n000 00 00.00\n011\n000 00 00.00\n016\n288 14 08.69\n032\n164 48 21.74\n041\n045 04 48.51\n012\n018 03 58.14\n019\n033\n245 00 16.48\n039\n129 58 13.33\n009\n067 54 04.11\n017\n000 00 00.00\n034\n245 07 00.98\n037\n191 36 47.49\n011\n018\n050 36 32.14\n029\n295 09 04.84\n038\n220 39 21.73\n028\n332 54 24.91\n057\n359 52 07.78\n021\n085 28 58.48\n041\n013\n017 18 26.78\n020\n165 39 02.69\n031\n043\n000 00 00.00\n012\n062 55 41.96\n000 00 00.00\n020\n034\n039\n177 37 22.46\n056\n104 21 06.86\n018\n359 59 59.80\n030\n058 20 35.25\n040\n233 44 15.88\n009\n133 48 49.78\n105 13 31.12\n057\n016 08 03.33\n023\n042\n293 42 23.25\n010\n199 54 13.41\n021\n019 47 10.14\n022\n126 57 51.46\n044\n322 24 48.76\n021\n160 46 37.53\n012\n023\n060 46 42.20\n259 56 38.95\n042\n056\n000 00 00.00\n024\n100 44 06.65\n056\n334 30 04.40\n032\n281 08 09.30\n044\n000 00 00.00\n009\n053 01 24.17\n019","250\nSan Fernando Earthquake of 1971\nTable 2A.-Preearthquake observed horizontal directions-Continued\nTable 2A.-Preearthquake observed horizontal directions-Continued\nStation\nObserved\nStation\nObserved\nStation\nObserved\nStation\nObserved\ndirection\ndirection\ndirection\ndirection\nFrom\nTo\nFrom\nTo\nFrom\nTo\nFrom\nTo\nO\nO\n\"\n042\n054\n061\n063\n043\n050\n35\n52.96\n056\n000 00 00.00\n033\n000\n00\n00.00\n062\n041 45 11.15\n041\n123\n39\n14.97\n012\n114 40 26.08\n059\n007\n52\n38.52\n064\n152 16 30.94\n039\n168\n30\n08.99\n013\n153 24 17.65\n056\n038\n27\n34.13\n039\n244 21 43.04\n040\n198 36 18.13\n057\n173 52 28.47\n058\n062\n29\n01.54\n059\n270 24 07.44\n043\n053\n197 35 41.29\n062\n058\n327 14 52.77\n045\n000 00 00.00\n055\n253 31 43.80\n063\n071\n29\n19.81\n064\n041\n161 17 17.70\n052\n262 09 08.20\n034\n084\n19\n45.68\n034\n359 59 59.63\n042\n201\n56\n19.18\n055\n059\n092\n17\n30.84\n056\n034 21 57.34\n044\n248 51 20.02\n054\n000 00 00.00\n060\n132\n28\n56.72\n039\n035 51 20.54\n046\n311 49 13.58\n057\n072 19 53.40\n057\n146\n55\n13.77\n063\n061 00 17.00\n044\n053\n089\n40\n07.28\n063\n060\n076\n26\n20.03\n046\n000 00 00.00\n051\n138\n16\n35.60\n060\n000 00 00.00\n035\n356\n47\n40.25\n045\n040 20 47.59\n052\n204\n01\n03.40\n043\n070 48 37.69\n056\n041\n125 39 25.27\n034\n359 59 59.92\nTable 2B.-Preearthquake measured lengths\n042\n153 17 43.61\n033\n000 02 41.55\n045\n032\n051 19 41.80\nStation\nMeasured\n047\n000 00 00.00\n031\n053 31 05.81\nlength\n043\n193 50 12.84\n016\n068 08 32.58\nFrom\nTo\n044\n232 13 44.11\n021\n101 27 57.96\n046\n287 06 46.88\n018\n121 33 09.92\nm\n048\n314 08 34.01\n015\n152 30 33.81\n1\n3\n12988.206\n046\n006\n187 05 39.37\n1\n17\n29502.131\n048\n000 00 00.00\n009\n202 33 59.32\n16\n56\n1139.270\n047\n088 47 29.92\n011\n218 41 32.64\n31\n32\n1049.944\n045\n123 35 03.13\n012\n228 40 52.10\n31\n34\n19695.796\n043\n162 07 42.38\n057\n244 49 49.64\n34\n64\n23866.161\n044\n208 21 11.14\n058\n245 06 10.17\n39\n63\n5237.752\n047\n054\n247 43 39.78\n60\n63\n13700.048\n049\n000 00 00.00\n052\n279 19 17.31\n045\n190 45 24.95\n060\n289 50 55.22\n* LAC adjusted length.\n046\n263 04 38.29\n061\n293 31 11.34\n048\n306 20 56.70\n039\n325 22 30.75\nvey. The corrections to the measured lengths are\n050\n320 02 20.64\n064\n326 02 41.53\n048\n059\n331 03 04.16\nlisted in tables 6A and 6B for preearthquake and\n050\n000 00 00.00\n057\n049\n081 54 31.96\npostearthquake surveys, respectively.\n062\n121 31 44.70\n047\n142 34 26.78\n060\n129 11 52.73\n045\n161 07 29.87\nAdjusted geographic positions and plane coordi-\n053\n165 21 17.34\n046\n190 30 38.97\n059\n174 18 54.59\nnates, based on the California Plane Coordinate Sys-\n049\n052\n187 50 00.20\n047\n000 00 00.00\ntem Zone 7, are listed in tables 7A (preearthquake)\n055\n197 31 28.54\n048\n065 41 01.91\n054\n225 32 20.64\nand 7B (postearthquake) From these listings, the\n050\n101 41 21.25\n016\n228 59 17.34\n056\n111 47 02.90\n056\n228 46 03.10\nposition shifts were computed for stations common\n052\n123 31 56.78\n020\n250 57 42.51\n051\n173 21 07.87\nto the preearthquake and postearthquake surveys.\n013\n255 54 55.98\n050\n015\n260 14 23.69\nThey are given in table 8A. Table 9A lists the error\n052\n000 00 00.00\n011\n278 08 45.37\n051\n067 40 16.00\n014\n279 54 05.61\nellipses and 95-percent confidence levels as they refer\n049\n121 20 34.27\n002\n307 45 57.40\n047\n159 41 35.64\nto station Cahuenga 2, and figure 2A illustrates the\n001\n338 52 18.06\n048\n183 25 44.06\n003\n352 08 37.84\nposition vectors and error ellipses between the\n051\n058\n049\n000 00 00.00\npreearthquake and postearthquake surveys. The posi-\n061\n000 00 00.00\n050\n054 39 54.19\n063\n030 06 41.27\n052\n086 25 43.37\ntion changes of greatest significance were in the areas\n059\n052 55 49.69\n055\n112 27 50.46\n056\n107 33 30.37\nof surface faulting, and the maximum change OC-\n053\n186 24 13.32\n052\n059\ncurred at station Pacoima L-1. Because independent\n058\n055\n000 00 00.00\n000 05 46.26\n061\n057\n072 33 33.86\n038 37 22.86\norientation was not available for each survey, some\n063\n053\n100 25 53.15\n048 48 09.06\nuncertainty was introduced into the direction of the\n033\n051\n227 56 40.63\n088 13 23.93\n032\n049\n293 11 59.67\n131\n58\n28.50\nposition vectors most distant from the control. Fig-\n056\n050\n320 40 21.94\n168 47 19.54\n056\nure 2A indicates a possibility of weakness in the\n294 02 53.35\n060\n054\n344 36 22.41\n064\n000 00 00.00\norientation of the net.\n053\n063\n012 17 26.82\n051\n000 00 00.00\n039\n028 45 59.38\nParameters of strain were computed using ad-\n052\n040 36 15.08\n034\n051 39 17.13\njusted data for triangles formed by common stations;\n055\n057 27 09.46\n056\n101 43 52.57\n054\n091 50 59.54\n057\n137 08 38.24\nthese parameters are listed in table 10. An\n057\n187\n56\n44.57\n062\n295 02 13.52","Horizontal Crustal Movements\n251\nTables 7C and 7D list the adjusted geographic po-\nexplanation of the method of computing strain and\nsitions, and figure 2B illustrates the vectors for the\nits interpretation is given by Pope (1969). Figures\nposition differences listed in table 8B. Vectors in the\n3A and 3B illustrate the maximum positive shear\nareas of surface faulting are very similar to the vec-\n(y) given in table 10. Maximum shear and 0 are the\ntors in figure 2A for adjustment 1. However, the re-\ncomponents least affected by errors of orientation\nquirement that the position shift at stations on the\nand scale. The orientation of maximum shear is 45°\nwest side of the net for the preearthquake survey be\nclockwise from the orientation of maximum exten-\nequal to the position shift at the respective stations\nsion (OE1) Because the position shifts are SO large in\nin the postearthquake survey increases the residuals\nthe area of surface breakage, a more detailed break-\nat some stations in both surveys. The increase is\ndown of the area should be used to clarify the shear\ngreater than expected from random error alone, par-\nadequately. Figure 3A shows the area where y\nticularly at station San Fernando. Adjustment 3 is\namounts to more than one part in 20,000.\nthe response to this analysis.\nFigure 3B illustrates y for all triangles in which\nshear is less than one part in 20,000. The outstand-\ning feature of this illustration is the consistent pat-\nAdjustment 3\ntern of shear in the Newhall-Saugus area. To sub-\nIn adjustment 3, the conditional equations affect-\nstantiate the fact that the adjustments do not\ning position changes at stations Chatsworth, San Fer-\nsignificantly affect these results, computations for\nnando, Pico L-9A, and Pico L-9 AUX 2 ECC 1\nshear-using a variation of Frank's (1966) formulas\nwere removed. All other input data for the preearth-\nfor unadjusted observations-were made as an inde-\nquake and postearthquake surveys remained the\npendent check. The pattern of y obtained from these\nsame as in adjustment 2. A variance-covariance ma-\ncomputations is essentially the same.\ntrix was also added to obtain error ellipses.\nFigure 4 illustrates the principal axes of strain.\nThe pattern for the Newhall-Saugus area is clear,\nResults\nbut other areas are not uniform.\nThe corrections applied to the horizontal direc-\ntions are given in table 5E for the preearthquake\nAdjustment 2\nsurvey and in table 5F for the postearthquake sur-\nAdjustment 2 required that position shifts for the\nvey. The corrections applied to the measured lengths\npreearthquake survey be the same position shifts as\nare listed in tables 6E and 6F for the preearthquake\nin the postearthquake survey for the following sta-\nand postearthquake surveys, respectively.\ntions: Calabasas, Flint, Hauser, Loma Verde, Paci-\nTables 7E (preearthquake) and 7F (postearth-\nfico, Pelona, Pelona ECC 2, Pico L-9A, Pico L-9\nquake) list the adjusted geographic positions and\nplane coordinates. The position differences between\nAUX 2 ECC 1, Red, San Fernando, Sawmill, Warm\nthe two surveys, as determined by adjustment 3, are\nSprings, Whitaker, and WPK A-7A AUX 1. To sat-\ngiven in table 8C. Table 9B lists the error ellipses\nisfy these conditions and to allow freedom of move-\nand 95-percent confidence regions, and figure 2C il-\nment at all stations except Cahuenga 2, it was neces-\nlustrates the position vectors and error ellipses. Re-\nsary to adjust the preearthquake and postearthquake\nmoving the conditional equations at the four stations\nsurveys simultaneously. A variance-covariance matrix\npermits the adjusted postearthquake positions to\nfor this adjustment was not considered essential.\nshift approximately 0.5 foot in a westward direction\nfrom the adjusted preearthquake positions. The pat-\nResults\ntern of vectors at stations in the Newhall-Saugus\narea is similar to the pattern of adjustment 1.\nThe corrections applied to the horizontal direc-\ntions are given in table 5C for the preearthquake\nsurvey and in table 5D for the postearthquake sur-\nCONCLUSIONS\nvey. The corrections applied to the measured lengths\nThe pattern of movement of stations in the area\nare listed in tables 6C and 6D for the preearthquake\nof surface breakage should be interpreted with a\nand postearthquake surveys, respectively.","252\nSan Fernando Earthquake of 1971\n768\nSAN FERNANDO EARTHQUAKE AREA\nPOST EARTHQUAKE FILE ADJ.\nSTATIONS ARE NOT NECESSARILY PLOTTED\nIN TRUE LOCATIONS IN CONGESTED AREAS\n767\n755\nHEAVY LINES MEASURED BY GEODIMETER\n7137\nMENTH\n765\n734\n757\n766\n733/\n753\n729\n758\n754\nphines\n762\n#756\n752\n757\n761\nAT\n750\n799,\n748\n730 A\n746\n747\n745.\n744\n741\n742\n727\n724\n739\n740\n735\n737\n736/\n713\n712\n707\n709\n705\n66\n715\n703\n718\n720\nNN719\ncourages\n701\n717\n702\nFigure 1B.-Postearthquake triangulation net.\nmore detailed breakdown of topography. Displace-\nStation\nRemarks\nments in this area are left lateral, with a maximum\nBum\nFew small cracks in hill.\nEast\nSmall cracks in ground near station.\nof 7 feet at station Pacoima L-1. The movement at\nLong\nNumerous small cracks in ground near\nvicinity of station.\nstation Pacoima No. 2 seems to be different, and the\nNewhall\nRM 3 disturbed by large crack in earth-\nfact that the station is located on a high steep hill\ntremendous amount of local earth dis-\nplacement in immediate vicinity of\nmay have some significance.\nstation.\nPacoima E-2 ECC 1.\nFew small cracks noted on the sides of the\nThe following information was obtained from the\nstation hill.\nPacoima L-1\nSeveral cracks and much upheaval of earth\n1971 recovery notes:\nin the immediate area of the station.","Horizontal Crustal Movements\n253\nTable 3A.-Postearthquake observed horizontal directions-Continued\nTable 3A.-Postearthquake observed horizontal directions\nObserved\nObserved\nStation\nObserved\nStation\nStation\nStation\nObserved\ndirection\ndirection\ndirection\ndirection\nFrom\nTo\nFrom\nTo\nFrom\nTo\nFrom\nTo\no\nO\nO\n/\no\n744\n734\n718\n701\n741\n123 31 58.04\n157 53 36.86\n721\n000 00 00.00\n752\n703\n000 00 00.00\n742\n173 21 07.17\n765\n174 48 37.51\n706\n043 28 26.99\n719\n093 02 52.78\n184 01 46.29\n745\n717\n172 29 06.18\n755\n702\n093 43 43.84\n743\n000 00 00.00\n211 29 16.35\n768\n719\n702\n744\n078 38 35.39\n000 00 00.00\n735\n701\n000 00 00.00\n717\n746\n139 10 36.14\n000 00 00.00\n712\n703\n044 34 10.81\n718\n049 55 29.04\n158 21 33.49\n038 25 23.58\n748\n713\n721\n085 28 57.02\n706\n098 50 38.81\n058 53 47.56\n747\n187 56 09.08\n736\n165 57 08.89\n715\n116 55 47.54\n720\n059 46 24.02\n746\n737\n720\n717\n171 04 58.02\n082 55 17.94\n748\n000 00 00.00\n740\n000 00 00.00\n719\n703\n747\n072 19 11.88\n138 51 18.88\n739\n045 29 09.34\n736\n000 00 00.00\n721\n745\n113 46 25.79\n147 28 41.43\n741\n724\n126 08 52.10\n738\n036 49 24.51\n743\n129 16 56.42\n245 19 41.58\n738\n706\n052 59 48.91\n721\n744\n169 14 36.71\n736\n732\n000 00 00.00\n702\n115 45 16.35\n766\n285 50 17.74\n000 00 00.00\n703\n731\n003 21 29.41\n701\n157 27 21.12\n752\n028 15 31.84\n236 13 09.35\n738\n727\n053 32 50.37\n704\n764\n271 39 40.07\n717\n285 26 35.04\n705\n000 00 00.00\n724\n088 57 20.55\n330 22 54.15\n232 49 29.46\n757\n735\n720\n140 11 19.61\n706\n048 52 29.59\n747\n713\n262 48 30.20\n719\n194 13 57.65\n709\n073 00 40.58\n752\n359 59 59.51\n710\n292 33 01.55\n241 20 12.49\n738\n277 22 15.59\n717\n745\n146 49 09.08\n715\n300 29 00.04\n737\n705\n236 36 21.45\n000 00 00.00\n746\n735\n330 28 21.97\n706\n000 00 00.00\n738\n265 46 20.43\n738\n002 55 43.42\n766\n709\n003 02 01.49\n724\n271 23 56.69\n748\n000 00 00.00\n713\n030 38 03.22\n704\n051 42 15.32\n729\n356 10 02.67\n299 51 01.14\n749\n230 21 45.04\n740\n738\n075 55 19.23\n720\n309 56 36.79\n752\n308 17 59.43\n750\n721\n278 28 04.33\n706\n748\n739\n331 52 50.70\n000 00 00.00\n727\n314 23 33.73\n715\n000 00 00.00\n747\n766\n255 22 09.26\n726\n339 08 58.21\n023 11 34.76\n717\n025 50 35.20\n745\n765\n255 22 09.25\n726\n702\n074 31 55.31\n072 53 12.84\n746\n764\n263 02 29.79\n729\n000 00 00.00\n701\n105 26 00.33\n153 43 46.11\n764\n115 16 16.78\n738\n137 30 00.96\n724\n703\n211 50 17.16\n757\n000 00 00.00\n157 08 45.73\n752\n263 04 22.49\n727\n738\n266 43 26.59\n750\n733\n028 59 35.90\n155 27 45.57\n732\n229 43 39.36\n709\n305 06 57.23\n749\n080 16 31.68\n732\n246 33 20.07\n727\n704\n174 48 54.28\n749\n000 00 00.00\n705\n325 58 35.54\n724\n705\n000 00 00.00\n747\n215 59 23.60\n721\n108 40 01.26\n706\n709\n040 20 47.59\n748\n231 21 50.66\n710\n177 33 04.84\n000 00 00.00\n732\n711\n070 48 37.69\n750\n709\n231 30 57.05\n726\n246 37 54.68\n712\n033 33 01.18\n756\n125 39 25.27\n247 58 06.96\n704\n704\n126 30 18.20\n729\n153 17 43.61\n751\n257 37 48.67\n730\n000 00 00.00\n712\n738\n134 24 43.01\n274 03 05.36\n750\n028 39 23.01\n737\n705\n184 49 23.84\n732\n748\n000 00 00.00\n276 40 38.86\n735\n094 47 52.74\n706\n191 16 32.92\n734\n091 04 37.54\n308 16 16.69\n757\n724\n316 05 06.47\n741\n711\n161 17 17.34\n130 24 44.54\n756\n721\n726\n359 57 45.82\n710\n000 00 00.00\n754\n187 05 04.75\n715\n181 27 14.43\n713\n178 00 17.66\n730\n752\n205 28 17.22\n000 00 00.00\n703\n254 14 38.89\n732\n712\n223 01 34.11\n311 49 13.60\n747\n080 18 39.83\n736\n273 38 24.53\n734\n709\n293 54 49.06\n248 51 20.02\n749\n766\n322 28 07.12\n729\n130 20 43.78\n712\n201 56 19.18\n318 47 50.97\n751\n080 11 55.44\n764\n000 00 00.00\n733\n735\n734\n028 56 55.56\n751\n046 16 51.11\n731\n738\n000 00 00.00\n749\n732\n000 00 00.00\n739\n099 18 16.18\n709\n050 35 52.96\n735\n000 00 00.00\n750\n149 54 25.67\n734\n078 51 54.02\n710\n123 39 14.97\n756\n737\n072 47 57.82\n711\n174 51 57.23\n732\n168 30 08.99\n755\n752\n000 00 00.00\n740\n089 40 05.34\n269 32 33.34\n713\n198 36 18.13\n754\n742\n138 16 33.67\n734\n033 01 12.04\n713\n204 00 58.54\n752\n000 00 00.00\n729\n070 28 18.20\n741\n735\n000 00 00.00\n738\n741\n051 07 10.44\n730\n091 28 11.41\n712\n039 25 22.19\n000 00 00.00\n737\n738\n091 25 16.38\n726\n091 30 20.16\n711\n747\n049 08 07.18\n050 33 20.98\n131 07 46.95\n735\n230 27 26.70\n731\n736\n746\n061 40 49.98\n065 56 57.81\n739\n231 59 06.54\n738\n287 44 54.35\n737\n756\n103 54 24.31\n114 45 08.05\n727\n129 50 36.57\n740\n715\n111 53 08.31\n154 10 24.59\n766\n742\n721\n187 24 45.46\n721\n000 00 00.00\n767\n139 45 28.58\n197 55 30.36\n744\n033 01 04.33\n717\n063 48 39.93\n733\n234 44 21.29\n734\n267 01 59.06\n743\n702\n125 06 45.61\n733\n732\n332 31 37.27\n000 00 00.00\n743\n706\n212 29 40.56\n729\n072 43 48.07\n000 00 00.00\n750\n741\n035 16 03.20\n730\n738\n261 01 53.84\n089 49 20.21\n764\n742\n067 40 14.64\n076 36 58.96\n732\n717\n754\n139 13 48.55\n744\n121 20 34.04\n100 03 54.96\n738\n702\n000 00 00.00\n755\n158 09 31.50\n746\n159 41 31.73\n734\n736\n043 10 33.89\n753\n207 39 49.16\n745\n185 00 23.50\n056 25 19.80\n729\n000 00 00.00\n706\n765\n111 54 44.55\n744\n064 32 45.50\n730\n035 10 04.51\n715\n000 00 00.00\n753\n746\n721\n121 35 18.31\n731\n073 22 52.73\n063 59 49.49\n752\n000 00 00.00\n076 24 25.08\n745\n719\n169 00 07.61\n732\n101 41 23.37\n754\n050 11 48.36\n099 48 31.97\n743\n718\n118 21 49.94\n738","254\nSan Fernando Earthquake of 1971\nTable 3A.-Postearthquake observed horizontal directions-Continued\nIn the Newhall-Saugus area, there is right-lateral\nStation\nObserved\nStation\nmovement of at least 0.5 foot. Since the preearth-\nObserved\ndirection\ndirection\nquake observations for this area were made in 1963,\nFrom\nTo\nFrom\nTo\nthe time interval is less than 8 years; and there is\no\nO\n/\n\"\n753\n760\ngood reason to believe that most of the movement\n755\n109 22 06.02\n757\n044\n16\n59.46\n754\n761\noccurred at the time of the earthquake.\n756\n000\n00\n00.00\n767\n000\n00\n00.00\n759\n044\n02\n39.07\n762\n007\n59\n47.06\nEven though some weakness in azimuth control\n755\n084\n53\n25.58\n757\n078\n23\n51.40\n753\n175\nmay be deduced from the illustration (fig. 2A) of\n34\n34.39\n760\n196\n15\n16.35\n752\n236\n56\n44.67\n764\n216\n27\n18.34\nthe free-adjustment vectors and 95-percent error el-\n750\n332\n03\n32.79\n762\n751\n314\n55\n11.49\n759\n000\n00\n00.00\nlipses, the results of the free adjustments give the\n755\n758\n024\n06\n19.23\n734\n000 00 00.00\n757\n084\n43\n34.58\nbest representation of the observed data. The as-\n753\n023 51 47.51\n761\n143\n54\n58.76\n752\n044\n59\n23.63\nsumption of no movement at all stations around the\n763\n318\n16\n26.70\n754\n054\n00\n20.34\n763\nperimeter of the net requires larger corrections to\n756\n093\n00\n02.78\n762\n000\n00\n00.00\n759\n119 33 06.51\n767\n161\n05\n44.96\nsome distances and directions than would normally\n764\n132 39 47.49\n759\n273\n20\n46.50\n767\n180\n32\n56.71\n758\n308\n48\n52.74\nbe expected to result from random error. These\n751\n073\n55\n58.54\n764\n768\n243\n18\n49.34\n768\n000\n00\n00.00\nlarger corrections were introduced at stations along\n756\n755\n028 45 57.93\n750\n000\n00\n00.00\nthe western side of the net. Allowing stations San\n761\n034\n43\n26.37\n757\n050 09 50.97\n757\n049\n21\n01.76\nFernando, Chatsworth, Pico L-9 AUX 2 ECC 1, and\n758\n102\n08\n27.84\n752\n052\n45\n20.76\n759\n150\n18\n17.77\n748\n077\n11\n53.07\nPico L-9A freedom of movement as explained in ad-\n755\n177\n37\n24.13\n746\n088\n01\n00.11\n754\n233\n44\n13.48\n738\n101\n43\n52.76\njustment 3 improves the relation of the movement\n752\n255\n21\n33.50\n737\n137\n05\n56.29\n751\n293\n42\n23.25\n765\n295\nvectors in the San Fernando-Newhal] area.\n02\n10.49\n749\n322\n24\n48.76\n767\n012\n17\n24.71\n757\n765\n764\n000\n00\n00.00\n767\n000\n00\n00.00\n762\n077 43 26.32\n734\n012\n50\n24.56\nREFERENCES\n758\n141\n34\n49.58\n752\n020\n48\n10.25\n756\n172 17 40.06\n738\n051\n22\n05.80\n750\n231 55 09.39\n764\n060\n59\n35.12\nFrank, F. C., \"On the Deduction of Earth Strains From Survey\n748\n265 57 23.43\n737\n075\n23\n02.35\n746\nData,\" Bulletin of the Seismological Society of America, Vol.\n277\n23\n11.81\n766\n761\n027\n18\n53.16\n737\n000\n00\n00.00\n56, No. 1, Feb. 1966, pp. 35-42.\n760\n357 12 56.36\n752\n305\n23\n37.74\n767\n108 42 19.84\n747\nPope, Allen J., \"Strain Analysis of Horizontal Crustal Move-\n328\n24\n55.99\n758\n746\n332\n46\n03.39\nments in Alaska Based on Triangulation Surveys Before and\n-759\n000 00 00.00\n738\n335\n58\n36.33\n756\n088\n12\n38.90\n767\nAfter the Prince William Sound Earthquake of March 27,\n757\n185\n31\n12.82\n768\n000\n00\n00.00\n1964,\" The Prince William Sound, Alaska, Earthquake of\n762\n241 02 33.38\n752\n118 07 32.78\n763\n304 01 30.62\n755\n092\n05\n11.36\n1964 and Aftershocks, Vol. III: Research Studies and Inter-\n759\n757\n173\n29\n27.46\npretive Results, Geodesy and Photogrammetry, Coast\n754\n000 00 00.00\n759\n132\n10\n46.39\n756\n052 31 23.78\n760\n197 43 03.06\nand Geodetic Survey, Environmental Science Services Ad-\n758\n096 08 54.98\n761\n193\n42\n09.68\nministration, U.S. Department of Commerce, Washington,\n762\n133 05 08.28\n763\n177 09 08.98\n755\n286 23 31.89\n764\n207\n43\n28.39\nD.C., 1969, pp. 99-111.\n763\n184\n42\n19.49\n765\n249\n28\n38.33\n767\n207\n28\n57.90\n768\nSavage, James C., correspondence from U.S. Geological Survey,\n760\n734\n000 00 00.00\nMenlo Park, Calif., to Dept. of County Engineer, Los\n767\n000\n00 00.00\n755\n035\n51\n21.12\n761\n012\n14 22.24\n764\n076\nAngeles, Calif., Mar. 12, 1971.\n26\n20.60","Horizontal Crustal Movements\n255\nTable 3B.-Postearthquake Geodimeter-measured distances in meters\nFrom\nTo\nDistance\nFrom\nTo\nDistance\nFrom\nTo\nDistance\n701\n702\n12312.320\n721\n732\n15466.399\n741\n743\n2489.515\n701\n703\n12988.248\n721\n738\n19822.690\n741\n744\n5714.684\n701\n706\n23689.237\n724\n730\n19012.978\n742\n743\n4665.227\n742\n702\n703\n18468.538\n727\n730\n8677.040\n744\n3959.540\n702\n706\n18433.678\n727\n732\n13335.795\n743\n744\n4009.449\n702\n715\n17784.643\n729\n730\n9754.135\n743\n745\n2500.442\n702\n717\n17277.090\n729\n732\n20746.517\n743\n746\n6113.238\n703\n736\n8834.865\n729\n734\n12979.516\n744\n745\n3665.062\n704\n705\n6707.119\n730\n732\n13054.013\n744\n746\n3873.355\n704\n706\n5354.937\n730\n734\n16875.648\n745\n746\n3998.506\n732\n1049.944\n704\n707\n4063.040\n731\n745\n747\n2647.091\n704\n709\n5918.553\n731\n734\n19695.934\n745\n748\n4999.769\n704\n738\n2874.647\n732\n734\n19520.397\n746\n747\n3006.661\n705\n706\n5139.684\n732\n738\n9930.636\n746\n748\n1795.146\n705\n709\n7537.743\n732\n752\n21216.619\n746\n752\n11557.006\n738\n24074.486\n705\n738\n6949.956\n733\n746\n757\n5948.545\n706\n707\n3149.940\n734\n738\n24119.961\n746\n764\n9442.006\n706\n709\n2420.603\n734\n752\n11690.213\n746\n766\n19312.904\n706\n715\n5728.547\n734\n755\n15646.220\n747\n748\n2997.346\n23866.176\n706\n738\n7572.380\n734\n768\n747\n752\n9626.233\n737\n7557.594\n709\n711\n4867.378\n735\n747\n766\n21882.673\n709\n712\n4749.053\n735\n738\n8427.302\n748\n750\n2506.212\n735\n739\n3728.717\n709\n738\n8619.200\n748\n757\n4476.773\n735\n740\n6600.029\n710\n711\n3779.620\n748\n764\n9559.881\n710\n712\n6111.645\n735\n741\n5717.114\n750\n754\n7081.447\n738\n15944.742\n710\n736\n10848.427\n736\n750\n757\n3662.679\n13421.494\n737\n710\n738\n738\n15966.080\n752\n754\n2435.725\n737\n739\n7768.221\n711\n712\n2777.813\n752\n755\n7283.864\n737\n740\n2991.420\n711\n713\n4280.273\n754\n755\n5042.169\n712\n713\n3037.845\n737\n752\n25079.104\n755\n767\n5237.757\n712\n735\n3805.260\n737\n766\n29334.857\n756\n757\n4488.173\n712\n738\n10595.807\n738\n741\n10810.436\n756\n758\n2311.136\n713\n735\n4888.063\n738\n752\n20501.246\n757\n758\n3564.582\n713\n737\n3492.387\n738\n764\n27174.347\n757\n760\n5123.042\n715\n738\n10030.937\n739\n740\n5467.488\n757\n761\n3074.378\n741\n2106.121\n717\n718\n9546.200\n739\n758\n762\n3672.189\n718\n721\n7177.706\n739\n742\n4796.027\n719\n720\n13991.396\n740\n741\n6620.000\n720\n724\n17855.019\n740\n742\n4268.324\n721\n727\n13993.997\n741\n742\n4374.583","San Fernando Earthquake of 1971\n256\nTable 4A.-Lines used for azimuth control\nTable 4B.-Average and maximum triangle closures for\npreearthquake and postearthquake surveys\nStation\nTriangle closure\nAzimuth\nSurvey\nFrom\nTo\nAverage Maximum\nO\n\"\n\"\nCalabasas\nChatsworth\n182\n03\n03.88\nPreearthquake\n0.99\n5.12\nCahuenga 2\nFlint\n256\n02\n35.92\nPostearthquake\n1.17\n4.53\nTable 4C.-Elevations of stations used in reduction of Geodimeter distances 1\nStation no.\nStation name\nElevation\nStation no.\nStation name\nElevation\nm\nm\n701\nCalabasas\n496.6\n738\nMay\n1203.0\n702\nRES K-9A\n590.2\n739\nEdison\n438.2\n703\nChatsworth\n704.2\n740\nTowsley\n874.0\n704\nSylmar F-8\n736.9\n741\nNewhall\n409.0\n705\nPacoima L-1\n485.0\n742\nLock\n507.2\n706\nPAC E-2 ECC 1\n413.9\n743\nSaugus\n378.0\n707\nSylmar I-12\n381\n744\nYucca\n393.3\n709\nReservoir\n394.7\n745\nFoot 2\n451.2\n710\nCorner 2\n300.0\n746\nLong\n500.6\n711\nBluff\n502.5\n747\nDry\n471.0\n712\nMission Pt\n843.8\n748\nBum\n570.7\n713\nRidge 2\n1008.9\n750\nSteer\n589.0\n715\nPacoima 2\n393.3\n752\nDeer\n1097.8\n717\nCahuenga 2\n554.2\n753\nHouse\n858.2\n718\nVerdugo AUX\n932.5\n754\nBrushy\n827.4\n719\nFlint\n575.9\n755\nRed\n1217.5\n720\nMTW E-10A\n1722.7\n756\nPowerhouse\n679.9\n721\nSister Elsie\n1547.0\n757\nCharlie\n641.2\n724\nPacifico\n2174.5\n758\nTaylor\n665.6\n726\nParker AUX 2\n1258.9\n759\nElizabeth\n804.5\n727\nMt. Gleason\n1931.4\n760\nCast C\n524.5\n729\nHauser\n1580.2\n761\nFork\n526.7\n730\nParker\n1259.1\n762\nDaires\n589.2\n731\nMagic\n1470.8\n763\nNecktie\n1088.5\n732\nPort\n1480.5\n764\nLoma Verde\n760.5\n733\nPelona ECC 2\n1474.7\n765\nWhitaker\n1255.3\n734\nPelona\n1478.5\n766\nWPK A-7A AUX 1\n1254.5\n735\nEast\n678.4\n767\nWarm Springs\n1224.7\n736\nPico L-9A\n1137.0\n768\nSawmill\n1680.3\n737\nPico L-9 AUX 2 ECC 1\n1136.7\n1 Most elevations were determined by vertical angle observations; some are subject to slight revision after precise level data are made\navailable.","Horizontal Crustal Movements\n257\nTable 5A.-Adjustment 1 corrections to preearthquake observed horizontal directions\nStation\nStation\nStation\nStation\nv\"\nv\"\nv\"\nv\"\nTo\nFrom\nTo\nFrom\nTo\nFrom\nFrom\nTo\n33\n1\n13\n21\n23\n0.50\n56\n0.51\n2\n-0.67\n11\n0.52\n0.14\n59\n3\n0.14\n12\n-0.54\n31\n-0.01\n14\n0.47\n54\n-0.20\n56\n0.59\n34\n26\n-0.29\n57\n0.06\n57\n0.22\n22\n0.24\n21\n0.37\n30\n2\n14\n31\n-1.01\n1\n0.63\n1\n-0.54\n23\n0.59\n0.22\n31\n-0.96\n35\n0.72\n3\n0.43\n2\n36\n0.32\n23\n14\n0.87\n3\n-0.65\n20\n-0.30\n39\n0.05\n15\n-0.24\n5\n0.17\n0.55\n0.37\n21\n-0.24\n56\n16\n-0.23\n6\n22\n-0.80\n60\n-1.05\n17\n-0.75\n15\n0.00\n64\n0.48\n0.83\n24\n0.90\n18\n-0.08\n16\n17\n-0.48\n26\n0.55\n35\n57\n-0.63\n0.08\n30\n-0.09\n34\n-0.89\n57\n3\n31\n-0.01\n36\n-0.36\n1\n0.36\n15\n37\n0.16\n2\n0.04\n24\n2\n-0.05\n0.00\n20\n-0.43\n38\n1.08\n14\n0.65\n4\n23\n-0.72\n39\n0.22\n16\n-0.75\n5\n-0.11\n1.15\n64\n-0.20\n57\n-0.21\n6\n-0.13\n26\n36\n9\n0.89\n25\n4\n34\n0.08\n5\n-0.09\n14\n-0.44\n27\n-0.58\n-0.92\n28\n0.21\n35\n-0.01\n6\n-0.01\n16\n17\n0.43\n29\n0.38\n37\n0.49\n7\n0.30\n-0.56\n8\n-0.10\n18\n0.10\n26\n38\n23\n-0.68\n37\n15\n-0.08\n21\n0.73\n-0.61\n56\n-0.25\n24\n0.76\n35\n5\n30\n0.36\n36\n0.17\n4\n0.24\n57\n-0.34\n34\n1.08\n38\n0.13\n6\n0.05\n16\n39\n0.41\n-0.18\n27\n7\n-0.20\n2\n40\n-0.08\n8\n0.01\n3\n-0.06\n25\n0.30\n14\n-0.23\n6\n0.08\n28\n0.23\n38\n0.46\n35\n0.16\n15\n0.14\n9\n0.99\n29\n0.58\n36\n0.29\n14\n-0.10\n30\n6\n37\n-0.42\n32\n-0.32\n4\n0.37\n15\n-0.74\n39\n-0.04\n5\n0.10\n17\n0.01\n33\n-0.32\n40\n0.02\n18\n-0.50\n28\n7\n-0.33\n0.08\n39\n21\n0.43\n27\n8\n-0.27\n-0.23\n34\n-0.79\n0.09\n29\n9\n0.29\n56\n35\n-0.02\n30\n0.15\n14\n0.03\n57\n-0.02\n37\n-0.05\n29\n15\n0.17\n17\n1.04\n25\n-0.85\n38\n0.07\n16\n-0.14\n2\n1.06\n40\n0.87\n56\n-0.22\n14\n0.35\n27\n0.35\n41\n0.57\n15\n0.21\n28\n7\n42\n30\n0.68\n-0.38\n4\n-0.84\n16\n-0.34\n56\n0.25\n-0.38\n32\n0.16\n5\n0.04\n18\n-0.77\n19\n-0.08\n33\n0.71\n60\n6\n0.40\n63\n0.63\n30\n8\n0.40\n20\n-0.29\n0.09\n64\n-0.40\n21\n-0.51\n23\n8\n26\n-0.57\n40\n4\n0.32\n18\n-0.74\n27\n0.14\n37\n-0.30\n5\n0.09\n2\n28\n-0.43\n38\n0.11\n6\n-0.23\n15\n-0.11\n39\n0.25\n7\n-0.16\n16\n-0.07\n29\n0.26\n17\n0.70\n31\n-0.36\n41\n0.14\n9\n0.44\n42\n0.29\n6\n-0.27\n19\n-0.39\n32\n20\n0.75\n33\n0.28\n41\n10\n0.45\n39\n-0.38\n21\n-0.03\n34\n0.15\n11\n0.45\n40\n-0.54\n12\n0.23\n56\n-0.12\n42\n0.35\n15\n0.53\n19\n31\n21\n-0.22\n43\n-0.11\n0.76\n16\n0.31\n17\n22\n0.69\n44\n0.66\n56\n-0.79\n18\n-0.20\n42\n20\n-0.45\n23\n0.40\n10\n39\n-0.15\n30\n0.33\n9\n0.04\n21\n-0.10\n0.21\n32\n-1.65\n40\n11\n0.71\n20\n-1.08\n41\n-0.04\n-0.02\n34\n12\n0.68\n17\n43\n-0.17\n18\n-0.16\n56\n1.52\n11\n44\n0.15\n0.67\n32\n9\n0.18\n19\n0.02\n43\n21\n-0.75\n27\n10\n0.05\n0.17\n29\n-0.30\n41\n-0.13\n12\n- 0.45\n23\n24\n0.73\n30\n-0.50\n42\n0.00\n13\n0.91\n44\n0.02\n-0.65\n31\n1.50\n56\n0.79\n57\n33\n0.22\n45\n-0.22\n57\n- 1.36\n21\n56\n-1.18\n46\n0.33\n15\n-0.23\n12\n59\n0.21\n44\n-0.89\n9\n0.23\n16\n41\n-0.79\n-0.43\n33\n10\n0.86\n17\n-0.10\n42\n0.29\n-0.05\n27\n11\n-0.61\n18\n-0.79\n43\n-0.31\n19\n0.65\n29\n13\n0.85\n45\n0.68\n0.52\n30\n-0.58\n54\n-0.19\n20\n0.82\n46\n0.14\n-0.65\n32\n56\n-1.14\n22","San Fernando Earthquake of 1971\n258\nTable 5A.-Adjustment 1 corrections to preearthquake observed horizontal directions-Continued\nStation\nStation\nStation\nStation\nv\"\nv\"\nv\"\nv\"\nFrom\nTo\nFrom\nTo\nFrom\nTo\nFrom\nTo\n45\n51\n56\n59\n43\n-0.27\n52\n-0.11\n18\n0.40\n32\n0.36\n44\n-0.38\n53\n- 0.11\n21\n0.22\n33\n0.24\n46\n0.11\n55\n0.31\n31\n0.19\n56\n0.69\n47\n-0.15\n52\n32\n- -0.54\n58\n- 0.32\n48\n0.72\n49\n0.60\n33\n- -0.05\n61\n0.81\n46\n50\n0.23\n34\n- -0.08\n63\n0.08\n43\n0.15\n51\n0.30\n39\n- 0.73\n60\n44\n0.31\n53\n- 0.07\n52\n1.06\n34\n-0.75\n45\n- -0.33\n54\n0.06\n54\n0.58\n39\n0.03\n47\n- 0.25\n55\n0.36\n57\n0.18\n56\n0.28\n48\n0.12\n56\n0.74\n58\n- 1.67\n57\n- 0.06\n47\n57\n0.61\n59\n- -0.34\n62\n- 0.39\n45\n-0.22\n53\n60\n- 1.17\n63\n0.35\n46\n0.46\n51\n- 0.26\n61\n0.84\n64\n0.55\n48\n-0.13\n52\n- 0.48\n64\n-0.60\n61\n49\n-0.65\n54\n0.83\n33\n- 0.78\n57\n50\n0.53\n55\n0.26\n56\n0.59\n1\n- -1.09\n48\n57\n- 0.38\n58\n0.13\n2\n- -0.88\n45\n-0.18\n54\n59\n0.06\n3\n0.93\n46\n0.31\n12\n- 0.07\n62\n11\n-0.30\n47\n-0.14\n13\n1.53\n34\n-0.76\n13\n1.59\n49\n-0.25\n52\n- 0.01\n57\n1.10\n14\n-0.42\n50\n0.27\n53\n0.77\n59\n0.11\n15\n-1.06\n49\n55\n0.40\n60\n-0.75\n16\n-0.66\n47\n-0.01\n56\n0.56\n63\n0.31\n20\n-0.03\n48\n0.40\n57\n0.85\n63\n52\n0.81\n50\n-0.28\n55\n39\n0.02\n53\n-0.03\n51\n-0.20\n51\n-0.80\n58\n0.52\n54\n0.00\n52\n-0.62\n52\n0.05\n59\n55\n0.69\n0.79\n56\n0.74\n53\n- 0.11\n60\n56\n0.66\n0.04\n50\n54\n0.65\n62\n59\n- -0.02\n0.50\n47\n-0.41\n57\n0.23\n64\n60\n0.59\n- 0.89\n48\n0.22\n56\n64\n62\n0.79\n49\n0.08\n6\n0.82\n34\n0.66\n58\n51\n- -0.05\n9\n0.61\n35\n-0.55\n56\n-0.01\n52\n0.19\n11\n0.20\n39\n- 0.03\n51\n59\n12\n-0.16\n- 0.06\n56\n0.03\n49\n- -0.41\n15\n1.58\n61\n- -0.14\n60\n- 0.22\n50\n0.34\n16\n- 0.20\n63\n0.31\n63\n0.11","Horizontal Crustal Movements\n259\nTable 5B.-Adjustment 1 corrections to postearthquake observed horizontal directions\nStation\nStation\nStation\nStation\nv\"\nv\"\nv\"\nv\"\nTo\nFrom\nTo\nFrom\nTo\nFrom\nTo\nFrom\n746\n701\n719\n735\n702\n0.07\n717\n-0.45\n737\n-0.19\n747\n-0.05\n748\n0.26\n703\n0.44\n718\n-0.17\n738\n-0.40\n0.61\n706\n-0.51\n720\n0.28\n739\n-0.21\n752\n-0.32\n757\n0.14\n702\n721\n0.35\n740\n0.56\n701\n0.24\n720\n741\n0.08\n764\n736\n766\n-1.21\n703\n0.26\n719\n-0.51\n706\n0.67\n721\n0.41\n703\n-0.90\n747\n710\n1.15\n745\n-1.01\n715\n0.54\n724\n0.11\n-0.59\n717\n0.71\n721\n713\n1.20\n746\n-0.94\n748\n0.00\n703\n715\n-1.62\n717\n749\n1.82\n701\n0.84\n717\n-0.41\n735\n0.49\n0.17\n702\n0.49\n719\n738\n1.02\n750\n0.06\n752\n-0.66\n706\n- 0.21\n720\n-0.16\n737\n0.41\n736\n0.26\n724\n0.48\n766\n713\n0.60\n738\n-0.39\n727\n-0.46\n735\n-0.16\n748\n704\n731\n0.82\n738\n-0.47\n745\n-0.12\n705\n0.03\n732\n0.97\n739\n0.67\n746\n-0.08\n706\n0.03\n738\n0.21\n740\n-0.66\n747\n0.15\n709\n0.05\n724\n752\n-0.29\n749\n-0.47\n738\n0.01\n720\n-0.11\n764\n0.34\n750\n0.07\n0.48\n705\n721\n765\n-0.02\n757\n0.23\n704\n0.34\n726\n-0.68\n766\n-0.03\n764\n0.23\n706\n0.05\n727\n-0.15\n738\n749\n0.46\n709\n0.25\n729\n703\n0.58\n747\n-0.75\n738\n-0.61\n726\n704\n-0.02\n748\n0.49\n724\n-0.16\n706\n705\n-0.01\n750\n-0.04\n727\n0.35\n701\n0.99\n706\n-0.62\n751\n0.60\n729\n-0.02\n702\n0.78\n709\n-0.45\n756\n-0.29\n732\n-0.16\n703\n1.60\n710\n-0.51\n750\n704\n- 0.38\n727\n712\n1.27\n747\n-0.03\n0.44\n705\n- 0.98\n721\n715\n0.40\n748\n-0.06\n709\n- 0.88\n724\n1.11\n721\n-0.39\n749\n-0.43\n715\n- 0.63\n726\n-0.42\n732\n0.27\n751\n-0.38\n-1.12\n717\n0.24\n732\n733\n-0.47\n752\n0.42\n738\n-0.74\n754\n0.29\n729\n734\n-1.79\n724\n-1.30\n735\n0.68\n756\n0.11\n709\n0.60\n757\n0.08\n704\n0.51\n726\n0.21\n736\n705\n0.55\n730\n0.21\n737\n-0.08\n751\n741\n1.16\n749\n0.02\n706\n- 0.08\n732\n1.26\n-0.27\n-0.05\n750\n711\n- 1.46\n734\n-0.38\n752\n-0.29\n712\n0.01\n730\n764\n-0.72\n754\n766\n0.18\n755\n0.42\n738\n0.45\n729\n-0.17\n0.11\n711\n732\n-0.10\n739\n756\n735\n0.18\n752\n709\n0.45\n733\n0.14\n-0.58\n710\n0.48\n734\n0.13\n737\n-0.89\n732\n740\n-0.11\n734\n-0.38\n712\n-0.03\n731\n737\n0.33\n713\n-0.89\n732\n0.26\n741\n0.23\n742\n0.59\n738\n0.17\n712\n734\n-0.25\n-0.24\n709\n-0.18\n732\n741\n746\n735\n0.49\n747\n-0.13\n710\n-0.92\n721\n0.69\n711\n0.73\n726\n-0.11\n738\n-0.66\n750\n1.13\n0.50\n713\n0.14\n727\n0.10\n739\n-0.58\n753\n740\n-0.38\n754\n-0.11\n735\n0.12\n729\n0.62\n0.58\n755\n1.20\n738\n0.40\n730\n-0.11\n742\n731\n-0.23\n743\n0.40\n756\n-1.20\n713\n744\n0.14\n764\n-1.09\n711\n1.41\n733\n-1.44\n-0.77\n712\n-0.12\n734\n-1.26\n743\n765\n741\n-0.80\n766\n2.04\n735\n0.44\n738\n1.19\n-0.14\n767\n-0.88\n736\n0.08\n752\n0.57\n742\n-0.39\n753\n737\n1.82\n733\n744\n752\n-0.27\n729\n-1.09\n745\n0.41\n715\n-0.31\n746\n0.94\n754\n-0.23\n702\n- 0.34\n730\n755\n0.49\n706\n- 0.60\n732\n0.39\n744\n717\n0.24\n738\n1.00\n741\n-0.69\n754\n750\n0.14\n721\n0.25\n734\n742\n0.32\n0.32\n0.15\n743\n-0.39\n751\n738\n0.45\n729\n730\n0.16\n745\n0.32\n752\n0.06\n717\n-0.06\n702\n0.71\n731\n1.32\n746\n0.44\n753\n-0.43\n745\n755\n0.22\n706\n0.02\n732\n756\n-0.52\n715\n-0.99\n738\n-0.26\n743\n-0.85\n-0.17\n0.14\n744\n0.36\n759\n718\n0.33\n752\n746\n0.11\n755\n719\n-0.49\n755\n0.51\n-0.65\n721\n0.51\n765\n-0.93\n747\n0.63\n734\n-0.66\n748\n-0.24\n751\n-0.31\n736\n-0.07\n768\n746\n752\n0.15\n718\n735\n0.85\n753\n-0.03\n717\n0.16\n712\n0.27\n743\n754\n0.27\n719\n-0.49\n713\n-0.09\n744\n-0.96\n721\n0.33\n736\n0.86\n745\n-0.20\n756\n-0.18","260\nSan Fernando Earthquake of 1971\nTable 5B.-Adjustment 1 corrections to postearthquake observed horizontal directions-Continued\nStation\nStation\nStation\nStation\nv\"\nv\"\nv\"\nv\"\nFrom\nTo\nFrom\nTo\nFrom\nTo\nFrom\nTo\n755\n758\n762\n765\n759\n0.17\n756\n0.16\n758\n0.41\n752\n0.41\n764\n-0.08\n757\n1.00\n759\n-0.14\n764\n0.60\n767\n0.60\n759\n0.05\n761\n0.10\n767\n-0.35\n768\n0.08\n762\n-0.07\n763\n-0.15\n766\n756\n763\n0.87\n763\n737\n1.36\n749\n0.57\n759\n758\n-0.72\n738\n0.35\n750\n-0.11\n754\n-0.72\n759\n-0.66\n746\n-1.74\n751\n0.34\n755\n0.32\n762\n0.77\n747\n0.86\n752\n0.43\n756\n0.03\n767\n0.60\n752\n-0.12\n754\n0.52\n758\n0.03\n764\n767\n755\n-1.87\n762\n0.17\n737\n0.14\n752\n0.31\n757\n-0.25\n763\n0.75\n738\n0.68\n755\n0.19\n758\n0.22\n767\n-0.53\n746\n0.10\n757\n-0.63\n759\n0.16\n760\n748\n0.31\n759\n-0.26\n757\n757\n-0.13\n752\n0.40\n760\n-0.13\n746\n-0.15\n761\n0.08\n755\n0.13\n761\n-1.14\n748\n-1.18\n767\n0.06\n757\n0.29\n763\n-0.24\n750\n-0.21\n761\n761\n-2.02\n764\n0.87\n756\n-0.26\n757\n-0.92\n765\n-0.04\n765\n0.16\n758\n0.30\n760\n-0.01\n767\n0.80\n768\n0.84\n760\n0.07\n762\n0.39\n768\n-0.78\n768\n761\n0.42\n764\n0.85\n765\n734\n-0.30\n762\n-0.27\n767\n-0.29\n734\n0.27\n755\n0.20\n764\n-0.03\n762\n737\n- 1.37\n764\n0.36\n767\n1.32\n757\n-0.23\n738\n0.43\n767\n-0.27\nTable 6A.-Adjustment 1 corrections to preearthquake observed lengths (U's) in meters\nStation\nObserved\nWeight\nV in\nV in\nAdjusted\nlength\nfactor\nseconds\nlength\nmeters\n1 part in\nFrom\nTo\n1\n3\n12988.206\n1.0\n-0.18\n-0.011\n12988.195\n1150,000\n1\n17\n29502.131\n1.0\n0.21\n0.030\n29502.161\n973,000\n16\n56\n1139.270\n0.3\n1.49\n0.008\n1139.278\n139,000\n31\n32\n1049.944\n0.1\n- -13.91\n- -0.071\n1049.873\n15,000\n31\n34\n19695.796\n2.4\n-0.11\n- -0.011\n19695.785\n1815,000\n34\n64\n23866.161\n2.4\n0.18\n0.021\n23866.182\n1152,000\n39\n63\n5237.752\n0.6\n-0.44\n-0.011\n5237.741\n469,000\n-\n60\n63\n13700.048\n1.6\n-0.11\n-0.007\n13700.041\n1954,000\nSTATISTICS\nNumber of lengths =\n8\nMaximum positive V in seconds =\n1.49\nMaximum negative V in meters =\n0.071\n-\nMaximum length\n= 29502.131\nMaximum negative V in seconds =\n13.91\nAverage length V in meters\n= 0.021\n-\nMinimum length\n= 1049.944\nAverage length V in seconds\n2.08\nThe sum of pvv in seconds\n=\n= 2.5678\nAverage length\n= 13397.413\nMaximum positive V in meters\n0.030\nThe sum of VV in seconds\n=\n= 196.0064","Horizontal Crustal Movements\n261\nTable 6B.-Adjustment 1 corrections to postearthquake observed lengths (U'S) in meters\nAdjusted\nV in\nV in\nObserved\nWeight\nStation\nlength\n1 part in\nseconds\nmeters\nlength\nfactor\nTo\nFrom\n12312.299\n592,000\n-0.021\n-0.35\n702\n12312.320\n1.0\n701\n12988.270\n604,000\n0.022\n0.34\n12988.248\n1.0\n703\n701\n23689.280\n547,000\n0.043\n0.38\n706\n23689.237\n1.0\n701\n18468.546\n2196,000\n0.008\n0.09\n18468.538\n1.0\n703\n702\n18433.732\n338,000\n0.054\n1.0\n0.61\n706\n18433.678\n702\n0.010\n17784.653\n1765,000\n0.12\n17784.643\n1.0\n715\n702\n0.002\n17277.092\n8800,000\n0.02\n1.0\n717\n17277.090\n702\n0.033\n8834.898\n266,000\n0.77\n8834.865\n1.0\n736\n703\n0.011\n6707.130\n592,000\n0.35\n6707.119\n1.2\n705\n704\n-0.003\n5354.934\n2013,000\n-0.10\n5354.937\n0.8\n706\n704\n4063.040\n22108,000\n0.01\n0.000\n4063.040\n0.6\n707\n704\n433,000\n-0.48\n-0.014\n5918.539\n0.8\n5918.553\n709\n704\n2874.640\n423,000\n-0.49\n-0.007\n2874.647\n0.4\n738\n704\n918,000\n-0.22\n-0.006\n5139.678\n0.8\n5139.684\n706\n705\n611,000\n-0.012\n7537.731\n-0.34\n1.2\n7537.743\n709\n705\n6949.963\n989,000\n0.21\n0.007\n0.7\n6949.956\n738\n705\n3149.940\n12227,000\n-0.02\n-0.000\n0.8\n3149.940\n707\n706\n-0.014\n2420.589\n169,000\n0.7\n-1.22\n2420.603\n709\n706\n5728.554\n825,000\n0.25\n0.007\n1.0\n715\n5728.547\n706\n-0.027\n7572.353\n286,000\n-0.72\n0.7\n738\n7572.380\n706\n-0.028\n4867.350\n176,000\n-1.17\n0.9\n711\n4867.378\n709\n551,000\n-0.37\n-0.009\n4749.044\n0.6\n712\n4749.053\n709\n2270,000\n0.09\n0.004\n8619.204\n0.7\n8619.200\n738\n709\n3779.619\n3984,000\n-0.05\n-0.001\n3779.620\n0.7\n711\n710\n1269,000\n-0.16\n-0.005\n6111.640\n6111.645\n0.7\n712\n710\n209,000\n-0.052\n10848.375\n-0.99\n10848.427\n0.8\n736\n710\n-0.078\n13421.416\n173,000\n1.0\n-1.19\n13421.494\n738\n710\n2777.796\n160,000\n-1.29\n-0.017\n2777.813\n0.5\n712\n711\n4280.263\n449,000\n-0.46\n-0.010\n0.5\n4280.273\n713\n711\n3037.851\n510,000\n0.40\n0.006\n3037.845\n0.6\n713\n712\n3805.261\n3220,000\n0.06\n0.001\n3805.260\n0.7\n735\n712\n10595.796\n938,000\n-0.22\n-0.011\n10595.807\n1.1\n738\n712\n3134,000\n-0.07\n-0.002\n4888.061\n4888.063\n0.7\n735\n713\n3492.385\n2094,000\n-0.10\n-0.002\n3492.387\n0.7\n737\n713\n10030.970\n300,000\n0.69\n0.033\n1.0\n10030.937\n738\n715\n9546.201\n10091,000\n0.001\n0.02\n1.1\n718\n9546.200\n717\n7177.683\n308,000\n-0.67\n-0.023\n7177.706\n0.8\n721\n718\n13991.414\n798,000\n0.018\n0.26\n13991.396\n0.9\n720\n719\n17855.026\n2561,000\n0.007\n0.08\n724\n17855.019\n1.4\n720\n13993.951\n306,000\n-0.68\n-0.046\n13993.997\n1.3\n727\n721\n15466.425\n598,000\n0.026\n0.35\n1.6\n15466.399\n732\n721\n19822.731\n481,000\n0.43\n0.041\n19822.690\n1.5\n738\n721\n19012.886\n207,000\n-0.092\n-0.99\n1.2\n19012.978\n730\n724\n8677.086\n189,000\n0.046\n1.09\n0.8\n8677.040\n730\n727\n1705,000\n13335.787\n-0.008\n-0.12\n1.0\n732\n13335.795\n727\n9754.134\n7422,000\n-0.001\n-0.03\n1.1\n730\n9754.135\n729\n755,000\n-0.027\n20746.490\n-0.27\n1.8\n20746.517\n732\n729\n541,000\n-0.38\n-0.024\n12979.492\n1.5\n734\n12979.516\n729\n13054.017\n3180,000\n0.06\n0.004\n1.4\n13054.013\n732\n730\n16875.676\n596,000\n0.35\n0.028\n1.5\n16875.648\n734\n730\n4303,000\n0.000\n1049.944\n0.05\n0.4\n1049.944\n732\n731\n4499,000\n19695.938\n0.05\n0.004\n1.8\n19695.934\n734\n731\n775,000\n19520.372\n-0.025\n-0.27\n1.8\n19520.397\n734\n732\n167,000\n-1.23\n-0.059\n9930.577\n9930.636\n1.2\n738\n732\n21216.544\n284,000\n-0.075\n-0.73\n21216.619\n1.5\n752\n732\n24074.520\n709,000\n0.034\n0.29\n24074.486\n1.7\n738\n733\n24119.988\n906,000\n0.027\n0.23\n24119.961\n1.7\n738\n734\n1625,000\n11690.206\n-0.007\n11690.213\n1.2\n-0.13\n752\n734\n15646.252\n496,000\n0.032\n0.42\n15646.220\n1.5\n755\n734\n23866.212\n660,000\n0.036\n0.31\n23866.176\n1.8\n768\n734\n728,000\n7557.584\n-0.010\n0.9\n-0.28\n7557.594\n737\n735\n8427.280\n386,000\n-0.022\n-0.53\n8427.302\n0.9\n738\n735\n3728.695\n172,000\n-0.022\n-1.20\n3728.717\n0.6\n739\n735\n6600.017\n562,000\n-0.012\n-0.37\n6600.029\n1.0\n740\n735\n636,000\n5717.105\n-0.009\n-0.32\n5717.114\n0.9\n741\n735\n373,000\n15944.785\n0.043\n0.55\n1.7\n738\n15944.742\n736\n254,000\n0.063\n15966.143\n0.81\n15966.080\n1.7\n738\n737\n7768.227\n1241,000\n0.006\n0.17\n7768.221\n0.8\n739\n737\n2991.417\n1078,000\n-0.003\n-0.19\n2991.420\n0.6\n740\n737\n269,000\n25079.197\n0.77\n0.093\n25079.104\n1.9\n752\n737\n861,000\n29334.891\n0.24\n0.034\n1.0\n766\n29334.857\n737\n394,000\n10810.409\n-0.027\n-0.52\n10810.436\n0.9\n741\n738\n686,000\n20501.276\n0.30\n0.030\n20501.246\n1.8\n752\n738\n436,000\n0.062\n27174.409\n0.47\n764\n27174.347\n1.6\n738\n401,000\n-0.014\n5467.474\n-0.51\n0.7\n740\n5467.488\n739\n226,000\n2106.112\n-0.009\n2106.121\n0.6\n-0.91\n741\n739","262\nSan Fernando Earthquake of 1971\nTable 6B.-Adjustment 1 corrections to postearthquake observed lengths (U's) in meters-Continued\nStation\nObserved\nWeight\nv in\nV in\nAdjusted\nlength\nfactor\nseconds\nmeters\nlength\n1 part in\nFrom\nTo\n739\n742\n4796.027\n1.0\n-0.45\n-0.011\n4796.016\n455,000\n740\n741\n6620.000\n0.8\n-1.13\n-0.036\n6619.964\n182,000\n740\n742\n4268.324\n0.6\n0.16\n0.003\n4268.327\n1301,000\n741\n742\n4374.583\n0.9\n0.23\n0.005\n4374.588\n912,000\n741\n743\n2489.515\n0.7\n-0.52\n-0.006\n2489.509\n395,000\n741\n744\n5714.684\n1.2\n-0.61\n-0.017\n5714.667\n336,000\n742\n743\n4665.227\n0.9\n0.17\n0.004\n4665.231\n1231,000\n742\n744\n3959.540\n0.8\n1.08\n0.021\n3959.561\n191,000\n743\n744\n4009.449\n1.0\n0.47\n0.009\n4009.458\n443,000\n743\n745\n2500.442\n0.6\n-0.58\n-0.007\n2500.435\n358,000\n743\n746\n6113.238\n1.1\n0.06\n0.002\n6113.240\n3365,000\n744\n745\n3665.062\n0.8\n0.18\n0.003\n3665.065\n1118,000\n744\n746\n3873.355\n0.8\n-0.01\n-0.000\n3873.355\n16216,000\n745\n746\n3998.506\n0.9\n-0.70\n-0.014\n3998.492\n295,000\n745\n747\n2647.091\n0.7\n-0.47\n-0.006\n2647.085\n441,000\n745\n748\n4999.769\n0.9\n-0.32\n-0.008\n4999.761\n638,000\n746\n747\n3006.661\n0.8\n0.90\n0.013\n3006.674\n228,000\n746\n748\n1795.146\n0.5\n-0.74\n-0.006\n1795.140\n280,000\n746\n752\n11557.006\n1.0\n0.09\n0.005\n11557.011\n2346,000\n746\n757\n5948.545\n1.0\n0.42\n0.012\n5948.557\n489,000\n746\n764\n9442.006\n1.1\n0.07\n0.003\n9442.009\n3041,000\n746\n766\n19312.904\n1.0\n-0.15\n-0.014\n19312.890\n1378,000\n747\n748\n2997.346\n0.7\n1.41\n0.020\n2997.366\n147,000\n747\n752\n9626.233\n0.9\n0.14\n0.006\n9626.239\n1500,000\n747\n766\n21882.673\n1.0\n-0.06\n0.006\n21882.667\n3554,000\n748\n750\n2506.212\n0.7\n0.12\n0.001\n2506.213\n1725,000\n748\n757\n4476.773\n0.9\n-0.23\n0.005\n4476.768\n878,000\n748\n764\n9559.881\n1.2\n0.00\n0.000\n9559.881\n84883,000\n750\n754\n7081.447\n1.0\n-0.33\n-0.011\n7081.436\n620,000\n750\n757\n3662.679\n0.8\n0.05\n0.001\n3662.680\n3977,000\n752\n754\n2435.725\n0.5\n0.16\n0.002\n2435.727\n1304,000\n752\n755\n7283.864\n1.2\n0.07\n0.002\n7283.866\n2940,000\n754\n755\n5042.169\n0.7\n-0.58\n0.014\n5042.155\n358,000\n755\n767\n5237.757\n1.2\n0.09\n0.002\n5237.759\n2350,000\n756\n757\n4488.173\n1.0\n-0.24\n0.005\n4488.168\n843,000\n756\n758\n2311.136\n0.6\n-1.82\n0.020\n2311.116\n113,000\n757\n758\n3564.582\n0.9\n-0.01\n- 0.000\n3564.582\n19386,000\n757\n760\n5123.042\n0.2\n-0.89\n0.022\n5123.020\n233,000\n757\n761\n3074.378\n0.7\n-0.83\n0.012\n3074.366\n249,000\n758\n762\n3672.189\n0.8\n-0.66\n0.012\n3672.177\n314,000\nSTATISTICS\nNumber of lengths\n116\nMaximum positive V in seconds = 1.41\n=\nMaximum negative V in meters = 0.092\nMaximum length\n29334.857\nMaximum negative V in seconds = - 1.82\n=\nAverage length V in meters\n= 0.018\nMinimum length\n= 1049.944\nAverage length V in seconds\n0.42\nThe sum of pvv in seconds\n=\n= 32.0645\nAverage length\n= 9401.455\nMaximum positive V in meters\n0.093\nThe sum of VV in seconds\n=\n= 36.7634","Horizontal Crustal Movements\n263\nTable 7A.-Adjustment 1 adjusted positions of preearthquake survey stations 1\nGeographic position\nPlane coordinates-Zone VII\nStation number\nLatitude\nLongitude\nX\nr\no\nFeet\n34 08 24 .13923\n118 38 41.07085\n4092459.20\n4163510.61\n01\n4132638.09\n4159283.99\n34 07 43.28132\n118 30 42.98600\n02\n4094114.19\n4206090.10\n34 15 25.40070\n118 38 22.90210\n03\n4150169.26\n4235236.24\n34 20 14.88075\n118 27 15.52113\n04\n4164914.46\n4218895.58\n34 17 33.37401\n118 24 19.55491\n05\n4217748.98\n34 17 21.86799\n118 27 40.66384\n4148038.84\n06\n4223582.53\n34 18 19.66953\n118 25 58.17073\n4156644.60\n07\n4230701.26\n34 19 30.09478\n118 25 51.38155\n4157220.97\n08\n4218584.42\n34 17 30.02505\n118 29 14.32599\n4140181.01\n09\n34 15 27.78137\n118 31 10.80743\n4130384.91\n4206243.24\n10\n34 17 14.47012\n118 32 23.72111\n4124286.36\n4217040.05\n11\n34 18 42.15189\n118 31 58.45349\n4126423.91\n4225899.53\n12\n34 19 12.75229\n118 33 53.40055\n4116788.41\n4229013.27\n13\n4139949.45\n4201820.71\n34 14 44.19042\n118 29 16.78301\n14\n4164313.76\n4208317.68\n34 15 48.73046\n118 24 26.62268\n15\n4161644.80\n4240965.92\n34 21 11.67283\n118 24 58.73696\n16\n4189241.55\n4162250.29\n34 08 13.09229\n118 19 29.67663\n17\n4190699.39\n18\n34 12 54.48156\n118 16 44.67239\n4203096.65\n34 09 48.84883\n118 11 45.00525\n4228288.67\n4171957.92\n19\n34 13 25.51247\n118 03 38.66826\n4269098.66\n4193941.90\n20\n34 16 08.38752\n118 14 17.09792\n4215472.01\n4210310.10\n21\n34 20 55.42361\n118 13 41.75065\n4218408.81\n4239329.42\n22\n4234585.00\n4249102.47\n34 22 31.89266\n118 10 28.65164\n23\n4277109.53\n4251502.70\n34 22 54.69144\n118 02 01.25939\n24\n4277109.53\n4251502.70\n34 22 54.69144\n118 02 01.25939\n25\n4256765.35\n4295062.54\n34 30 06.10342\n118 06 02.79556\n26\n4253219.23\n34 23 12.65722\n118 11 01.76593\n4231803.21\n27\n4305564.17\n34 31 50.26668\n118 08 50.24810\n4242730.65\n28\n4311744.44\n34 32 51.69901\n118 12 52.65572\n4222441.22\n29\n4279756.64\n34 27 35.29551\n118 13 04.37995\n4221496.63\n30\n34 23 10.27034\n118 19 02.70009\n4191495.06\n4252945.28\n31\n34 23 10.87195\n118 19 43.79059\n4188051.14\n4253005.75\n32\n34 33 37.91250\n118 21 18.25320\n4180147.46\n4316396.35\n33\n118 21 18.46343\n4180129.91\n4316556.93\n34 33 39.50083\n34\n4167499.39\n4330656.15\n34 35 58.91097\n118 23 49.57945\n35\n4163053.28\n4318768.01\n34 34 01.28886\n118 24 42.65223\n36\n4150839.50\n4330233.67\n34 35 54.58443\n118 27 08.85071\n37\n4145557.25\n4315049.20\n34 33 24.32169\n118 28 11.79036\n38\n4325926.97\n34 35 11.66816\n118 31 22.10029\n4129659.11\n39\n4310992.85\n34 32 44.06939\n118 29 56.70543\n4136775.13\n40\n4306628.62\n34 32 00.68913\n118 32 17.12216\n4125019.77\n41\n4300767.77\n34 31 02.84812\n118 30 52.32614\n4132104.01\n42\n34 29 52.17062\n118 33 00.98563\n4121322.24\n4293643.66\n43\n4131117.62\n4291298.87\n34 29 29.16713\n118 31 03.90903\n44\n4116652.43\n4286875.95\n34 28 45.12452\n118 33 56.59210\n45\n4124414.01\n4280837.53\n34 27 45.55887\n118 32 23.73840\n46\n4114564.01\n4281369.25\n34 27 50.60574\n118 34 21.38292\n47\n4271755.49\n34 26 15.70703\n118 32 31.66863\n4123731.38\n48\n4268854.80\n34 25 46.76276\n118 34 47.40713\n4112354.62\n49\n4263990.73\n34 24 58.91571\n118 32 21.39086\n4124576.61\n50\n118 34 56.13016\n4111592.27\n4255886.55\n34 23 38.46348\n51\n118 32 04.87432\n4125944.53\n4255938.36\n34 23 39.28902\n52\n34 21 21.89022\n118 35 24.06567\n4109216.42\n4242086.03\n53\n34 20 39.20798\n118 31 11.00075\n4130426.16\n4237725.21\n54\n118 32 06.97026\n4125755.22\n4249031.19\n34 22 30.95957\n55\n4157924.63\n4240603.70\n34 21 08.05753\n118 25 43.10223\n56\n4106161.80\n4232522.54\n34 19 47.20988\n118 36 00.20030\n57\n4106131.41\n4232769.35\n34 19 49.65055\n118 36 00.57029\n58\n4143191.96\n4306230.71\n34 31 57.06056\n118 28 39.91917\n59\n4293188.62\n34 29 46.72421\n118 40 03.80289\n4085929.74\n60\n4319153.53\n118 44 30.62807\n4063699.15\n34 34 02.75797\n61\n4319193.70\n34 34 03.15459\n118 44 30.86595\n4063679.42\n62\n4329225.29\n34 35 43.93793\n118 34 43.89374\n4112794.13\n63\n34 41 35.33648\n118 33 37.72068\n4118405.61\n4364738.39\n64\nThe geographic position of station Cahuenga 2, No. 17, is adjusted to North American Datum of 1927. All other stations depend on this\n1\nposition.","San Fernando Earthquake of 1971\n264\nTable .-Adjustment 1 adjusted positions of postearthquake survey stations 1\nGeographic position\nPlane coordinates-Zone VII\nStation number\nLatitude\nLongitude\nX\nr\nFeet\n701\n34 08 24.14020\n118\n38 41.07913\n4092458.50\n4163510.71\n702\n34 07 43.64195\n118 30 43.02693\n4132634.71\n4159320.45\n703\n34\n15\n25.40419\n118 38 22.91341\n4094113.24\n4206090.46\n704\n34\n20\n14.87897\n118 27 15.53396\n4150168.18\n4235236.06\n705\n34 17 33.38822\n118 24 19.63760\n4164907.52\n4218897.02\n706\n34 17 22.29305\n118 27 40.15621\n4148081.49\n4217791.90\n707\n34 18 19.67349\n118 25 58.21549\n4156640.85\n4223582.93\n709\n34 17 30.02622\n118 29 14.34207\n4140179.66\n4218584.54\n710\n34 15 27.78918\n118 31 10.81176\n4130384.55\n4206244.03\n711\n34 17 14.47639\n118 32 23.72981\n4124285.63\n4217040.69\n712\n34 18 42.15556\n118 31 58.46355\n4126423.07\n4225899.90\n713\n34 19 12.81828\n118 33 51.38749\n4116957.28\n4229019.56\n715\n34 15 48.74704\n118 24 26.61947\n4164314.03\n4208319.36\n717\n34 08 13.09229\n118 19 29.67663\n4189241.55\n4162250.29\n718\n34 12 52.92448\n118 16 49.68356\n4202675.88\n4190541.77\n719\n34 09 48.84660\n118 11 45.00406\n4228288.77\n4171957.69\n720\n34 13 21.28449\n118 03 42.05309\n4268815.56\n4193513.75\n721\n34 16 08.38688\n118 14 17.09381\n4215472.36\n4210310.04\n724\n34 22 54.68992\n118 02 01.25868\n4277109.59\n4251502.55\n726\n34 27 35.11248\n118 13 04.13387\n4221517.25\n4279738.16\n727\n34 23 12.65529\n118 11 01.76915\n4231802.94\n4253219.03\n729\n34 32 51.69627\n118 12 52.64923\n4222441.76\n4311744.16\n730\n34 27 35.29071\n118 13 04.37613\n4221496.95\n4279756.15\n731\n34 23 10.26417\n118 19 02.69809\n4191495.22\n4252944.65\n732\n34\n23\n10.86569\n118 19 43.79137\n4188051.07\n4253005.12\n733\n34\n33\n37.91200\n118 21 18.24694\n4180147.98\n4316396.30\n734\n34\n33\n39.50033\n118 21 18.45717\n4180130.43\n4316556.88\n735\n34 20 39.20911\n118 31 11.01028\n4130425.36\n4237725.33\n736\n34 19 46.09310\n118 35 59.05789\n4106257.32\n4232409.39\n737\n34 19 49.65577\n118 36 00.58040\n4106130.57\n4232769.88\n738\n34 21 08.04720\n118 25 43.11453\n4157923.60\n4240602.65\n739\n34 22 30.96428\n118 32 06.97924\n4125754.47\n4249031.67\n740\n34 21 21.89643\n118 35 24.07459\n4109215.68\n4242086.66\n741\n34 23 39.29397\n118 32 04.88375\n4125943.74\n4255938.86\n742\n34 23 38.47045\n118 34 56.13854\n4111591.57\n4255887.26\n743\n34 24 58.92016\n118 32 21.39831\n4124575.98\n4263991.18\n744\n34 25 46.76987\n118 34 47.41398\n4112354.05\n4268855.52\n745\n34 26 19.79007\n118 32 29.50673\n4123913.31\n4272167.89\n746\n34 27 50.61142\n118 34 21.38809\n4114563.57\n4281369.82\n747\n34 27 45.56482\n118 32 23.74249\n4124413.67\n4280838.13\n748\n34 28 45.13156\n118 33 6.59600\n4116652.10\n4286876.66\n749\n34 29 29.17290\n118 31 3.91224\n4131117.35\n4291299.46\n750\n34 29 52.17740\n118 33 00.98803\n4121322.04\n4293644.34\n751\n34 31 02.85334\n118 30 52.32809\n4132103.85\n4300768.30\n752\n34 31 57.06446\n118 28 39.91392\n4143192.40\n4306231.11\n753\n34 33 24.32593\n118 28 11.78874\n4145557.38\n4315049.63\n754\n34 32 44.07428\n118 29 56.70611\n4136775.07\n4310993.35\n755\n34 35 11.67326\n118 31 22.09766\n4129659.34\n4325927.48\n756\n34 32 00.69492\n118 32 17.12271\n4125019.73\n4306629.21\n757\n34 31 01.29329\n118 34 57.80237\n4111561.49\n4300653.91\n758\n34 32 35.80874\n118 33 37.20888\n4118327.06\n4310193.22\n759\n34 33 46.16172\n118 32 48.70588\n4122399.56\n4317296.86\n760\n34 30 06.68637\n118 38 07.49410\n4095671.17\n4295176.33\n761\n34 31 20.21196\n118 36 56.15203\n4101662.91\n4302592.27\n762\n34 32 37.32574\n118 36 01.21302\n4106280.48\n4310375.73\n763\n34 34 40.92363\n118 34 51.89194\n4112109.98\n4322856.36\n764\n34 29 46.73712\n118 40 03.80613\n4085929.47\n4293189.93\n765\n34 34 03.16718\n118 44 30.86318\n4063679.65\n4319194.97\n766\n34 34 02.77056\n118 44 30.62530\n4063699.39\n4319154.80\n767\n34 35 43.94567\n118 34 43.89125\n4112794.34\n4329226.07\n768\n34 41 35.34187\n118 33 37.71039\n4118406.47\n4364738.93\n1\nThe geographic position of station Cahuenga 2, No. 717, is adjusted to North American Datum of 1927. All other stations depend on this\nposition.","Horizontal Crustal Movements\n265\nTable 8A.-Adjustment 1 position shifts referred to station Cahuenga 2\nResultant vector\nPostearthquake minus preearthquake\nStation\nL\nAzimuth\nor\nAX\nFeet\nO\nFeet\nFeet\n0.97\n130\n+0.64\n-0.73\nBluff\n175\n+0.50\n0.50\n-0.06\nBrushy\n+0.71\n0.78\n155\n-0.33\nBum\n0\n0\n0\nCahuenga 2\n0.71\n100\n+0.10\n-0.70\nCalabasas\n1.02\n110\n+0.36\n-0.95\nChatsworth\n155\n+0.79\n0.87\n-0.36\nCorner 2\n+0.40\n0.59\n230\n+0.44\nDeer\n150\n+0.60\n0.69\n-0.34\nDry\n+0.12\n0.81\n100\n-0.80\nEast\n125\n+0.48\n0.89\n-0.75\nEdison\n0.25\n335\n-0.23\n+0.10\nFlint\n0.61\n295\n-0.28\n+0.54\nHauser\n0.45\n195\n+0.43\n+0.13\nHouse\n1.00\n135\n+0.71\n-0.70\nLock\n170\n+1.31\n1.34\n-0.27\nLoma Verde\n+0.57\n0.72\n140\n-0.44\nLong\n0.65\n345\n-0.63\n+0.16\nMagic\n1.47\n45\n-1.05\n-1.03\nMay\n0.92\n115\n+0.37\n-0.84\nMission Pt\n0.34\n55\n-0.20\n-0.27\nMt. Gleason\n0.93\n120\n+0.50\n-0.79\nNewhall\n0.16\n340\n-0.15\n+0.06\nPacifico\n0.36\n10\n-0.35\n-0.07\nPacoima E-2 ECC 1\n7.09\n100\n+1.44\n-6.94\nPacoima L-1\n1.70\n190\n+1.68\n+0.27\nPacoima No. 2\n0.58\n325\n-0.48\n+0.32\nParker\n0.52\n275\n-0.05\n+0.52\nPelona\n0.52\n275\n-0.05\n+0.52\nPelona ECC 2\n0.99\n120\n+0.53\n-0.84\nPico L-9 AUX 2 ECC 1\n0.63\n5\n-0.63\n-0.07\nPort\n0.59\n175\n+0.59\n-0.04\nPowerhouse\n205\n+0.51\n0.56\n+0.23\nRed\n1.36\n95\n+0.12\n-1.35\nReservoir\n0.55\n165\n+0.53\n-0.16\nRock\n0.77\n125\n+0.45\n-0.63\nSaugus\n1.02\n240\n+0.54\n+0.86\nSawmill\n0.36\n280\n-0.06\n+0.35\nSister Elsie\n0.71\n165\n+0.68\n-0.20\nSteer\n1.09\n80\n-0.18\n-1.08\nSylmar F-8\n3.77\n95\n+0.40\n-3.75\nSylmar I-12\n0.97\n130\n+0.63\n-0.74\nTowsley\n0.22\n310\n-0.14\n+0.17\nVerdugo AUX\n0.65\n155\n+0.59\n-0.27\nView\n0.81\n195\n+0.78\n+0.21\nWarm Springs\n1.29\n190\n+1.27\n+0.23\nWhitaker\n1.29\n190\n+1.27\n+0.24\nWPK A-7A AUX 1\n0.92\n140\n+0.72\n-0.57\nYucca","266\nSan Fernando Earthquake of 1971\nTable 9A.-Adjustment 1 95-percent error ellipses referred to station Cahuenga 2\nAxes (Feet)\nOrientation\nStation\nOne sigma\n95 percent\nof semimajor\naxis (°) O'\nat\nb1\nat\nb1\nBluff\n0.39\n0.21\n0.96\n0.52\n56\nBum\n.64\n.26\n1.58\n.64\n34\nCahuenga 2\n0\n0\n0\n0\nCalabasas\n.46\n.25\n1.12\n.60\n87\nChatsworth\n.47\n.23\n1.16\n.57\n70\nCorner 2\n.36\n.22\n.88\n.53\n62\nDeer\n.67\n.26\n1.64\n.63\n19\nDry\n.60\n.25\n1.48\n.62\n33\nEast\n.43\n.22\n1.06\n.53\n43\nEdison\n.48\n.23\n1.18\n.56\n41\nFlint\n.21\n.16\n.52\n.40\n14\nHauser\n.68\n.30\n1.68\n.73\n165\nHouse\n.70\n.26\n1.72\n.65\n17\nLock\n.55\n.24\n1.34\n.59\n45\nLong\n.63\n.26\n1.54\n.63\n36\nMagic\n.41\n.22\n1.01\n.55\n1\nMay\n.38\n.20\n.93\n.49\n26\nMission Pt\n.41\n.21\n1.00\n.52\n50\nMt. Gleason\n.46\n.26\n1.12\n.65\n152\nNewhall\n.51\n.23\n1.24\n.57\n39\nPacifico\n.57\n.34\n1.40\n.84\n129\nPacoima E-2 ECC 1\n.32\n.19\n.79\n.47\n42\nPacoima L-1\n.30\n.19\n.73\n.46\n28\nPacoima No. 2\n.26\n.18\n.63\n.44\n32\nParker\n.54\n.27\n1.32\n.66\n163\nPelona\n.68\n.25\n1.67\n.62\n4\nPelona ECC 2\n.68\n.25\n1.67\n.62\n4\nPico L-9 AUX 2 ECC 1\n.49\n.23\n1.20\n.56\n56\nPort\n.41\n.22\n1.01\n.54\n4\nPowerhouse\n.70\n.26\n1.72\n.65\n27\nRed\n.77\n.27\n1.89\n.66\n22\nReservoir\n.35\n.20\n.85\n.49\n46\nRock\n.66\n.26\n1.63\n.65\n25\nSaugus\n.54\n.24\n1.32\n.59\n37\nSawmill\n.96\n.31\n2.36\n.76\n22\nSister Elsie\n.25\n.19\n.61\n.46\n155\nSteer\n.66\n.26\n1.61\n.64\n31\nSylmar F-8\n.38\n.22\n.93\n.55\n35\nSylmar I-12\n.33\n.21\n.80\n.51\n33\nTowsley\n.51\n.23\n1.26\n.57\n51\nVerdugo AUX\n.17\n.14\n.41\n.34\n1\nView\n.63\n.26\n1.54\n.64\n27\nWarm Springs\n.82\n.27\n2.00\n.67\n27\nWhitaker\n.91\n.33\n2.22\n.82\n42\nWPK A-7A AUX 1\n.91\n.33\n2.22\n.82\n42\nYucca\n.59\n.25\n1.45\n.61\n41\nSemimajor axis.\nSemiminor axis.\nAngle of orientation is measured positive counterclockwise from east.","Horizontal Crustal Movements\n267\nAPPARENT HORIZONTAL DISPLACEMENT\n5 Miles\n0\n5\n10\nKm\n0\n768\nScale for Vectors and Ellipses\n0 1 2 3 4 5 6 7 Feet\n2 Meters\n0\n1\n767\n755\n734\n765\n753\n729\n756\n752\nX51\n750\n749\n764\n48\n730\n747\n746\n744\n743\nEpicenter\n732\nC\n741\n727\n724\n742\nt\n739\n740\n38\n735\n704\n737\n71\n707\n7\n05\n,706\n09\n711\nSan Fernando\n15\n721\n710\n703\n718\n719\n717\n701\nCAHUENGA 2\n( Held Fixed )\nFigure 2A.-Adjustment 1 position vectors and 95-percent error ellipses referred to station Cahuenga 2.","San Fernando Earthquake of 1971\n268\nTable 10.-Adjustment 1 parameters of strain (adjusted observations)\nUnits X 10-\nTriangle (stations)*\nE1\nE2\nOE1\nr\np\nw\no\n701-703-706\n+\n24\n+\n0.3\n149\n24\n+\n12\n+\n4\n703-711-710\n+\n18\n9\n165\n27\n5\n18\n-\n-\n703-737-711\n10\n0.4\n33\n10\n+\n5\n4\n-\n703-737-738\n28\n- 11\n113\n38\n+\n8\n+ 20\n703-738-706\n42\n- 41\n156\n83\n+\n0.2\n24\n704-705-706\n+\n3\n-414\n83\n416\n-205\n- 58\n704-705-709\n3\n-276\n65\n273\n-139\n+ 49\n704-706-709\n+182\n11\n158\n192\n+ 86\n9\n704-707-706\n+\n3\n-429\n85\n432\n-213\n48\n704-738-705\n36\n-236\n49\n199\n-136\n+126\n704-738-706\n+136\n60\n139\n195\n+ 38\n+ 33\n704-738-709\n+126\n50\n119\n176\n+ 38\n+ 96\n705-706-738\n- 38\n-458\n72\n421\n-248\n+ 13\n705-709-738\n20\n-306\n59\n285\n-163\n+ 72\n705-715-709\n+201\n-444\n126\n645\n-122\n-362\n706-709-738\n+188\n- 41\n157\n229\n+ 73\n- 24\n706-715-717\n+227\n- 39\n58\n266\n+ 94\n- 94\n706-738-715\n4\n- 75\n17\n79\n- 35\n- 63\n709-710-711\n9\n- 74\n134\n83\n32\n- 12\n709-710-712\n5\n- 79\n124\n74\n- 42\n- 1\n709-711-712\n12\n- 49\n123\n37\n31\n+ 14\n709-712-738\n20\n- 27\n174\n7\n24\n+ 32\n709-715-710\n+ 35\n- 89\n163\n124\n27\n- 65\n710-711-712\n+ 34\n- 32\n162\n66\n+ 1\n+\n1\n711-737-735\n+\n5\n- 24\n163\n29\n9\n+\n4\n-\n712-735-738\n+ 10\n- 26\n133\n35\n8\n+\n24\n-\n715-721-717\n+ 26\n7\n120\n33\n+ 9\n+ 21\n-\n715-738-721\n+ 15\n102\n162\n117\n- 44\n5\n-\n717-718-719\n+\n1\n2\n1\n4\n1\n+\n5\n-\n-\n717-721-719\n+\n2\n+\n1\n83\n1\n+\n2\n+\n7\n718-721-719\n+\n7\n0.1\n52\n7\n+\n3\n+\n4\n-\n721-727-724\n+ 11\n8\n151\n19\n+\n2\n9\n-\n721-731-727\n7\n- 11\n87\n3\n9\n11\n-\n-\n721-732-731\n+\n71\n- 17\n11\n87\n+ 27\n+ 17\n721-732-727\n4\n8\n156\n4\n6\n- 11\n-\n-\n721-738-732\n+\n32\n7\n18\n40\n+ 12\n3\n-\n724-727-730\n-\n15\n- 17\n27\n32\n1\n+ 12\n724-730-729\n11\n6\n57\n17\n+\n2\n1\n-\n727-732-730\n9\n21\n43\n30\n6\n5\n-\n729-730-732\n+\n9\n+\n3\n45\n6\n+\n6\n4\n729-730-734\n+\n7\n+\n1\n79\n6\n+\n4\n6\n729-732-734\n+\n9\n+\n1\n72\n9\n5\n+\n7\n730-732-733\n+\n11\n2\n62\n9\n6\n+\n6\n730-732-734\n+\n11\n+\n2\n62\n9\n6\n6\n+\n731-732-734\n+\n68\n+\n8\n9\n61\n38\n9\n732-738-733\n+\n32\n+\n5\n27\n28\n19\n1\n732-738-734\n+\n32\n+\n5\n27\n28\n19\n1\n732-738-752\n+\n38\n+\n6\n47\n32\n22\n+\n11\n732-752-734\n+\n8\n1\n106\n9\n3\n+\n12\n-\n734-738-752\n+\n18\n4\n85\n22\n7\n+\n19\n-\n734-752-755\n11\n9\n145\n20\n+\n1\n+\n2\n-\n734-752-765\n+\n7\n7\n146\n14\n0.2\n5\n-\n734-755-768\n+\n10\n4\n16\n14\n+\n3\n15\n-\n735-737-739\n+ 26\n2\n109\n28\n12\n13\n-\n735-737-740\n+\n19\n2\n104\n20\n+\n8\n+ 16\n-\n735-739-741\n+\n29\n- 47\n124\n76\n+ 30\n9\n735-740-739\n+\n26\n4\n105\n30\n+ 11\n+\n11\n-\n735-740-741\n+ 20\n8\n114\n28\n+ 10\n6\n-\n735-741-738\n+\n25\n- 23\n124\n49\n1\n+ 21\n737-740-739\n+ 16\n6\n94\n22\n+\n5\n+ 14\n-\n737-752-738\n+ 16\n8\n104\n25\n+\n4\n+ 27\n-\n737-764-738\n+ 11\n- 13\n126\n24\n1\n+ 19\n737-764-752\n+ 11\n+\n6\n148\n+ 15\n5\n+\n8\n737-765-752\n+\n7\n+ 2\n35\n+ 13\n5\n+\n4\n737-765-764\n+\n27\n- 24\n72\n51\n+\n2\n- 12\n737-766-738\n+\n4\n15\n136\n20\n6\n+ 20\n-\n737-766-752\n+\n7\n+\n2\n36\n5\n+\n4\n+ 13\n738-764-752\n+\n18\n7\n80\n11\n+\n12\n+ 22\n738-766-752\n+\n24\n+\n3\n65\n21\n+\n13\n16\n739-740-741\n+\n11\n6\n133\n16\n3\n2\n-\n739-740-742\n+ 10\n4\n111\n13\n+\n3\n8\n739-742-741\n+ 10\n13\n122\n22\n1\n5\n-\n740-742-741\n+ 10\n8\n108\n18\n+\n1\n+\n9\n741-742-743\n5\n- 10\n30\n5\n8\n-\n+\n17\nSee footnotes at end of table.","Horizontal Crustal Movements\n269\nTable 10.-Adjustment 1 parameters of strain (adjusted observations)-Continued\nUnits X 10-6\nTriangle (stations)*\nE2\n0E1\nE1\nr\np\n2\n+\n13\n104\n9\n7\n2\n-\n+\n741-742-744\n-\n4\n23\n15\n168\n- 11\n-\n4\n741-744-743\n+ 16\n12\n+\n1\n128\n- 5\n+\n6\n742-744-743\n+ 18\n16\n4\n148\n- 12\n+\n4\n743-744-746\n6\n24\n+ 17\n+\n61\n+ 5\n+ 29\n746-748-747\n1\n+ 10\n25\n33\n- 15\n+ 17\n746-752-747\n+ 16\n+ 16\n29\n84\n+ 31\n+\n2\n746-764-748\n11\n24\n13\n68\n+ 17\n+\n4\n746-764-752\n18\n+ 15\n40\n54\n2\n+ 38\n-\n746-766-747\n+ 19\n17\n6\n42\n+ 15\n3\n-\n746-766-752\n7\n6\n4\n+\n120\n+\n1\n7\n747-748-749\n6\n12\n6\n+\n8\n3\n9\n+\n747-748-750\n0.3\n+\n9\n85\n9\n5\n-\n4\n-\n747-750-749\n+ 15\n17\n+\n11\n2\n20\n+\n3\n747-750-752\n+ 18\n16\n+\n3\n33\n12\n5\n-\n747-766-752\n0.3\n+ 15\n13\n54\n7\n6\n-\n748-750-749\n+ 11\n2\n5\n29\n6\n-\n4\n-\n749-750-751\n+ 12\n4\n3\n44\n6\n-\n2\n-\n749-750-756\n+ 12\n6\n2\n95\n7\n-\n5\n-\n749-756-751\n+ 14\n10\n+\n0.5\n106\n6\n5\n-\n750-754-751\n+ 26\n11\n70\n157\n9\n61\n-\n750-754-752\n+ 13\n5\n3\n64\n+\n8\n+\n2\n750-756-751\n8\n31\n+ 11\n+\n175\n4\n+ 27\n-\n750-756-752\n6\n+ 10\n9\n51\n- 11\n2\n-\n750-756-754\n3\n69\n+ 33\n166\n-\n+ 68\n- 1\n751-754-752\n9\n14\n6\n+\n65\n6\n-\n+ 11\n-\n751-755-754\n+ 10\n73\n9\n3\n7\n-\n+ 1\n-\n751-756-754\n+ 12\n6\n3\n59\n6\n- 0.2\n-\n-\n751-756-755\n68\n+ 25\n- 18\n151\n9\n+ 59\n-\n752-754-753\n+ 66\n+ 55\n166\n11\n- 17\n+149\n752-754-755\n- 11\n- 13\n43\n113\n- 32\n+ 10\n752-755-753\n+ 16\n- 31\n84\n141\n+ 18\n82\n752-756-754\n+ 12\n+\n9\n28\n177\n- 2\n27\n752-756-755\n6\n24\n+ 4\n+\n158\n- 8\n16\n752-764-755\n23\n3\n+\n19\n- 14\n16\n-\n8\n752-764-765\n18\n+\n4\n10\n163\n- 5\n13\n752-764-767\n19\n+\n2\n1\n133\n- 7\n11\n752-765-767\n3\n4\n140\n29\n- 18\n-\n11\n752-767-755\n16\n22\n+\n4\n27\n- 7\n+ 15\n753-754-755\n11\n10\n5\n59\n+ 0.1\n- 10\n-\n754-756-755\n8\n+\n0.4\n14\n158\n+ 0.4\n6\n755-764-767\n+ 16\n2\n5\n3\n- 4\n-\n1\n755-764-768\n-\n+ 17\n+\n0.3\n2\n9\n- 4\n+ 5\n755-767-768\n+ 12\n6\n29\n9\n- 11\n2\n764-765-767\n-\n+ 17\n7\n61\n7\n- 10\n-\n3\n764-768-767\n-\nTotal shear r=\nStations are identified by postearthquake station numbers.\nr\np Dilatation-positive for expansion, negative for contraction.\nE1, E2 Principal axes of strain.\nw Rotation positive clockwise.\n0 Direction of E1 principal axis of strain measured positive\ncounterclockwise from east.","270\nSan Fernando Earthquake of 1971\nMAXIMUM RIGHT LATERAL SHEAR (y)\n(OVER 50 X 10-6 Radians)\nScale for Gamma (y)\n0\n600 X 10 6 Radians\n765 A\n753\n754\nit\n756\n752\n751\n0\n5 Miles\n764 A\n0\n5\n10 Km\nEpicenter\nO\n738\n704\n737\n712\no\n707\n709\n705\n711 x\n706\nSan Fernando\n721\n715\n710\n717\nCAHUENGA 2\n( Held Fixed )\nFigure 3A.-Adjustment 1 maximum shear (y), showing direction and magnitude of maximum positive simple shear for triangular\nareas in which shear is greater than 50 X 10-6 radians.","Horizontal Crustal Movements\n271\nRIGHT LATERAL SHEAR (y)\nScale for Gamma (y)\n50 X 10- 6 Radians\n0\n10 Km\n5\n0\n5 Miles\nO Epicenter\nSan Fernando\n8\n717\n8\nCAHUENGA 2\n(Held Fixed 1\nFigure 3B.-Adjustment 1 maximum shear (y), showing direction and magnitude of maximum\npositive simple shear for triangular areas in which shear is less than 50 X 10-6 radians.","San Fernando Earthquake of 1971\n272\nPRINCIPAL AXES OF STRAIN E1, E2\nScale for E1, E2\n50 X 10- 6 Radians\n0\n0\n5\nMiles\n0\n5\n10 Km\nt\nt\nGabriel\nO Epicenter\n....\nSan Fernando\n717\nCAHUENGA 2\n( Held Fixed )\nFigure 4.-Adjustment 1 principal axes of strain, showing direction and magnitude of maximum (E1) and minimum (E2)\nelongation (solid line) or contraction (dashed line). Triangular areas are identical to those in figure 3B.","Horizontal Crustal Movements\n273\nTable 5C.-Adjustment 2 corrections to preearthquake observed horizontal directions\nStation\nStation\nStation\nStation\nv\"\nv\"\nv\"\nv\"\nTo\nFrom\nTo\nFrom\nTo\nFrom\nTo\nFrom\n32\n1\n12\n21\n31\n1.46\n15\n-0.11\n2\n-0.24\n13\n0.82\n0.29\n-0.82\n33\n3\n-0.45\n54\n-0.21\n16\n56\n-0.95\n14\n0.85\n56\n-0.84\n17\n-0.59\n18\n-0.09\n59\n-0.14\n57\n-0.15\n13\n19\n0.37\n33\n2\n11\n0.55\n-0.43\n20\n0.59\n27\nI\n0.76\n12\n-0.63\n29\n1.00\n22\n-0.64\n3\n0.09\n54\n-0.12\n0.87\n23\n0.50\n30\n14\n1.03\n57\n0.20\n0.81\n15\n-0.05\n31\n0.08\n32\n14\n56\n0.88\n16\n-0.07\n56\n0.71\n1\n-0.47\n59\n0.61\n17\n-1.03\n22\n2\n0.36\n21\n0.28\n34\n18\n0.12\n3\n0.58\n26\n-0.67\n23\n0.56\n57\n-0.86\n5\n0.29\n30\n0.23\n31\n-0.84\n3\n6\n0.46\n31\n- 1.28\n1\n-0.35\n23\n15\n0.11\n0.51\n20\n-0.31\n35\n2\n-0.22\n16\n0.96\n36\n0.41\n21\n-0.33\n14\n0.90\n17\n1.10\n0.21\n39\n22\n-0.81\n16\n-0.21\n57\n0.04\n0.74\n56\n57\n-0.14\n24\n0.65\n15\n60\n-0.07\n26\n0.65\n4\n2\n0.20\n64\n0.36\n30\n0.02\n5\n-0.08\n4\n0.03\n35\n6\n0.02\n31\n0.13\n5\n0.11\n34\n-1.13\n7\n0.29\n24\n6\n0.16\n36\n-0.24\n-0.55\n8\n-0.10\n20\n9\n0.86\n0.19\n23\n-0.72\n37\n15\n-0.11\n14\n0.34\n26\n1.27\n38\n1.31\n5\n16\n0.84\n39\n0.29\n4\n0.25\n25\n17\n0.32\n64\n-0.43\n-0.74\n6\n0.04\n27\n18\n0.04\n36\n28\n0.23\n7\n-0.19\n21\n0.87\n34\n-0.01\n8\n0.02\n29\n0.51\n56\n-0.05\n-0.04\n35\n14\n-0.18\n26\n57\n-0.20\n37\n0.45\n23\n-0.71\n15\n0.08\n16\n-0.40\n24\n-1.01\n38\n6\n2\n-0.19\n37\n30\n0.48\n4\n0.37\n0.15\n3\n35\n-0.75\n5\n0.05\n34\n1.25\n6\n0.10\n36\n0.10\n7\n-0.34\n27\n9\n1.10\n38\n0.24\n-0.03\n8\n-0.27\n25\n14\n-0.11\n39\n0.31\n28\n0.33\n9\n0.29\n15\n-0.80\n40\n0.10\n-0.20\n14\n0.00\n29\n17\n-0.55\n38\n30\n0.60\n15\n0.04\n18\n-0.70\n35\n0.06\n16\n-0.08\n32\n-0.37\n21\n0.39\n36\n0.29\n33\n-0.33\n56\n-0.03\n56\n0.22\n37\n-0.46\n28\n7\n57\n0.36\n39\n-0.07\n27\n0.04\n4\n-0.85\n17\n40\n0.19\n29\n-0.15\n5\n0.04\n2\n1.00\n0.13\n39\n6\n0.42\n30\n14\n-0.01\n34\n-1.00\n8\n0.40\n29\n15\n-0.27\n35\n-0.27\n25\n- 1.15\n8\n16\n-0.49\n37\n-0.30\n27\n- 1.05\n4\n0.30\n18\n-0.38\n38\n0.04\n28\n0.31\n5\n0.10\n19\n0.54\n40\n1.02\n6\n-0.21\n30\n0.90\n20\n0.00\n41\n0.41\n0.41\n7\n-0.17\n32\n21\n-0.39\n42\n-0.37\n33\n0.57\n9\n18\n56\n-0.56\n6\n-0.36\n30\n0.01\n2\n-0.51\n60\n23\n-0.13\n10\n-0.39\n15\n-0.11\n63\n1.03\n26\n-0.65\n11\n0.54\n16\n-0.07\n64\n0.00\n27\n0.02\n12\n0.15\n17\n0.50\n40\n15\n0.30\n28\n-0.45\n19\n0.55\n29\n0.59\n37\n-0.39\n16\n0.37\n20\n0.79\n31\n-0.22\n38\n0.17\n56\n-0.61\n21\n0.01\n32\n0.65\n39\n-0.22\n10\n56\n-0.06\n0.09\n33\n0.16\n41\n9\n-0.01\n34\n0.03\n42\n0.35\n11\n- 0.65\n19\n0.66\n17\n1.22\n12\n31\n41\n18\n-0.31\n21\n-0.53\n39\n-0.47\n11\n20\n-0.66\n-0.40\n22\n0.51\n40\n9\n0.07\n21\n-0.26\n23\n0.24\n42\n0.38\n10\n0.09\n30\n0.48\n43\n-0.12\n12\n0.49\n20\n0.61\n32\n-1.58\n44\n13\n0.94\n17\n0.03\n34\n-0.99\n42\n56\n0.93\n18\n-0.15\n56\n1.86\n39\n-0.18\n57\n- 1.35\n19\n0.40\n40\n0.33\n21\n-0.62\n32\n12\n27\n-0.27\n41\n-0.12\n23\n0.30\n9\n0.00\n43\n-0.14\n0.51\n29\n-0.03\n10\n0.81\n24\n-0.39\n44\n0.10\n-0.47\n30\n11\n- 0.59\n57","San Fernando Earthquake of 1971\n274\nTable 5C.-Adjustment 2 corrections to preearthquake observed horizontal dirertions-Continued\nStation\nStation\nStation\nStation\nv\"\nv\"\nv\"\nv\"\nFrom\nTo\nFrom\nTo\nFrom\nTo\nFrom\nTo\n43\n50\n56\n58\n41\n-0.13\n47\n0.33\n9\n-0.78\n63\n0.23\n42\n0.14\n48\n0.18\n11\n0.19\n59\n44\n0.00\n49\n0.09\n12\n0.03\n32\n- 0.31\n45\n- 0.22\n51\n0.04\n15\n1.24\n33\n- 0.03\n46\n0.21\n52\n0.01\n16\n-0.47\n56\n- 1.05\n44\n51\n18\n-0.14\n58\n0.11\n41\n- -0.80\n49\n-0.22\n21\n-0.19\n61\n1.16\n42\n0.39\n50\n0.25\n31\n0.41\n63\n0.12\n43\n- 0.30\n52\n-0.30\n32\n- 0.31\n60\n45\n0.67\n53\n0.06\n33\n0.39\n34\n- 0.48\n46\n0.05\n55\n0.19\n34\n0.36\n39\n0.48\n45\n52\n39\n- 0.94\n56\n- 0.30\n43\n-0.17\n49\n0.72\n52\n0.96\n57\n0.33\n44\n-0.32\n50\n0.18\n54\n0.63\n62\n0.90\n46\n0.05\n51\n0.41\n57\n0.20\n63\n0.59\n47\n-0.13\n53\n0.00\n58\n- 1.66\n64\n0.95\n48\n0.57\n54\n- 0.18\n59\n- 0.38\n61\n46\n55\n0.32\n60\n- 0.80\n33\n43\n0.19\n- 0.80\n56\n-0.85\n61\n1.10\n56\n44\n0.35\n0.25\n57\n-0.62\n64\n- 0.43\n45\n-0.32\n58\n0.40\n53\n57\n47\n-0.24\n59\n0.14\n51\n0.03\nI\n- 2.05\n48\n0.02\n52\n- 0.59\n62\n2\n- 1.55\n47\n54\n0.85\n34\n-0.75\n3\n0.39\n45\n-0.12\n55\n0.12\n11\n- 0.32\n57\n1.39\n46\n0.49\n57\n0.41\n13\n1.54\n59\n0.21\n48\n-0.24\n54\n14\n- 0.96\n60\n0.88\n49\n-0.54\n12\n- 0.26\n0.03\n15\n63\n- 1.34\n50\n0.40\n13\n1.51\n16\n- 0.56\n63\n48\n52\n-0.08\n20\n- 0.30\n39\n0.19\n45\n-0.12\n53\n0.54\n52\n0.91\n58\n- -0.90\n46\n0.35\n55\n0.42\n53\n0.24\n59\n- 1.13\n47\n-0.13\n56\n0.64\n54\n0.08\n60\n1.06\n49\n- 0.23\n57\n- 0.85\n55\n0.82\n62\n- -0.53\n50\n0.14\n55\n56\n0.09\n64\n1.31\n49\n51\n- 0.62\n59\n1.36\n64\n47\n0.23\n52\n0.00\n60\n- 0.10\n34\n0.08\n48\n0.43\n53\n0.08\n62\n1.76\n35\n- 1.20\n50\n- 0.35\n54\n0.58\n58\n39\n0.27\n51\n0.08\n57\n0.13\n56\n-0.52\n56\n-0.51\n52\n- 0.71\n56\n59\n0.08\n60\n0.43\n56\n0.41\n6\n0.58\n61\n0.21\n63\n0.94","Horizontal Crustal Movements\n275\nTable 5D.-Adjustment 2 corrections to postearthquake observed horizontal directions\nStation\nStation\nStation\nStation\nv\"\nv\"\nv\"\nv\"\nTo\nFrom\nTo\nFrom\nTo\nFrom\nTo\nFrom\n746\n701\n719\n735\n747\n-0.05\n737\n-0.25\n702\n-0.18\n717\n-0.95\n748\n0.26\n703\n0.84\n718\n-0.21\n738\n-0.47\n0.59\n706\n-0.66\n720\n0.37\n739\n-0.21\n752\n0.16\n-0.34\n757\n702\n721\n0.78\n740\n764\n0.24\n741\n0.05\n701\n0.23\n720\n766\n-1.18\n736\n703\n0.34\n719\n-0.52\n706\n-0.55\n721\n0.33\n703\n-0.54\n747\n745\n-0.95\n710\n1.14\n715\n-0.54\n724\n0.19\n746\n-0.61\n713\n1.02\n717\n0.52\n721\n-0.03\n-0.45\n748\n703\n715\n-1.97\n717\n749\n1.82\n701\n1.53\n717\n-0.35\n735\n0.17\n-1.34\n750\n0.06\n702\n-0.36\n719\n0.55\n738\n752\n-0.69\n737\n706\n-0.62\n720\n-0.18\n766\n0.43\n713\n0.97\n736\n0.32\n724\n0.38\n748\n735\n0.05\n738\n-0.86\n727\n-0.70\n745\n-0.03\n704\n731\n0.94\n738\n-0.27\n746\n-0.04\n739\n0.78\n705\n0.08\n732\n1.07\n747\n0.19\n-0.76\n706\n0.18\n738\n0.25\n740\n749\n-0.47\n752\n-0.36\n709\n-0.11\n724\n750\n0.07\n764\n0.13\n738\n-0.16\n720\n-0.02\n757\n0.31\n0.33\n765\n-0.27\n705\n721\n-0.28\n764\n-0.03\n-0.57\n766\n704\n0.34\n726\n749\n738\n706\n0.06\n727\n-0.04\n0.72\n747\n-0.72\n0.29\n703\n709\n0.27\n729\n748\n0.46\n704\n-0.03\n738\n-0.67\n726\n0.17\n750\n0.05\n724\n0.34\n705\n706\n0.60\n-0.41\n751\n701\n1.21\n727\n0.40\n706\n756\n-0.28\n709\n-0.37\n702\n1.04\n729\n-0.34\n-0.41\n710\n-0.55\n750\n703\n1.28\n732\n747\n0.01\n712\n1.23\n704\n-0.56\n727\n0.31\n715\n0.92\n748\n-0.09\n705\n-1.24\n721\n-0.43\n0.23\n749\n709\n-1.03\n724\n1.40\n721\n751\n0.38\n732\n-0.07\n715\n-0.54\n726\n-0.60\n-1.12\n733\n-0.88\n752\n0.43\n717\n0.88\n732\n754\n0.29\n734\n-2.20\n738\n-1.04\n729\n0.65\n756\n0.13\n724\n-0.92\n735\n709\n0.05\n0.58\n757\n704\n0.44\n726\n0.05\n736\n751\n737\n-0.10\n705\n0.61\n730\n0.04\n749\n0.03\n741\n1.27\n706\n0.08\n732\n1.05\n750\n-0.27\n-0.11\n711\n- -1.54\n734\n0.22\n752\n754\n-0.29\n764\n-0.98\n712\n0.08\n730\n755\n0.45\n766\n-0.04\n738\n0.35\n729\n-0.33\n756\n0.10\n732\n0.20\n739\n711\n752\n735\n0.28\n709\n0.34\n733\n0.28\n732\n-0.06\n737\n-0.95\n710\n0.50\n734\n0.26\n734\n-0.46\n740\n-0.11\n712\n-0.01\n731\n737\n0.36\n0.29\n741\n0.23\n713\n-0.85\n732\n738\n0.43\n742\n0.55\n734\n-0.28\n712\n746\n-0.37\n741\n709\n-0.10\n732\n747\n-0.24\n735\n0.56\n710\n-0.93\n721\n1.31\n750\n1.02\n-0.51\n711\n0.77\n726\n-0.19\n738\n753\n0.53\n739\n-0.58\n727\n0.50\n713\n-0.14\n754\n-0.07\n740\n-0.39\n735\n0.20\n729\n0.43\n755\n1.22\n0.54\n730\n-0.20\n742\n738\n0.18\n756\n-1.29\n0.36\n731\n-0.31\n743\n713\n764\n-1.37\n744\n0.01\n711\n1.51\n733\n-1.60\n765\n-0.79\n1.42\n743\n712\n-0.10\n734\n2.03\n766\n741\n-0.69\n735\n0.36\n738\n0.78\n767\n-0.94\n-0.07\n752\n0.70\n742\n736\n0.05\n744\n-0.42\n753\n737\n-1.83\n733\n752\n-0.22\n745\n0.35\n729\n-0.83\n715\n754\n-0.31\n0.83\n-0.08\n746\n702\n-0.36\n730\n755\n0.51\n732\n0.31\n744\n706\n-0.67\n741\n-0.63\n754\n717\n0.91\n738\n0.60\n750\n0.09\n742\n0.37\n721\n-0.18\n734\n751\n0.28\n-0.39\n0.53\n743\n738\n0.31\n729\n752\n0.18\n0.28\n730\n0.51\n745\n717\n753\n-0.08\n746\n0.36\n702\n0.44\n731\n1.37\n755\n0.29\n-0.39\n745\n706\n0.42\n732\n756\n-0.58\n743\n-0.78\n715\n-0.38\n738\n-0.55\n759\n-0.20\n744\n0.41\n-0.13\n718\n0.28\n752\n755\n746\n0.06\n719\n-1.18\n755\n0.48\n734\n-0.34\n747\n0.61\n721\n0.42\n765\n-1.10\n-0.27\n751\n748\n-0.30\n-0.73\n736\n-0.01\n768\n752\n0.31\n746\n735\n718\n0.11\n753\n0.97\n712\n0.48\n743\n717\n0.25\n754\n0.40\n-0.06\n744\n-0.84\n719\n- -0.58\n713\n756\n-0.19\n745\n-0.14\n0.80\n721\n0.33\n736","276\nSan Fernando Earthquake of 1971\nTable 5D.-Adjustment 2 corrections to postearthquake observed horizontal directions-Continued\nStation\nStation\nStation\nStation\nv\"\nv\"\nv\"\nv\"\nFrom\nTo\nFrom\nTo\nFrom\nTo\nFrom\nTo\n755\n758\n762\n765\n759\n0.03\n756\n0.15\n758\n0.40\n752\n0.38\n764\n-0.26\n757\n1.05\n759\n-0.20\n764\n0.63\n767\n0.41\n759\n-0.01\n761\n0.01\n767\n-0.25\n768\n-0.17\n762\n-0.11\n763\n-0.05\n766\n763\n1.01\n763\n756\n737\n1.26\n759\n758\n-0.66\n749\n0.60\n738\n-0.21\n754\n-0.67\n759\n-0.71\n750\n-0.08\n746\n1.79\n755\n0.21\n762\n0.77\n751\n0.35\n747\n0.83\n756\n0.08\n767\n0.62\n752\n0.48\n752\n-0.09\n758\n-0.08\n764\n754\n0.52\n767\n762\n0.09\n737\n755\n0.29\n-1.88\n752\n0.41\n763\n0.78\n738\n1.00\n757\n-0.36\n755\n0.03\n767\n-0.39\n746\n758\n0.19\n0.07\n757\n-0.55\n760\n748\n759\n0.15\n0.17\n759\n-0.13\n757\n-0.13\n752\n0.37\n760\n-0.16\n757\n761\n0.04\n755\n0.07\n761\n-1.12\n746\n-0.04\n767\n0.07\n757\n0.12\n763\n-0.15\n748\n1.07\n761\n-2.17\n761\n764\n0.82\n750\n0.18\n765\n0.28\n757\n-0.92\n765\n0.45\n756\n0.32\n767\n0.85\n760\n0.00\n768\n0.41\n758\n0.27\n768\n-0.90\n762\n0.37\n760\n0.05\n768\n764\n0.71\n761\n0.34\n765\n734\n0.14\n767\n-0.17\n762\n0.22\n734\n0.28\n755\n0.12\n764\n- 0.28\n762\n737\n1.53\n764\n0.29\n767\n1.42\n757\n-0.17\n738\n0.50\n767\n-0.55\nTable 6C.-Adjustment 2 corrections to preearthquake observed lengths (v's) in meters\nStation\nObserved\nWeight\nV in\nV in\nAdjusted\nlength\nfactor\nseconds\nmeters\nlength\n1 part in\nFrom\nTo\n1\n3\n12988.206\n1.0\n0.60\n0.038\n12988.244\n343,000\n1\n17\n29502.131\n1.0\n1.37\n0.196\n29502.327\n151,000\n16\n56\n1139.270\n0.3\n1.29\n0.007\n1139.277\n160,000\n31\n32\n1049.944\n0.1\n- 12.44\n- 0.063\n1049.881\n17,000\n31\n34\n19695.796\n2.4\n- 0.26\n- 0.025\n19695.771\n784,000\n34\n64\n23866.161\n2.4\n0.58\n0.067\n23866.228\n358,000\n39\n63\n5237.752\n0.6\n0.19\n0.005\n5237.757\n1096,000\n60\n63\n13700.048\n1.6\n0.47\n- 0.031\n13700.017\n441,000\nSTATISTICS\nNumber of lengths =\n8\nMaximum positive V in seconds\n1.37\nMaximum negative V in meters\n= - 0.063\n=\nMaximum length\n= 29502.131\nMaximum negative V in seconds =\n12.44\nAverage length V in meters\n= 0.054\n-\nMinimum length\n= 1049.944\nAverage length V in seconds\n2.15\nThe sum of pvv in seconds\n= 6.8170\n=\nAverage length\n= 13397.413\nMaximum positive V in meters\n0.196\nThe sum of VV in seconds\n=\n= 159.3183","Horizontal Crustal Movements\n277\nTable 6D.-Adjustment 2 corrections to postearthquake observed lengths (U's) in meters\nWeight\nV in\nV in\nAdjusted\nStation\nObserved\n1 part in\nlength\nlength\nfactor\nseconds\nmeters\nFrom\nTo\n1.0\n-0.23\n-0.014\n12312.306\n901,000\n701\n702\n12312.320\n3113,000\n-0.004\n12988.244\n701\n703\n12988.248\n1.0\n-0.07\n380,000\n0.54\n0.062\n23689.299\n701\n706\n23689.237\n1.0\n-0.37\n-0.033\n18468.505\n558,000\n702\n703\n18468.538\n1.0\n18433.742\n287,000\n702\n706\n18433.678\n1.0\n0.72\n0.064\n1.0\n0.28\n0.024\n17784.667\n743,000\n702\n715\n17784.643\n337,000\n-0.051\n17277.039\n702\n717\n17277.090\n1.0\n-0.61\n0.031\n8834.896\n281,000\n703\n736\n8834.865\n1.0\n0.73\n475,000\n0.014\n6707.133\n704\n705\n6707.119\n1.2\n0.43\n20856,000\n704\n706\n5354.937\n0.8\n-0.01\n-0.000\n5354.937\n4063.040\n27911,000\n0.01\n0.000\n704\n707\n4063.040\n0.6\n5918.539\n418,000\n704\n709\n5918.553\n0.8\n-0.49\n-0.014\n0.4\n-0.46\n-0.006\n2874.641\n449,000\n704\n738\n2874.647\n4780,000\n-0.001\n5139.683\n705\n706\n5139.684\n0.8\n-0.04\n562,000\n705\n709\n7537.743\n1.2\n-0.37\n-0.013\n7537.730\n6949.969\n543,000\n0.38\n0.013\n705\n738\n6949.956\n0.7\n3149.940\n21352,000\n706\n707\n3149.940\n0.8\n-0.01\n-0.000\n2420.583\n122,000\n0.7\n-1.69\n-0.020\n706\n709\n2420.603\n5728.546\n10417,000\n706\n715\n5728.547\n1.0\n-0.02\n-0.001\n-0.021\n7572.359\n353,000\n0.7\n-0.58\n706\n738\n7572.380\n128,000\n-0.038\n4867.340\n4867.378\n0.9\n-1.61\n709\n711\n245,000\n4749.053\n0.6\n-0.84\n-0.019\n4749.034\n709\n712\n0.10\n0.004\n8619.204\n2055,000\n709\n738\n8619.200\n0.7\n3779.621\n3068,000\n710\n711\n3779.620\n0.7\n0.07\n0.001\n0.7\n-0.17\n-0.005\n6111.640\n1203,000\n710\n712\n6111.645\n168,000\n-0.065\n10848.362\n710\n736\n10848.427\n0.8\n-1.23\n165,000\n-1.25\n0.081\n13421.413\n710\n738\n13421.494\n1.0\n139,000\n-1.49\n-0.020\n2777.793\n711\n712\n2777.813\n0.5\n278,000\n711\n713\n4280.273\n0.5\n-0.74\n-0.015\n4280.258\n0.09\n0.001\n3037.846\n2366,000\n712\n713\n3037.845\n0.6\n3805.261\n3710,000\n712\n735\n3805.260\n0.7\n0.06\n0.001\n1.1\n-0.40\n-0.021\n10595.786\n512,000\n712\n738\n10595.807\n1310,000\n-0.004\n4888.059\n713\n735\n4888.063\n0.7\n-0.16\n309,000\n713\n737\n3492.387\n0.7\n-0.67\n-0.011\n3492.376\n10030.978\n247,000\n0.84\n0.041\n715\n738\n10030.937\n1.0\n9546.218\n521,000\n717\n718\n9546.200\n1.1\n0.40\n0.018\n0.8\n-0.26\n-0.009\n7177.697\n799,000\n718\n721\n7177.706\n0.025\n13991.421\n555,000\n719\n720\n13991.396\n0.9\n0.37\n0.010\n17855.029\n1716,000\n1.4\n0.12\n720\n724\n17855.019\n465,000\n-0.030\n13993.967\n721\n727\n13993.997\n1.3\n-0.44\n421,000\n0.49\n0.037\n15466.436\n721\n732\n15466.399\n1.6\n19822.686\n4797,000\n-0.04\n-0.004\n721\n738\n19822.690\n1.5\n19012.921\n333,000\n724\n730\n19012.978\n1.2\n-0.62\n-0.057\n1.64\n0.069\n8677.109\n126,000\n0.8\n727\n730\n8677.040\n718,000\n-0.019\n13335.776\n727\n732\n13335.795\n1.0\n-0.29\n950,000\n0.22\n0.010\n9754.145\n729\n730\n9754.135\n1.1\n774,000\n-0.27\n-0.027\n20746.490\n729\n732\n20746.517\n1.8\n609,000\n12979.495\n729\n734\n12979.516\n1.5\n-0.34\n-0.021\n2862,000\n-0.07\n-0.005\n13054.008\n730\n732\n13054.013\n1.4\n16875.698\n339,000\n730\n734\n16875.648\n1.5\n0.61\n0.050\n0.4\n-0.06\n-0.000\n1049.944\n3181,000\n731\n732\n1049.944\n682,000\n0.029\n19695.963\n731\n734\n19695.934\n1.8\n0.30\n21221,000\n732\n734\n19520.397\n1.8\n-0.01\n-0.001\n19520.396\n116,000\n-1.77\n-0.085\n9930.551\n732\n738\n9930.636\n1.2\n21216.537\n260,000\n732\n752\n21216.619\n1.5\n-0.79\n-0.082\n488,000\n1.7\n0.42\n0.049\n24074.535\n733\n738\n24074.486\n572,000\n0.042\n24120.003\n734\n738\n24119.961\n1.7\n0.36\n341,000\n-0.60\n-0.034\n11690.179\n734\n752\n11690.213\n1.2\n1708,000\n0.009\n15646.229\n734\n755\n15646.220\n1.5\n0.12\n461,000\n0.45\n0.052\n23866.228\n734\n768\n23866.176\n1.8\n7557.573\n354,000\n-0.58\n-0.021\n735\n737\n7557.594\n0.9\n8427.266\n237,000\n735\n738\n8427.302\n0.9\n-0.87\n-0.036\n-0.023\n3728.694\n163,000\n0.6\n-1.27\n735\n739\n3728.717\n392,000\n-0.017\n6600.012\n735\n740\n6600.029\n1.0\n-0.53\n551,000\n735\n741\n5717.114\n0.9\n-0.37\n-0.010\n5717.104\n0.24\n0.018\n15944.760\n862,000\n736\n738\n15944.742\n1.7\n15966.118\n419,000\n737\n738\n15966.080\n1.7\n0.49\n0.038\n-0.07\n-0.003\n7768.218\n2854,000\n0.8\n737\n739\n7768.221\n2991.413\n444,000\n0.6\n-0.46\n-0.007\n737\n740\n2991.420\n0.088\n25079.192\n285,000\n1.9\n0.72\n737\n752\n25079.104\n745,000\n0.039\n29334.896\n29334.857\n1.0\n0.28\n737\n766\n264,000\n10810.436\n0.9\n-0.78\n-0.041\n10810.395\n738\n741\n20501.292\n450,000\n0.46\n0.046\n738\n752\n20501.246\n1.8\n633,000\n27174.347\n1.6\n0.33\n0.043\n27174.390\n738\n764\n5467.471\n317,000\n-0.65\n-0.017\n739\n740\n5467.488\n0.7\n2106.111\n215,000\n0.6\n-0.96\n-0.010\n739\n741\n2106.121\n-0.012\n4796.015\n401,000\n1.0\n-0.51\n739\n742\n4796.027\n164,000\n-0.040\n6619.960\n6620.000\n0.8\n-1.25\n740\n741\n-0.000\n4268.324\n40845,000\n4268.324\n0.6\n-0.01\n740\n742","278\nSan Fernando Earthquake of 1971\nTable 6D.-Adjustment 2 corrections to postearthquake observed lengths (U's) in meters-Continued\nStation\nObserved\nWeight\nV in\nV in\nAdjusted\nlength\nfactor\nseconds\nmeters\nlength\n1 part in\nFrom\nTo\n741\n742\n4374.583\n0.9\n0.18\n0.004\n4374.587\n1127,000\n741\n743\n2489.515\n0.7\n-0.47\n-0.006\n2489.509\n437,000\n741\n744\n5714.684\n1.2\n-0.64\n-0.018\n5714.666\n323,000\n742\n743\n4665.227\n0.9\n0.14\n0.003\n4665.230\n1448,000\n742\n744\n3959.540\n0.8\n0.97\n0.019\n3959.559\n213,000\n743\n744\n4009.449\n1.0\n0.46\n0.009\n4009.458\n452,000\n743\n745\n2500.442\n0.6\n-0.53\n-0.006\n2500.436\n392,000\n743\n746\n6113.238\n1.1\n0.03\n0.001\n6113.239\n6710,000\n744\n745\n3665.062\n0.8\n0.17\n0.003\n3665.065\n1225,000\n744\n746\n3873.355\n0.8\n-0.13\n-0.002\n3873.353\n1590,000\n745\n746\n3998.506\n0.9\n-0.74\n- 0.014\n3998.492\n277,000\n745\n747\n2647.091\n0.7\n-0.45\n-0.006\n2647.085\n457,000\n745\n748\n4999.769\n0.9\n-0.35\n- -0.008\n4999.761\n592,000\n746\n747\n3006.661\n0.8\n0.88\n0.013\n3006.674\n233,000\n746\n748\n1795.146\n0.5\n-0.77\n-0.007\n1795.139\n269,000\n746\n752\n11557.006\n1.0\n0.11\n0.006\n11557.012\n1832,000\n746\n757\n5948.545\n1.0\n0.39\n0.011\n5948.556\n524,000\n746\n764\n9442.006\n1.1\n-0.00\n-0.000\n9442.006\n75555,000\n746\n766\n19312.904\n1.0\n0.11\n0.010\n19312.914\n1842,000\n747\n748\n2997.346\n0.7\n1.39\n0.020\n2997.366\n149,000\n747\n752\n9626.233\n0.9\n0.17\n0.008\n9626.241\n1185,000\n747\n766\n21882.673\n1.0\n0.17\n0.018\n21882.691\n1225,000\n748\n750\n2506.212\n0.7\n0.21\n0.003\n2506.215\n1002,000\n748\n757\n4476.773\n0.9\n-0.27\n- 0.006\n4476.767\n761,000\n748\n764\n9559.881\n1.2\n-0.01\n- 0.000\n9559.881\n23072,000\n750\n754\n7081.447\n1.0\n-0.26\n- 0.009\n7081.438\n789,000\n750\n757\n3662.679\n0.8\n-0.05\n- 0.001\n3662.678\n4556,000\n752\n754\n2435.725\n0.5\n0.19\n0.002\n2435.727\n1072,000\n752\n755\n7283.864\n1.2\n0.25\n0.009\n7283.873\n836,000\n754\n755\n5042.169\n0.7\n-0.34\n0.008\n5042.161\n604,000\n755\n767\n5237.757\n1.2\n-0.01\n0.000\n5237.757\n19814,000\n756\n757\n4488.173\n1.0\n-0.22\n- 0.005\n4488.168\n955,000\n756\n758\n2311.136\n0.6\n-1.83\n- 0.021\n2311.115\n113,000\n757\n758\n3564.582\n0.9\n0.07\n0.001\n3564.583\n3152,000\n757\n760\n5123.042\n0.2\n-1.02\n0.025\n5123.017\n202,000\n757\n761\n3074.378\n0.7\n-0.89\n0.013\n3074.365\n232,000\n758\n762\n3672.189\n0.8\n-0.67\n0.012\n3672.177\n307,000\nSTATISTICS\nNumber of lengths\n116\nMaximum positive V in seconds =\n1.64\nMaximum negative V in meters\n=\n= - 0.085\nMaximum length\n= 29334.857\nMaximum negative V in seconds = -\n1.83\nAverage length V in meters\n= 0.020\nMinimum length\n= 1049.944\nAverage length V in seconds\n0.48\nThe sum of pvv in seconds\n= 38.8823\n=\nAverage length\n= 9401.455\nMaximum positive V in meters\n0.088\nThe sum of VV in seconds\n= 46.9722\n=","Horizontal Crustal Movements\n279\nTable 7C.-Adjustment 2 adjusted positions of preearthquake survey stations 1\nPlane coordinates-Zone VII\nGeographic position\nStation number\nr\nX\nLongitude\nLatitude\nFeet\n\"\n4163510.67\n4092458.65\n118 38 41.07730\n34 08 24.13977\n01\n4159283.96\n4132637.67\n118 30 42.99104\n34 07 43.28100\n02\n4206090.32\n4094113.52\n118 38 22.91005\n34 15 25.40288\n03\n4235236.47\n4150169.04\n118 27 15.52367\n34 20 14.88310\n04\n4218895.72\n4164914.29\n118 24 19.55698\n34 17 33.37539\n05\n4217749.14\n4148038.58\n118 27 40.66687\n34 17 21.86958\n06\n4223582.70\n4156644.40\n118 25 58.17314\n34 18 19.67125\n07\n4230701.46\n4157220.78\n118 25 51.38379\n34 19 30.09681\n08\n4218584.60\n4140180.70\n118 29 14.32964\n34 17 30.02684\n09\n4206243.31\n4130384.47\n118 31 10.81270\n34 15 27.78210\n10\n4217040.26\n4124285.88\n118 32 23.72676\n34 17 14.47217\n11\n4225899.81\n4126423.48\n118 31 58.45860\n34 18 42.15464\n12\n4229013.60\n4116787.92\n118 33 53.40644\n34 19 12.75554\n13\n4201820.82\n4139949.14\n118 29 16.78673\n34 14 44.19154\n14\n4208317.78\n4164313.57\n118 24 26.62495\n34 15 48.73143\n15\n4240966.16\n4161644.66\n118 24 58.73869\n34 21 11.67515\n16\n4162250.29\n4189241.55\n118 19 29.67663\n34 08 13.09229\n17\n4190699.36\n4203096.64\n118 16 44.67255\n34 12 54.48125\n18\n4171957.81\n4228288.74\n118 11 45.00436\n34 09 48.84776\n19\n4193941.79\n4269098.71\n118 03 38.66758\n34 13 25.51139\n20\n4210310.10\n4215472.05\n118 14 17.09743\n34 16 08.38754\n21\n4239329.46\n4218408.90\n118 13 41.74959\n34 20 55.42401\n22\n4249102.49\n4234585.11\n118 10 28.65024\n34 22 31.89283\n23\n4251502.69\n4277109.61\n118 02 01.25847\n34 22 54.69132\n24\n4251502.69\n4277109.61\n118 02 01.25847\n34 22 54.69132\n25\n4295062.44\n4256765.54\n118 06 02.79330\n34 30 06.10235\n26\n4253219.27\n4231803.32\n118 11 01.76462\n34 23 12.65759\n27\n4305564.10\n4242730.91\n118 08 50.24493\n34 31 50.26596\n28\n4311744.42\n4222441.58\n118 12 52.65141\n34 32 51.69884\n29\n4279756.66\n4221496.83\n118 13 04.37755\n34 27 35.29576\n30\n4252945.41\n4191495.13\n118 19 02.69923\n34 23 10.27166\n31\n4253005.90\n4188051.18\n118 19 43.79002\n34 23 10.87340\n32\n4316396.48\n4180147.78\n118 21 18.24934\n34 33 37.91377\n33\n4316557.06\n4180130.23\n118 21 18.45957\n34 33 39.50210\n34\n4330656.45\n4167499.66\n118 23 49.57613\n34 35 58.91390\n35\n4318768.25\n4163053.45\n118 24 42.65010\n34 34 01.29127\n36\n4330234.06\n4150839.67\n118 27 08.84868\n34 35 54.58823\n37\n4315049.54\n4145557.29\n118 28 11.78987\n34 33 24.32504\n38\n4325927.45\n4129659.17\n118 31 22.09963\n34 35 11.67296\n39\n4310993.24\n4136775.09\n118 29 56.70585\n34 32 44.07320\n40\n4306629.09\n4125019.70\n118 32 17.12304\n34 32 00.69375\n41\n4300768.19\n4132103.90\n118 30 52.32750\n34 31 02.85228\n42\n4293644.16\n4121322.09\n118 33 00.98747\n34 29 52.17562\n43\n4291299.32\n4131117.44\n118 31 03.91114\n34 29 29.17153\n44\n4286876.49\n4116652.23\n118 33 56.59444\n34 28 45.12985\n45\n4280838.03\n4124413.78\n118 32 23.74117\n34 27 45.56377\n46\n4281369.80\n4114563.78\n118 34 21.38566\n34 27 50.61120\n47\n4271756.00\n4123731.10\n118 32 31.67196\n34 26 15.71204\n48\n4268855.36\n4112354.32\n118 34 47.41080\n34 25 46.76831\n49\n4263991.22\n4124576.30\n118 32 21.39459\n34 24 58.92063\n50\n4255887.09\n4111591.88\n118 34 56.13483\n34 23 38.46881\n51\n4255938.83\n4125944.20\n118 32 04.87837\n34 23 39.29371\n52\n4242086.50\n4109215.93\n118 35 24.07154\n34 21 21.89486\n53\n4237725.55\n4130425.79\n118 31 11.00518\n34 20 39.21131\n54\n4249031.63\n4125754.85\n118 32 06.97463\n34 22 30.96394\n55\n4240603.94\n4157924.49\n118 25 43.10393\n34 21 08.05995\n56\n4232522.93\n4106161.23\n118 36 00.20706\n34 19 47.21373\n57\n4232769.74\n4106130.85\n118 36 00.57705\n34 19 49.65440\n58\n4306231.04\n4143192.06\n118 28 39.91802\n34 31 57.06378\n59\n4293189.59\n4085929.47\n118 40 03.80617\n34 29 46.73378\n60\n4319154.45\n4063699.20\n118 44 30.62758\n34 34 02.76707\n61\n4319194.62\n4063679.46\n118 44 30.86546\n34 34 03.16369\n62\n4329225.93\n4112794.17\n118 34 43.89337\n34 35 43.94430\n63\n4364738.89\n4118406.03\n118 33 37.71564\n34 41 35.34144\n64\n1 The geographic position of station Cahuenga 2, No. 17, is adjusted to North American Datum of 1927. All other stations depend on\nthis position.","280\nSan Fernando Earthquake of 1971\nTable D.-Adjustment 2 adjusted positions of postearthquake survey stations\nGeographic position\nPlane coordinates-Zone VII\nStation number\nLatitude\nLongitude\nX\nr\no\n\"\nFeet\n701\n34 08 24.13977\n118 38 41.07730\n4092458.65\n4163510.67\n702\n34 07 43.64153\n118 30 43.02482\n4132634.89\n4159320.41\n703\n34 15 25.40288\n118 38 22.91005\n4094113.52\n4206090.32\n704\n34 20 14.87888\n118 27 15.53168\n4150168.37\n4235236.05\n705\n34 17 33.38836\n118 24 19.63485\n4164907.75\n4218897.04\n706\n34 17 22.29285\n118 27 40.15361\n4148081.70\n4217791.87\n707\n34 18 19.67348\n118 25 58.21304\n4156641.05\n4223582.93\n709\n34 17 30.02589\n118 29 14.33927\n4140179.90\n4218584.51\n710\n34 15 27.78853\n118 31 10.80821\n4130384.85\n4206243.96\n711\n34 17 14.47568\n118 32 23.72656\n4124285.90\n4217040.62\n712\n34 18 42.15481\n118 31 58.46054\n4126423.32\n4225899.83\n713\n34 19 12.81727\n118 33 51.38439\n4116957.54\n4229019.46\n715\n34 15 48.74701\n118 24 26.61709\n4164314.23\n4208319.36\n717\n34 08 13.09229\n118 19 29.67663\n4189241.55\n4162250.29\n718\n34 12 52.92497\n118 16 49.68322\n4202675.91\n4190541.82\n719\n34 09 48.84776\n118 11 45.00436\n4228288.74\n4171957.81\n720\n34 13 21.28581\n118 03 42.05315\n4268815.55\n4193513.88\n721\n34 16 08.38780\n118 14 17.09324\n4215472.40\n4210310.13\n724\n34 22 54.69132\n118 02 01.25847\n4277109.61\n4251502.69\n726\n34 27 35.11464\n118 13 04.13472\n4221517.18\n4279738.37\n727\n34 23 12.65693\n118 11 01.76913\n4231802.94\n4253219.20\n729\n34 32 51.69884\n118 12 52.65141\n4222441.58\n4311744.42\n730\n34\n35.29287\n118 13 04.37698\n4221496.87\n4279756.37\n731\n34\n23\n10.26555\n118 19 02.69767\n4191495.26\n4252944.79\n732\n34\n23\n10.86696\n118 19 43.79093\n4188051.11\n4253005.25\n733\n34\n33 37.91377\n118 21 18.24934\n4180147.78\n4316396.48\n734\n34\n33 39.50210\n118 21 18.45957\n4180130.23\n4316557.06\n735\n34\n20 39.20843\n118 31 11.00754\n4130425.59\n4237725.26\n736\n34 19 46.09173\n118 35 59.05454\n4106257.60\n4232409.25\n737\n34 19 49.65440\n118 36 00.57705\n4106130.85\n4232769.74\n738\n34 21 08.04736\n118 25 43.11244\n4157923.78\n4240602.67\n739\n34 22 30.96343\n118 32 06.97687\n4125754.67\n4249031.58\n740\n34 21 21.89508\n118 35 24.07181\n4109215.91\n4242086.52\n741\n34 23 39.29311\n118 32 04.88166\n4125943.92\n4255938.77\n742\n34 23 38.46908\n118 34 56.13641\n4111591.75\n4255887.12\n743\n34 24 58.91927\n118 32 21.39657\n4124576.13\n4263991.09\n744\n34 25 46.76846\n118 34 47.41248\n4112354.18\n4268855.38\n745\n34 26 19.78917\n118 32 29.50542\n4123913.42\n4272167.80\n746\n34 27 50.61004\n118 34 21.38730\n4114563.64\n4281369.68\n747\n34 27 45.56395\n118 32 23.74168\n4124413.74\n4280838.04\n748\n34 28 45.13028\n118 33 56.59556\n4116652.14\n4286876.53\n749\n34 29 29.17241\n118 31 03.91204\n4131117.36\n4291299.41\n750\n34 29 52.17640\n118 33 00.98801\n4121322.04\n4293644.24\n751\n34 31 02.85293\n118 30 52.32848\n4132103.82\n4300768.26\n752\n34 31 57.06461\n118 28 39.91467\n4143192.34\n4306231.12\n753\n34 33 24.32628\n118 28 11.78994\n4145557.28\n4315049.66\n754\n34 32 44.07415\n118 29 56.70713\n4136774.99\n4310993.34\n755\n34 35 11.67296\n118 31 22.09963\n4129659.17\n4325927.45\n756\n34 32 00.69415\n118 32 17.12349\n4125019.66\n4306629.13\n757\n34 31 01.29173\n118 34 57.80275\n4111561.46\n4300653.75\n758\n34 32 35.80760\n118 33 37.20989\n4118326.97\n4310193.11\n759\n34 33 46.16086\n118 32 48.70735\n4122399.44\n4317296.77\n760\n34 30 06.68395\n118 38 07.49398\n4095671.18\n4295176.09\n761\n34 31 20.20981\n118 36 56.15251\n4101662.87\n4302592.06\n762\n34 32 37.32392\n118 36 01.21403\n4106280.40\n4310375.55\n763\n34 34 40.92218\n118 34 51.89368\n4112109.84\n4322856.22\n764\n34 29 46.73378\n118 40 03.80617\n4085929.47\n4293189.59\n765\n34 34 03.16369\n118 44 30.86546\n4063679.46\n4319194.62\n766\n34 34 02.76707\n118 44 30.62758\n4063699.20\n4319154.45\n767\n34 35 43.94430\n118 34 43.89337\n4112794.17\n4329225.93\n768\n34 41 35.34144\n118 33 37.71564\n4118406.03\n4364738.89\n1 The geographic position of station Cahuenga 2, No. 717, is adjusted to North American Datum of 1927. All other stations depend on this\nposition.","Horizontal Crustal Movements\n281\nTable 8B.-Adjustment 2 position shifts referred to station Cahuenga 2\nResultant vector\nPostearthquake minus preearthquake\nStation\nAzimuth\nL\nar\nAX\no\nFeet\nFeet\nFeet\n180\n0.36\n+0.36\n+0.02\nBluff\n135\n0.14\n+0.10\n-0.10\nBrushy\n115\n0.10\n+0.04\n-0.09\nBum\n0\n0\n0\nCahuenga 2\n0\n0\n0\nCalabasas\n0\n0\n0\nChatsworth\n210\n0.75\n+0.65\n+0.38\nCorner 2\n255\n0.29\n+0.08\n+0.28\nDeer\n105\n0.04\n+0.01\n-0.04\nDry\n35\n0.35\n-0.29\n-0.20\nEast\n75\n0.19\n-0.05\n-0.18\nEdison\n0\n0\n0\nFlint\n0\n0\n0\nHauser\n175\n0.12\n+0.12\n-0.01\nHouse\n105\n0.13\n+0.03\n-0.13\nLock\n0\n0\n0\nLoma Verde\n50\n0.18\n-0.12\n-0.14\nLong\n350\n0.63\n-0.62\n+0.13\nMagic\n30\n1.45\n-1.27\n-0.71\nMay\n95\n0.16\n+0.02\n-0.16\nMission Pt\n80\n0.39\n-0.07\n-0.38\nMt. Gleason\n80\n0.29\n-0.06\n-0.28\nNewhall\n0\n0\n0\nPacifico\n325\n0.67\n-0.54\n+0.40\nPacoima E-2 ECC 1\n100\n6.67\n+1.32\n-6.54\nPacoima L-1\n205\n1.71\n+1.58\n+0.66\nPacoima No. 2\n350\n0.29\n-0.29\n+0.04\nParker\n0\n0\n0\nPelona\n0\n0\n0\nPelona ECC 2\n0\n0\n0\nPico L-9 AUX 2 ECC 1\n5\n0.65\n-0.65\n-0.07\nPort\n135\n0.06\n+0.04\n-0.04\nPowerhouse\n0\n0\n0\nRed\n85\n0.80\n-0.09\n-0.80\nReservoir\n130\n0.11\n+0.07\n-0.08\nRock\n55\n0.21\n-0.13\n-0.17\nSaugus\n0\n0\n0\nSawmill\n265\n0.35\n+0.03\n+0.35\nSister Elsie\n150\n0.09\n+0.08\n-0.05\nSteer\n60\n0.79\n-0.42\n-0.67\nSylmar F-8\n95\n3.36\n+0.23\n-3.35\nSylmar I-12\n135\n0.03\n+0.02\n-0.02\nTowsley\n285\n0.22\n-0.06\n+0.21\nVerdugo AUX\n140\n0.12\n+0.09\n-0.08\nView\n0\n0\n0\nWarm Springs\n0\no\n0\nWhitaker\n0\n0\n0\nWPK A-7A AUX 1\n100\n0.14\n+0.02\n-0.14\nYucca","282\nSan Fernando Earthquake of 1971\nAPPARENT HORIZONTAL DISPLACEMENT\nScale for Vectors and Ellipses\n0\n1\n2\n3\n4\n5\n6\n7 Feet\n768 A\n0\n1\n2 Meters\n0\n5 Miles\n0\n5\n10\nKm\n767 A\n7554\n765\nAN 734\n766\nR 753\n733\n754\nA729\n756 O\n- 752\n751\n764 A\n750\n749\n748 €\n746\n747\n9 730\n744\n743\nEpicenter\n742 .\n741\n732 I of 731\n727\n739\nA 724\n740\n738\n735\n704\n737,\n736\n712\n707\n709\n705\n711 $\n706\nSan Fernando\n721 -\n703A\n715\n710\n8 720\n718\na\nA\n719\n717\nA\n701\n8\nCAHUENGA 2\n702\n( Held Fixed )\nFigure 2B.-Adjustment 2 position vectors referred to station Cahuenga 2.","Horizontal Crustal Movements\n283\nTable 5E.-Adjustment 3 corrections to preearthquake observed horizontal directions\nStation\nStation\nStation\nStation\nv\"\nv\"\nv\"\nv\"\nFrom\nTo\nFrom\nTo\nFrom\nTo\nFrom\nTo\n33\n21\n13\n1\n0.52\n59\n23\n0.49\n11\n0.56\n2\n-0.73\n0.09\n34\n31\n12\n-0.57\n3\n0.04\n26\n-0.64\n56\n0.67\n54\n-0.18\n14\n0.61\n0.24\n30\n22\n57\n0.21\n57\n0.09\n- 1.39\n31\n21\n0.31\n14\n2\n0.59\n35\n0.57\n23\n1\n-0.31\n1\n0.71\n0.49\n36\n-0.88\n31\n2\n0.31\n3\n0.20\n0.27\n39\n23\n3\n-0.84\n14\n1.00\n0.45\n56\n20\n-0.27\n5\n0.22\n15\n0.12\n0.05\n60\n21\n-0.32\n6\n0.42\n16\n-0.10\n0.41\n64\n22\n-0.81\n15\n0.04\n17\n-1.09\n35\n24\n0.65\n16\n0.93\n18\n-0.01\n-1.08\n34\n26\n0.64\n17\n-0.93\n57\n-0.58\n-0.27\n36\n0.04\n30\n57\n0.17\n3\n0.21\n37\n31\n0.06\n1\n0.40\n15\n1.22\n38\n24\n2\n0.09\n2\n-0.26\n0.34\n39\n20\n-0.57\n0.03\n14\n0.52\n4\n-0.41\n64\n23\n-0.73\n5\n-0.10\n16\n-0.58\n26\n1.30\n36\n-0.11\n57\n-0.07\n6\n0.05\n34\n25\n9\n0.92\n4\n-0.06\n35\n27\n-0.78\n14\n-0.41\n5\n-0.10\n0.49\n37\n28\n0.27\n16\n-0.90\n6\n0.01\n-0.47\n38\n29\n0.52\n17\n-0.07\n7\n0.30\n37\n26\n18\n0.08\n8\n-0.13\n-0.69\n23\n-0.74\n35\n21\n0.82\n15\n-0.10\n0.18\n24\n-0.99\n36\n56\n-0.15\n5\n0.14\n0.44\n38\n30\n57\n-0.20\n4\n0.24\n0.45\n39\n34\n1.29\n6\n0.06\n16\n-0.06\n40\n27\n2\n-0.20\n7\n-0.20\n25\n-0.01\n38\n3\n-0.04\n8\n0.02\n0.34\n0.10\n28\n35\n6\n0.12\n14\n-0.23\n29\n-0.22\n0.33\n36\n9\n1.11\n15\n0.10\n0.60\n0.47\n30\n37\n14\n-0.10\n6\n-0.41\n0.02\n32\n39\n15\n-0.79\n4\n0.36\n-0.30\n0.03\n33\n40\n17\n-0.36\n5\n0.07\n28\n18\n-0.61\n39\n7\n-0.34\n27\n0.04\n-0.89\n34\n21\n0.41\n8\n-0.28\n29\n-0.14\n-0.15\n56\n0.20\n35\n9\n0.33\n0.11\n30\n-0.14\n0.22\n37\n57\n14\n-0.03\n29\n0.06\n38\n17\n15\n0.11\n25\n-1.08\n0.84\n2\n0.83\n40\n16\n-0.11\n27\n1.07\n0.16\n41\n14\n0.08\n56\n-0.11\n28\n0.32\n-0.65\n15\n-0.09\n42\n7\n30\n0.85\n-0.69\n56\n16\n-0.43\n-0.84\n4\n0.20\n32\n0.31\n60\n18\n-0.35\n5\n0.02\n0.68\n33\n1.18\n63\n19\n0.44\n6\n0.43\n0.08\n30\n64\n20\n-0.08\n8\n0.40\n23\n-0.07\n21\n-0.41\n40\n8\n26\n-0.63\n-0.27\n37\n18\n4\n0.28\n27\n0.02\n0.21\n-0.68\n0.09\n2\n38\n5\n-0.46\n28\n-0.13\n15\n-0.08\n39\n6\n-0.22\n0.53\n29\n-0.02\n16\n-0.05\n41\n7\n-0.16\n31\n-0.26\n0.20\n17\n0.59\n42\n9\n0.56\n32\n19\n-0.48\n6\n-0.32\n41\n0.22\n33\n20\n0.77\n-0.31\n10\n-0.42\n39\n0.10\n34\n21\n-0.01\n-0.36\n11\n0.53\n40\n56\n-0.06\n31\n0.39\n12\n0.17\n42\n21\n-0.42\n-0.28\n15\n0.38\n19\n43\n22\n0.54\n17\n1.15\n0.53\n16\n0.34\n44\n23\n0.24\n18\n-0.26\n56\n-0.68\n42\n30\n0.49\n20\n-0.67\n-0.02\n10\n39\n32\n-1.54\n21\n-0.23\n0.36\n9\n0.01\n40\n34\n-0.98\n11\n-0.68\n20\n-0.10\n41\n1.69\n56\n17\n0.04\n-0.27\n12\n0.65\n43\n18\n-0.15\n32\n0.01\n11\n44\n27\n-0.25\n19\n0.43\n9\n0.14\n43\n-0.07\n29\n21\n0.64\n10\n-0.09\n-0.09\n41\n-0.42\n30\n0.33\n12\n-0.50\n23\n0.18\n42\n1.51\n31\n24\n0.48\n13\n0.93\n0.02\n44\n0.27\n33\n57\n-0.49\n56\n0.87\n-0.28\n45\n-1.09\n56\n57\n-1.34\n21\n0.17\n46\n0.09\n59\n15\n-0.16\n12\n44\n-0.84\n33\n0.11\n16\n9\n-0.73\n41\n27\n-0.36\n17\n-0.53\n10\n0.83\n0.43\n42\n29\n-0.85\n18\n-0.09\n11\n-0.59\n-0.32\n43\n-0.77\n0.44\n30\n19\n13\n0.86\n0.62\n45\n0.76\n32\n20\n0.57\n54\n-0.25\n-0.03\n46\n0.70\n56\n22\n-0.64\n56\n-0.95","284\nSan Fernando Earthquake of 1971\nTable 5E.-Adjustment 3 corrections to preearthquake observed horizontal directions-Continued\nStation\nStation\nStation\nStation\nv\"\nv\"\nv\"\nv\"\nFrom\nTo\nFrom\nTo\nFrom\nTo\nFrom\nTo\n45\n51\n56\n59\n43\n0.20\n50\n0.27\n16\n-0.40\n32\n- 0.12\n44\n- 0.30\n52\n-0.10\n18\n0.01\n33\n- 0.12\n46\n0.06\n53\n-0.01\n21\n-0.09\n56\n- 0.96\n47\n- 0.17\n55\n0.33\n31\n0.27\n58\n- 0.30\n48\n0.60\n52\n32\n-0.44\n61\n1.39\n46\n49\n0.61\n33\n0.25\n63\n0.10\n43\n0.18\n50\n0.13\n34\n0.22\n60\n44\n0.34\n51\n0.30\n39\n-0.96\n34\n- 0.34\n45\n- 0.31\n53\n-0.05\n52\n0.84\n39\n0.64\n47\n- 0.22\n54\n-0.08\n54\n0.53\n56\n- 0.24\n48\n0.01\n55\n0.35\n57\n0.12\n57\n1.07\n47\n56\n-0.71\n58\n- 1.73\n62\n0.79\n57\n-0.56\n45\n- -0.17\n59\n- 0.24\n63\n0.74\n53\n46\n0.49\n60\n- 0.60\n64\n1.05\n51\n-0.24\n48\n- 0.18\n61\n1.29\n61\n52\n-0.53\n49\n- 0.59\n64\n- 0.39\n33\n- 0.68\n54\n0.90\n50\n0.47\n57\n56\n0.33\n55\n0.20\n1\n- 1.28\n48\n58\n0.05\n57\n-0.34\n2\n- 1.19\n45\n-0.14\n59\n0.30\n54\n3\n46\n0.29\n0.71\n62\n12\n-0.14\n11\n47\n- -0.27\n-0.10\n34\n- 0.66\n13\n1.59\n49\n13\n1.56\n- 0.21\n57\n1.00\n52\n-0.12\n14\n0.64\n50\n0.16\n59\n0.33\n53\n-0.73\n15\n- 1.22\n60\n49\n- 0.79\n55\n-0.47\n16\n- 0.63\n63\n47\n0.11\n0.04\n56\n0.66\n20\n-0.21\n63\n48\n0.34\n57\n-0.78\n52\n0.71\n39\n50\n-0.34\n0.36\n55\n53\n- -0.07\n58\n51\n- 1.45\n-0.39\n51\n-0.81\n54\n0.02\n59\n52\n-0.69\n- 1.18\n52\n0.01\n55\n0.69\n56\n60\n0.64\n1.25\n53\n- -0.12\n56\n0.01\n62\n0.39\n50\n54\n0.65\n59\n0.99\n64\n1.41\n47\n- -0.36\n57\n0.26\n60\n- 0.71\n64\n48\n0.14\n56\n62\n1.52\n34\n0.10\n49\n0.15\n6\n0.62\n58\n35\n- 1.19\n51\n- 0.09\n9\n- 0.73\n56\n- 0.31\n39\n0.29\n52\n0.14\n11\n0.17\n59\n0.00\n56\n-0.64\n51\n12\n- 0.04\n61\n0.26\n60\n0.49\n49\n- -0.50\n15\n1.28\n63\n0.05\n63\n0.95","Horizontal Crustal Movements\n285\nTable 5F.-Adjustment 3 corrections to postearthquake observed horizontal directions\nStation\nStation\nStation\nStation\nv\"\nv\"\nv\"\nv\"\nFrom\nTo\nFrom\nTo\nFrom\nTo\nFrom\nTo\n746\n735\n719\n701\n-0.07\n747\n737\n-0.22\n717\n-0.91\n702\n0.15\n0.28\n748\n-0.56\n738\n718\n-0.21\n703\n0.41\n0.52\n752\n-0.15\n739\n0.44\n720\n706\n-0.56\n0.14\n757\n740\n-0.35\n0.67\n721\n702\n0.20\n764\n741\n0.17\n0.25\n720\n701\n-1.30\n766\n736\n719\n-0.51\n703\n0.27\n703\n-0.86\n747\n0.31\n721\n706\n-0.68\n745\n-0.85\n710\n1.12\n724\n0.20\n715\n0.60\n746\n-0.61\n713\n1.13\n721\n717\n0.76\n748\n-0.05\n717\n-0.63\n715\n-1.86\n703\n749\n1.83\n735\n0.42\n717\n-0.45\n701\n0.86\n750\n0.07\n-1.17\n738\n719\n0.43\n702\n-0.36\n752\n-0.74\n720\n-0.16\n737\n706\n-0.25\n766\n0.34\n0.71\n713\n724\n0.50\n0.25\n736\n-0.06\n748\n735\n727\n-0.62\n-0.50\n738\n745\n0.02\n-0.44\n738\n731\n0.91\n704\n746\n0.00\n0.87\n739\n732\n1.05\n0.05\n705\n747\n0.16\n-0.60\n740\n738\n0.20\n0.11\n706\n749\n-0.50\n-0.31\n752\n724\n709\n-0.07\n750\n0.07\n0.29\n764\n720\n-0.03\n-0.09\n738\n757\n0.30\n-0.24\n765\n721\n0.40\n705\n764\n-0.08\n-0.25\n766\n726\n-0.62\n0.34\n704\n749\n738\n727\n-0.05\n706\n0.06\n747\n-0.69\n0.69\n703\n729\n0.30\n0.25\n709\n748\n0.45\n-0.04\n704\n-0.63\n726\n738\n750\n-0.06\n705\n0.09\n724\n0.22\n706\n751\n0.58\n706\n-0.51\n727\n0.40\n701\n0.95\n756\n-0.30\n709\n-0.41\n729\n-0.28\n702\n0.84\n710\n-0.52\n750\n732\n-0.35\n703\n1.51\n747\n0.06\n712\n1.25\n704\n-0.46\n727\n748\n-0.05\n715\n0.68\n721\n0.32\n705\n-1.11\n749\n-0.43\n721\n-0.01\n724\n1.36\n709\n-0.96\n751\n-0.41\n732\n0.01\n726\n-0.55\n715\n-0.57\n0.39\n752\n733\n-0.72\n732\n-1.13\n717\n0.70\n754\n0.27\n734\n-2.04\n738\n-0.88\n729\n756\n0.13\n735\n0.63\n724\n-1.01\n709\n757\n0.04\n736\n0.62\n726\n0.08\n704\n0.49\n737\n-0.06\n751\n730\n0.08\n705\n0.58\n749\n0.04\n741\n1.20\n732\n1.11\n706\n0.00\n750\n-0.28\n752\n0.02\n734\n-0.27\n711\n- 1.51\n754\n-0.30\n764\n-0.90\n0.04\n730\n712\n755\n0.44\n766\n0.01\n729\n-0.31\n738\n0.41\n756\n0.09\n739\n732\n-0.17\n711\n752\n735\n0.17\n733\n0.25\n709\n0.38\n732\n-0.16\n737\n0.89\n734\n0.23\n710\n0.51\n734\n-0.57\n740\n0.08\n-0.02\n731\n712\n737\n0.56\n0.26\n741\n732\n0.24\n-0.88\n713\n738\n0.51\n742\n0.53\n734\n-0.27\n712\n746\n-0.33\n741\n-0.17\n732\n709\n747\n-0.21\n735\n0.54\n721\n1.12\n710\n-0.92\n750\n1.02\n738\n-0.78\n726\n-0.17\n711\n0.74\n753\n0.56\n739\n-0.52\n727\n0.40\n713\n-0.16\n754\n-0.08\n740\n-0.29\n729\n0.47\n735\n0.24\n1.23\n755\n742\n0.53\n730\n-0.17\n738\n0.28\n-1.31\n756\n743\n0.48\n731\n0.32\n713\n764\n-1.38\n744\n0.06\n733\n1.55\n711\n1.43\n765\n-0.84\n743\n734\n- 1.36\n712\n-0.13\n1.98\n766\n741\n-0.65\n738\n0.89\n735\n0.46\n767\n-0.97\n742\n-0.06\n0.68\n752\n736\n0.07\n753\n744\n-0.44\n737\n-1.82\n733\n752\n-0.19\n745\n0.39\n729\n-0.93\n715\n754\n-0.32\n746\n0.78\n730\n-0.14\n702\n-0.44\n755\n0.51\n0.33\n744\n732\n706\n-0.66\n754\n741\n-0.66\n738\n0.74\n717\n0.70\n750\n0.11\n742\n0.41\n721\n0.03\n734\n751\n0.30\n743\n-0.41\n729\n0.46\n738\n0.36\n752\n0.17\n745\n0.29\n730\n0.47\n717\n753\n-0.09\n746\n0.36\n731\n1.42\n0.66\n702\n755\n0.30\n732\n-0.34\n745\n706\n0.29\n756\n-0.58\n-0.71\n743\n738\n-0.37\n715\n-0.58\n759\n-0.21\n0.46\n744\n752\n-0.17\n0.28\n718\n0.00\n755\n746\n755\n0.44\n1.04\n719\n734\n-0.43\n0.61\n747\n765\n-1.11\n0.43\n721\n-0.22\n751\n-0.36\n748\n768\n-0.78\n-0.03\n736\n752\n0.34\n746\n735\n718\n0.14\n753\n1.05\n743\n712\n0.37\n0.22\n717\n0.43\n754\n-0.72\n744\n713\n-0.08\n-0.53\n719\n756\n-0.15\n-0.11\n745\n736\n0.83\n0.31\n721","286\nSan Fernando Earthquake of 1971\nTable 5F.-Adjustment 3 corrections to postearthquake observed horizontal directions-Continued\nStation\nStation\nStation\nStation\nv\"\nv\"\nv\"\nv\"\nFrom\nTo\nFrom\nTo\nFrom\nTo\nFrom\nTo\n755\n758\n762\n765\n759\n0.04\n756\n0.15\n758\n0.40\n752\n0.34\n764\n-0.26\n757\n- 1.02\n759\n-0.19\n764\n0.57\n767\n0.37\n759\n0.00\n761\n0.00\n767\n-0.32\n768\n-0.28\n762\n0.12\n763\n-0.04\n766\n756\n763\n1.01\n763\n737\n1.42\n749\n0.62\n759\n758\n-0.65\n738\n-0.24\n750\n-0.05\n754\n-0.67\n759\n-0.72\n746\n-1.82\n751\n0.35\n755\n0.20\n762\n0.79\n747\n0.80\n752\n0.45\n756\n0.11\n767\n0.59\n752\n-0.17\n754\n0.50\n758\n-0.06\n764\n767\n755\n1.88\n762\n0.09\n737\n0.59\n752\n0.43\n757\n-0.36\n763\n0.77\n738\n1.02\n755\n0.01\n758\n0.17\n767\n-0.43\n746\n-0.02\n757\n-0.50\n759\n0.17\n760\n748\n0.18\n759\n-0.14\n757\n757\n-0.11\n752\n0.35\n760\n-0.13\n746\n0.02\n761\n0.04\n755\n0.03\n761\n1.08\n748\n-1.01\n767\n0.07\n757\n0.09\n763\n-0.15\n750\n-0.17\n761\n761\n2.22\n764\n0.83\n756\n-0.32\n757\n-0.93\n765\n0.18\n765\n0.40\n758\n0.29\n760\n0.02\n767\n0.80\n768\n0.32\n760\n0.04\n762\n0.36\n768\n- 1.00\n768\n761\n0.29\n764\n0.70\n765\n734\n0.14\n762\n-0.22\n767\n-0.16\n734\n0.21\n755\n0.11\n764\n-0.31\n762\n737\n- 1.33\n764\n0.34\n767\n1.41\n757\n-0.14\n738\n0.52\n767\n-0.57\nTable 6E.-Adjustment 3 corrections to preearthquake observed lengths (v's) in meters\nStation\nObserved\nWeight\nV in\nv in\nAdjusted\nlength\nfactor\nseconds\nmeters\nlength\n1 part in\nFrom\nTo\nI\n3\n12988.206\n1.0\n0.27\n0.017\n12988.223\n762,000\n1\n17\n29502.131\n1.0\n1.24\n0.177\n29502.308\n166,000\n16\n56\n1139.270\n0.3\n1.39\n0.008\n1139.278\n148,000\n31\n32\n1049.944\n0.1\n- 13.39\n-0.068\n1049.876\n15,000\n31\n34\n19695.796\n2.4\n0.18\n-0.017\n19695.779\n1134,000\n34\n64\n23866.161\n2.4\n0.58\n0.068\n23866.229\n353,000\n39\n63\n5237.752\n0.6\n0.18\n0.004\n5237.756\n1170,000\n60\n63\n13700.048\n1.6\n- 0.56\n-0.037\n13700.011\n370,000\nSTATISTICS\nNumber of lengths =\n8\nMaximum positive V in seconds =\n1.39\nMaximum negative V in meters = - 0.068\nMaximum length\n= 29502.131\nMaximum negative V in seconds =\n13.39\nAverage length V in meters\n= 0.050\nMinimum length\n= 1049.944\nAverage length V in seconds\n2.22\n=\nThe sum of pvv in seconds\n= 6.5379\nAverage length\n= 13397.413\nMaximum positive V in meters\n0.177\nThe sum of VV in seconds\n=\n= 183.6757","Horizontal Crustal Movements\n287\nTable 6F.-Adjustment 3 corrections to postearthquake observed lengths (U'S) in meters\nStation\nObserved\nWeight\nV in\nV in\nAdjusted\nlength\nfactor\nseconds\nmeters\nlength\n1 part in\nFrom\nTo\n701\n702\n12312.320\n1.0\n-0.66\n- -0.039\n12312.281\n312,000\n701\n703\n12988.248\n1.0\n0.15\n0.010\n12988.258\n1366,000\n701\n706\n23689.237\n1.0\n0.24\n0.027\n23689.264\n864,000\n702\n703\n18468.538\n1.0\n-0.10\n-0.009\n18468.529\n2000,000\n702\n706\n18433.678\n1.0\n0.58\n0.051\n18433.729\n358,000\n702\n715\n17784.643\n1.0\n0.08\n0.007\n17784.650\n2548,000\n702\n717\n17277.090\n1.0\n-0.54\n-0.045\n17277.045\n382,000\n703\n736\n8834.865\n1.0\n0.56\n0.024\n8834.889\n368,000\n704\n705\n6707.119\n1.2\n0.39\n0.013\n6707.132\n536,000\n704\n706\n5354.937\n0.8\n-0.06\n-0.001\n5354.936\n3617,000\n704\n707\n4063.040\n0.6\n-0.00\n-0.000\n4063.040\no\n704\n709\n5918.553\n0.8\n-0.48\n-0.014\n5918.539\n430,000\n704\n738\n2874.647\n0.4\n-0.45\n-0.006\n2874.641\n462,000\n705\n706\n5139.684\n0.8\n-0.13\n-0.003\n5139.681\n1618,000\n705\n709\n7537.743\n1.2\n-0.35\n-0.013\n7537.730\n596,000\n705\n738\n6949.956\n0.7\n0.30\n0.010\n6949.966\n694,000\n706\n707\n3149.940\n0.8\n0.01\n0.000\n3149.940\n22251,000\n706\n709\n2420.603\n0.7\n-1.45\n-0.017\n2420.586\n142,000\n706\n715\n5728.547\n1.0\n0.10\n0.003\n5728.550\n2040,000\n706\n738\n7572.380\n0.7\n-0.64\n-0.024\n7572.356\n322,000\n709\n711\n4867.378\n0.9\n-1.36\n-0.032\n4867.346\n152,000\n709\n712\n4749.053\n0.6\n-0.58\n-0.013\n4749.040\n353,000\n709\n738\n8619.200\n0.7\n0.11\n0.005\n8619.205\n1876,000\n710\n711\n3779.620\n0.7\n-0.00\n-0.000\n3779.620\n61572,000\n710\n712\n6111.645\n0.7\n-0.16\n-0.005\n6111.640\n1305,000\n710\n736\n10848.427\n0.8\n-1.04\n-0.055\n10848.372\n198,000\n710\n738\n13421.494\n1.0\n-1.20\n-0.078\n13421.416\n172,000\n711\n712\n2777.813\n0.5\n-1.36\n-0.018\n2777.795\n152,000\n711\n713\n4280.273\n0.5\n-0.56\n-0.012\n4280.261\n366,000\n712\n713\n3037.845\n0.6\n0.29\n0.004\n3037.849\n709,000\n712\n735\n3805.260\n0.7\n0.04\n0.001\n3805.261\n4747,000\n712\n738\n10595.807\n1.1\n-0.29\n-0.015\n10595.792\n714,000\n713\n735\n4888.063\n0.7\n-0.06\n-0.001\n4888.062\n3531,000\n713\n737\n3492.387\n0.7\n-0.20\n-0.003\n3492.384\n1034,000\n715\n738\n10030.937\n1.0\n0.77\n0.037\n10030.974\n269,000\n717\n718\n9546.200\n1.1\n0.28\n0.013\n9546.213\n743,000\n718\n721\n7177.706\n0.8\n-0.39\n-0.014\n7177.692\n527,000\n719\n720\n13991.396\n0.9\n0.31\n0.021\n13991.417\n676,000\n720\n724\n17855.019\n1.4\n0.05\n0.004\n17855.023\n4040,000\n721\n727\n13993.997\n1.3\n-0.52\n-0.035\n13993.962\n396,000\n721\n732\n15466.399\n1.6\n0.46\n0.035\n15466.434\n447,000\n721\n738\n19822.690\n1.5\n0.15\n0.014\n19822.704\n1406,000\n724\n730\n19012.978\n1.2\n-0.64\n-0.059\n19012.919\n325,000\n727\n730\n8677.040\n0.8\n1.52\n0.064\n8677.104\n136,000\n727\n732\n13335.795\n1.0\n-0.23\n-0.015\n13335.780\n905,000\n729\n730\n9754.135\n1.1\n0.20\n0.009\n9754.144\n1053,000\n729\n732\n20746.517\n1.8\n-0.24\n-0.024\n20746.493\n865,000\n729\n734\n12979.516\n1.5\n-0.36\n-0.023\n12979.493\n568,000\n730\n732\n13054.013\n1.4\n-0.01\n-0.001\n13054.012\n20422,000\n730\n734\n16875.648\n1.5\n0.55\n0.045\n16875.693\n377,000\n731\n732\n1049.944\n0.4\n-0.01\n-0.000\n1049.944\n16648,000\n731\n734\n19695.934\n1.8\n0.25\n0.024\n19695.958\n817,000\n732\n734\n19520.397\n1.8\n-0.06\n-0.005\n19520.392\n3637,000\n732\n738\n9930.636\n1.2\n-1.48\n-0.071\n9930.565\n140,000\n732\n752\n21216.619\n1.5\n-0.86\n-0.088\n21216.531\n241,000\n733\n738\n24074.486\n1.7\n0.45\n0.052\n24074.538\n459,000\n734\n738\n24119.961\n1.7\n0.39\n0.045\n24120.006\n533,000\n734\n752\n11690.213\n1.2\n-0.52\n-0.030\n11690.183\n396,000\n734\n755\n15646.220\n1.5\n0.13\n0.010\n15646.230\n1636,000\n734\n768\n23866.176\n1.8\n0.46\n0.053\n23866.229\n453,000\n735\n737\n7557.594\n0.9\n-0.31\n-0.012\n7557.582\n657,000\n735\n738\n8427.302\n0.9\n-0.71\n-0.029\n8427.273\n290,000\n735\n739\n3728.717\n0.6\n-1.42\n-0.026\n3728.691\n145,000\n735\n740\n6600.029\n1.0\n-0.38\n-0.012\n6600.017\n548,000\n735\n741\n5717.114\n0.9\n-0.50\n-0.014\n5717.100\n417,000\n736\n738\n15944.742\n1.7\n0.45\n0.035\n15944.777\n456,000\n737\n738\n15966.080\n1.7\n0.71\n0.055\n15966.135\n292,000\n737\n739\n7768.221\n0.8\n0.15\n0.006\n7768.227\n1362,000\n737\n740\n2991.420\n0.6\n-0.25\n-0.004\n2991.416\n831,000\n737\n752\n25079.104\n1.9\n0.79\n0.096\n25079.200\n260,000\n737\n766\n29334.857\n1.0\n0.10\n0.014\n29334.871\n2119,000\n738\n741\n10810.436\n0.9\n-0.80\n-0.042\n10810.394\n257,000\n738\n752\n20501.246\n1.8\n0.36\n0.036\n20501.282\n571,000\n738\n764\n27174.347\n1.6\n0.20\n0.026\n27174.373\n1047,000\n739\n740\n5467.488\n0.7\n-0.45\n-0.012\n5467.476\n455,000\n739\n741\n2106.121\n0.6\n-0.98\n-0.010\n2106.111\n211,000\n739\n742\n4796.027\n1.0\n-0.56\n-0.013\n4796.014\n366,000\n740\n741\n6620.000\n0.8\n-1.10\n-0.035\n6619.965\n187,000\n740\n742\n4268.324\n0.6\n0.06\n0.001\n4268.325\n3199,000","San Fernando Earthquake of 1971\n288\nTable 6F.-Adjustment 3 corrections to postearthquake observed lengths (v's) in meters-Continued\nStation\nObserved\nWeight\nV in\nV in\nAdjusted\nlength\nfactor\nseconds\nlength\n1 part in\nmeters\nFrom\nTo\n741\n742\n4374.583\n0.9\n0.16\n0.003\n4374.586\n1317,000\n2489.507\n325,000\n741\n743\n2489.515\n0.7\n-0.63\n-0.008\n741\n744\n5714.684\n1.2\n-0.73\n0.020\n5714.664\n281,000\n4665.230\n1374,000\n742\n743\n4665.227\n0.9\n0.15\n0.003\n742\n744\n3959.540\n0.8\n0.93\n0.018\n3959.558\n221,000\n1.0\n0.43\n0.008\n4009.457\n485,000\n743\n744\n4009.449\n0.6\n-0.59\n-0.007\n2500.435\n349,000\n743\n745\n2500.442\n-0.001\n6113.237\n4884,000\n743\n746\n6113.238\n1.1\n-0.04\n744\n745\n3665.062\n0.8\n0.17\n0.003\n3665.065\n1198,000\n-0.004\n3873.351\n868,000\n744\n746\n3873.355\n0.8\n-0.24\n745\n746\n3998.506\n0.9\n-0.79\n-0.015\n3998.491\n263,000\n-0.006\n2647.085\n481,000\n745\n747\n2647.091\n0.7\n-0.43\n527,000\n745\n748\n4999.769\n0.9\n-0.39\n-0.009\n4999.760\n0.013\n3006.674\n234,000\n746\n747\n3006.661\n0.8\n0.88\n249,000\n746\n748\n1795.146\n0.5\n-0.83\n-0.007\n1795.139\n0.12\n0.007\n11557.013\n1667,000\n746\n752\n11557.006\n1.0\n614,000\n746\n757\n5948.545\n1.0\n0.34\n0.010\n5948.555\n-0.008\n9441.998\n1186,000\n746\n764\n9442.006\n1.1\n-0.17\n746\n766\n19312.904\n1.0\n-0.04\n0.003\n19312.901\n5754,000\n0.020\n2997.366\n153,000\n747\n748\n2997.346\n0.7\n1.35\n747\n752\n9626.233\n1034,000\n0.9\n0.20\n0.009\n9626.242\n0.005\n21882.678\n4633,000\n747\n766\n21882.673\n1.0\n0.04\n924,000\n748\n750\n2506.212\n0.7\n0.22\n0.003\n2506.215\n652,000\n-0.32\n-0.007\n4476.766\n748\n757\n4476.773\n0.9\n1249,000\n748\n764\n9559.881\n1.2\n-0.17\n-0.008\n9559.873\n-0.26\n-0.009\n7081.438\n802,000\n750\n754\n7081.447\n1.0\n2437,000\n750\n757\n3662.679\n0.8\n-0.08\n-0.002\n3662.677\n0.13\n0.002\n2435.727\n1573,000\n752\n754\n2435.725\n0.5\n7283.871\n977,000\n752\n755\n7283.864\n1.2\n0.21\n0.007\n-0.36\n-0.009\n5042.160\n567,000\n754\n755\n5042.169\n0.7\n5237.756\n9300,000\n755\n767\n5237.757\n1.2\n-0.02\n-0.001\n1.0\n-0.23\n-0.005\n4488.168\n906,000\n756\n757\n4488.173\n2311.115\n110,000\n756\n758\n2311.136\n0.6\n-1.88\n-0.021\n757\n758\n3564.582\n0.9\n0.04\n0.001\n3564.583\n4591,000\n5123.014\n181,000\n757\n760\n5123.042\n0.2\n-1.14\n-0.028\n757\n761\n3074.378\n0.7\n-0.98\n-0.015\n3074.363\n211,000\n-0.012\n3672.177\n296,000\n758\n762\n3672.189\n0.8\n-0.70\nSTATISTICS\nNumber of lengths =\n116\nMaximum positive V in seconds =\n1.52\nMaximum negative V in meters = - 0.088\nMaximum length\n= 29334.857\nMaximum negative V in seconds = 1.88\nAverage length V in meters\n= 0.018\n0.45\nThe sum of pvv in seconds\n= 35.5438\nMinimum length\n= 1049.944\nAverage length V in seconds\n=\nAverage length\n= 9401.455\nMaximum positive V in meters\n0.096\nThe sum of VV in seconds\n= 42.0914\n=","Horizontal Crustal Movements\n289\nTable 7E.-Adjustment 3 adjusted positions of preearthquake survey stations 1\nGeographic position\nPlane coordinates-Zon VII\nStation number\nLatitude\nLongitude\nX\nr\nFeet\n01\n34 08 24.13961\n118 38 41.07658\n4092458.71\n4163510.65\n02\n34 07 43.28089\n118 30 42.98940\n4132637.81\n4159283.95\n03\n34 15 25.40198\n118 38 22.90715\n4094113.76\n4206090.23\n04\n34 20 14.88248\n118 27 15.52227\n4150169.16\n4235236.41\n05\n34 17 33.37499\n118 24 19.55582\n4164914.38\n4218895.68\n06\n34 17 21.86922\n118 27 40.66543\n4148038.70\n4217749.10\n07\n34 18 19.67079\n118 25 58.17186\n4156644.51\n4223582.65\n08\n34 19 30.09626\n118 25 51.38251\n4157220.89\n4230701.41\n09\n34 17 30.02648\n118 29 14.32800\n4140180.84\n4218584.57\n10\n34 15 27.78229\n118 31 10.81051\n4130384.65\n4206243.33\n11\n34 17 14.47188\n118 32 23.72430\n4124286.09\n4217040.23\n12\n34 42.15401\n118 31 58.45628\n4126423.68\n4225899.75\n13\n12.75478\n118 33 53.40370\n4116788.15\n4229013.53\n14\n34 14 44.19126\n118 29 16.78522\n4139949.27\n4201820.79\n15\n34 15 48.73113\n118 24 26.62380\n4164313.67\n4208317.75\n16\n34 21 11.67440\n118 24 58.73755\n4161644.76\n4240966.08\n17\n34 08 13.09229\n118 19 29.67663\n4189241.55\n4162250.29\n18\n34 12 54.48116\n118 16 44.67235\n4203096.66\n4190699.35\n19\n34 09 48.84773\n118 11 45.00457\n4228288.72\n4171957.80\n20\n34 13 25.51123\n118 03 38.66780\n4269098.69\n4193941.78\n21\n34 16 08.38729\n118 14 17.09732\n4215472.06\n4210310.08\n22\n20 55.42368\n118 13 41.74947\n4218408.91\n4239329.42\n23\n34 31.89249\n118 10 28.65017\n4234585.12\n4249102.46\n24\n34 54.69098\n118 02 01.25878\n4277109.58\n4251502.66\n25\n34 22 54.69098\n118 02 01.25878\n4277109.58\n4251502.66\n26\n34 30 06.10181\n118 06 02.79338\n4256765.53\n4295062.38\n27\n34 23 12.65721\n118 11 01.76443\n4231803.33\n4253219.23\n28\n34 31 50.26551\n118 08 50.24486\n4242730.92\n4305564.06\n29\n34 32 51.69838\n118 12 52.65141\n4222441.58\n4311744.37\n30\n34 27 35.29528\n118 13 04.37738\n4221496.84\n4279756.61\n31\n34 23 10.27113\n118 19 02.69884\n4191495.16\n4252945.36\n32\n34 23 10.87286\n118 19 43.78944\n4188051.23\n4253005.84\n33\n34 33 37.91345\n118 21 18.24926\n4180147.79\n4316396.45\n34\n34 33 39.50178\n118 21 18.45949\n4180130.24\n4316557.03\n35\n34 35 58.91362\n118 23 49.57592\n4167499.68\n4330656.42\n36\n34 34 01.29103\n118 24 42.64990\n4163053.47\n4318768.23\n37\n34 35 54.58802\n118 27 08.84838\n4150839.69\n4330234.04\n38\n34 33 24.32481\n118 28 11.78951\n4145557.32\n4315049.51\n39\n34 35 11.67289\n118 31 22.09951\n4129659.18\n4325927.44\n40\n34 32 44.07289\n118 29 56.70540\n4136775.13\n4310993.21\n41\n34 32 00.69314\n118 32 17.12277\n4125019.72\n4306629.03\n42\n31 02.85169\n118 30 52.32691\n4132103.95\n4300768.13\n43\n34 29 52.17461\n118 33 00.98687\n4121322.14\n4293644.06\n44\n34 29 29.17076\n118 31 03.91028\n4131117.51\n4291299.24\n45\n34 28 45.12859\n118 33 56.59366\n4116652.30\n4286876.36\n46\n34 27 45.56265\n118 32 23.74002\n4124413.88\n4280837.91\n47\n34 27 50.60979\n118 34 21.38470\n4114563.86\n4281369.66\n48\n34 26 15.71070\n118 32 31.67048\n4123731.23\n4271755.86\n49\n34 25 46.76662\n118 34 47.40939\n4112354.43\n4268855.19\n50\n34 24 58.91915\n118 32 21.39283\n4124576.44\n4263991.07\n51\n34 23 38.46694\n118 34 56.13271\n4111592.06\n4255886.90\n52\n34 23 39.29217\n118 32 04.87640\n4125944.36\n4255938.68\n53\n34 21 21.89333\n118 35 24.06873\n4109216.17\n4242086.34\n54\n34 20 39.21035\n118 31 11.00308\n4130425.97\n4237725.45\n55\n34 22 30.96253\n118 32 06.97252\n4125755.03\n4249031.49\n56\n34 21 08.05919\n118 25 43.10281\n4157924.58\n4240603.86\n57\n34 19 47.21278\n118 36 00.20378\n4106161.51\n4232522.83\n58\n34 19 49.65345\n118 36 00.57377\n4106131.12\n4232769.64\n59\n34 31 57.06340\n118 28 39.91690\n4143192.15\n4306231.00\n60\n34 29 46.73421\n118 40 03.80624\n4085929.46\n4293189.64\n61\n34 34 02.76744\n118 44 30.62725\n4063699.22\n4319154.48\n62\n34 34 03.16406\n118 44 30.86513\n4063679.49\n4319194.66\n63\n34 35 43.94435\n118 34 43.89321\n4112794.18\n4329225.94\n64\n34 41 35.34140\n118 33 37.71534\n4118406.05\n4364738.88\nThe geographic position of station Cahuenga 2, No. 17, is adjusted to North American Datum of 1927. All other stations depend on\n1\nthis position.","San Fernando Earthquake of 1971\n290\nTable JF.-Adjustment 3 adjusted positions of postearthquake survey stations 1\nGeographic position\nPlane coordinates-Zone VII\nStation number\nLatitude\nLongitude\nX\nr\nFeet\n4163510.65\n701\n34 08 24.13961\n118 38 41.07658\n4092458.71\n4159320.43\n702\n34 07 43.64172\n118 30 43.02507\n4132634.87\n4206090.36\n703\n34 15 25.40323\n118 38 22.91153\n4094113.40\n704\n34\n20\n14.87885\n118 27 15.53307\n4150168.26\n4235236.04\n705\n34 17 33.38834\n118 24 19.63632\n4164907.63\n4218897.03\n706\n34 17 22.29286\n118 27 40.15500\n4148081.59\n4217791.88\n707\n34 18 19.67347\n118 25 58.21440\n4156640.94\n4223582.93\n709\n34 17 30.02590\n118 29 14.34077\n4140179.77\n4218584.51\n710\n34\n15\n27.78861\n118 31 10.81001\n4130384.69\n4206243.97\n711\n34 17 14.47574\n118 32 23.72830\n4124285.76\n4217040.62\n712\n34 18 42.15492\n118 31 58.46224\n4126423.18\n4225899.84\n713\n34\n19\n12.81744\n118 33 51.38619\n4116957.39\n4229019.48\n715\n34\n15\n48.74706\n118 24 26.61830\n4164314.13\n4208319.36\n717\n34 08 13.09229\n118 19 29.67663\n4189241.55\n4162250.29\n718\n34 12 52.92490\n118 16 49.68354\n4202675.89\n4190541.81\n719\n34 09 48.84773\n118 11 45.00457\n4228288.72\n4171957.80\n720\n34 13 21.28567\n118 03 42.05349\n4268815.52\n4193513.87\n721\n34 16 08.38768\n118 14 17.09380\n4215472.36\n4210310.12\n724\n34 22 54.69098\n118 02 01.25878\n4277109.58\n4251502.66\n726\n34 27 35.11422\n118 13 04.13501\n4221517.16\n4279738.33\n4231802.90\n4253219.17\n727\n34 23 12.65661\n118 11 01.76963\n4222441.58\n4311744.37\n729\n34 32 51.69838\n118 12 52.65141\n730\n34 27 35.29245\n118 13 04.37727\n4221496.85\n4279756.33\n4191495.21\n4252944.76\n731\n34 23 10.26528\n118 19 02.69831\n4188051.05\n4253005.22\n732\n34 23 10.86671\n118 19 43.79158\n4180147.79\n4316396.45\n733\n34 33 37.91345\n118 21 18.24926\n4180130.24\n4316557.03\n734\n34 33 39.50178\n118 21 18.45949\n4130425.46\n4237725.27\n735\n34 20 39.20851\n118 31 11.00916\n4232409.29\n736\n34 19 46.09204\n118 35 59.05661\n4106257.42\n4232769.77\n737\n34 19 49.65471\n118 36 00.57912\n4106130.67\n4240602.66\n738\n34 21 08.04728\n118 25 43.11378\n4157923.66\n4249031.59\n739\n34 22 30.96349\n118 32 06.97826\n4125754.55\n4242086.55\n740\n34 21 21.89541\n118 35 24.07356\n4109215.76\n4255938.78\n741\n34 23 39.29316\n118 32 04.88288\n4125943.82\n4255887.15\n742\n34 23 38.46938\n118 34 56.13761\n4111591.65\n4263991.09\n743\n34 24 58.91929\n118 32 21.39755\n4124576.05\n744\n34 25 46.76872\n118 34 47.41332\n4112354.11\n4268855.40\n745\n34 26 19.78918\n118 32 29.50617\n4123913.36\n4272167.80\n746\n34 27 50.61019\n118 34 21.38784\n4114563.59\n4281369.70\n747\n34 27 45.56396\n118 32 23.74223\n4124413.70\n4280838.05\n748\n34 28 45.13038\n118 33 56.59600\n4116652.10\n4286876.54\n749\n34 29 29.17233\n118 31 03.91240\n4131117.33\n4291299.40\n750\n34 29 2.17644\n118 33 00.98833\n4121322.02\n4293644.25\n751\n34 31 02.85285\n118 30 52.32870\n4132103.80\n4300768.25\n4143192.33\n4306231.10\n752\n34 31 57.06443\n118 28 39.91483\n753\n34 33 24.32606\n118 28 11.78998\n4145557.28\n4315049.64\n4136774.98\n4310993.32\n754\n34 32 44.07402\n118 29 56.70721\n755\n34 35 11.67289\n118 31 22.09951\n4129659.18\n4325927.44\n4125019.65\n4306629.13\n756\n34 32 00.69414\n118 32 17.12362\n4111561.44\n4300653.76\n757\n34 31 01.29187\n118 34 57.80295\n4118326.97\n4310193.11\n758\n34 32 35.80765\n118 33 37.20996\n759\n34 33 46.16086\n118 32 48.70733\n4122399.44\n4317296.77\n4295176.12\n760\n34 30 06.68429\n118 38 07.49414\n4095671.16\n118 36 56.15264\n4101662.86\n4302592.08\n761\n34 31 20.21003\n118 36 01.21408\n4106280.39\n4310375.57\n762\n34 32 37.32409\n34 34 40.92227\n118 34 51.89358\n4112109.84\n4322856.22\n763\n118 40 03.80624\n4085929.46\n4293189.64\n764\n34 29 46.73421\n118 44 30.86513\n4063679.49\n4319194.66\n765\n34 34 03.16406\n118 44 30.62725\n4063699.22\n4319154.48\n766\n34 34 02.76744\n118 34 43.89321\n4112794.18\n4329225.94\n767\n34 35 43.94435\n118 33 37.71534\n4118406.05\n4364738.88\n768\n34 41 35.34140\nThe geographic position of station Cahuenga 2, No. 717, is adjusted to North American Datum of 1927. All other stations depend on\n1\nthis position.","Horizontal Crustal Movements\n291\nTable 8C.-Adjustment 3 position shifts referred to station Cahuenga 2\nPostearthquake minus preearthquake\nResultant vector\nStation\nAX\nor\nL\nAzimuth\nFeet\nFeet\nFeet\nO\nBluff\n-0.33\n+0.39\n0.51\n140\nBrushy\n-0.15\n+0.11\n0.19\n125\nBum\n0.20\n+0.18\n0.27\n130\nCahuenga 2\no\n0\n0\nCalabasas\no\n0\n0\nChatsworth\n-0.36\n+0.13\n0.38\n110\nCorner 2\n+0.04\n+0.64\n0.64\n185\nDeer\n+0.18\n+0.10\n0.21\n240\nDry\n-0.18\n+0.14\n0.23\n130\nEast\n-0.51\n-0.18\n0.54\n70\nEdison\n-0.48\n+0.10\n0.49\n100\nFlint\n0\n0\n0\nHauser\n0\n0\n0\nHouse\n-0.04\n+0.13\n0.14\n165\nLock\n-0.41\n+0.25\n0.48\n120\nLoma Verde\n0\n0\n0\nLong\n-0.27\n+0.04\n0.27\n100\nMagic\n+0.05\n-0.60\n0.60\n355\nMay\n-0.92\n-1.20\n1.51\n40\nMission Pt\n-0.50\n+0.09\n0.51\n100\nMt. Gleason\n-0.43\n-0.06\n0.43\n80\nNewhall\n-0.54\n+0.10\n0.55\n100\nPacifico\n0\n0\n0\nPacoima E-2 ECC 1\n+0.17\n-0.50\n0.53\n340\nPacoima L-1\n-6.75\n+1.35\n6.88\n100\nPacoima No. 2\n+0.46\n+1.61\n1.67\n195\nParker\n+0.01\n-0.28\n0.28\n0\nPelona\n0\n0\n0\nPelona ECC 2\n0\n0\n0\nPico L-9 AUX 2 ECC 1\n-0.45\n+0.13\n0.47\n95\nPort\n-0.18\n-0.62\n0.65\n15\nPowerhouse\n-0.07\n+0.10\n0.12\n145\nRed\n0\n0\n0\nReservoir\n1.07\n-0.06\n1.07\n85\nRock\n-0.15\n+0.12\n0.19\n130\nSaugus\n-0.39\n+0.02\n0.39\n95\nSawmill\n0\n0\n0\nSister Elsie\n+0.30\n+0.04\n0.30\n160\nSteer\n-0.12\n+0.19\n0.22\n150\nSylmar F-8\n-0.90\n-0.37\n0.97\n70\nSylmar I-12\n-3.57\n+0.28\n3.58\n95\nTowsley\n-0.41\n+0.21\n0.46\n115\nVerdugo AUX\n+0.17\n-0.06\n0.18\n290\nView\n-0.18\n+0.16\n0.24\n130\nWarm Springs\no\n0\no\nWhitaker\n0\n0\n0\nWPK A-7A AUX 1\n0\n0\n0\nYucca\n-0.32\n+0.21\n0.38\n125","San Fernando Earthquake of 1971\n292\nTable 9B.-Adjustment 3 95-percent error ellipses referred to station Cahuenga 2\nAxes (Feet)\nOrientation\nOne Sigma\n95 percent\nof semimajor\nStation\naxis (°) 0*\nat\nb1\nat\nb1\n0.30\n0.16\n0.73\n0.40\n55\nBluff\n.42\n34\n.48\n.17\n1.17\nBum\n0\n0\n0\nCahuenga 2\n0\n.36\n.17\n.89\n.41\n70\nChatsworth\n62\n.28\n.18\n.68\n.43\nCorner 2\n.50\n.16\n1.22\n.40\n18\nDeer\n.45\n.17\n1.10\n.42\n33\nDry\n.33\n.15\n.80\n.37\n42\nEast\n.36\n.16\n.89\n.39\n41\nEdison\n.52\n.16\n1.27\n.38\n17\nHouse\n.41\n44\n.41\n.17\n1.01\nLock\n36\n.47\n.17\n1.15\n.42\nLong\n.31\n.14\n.76\n.35\n1\nMagic\n.29\n.14\n.70\n.34\n24\nMay\n.38\n49\n.31\n.16\n.75\nMission Pt\n.38\n.16\n.93\n.39\n38\nNewhall\n.14\n.60\n.35\n40\nPacoima E-2 ECC 1\n.25\n.57\n.36\n26\n.23\n.15\nPacoima L-1\n.20\n.15\n.49\n.36\n27\nPacoima No. 2\n.40\n.17\n.98\n.41\n164\nParker\n.16\n.90\n.39\n55\nPico L-9 AUX 2 ECC 1\n.37\n.31\n.14\n.77\n.35\n3\nPort\n1.27\n.39\n27\n.52\n.16\nPowerhouse\n.35\n21\n.57\n.14\n1.38\nRed\n43\n.26\n.15\n.65\n.37\nReservoir\n.49\n.17\n1.20\n.41\n25\nRock\n.40\n.16\n.99\n.40\n37\nSaugus\n.35\n151\n.20\n.14\n.48\nSister Elsie\n.49\n.17\n1.20\n.42\n31\nSteer\n.29\n.18\n.71\n.43\n34\nSylmar F-8\n.41\n31\n.25\n.17\n.62\nSylmar I-12\n50\n.38\n.16\n.94\n.40\nTowsley\n.14\n.12\n.34\n.29\n171\nVerdugo AUX\n.47\n.17\n1.14\n.43\n28\nView\n40\n.44\n.17\n1.08\n.42\nYucca\nSemimajor axis.\nSemiminor axis.\nAngle of orientation is measured positive counterclockwise from east.","Horizontal Crustal Movements\n293\nAPPARENT HORIZONTAL DISPLACEMENT\nScale for Vectors and Ellipses\no 1 2 3 4 5 6 7 Feet\n768 A\n0\n1\n2 Meters\n0\n5 Miles\n0\n5\n10 Km\n767A\n755s\n765\n734\n766\n753\no\n754\nA 729\n756\n752\n.\n751\n750.\n764 A\n749\n748\n9730\n747\n746\n7(44\n7.44\nEpicenter\no\n741\n7(42\n732\n731\n727\n724\n738\n740\n735\n704\n737\nP\n712\n0707\n709\n05\n06\n721\nSan Fernando\n715\n703\n7/10\n770\n718\nA\n719\n717\n701\n8\nCAHUENGA 2\n702\n( Held Fixed )\nFigure 2C.-Adjustment 3 position vectors and 95-percent error ellipses referred to station Cahuenga 2.","","Vertical Crustal Movements\nDetermined From Surveys\nBefore and After\nSan Fernando Earthquake\nINTRODUCTION\nThe earthquake which struck the San Fernando\narea on the morning of February 9, 1971, caused\nwidespread surface ruptures. The main concern of\nthis paper is not with the actual breaks in the sur-\nface, which can take place only along a fault, but\nCONTENTS\nrather with the widespread vertical deformations re-\nPage\nsulting from the shock waves. The magnitude and\n295 INTRODUCTION\nextent of vertical crustal movement, determined by\n295\nPREARTHQUAKE AND POSTEARTHQUAKE\ncomparing the results of leveling surveys before the\nLEVEL NET\n297 ADJUSTMENT\nearthquake with those of special surveys after the dis-\n297\nERROR PROPAGATION\nturbance, are described in this paper.\n298\nRESULTS\n304 CONCLUSIONS\n305 ACKNOWLEDGMENTS\nPREEARTHQUAKE AND POSTEARTHQUAKE\n305 REFERENCES\nAPpENDIX-TABLES OF OBSERVED\nLEVEL NET\n305\nELEVATION DIFFERENCES\nThe area of general interest is shown in figure 1.\nAwareness of earth movement as an ongoing process\nin several areas of southern California led to a com-\nprehensive leveling program during the period from\nJanuary 31, 1968, to December 5, 1969, undertaken\nby the National Geodetic Survey (NGS) of the\nNational Oceanic and Atmospheric Administration\n(NOAA), by San Bernardino, San Diego, Los\nAngeles, Orange, Riverside, and Ventura Counties,\nand by Los Angeles city. All leveling was first-order\nwork, with a rejection limit of 3 mm VK, where K is\nthe distance in kilometers.\nAt the time of the earthquake, an NGS leveling\nparty was working in the vicinity of Point Mugu on\na line from Santa Margarita to San Pedro. The line\nNANCY L. MORRISON\nwas finished and then portions were releveled to\nNational Geodetic Survey\nmake certain there were good ties between pre-\nNational Ocean Survey, NOAA\n295","San Fernando Earthquake of 1971\n296\nGrapevine\n+8.7\nRosamand\n52.11\nLebec\n-8.2\n50.03\nFairmont\n+4.0\n92.79\n-19.0\n214.53\nPalmdale\nCastaic Junction\nSaugus\n* EPICENTER\nOlive View\nSanatorium\nVentura\nSan Fernando\nChatsworth\nSunland\nMontalvo\nGranada Hills\nPacoima\nTujunga\n+30.1\n210.47\nLa Canada\nBurbank\nPort Hueneme\nWoodland Hills\n-1.0\n141.34\n+21.2\n210.03\nPoint Mugu\nlos Angeles\nTopanga Beach\nLechusa Pt\nSanta Monica\nRedondo Beach\nSan\nPedro\nFigure 1.-Level net for study of San Fernando earthquake, with indication of 1972 misclosures in mm/km.","Vertical Crustal Movements\n297\nearthquake and postearthquake levelings. The re-\ntions. A single mark is assumed stable at a fixed ele-\nsources of NGS, Los Angeles city, and Los Angeles\nvation, and all other elevations are adjusted in rela-\nCounty were used to relevel enough lines of the\ntion to it. Therefore, any comparison of the\n1968-69 net to provide information for the study of\nfree-adjusted elevation of a mark in one epoch to\nthat of a second epoch with the same fixed point in-\npossible widespread crustal disturbances as a result\nof the earthquake. This program consisted of 1,080\ndicates apparent movement between the two level-\nings. Bench Mark Tidal 8 at San Pedro (El. 3.3924\nkm of releveling, plus 88 km of original leveling\nm), considered stable by oceanographers, is the fixed\ndone between February 9, 1971, and December 15,\n1971. A total of 1,162 marks were recovered. Again,\npoint in each case. The adjustment of 1970 includes\nall leveling was 3-mm VK first-order. The area is\n134 unknowns and 198 links; the 1972 adjustment\nconsists of 67 unknowns and 104 links. The weight\ncovered by 10 major loops, as shown in figures 1 and\nof a link is expressed as\n1A with their misclosures. In addition, there are 28\nminor loops. Figure 1A shows the loop misclosures\nin the vicinity of Saugus. All exceed the 3-mm VK\nlimit. These lines were run within a 3-month period,\nwhere Di is the distance associated with the ith\nbut since there were aftershocks occurring during this\nobservation and t is a constant of proportionality\ntime, it is impossible to determine whether the dis-\nreflecting the precision of the observation. Because\nagreement is caused by actual movement or by an\nall leveling was 3-mm VK first-order, as a matter of\nerror in leveling. It should be noted that the resultant\nconvenience, t was chosen to be equal to unity for\nof the three misclosures is well within the 3-mm VK\neach link.\nlimit.\nThe adjustments yielded the following results:\nUnit of\nADJUSTMENT\n1970\n1972\nmeasurement\nStandard deviation of an obser-\nPreliminary reduction of data included computa-\nvation of unit weight\n1\n1.86\n1.75\nmm\ntion of temperature and rod corrections, a correction\nmm/km\nAverage correction rate\n0.187703\n0.204302\nfor instrument error, and an orthometric correction\nThe results for all recovered marks are tabulated\nto account for the nonparallelism of level surfaces to\nin the appendix, and after allowing for propagation\nproduce an observed orthometric elevation for each\nof the error that results from leveling, they may be\nmark (henceforth referred to as the observed eleva-\nconsidered to reflect the magnitude of the move-\ntion).\nments. Movement is calculated as the 1972 free-ad-\nIndependent free adjustments for each epoch of\njusted elevation minus the 1970 free-adjusted eleva-\nleveling were made using the variation of parameters\ntion. A plus sign (+) therefore, indicates uplift,\nmethod of least squares. In a free adjustment, the net\nwhile a minus sign (-) indicates subsidence. Eleva-\ntions are not to be considered as absolute, but only\nis not constrained to fit previously established eleva-\nas based on Bench Mark Tidal 8 at San Pedro.\nERROR PROPAGATION\nIn a large net, such as described here, only a small\nCastaic Junction\npercentage of the total number of bench marks is\nused as unknowns in the adjustment. An adjusted\n+39.2\nelevation is computed for each unknown, and an\nSaugus\n59.19\n-29.2\nassociated standard deviation may be computed from\n-28.5\n35.48\nthe covariance matrix. To determine the adjusted\n35,06\nelevation of an intermediate bench mark, Pi, lying\non a level line between two bench marks, PA and PB,\n1 An observation of unit weight is a double-run difference of\nelevation obtained over a distance of 1 km.\nFigure 1A.-Detail of misclosures (mm/km) in vicinity of Saugus.","San Fernando Earthquake of 1971\n298\nwhich are unknowns in the adjustment, the following\nvarious intermediate points for which the linear\nweighted mean is used:\ninterpolation equation (4),\n(1)\n(4)\nwhere\nwas used as an approximation in place of equation\nHA is the adjusted elevation of PA,\n(3).\nlai is the observed difference of elevation from\nPA to pi,\nHB is the adjusted elevation of PB, and\nRESULTS\nlbi is the observed difference of elevation from\nBecause of the short interval of time between the\nPB to Pi;\npreearthquake and postearthquake leveling, the re-\nand the respective weights are determined as follows:\nsulting evaluation of displacements should reflect, for\nthe most part, only movements caused directly by the\nearthquake. Awareness of persisting crustal move-\nment was a basic reason for the comprehensive level\nnet of 1968-69; thus, in any analysis of apparent\nwhere\nmovement, an attempt must be made to separate\nS1 is the distance from PA TO Pi,\nthis tectonic movement from the abrupt elevation\nis the distance from PB to pi, and\nchanges that result from seismic activity. Several\nt is equal to unity as explained previously, and\nareas in California are known to undergo subsidence\nsimilarly, for way\nwhere, for various reasons, there is a widespread low-\nering of the land surface with respect to mean sea\nThe apparent movement, Mi, of point pi is calcu-\nlevel, caused by compaction of sediments (Holdahl\nlated as the 1972 free-adjusted elevation, H'i, minus\n1969 and 1970). This subsidence is a relatively slow\nthe 1970 free-adjusted elevation, Hi, SO that\nprocess and generally remains undetected without re-\npeated surveys until enough small movements have\nM{=H'-Hi,\naccumulated to cause noticeable property damage. In\nand an associated standard deviation, OMi' is found by\ncontrast, there are no zones of definite upheaval as\nwould be associated with mountain building, but\nand\n(2)\npast leveling has indicated that such areas may exist.\nCovariances are not involved because the old and\nWhere continual small movements are indicated,\nnew adjusted levelings are independent.\ncaution must be used before any cause-and-effect re-\nApplying the laws of error propagation (Hirvonen\nlation is established.\n1971) to equation (1) and knowing the variances of\nIn addition, it is possible that in a statistical,\nthe end points of a link, PA and PB, we have\nleast-squares solution, the standard deviations may\nsometimes exceed the effects of small, real earth\nmovements. For this reason, movement is considered\nto be significant if it consistently exceeds o rather\n(3)\nthan the 20 required for a 95-percent confidence\ninterval.\nand similarly for OH'\nPortions of lines in the net, indicating significant\nHowever, because of the shortage of time between\nmovement, are shown in figure 2. Each line segment\nthe receipt of data from the field and the publication\nis labeled with the number of the figure in which a\ndeadline of this volume and because of the necessity\ngraph of the movement will be found. To avoid con-\nof manually computing these o's, standard deviations\nfusion, some graphs contain only representative\nhave been calculated for only a representative sample\npoints. Detail of significant movement, such as uplift\nof points. This includes all points occurring as junc-\nand subsidence, is shown in figure 2A.\ntions in both adjustments, for which standard devia-\nAn area of definite vertical displacement begins in\ntions are available from the covariance matrix, and\nthe vicinity of Sun Valley (fig. 3) at BM 08-25620","Vertical Crustal Movements\n299\nGrapevine\nRosamond\nLebec\nFig.6\nFairmont\nPalmdale\nCastaic Junction\nFig\nSaugus\n* EPICENTER\nOlive View\nSanatorium\nFig 4\nSan Fernando\nChatsworth\nGranada Hills\nPacoima\nSunland\nMontalvo\nTujunga\nLaCanada\nBurbank\nWoodland Hills\nPort Hueneme\nPoint Mugu\nFig. 7\nLos Angeles\nTopanga Beach\nL echusa Point\nSanta Monica\nRedondo Beach\nSan\nPedro\nFigure 2.-Portions of leveling lines along which significant movement occurred.\nGraph of apparent vertical displacement along line is shown in indicated figure.","San Fernando Earthquake of 1971\n300\nGrapevine\nRosamond\nLebec\nPalmdale\nCastaic\nJunction\nSaugus\nChatsworth\nSunland\nGranada\nTujunga\nHills\nLa Canada\nBurbank\nPoint Mugu\nLos\nAngeles\nLechusa Point\nSanta Monica\nSan\nPedro\nSubsidence\nUplift\nFigure 2A.-Detail of significant movement shown as uplift or subsidence.","Vertical Crustal Movements\n301\n600\n500\n400\n300\no\n200\n100\n70\n100\n80\n90\no\nKilometers\n100\nFigure 3.-Graph of apparent vertical 14 displacement: mm at Sun 1972 Valley free-adjusted to 16 mm elevation north of minus Van Norman 1970 free-adjusted Lake. Distance is calculated in\nStandard\nelevation.\ndeviation\nfor\nthese displacements varies from\nkm\nfrom\nTidal Bench Mark 8 at San Pedro.","302\nSan Fernando Earthquake of 1971\n(City of Los Angeles-C of LA). The apparent\n(LACo) near Saugus and reaches a maximum about\nmovement here is 23 mm, o = 14 mm. This sub-\n10 km north of Saugus of + 141 mm, o = 18 mm, at\nsidence increases in magnitude to a sustained\nBM 201-111A (LACo) For the next 38 km, the\n- 63 mm, o = 15 mm, at BM 03-01685 (C of LA),\nreleveling program followed a route different from\nBM 03-01687 (C of LA), and BM 03-01710 (C of\nthat of the 1968-69 net; consequently, there are no\nLA) Then follows a decrease in movement to\nmarks available for comparison. However, where the\n- 41 mm, o = 15 mm, at BM N 898 = 03-01930\nreleveling line rejoins the old line, continued uplift\n(C of LA) and BM 03-01950 (C of LA) in the\nis indicated, and one may assume an average move-\nvicinity of Pacoima, and another increase in magni-\nment over the uncompared section of approximately\ntude to - 69 mm, o = 15 mm, at BM S 43 Reset\n+ 90 mm, o = 20 mm. As the line passes through\n1966 = 03-02251 (C of LA) A second decrease in\nPalmdale, the apparent displacement decreases in\nmagnitude occurs from this point to BM 03-02429\nmagnitude and changes sign. BM S 811 Reset\n(C of LA), with apparent movement of - 21 mm,\n1955 = 101-127 37 mm, o = 23 mm) is the be-\no = 15 mm. At a distance of 0.2 km farther,\nginning of a vigorous downthrust continuing to\nBM 03-02440 (C of LA) shows an uplift of\n- 146 mm, o = 23 mm, at BM 2356 (USGS) =\n+ 29 mm, o = 15 mm. This is the beginning of a\n101-131A. This magnitude decreases to a fairly con-\nzone of sustained uplift over a 15-km section of north-\nstant - 90 mm, o = 23 mm, for the next 10 km and\nsouth leveling located a short distance to the east of\nthen decreases rapidly to - 38 mm, o = 23 mm, at\nVan Norman Lake. A mark-by-mark tabulation of the\nBM M 487 = 101-151 which is the end of the level-\ndisplacements to a maximum of + 615 mm,\ning line 6.9 km south of Rosamond.\no = 15 mm, will be found in table 1 of the appendix.\nIt should be noted at this point that previous level-\nThe apparent movement decreases to the noise level\ning in the Palmdale-Rosamond vicinity indicates that\nat BM 60-30A (CSDH) This displaced region has\nthe area is gradually subsiding. It is possible, there-\na maximum extent of 29 km.\nfore, that the uplift near Saugus is related to the\nA second area of definite vertical displacement\nearthquake, but that the subsidence between Palm-\nbegins in the vicinity of Granada Hills (fig. 4) The\ndale and Rosamond is a continuing process, totally\napparent movement is consistently within o over the\nunaffected by the earthquake or only slightly SO.\nline from Topanga Creek to Granada Hills where\nA second area of probable uplift (fig. 6) begins\nBM 04-05610 (C of LA), showing an uplift of\nabout 9 km south of Gorman at Quail F RM 1 =\n+ 37 mm, o = 16 mm, is the beginning of the most\n102-82B (LACo) showing an apparent displacement\ndramatic area of upheaval in the region under study.\nof + 31 mm, o = 23 mm. This displacement in-\nThis 27-km section runs in an east-west direction\ncreases gradually in magnitude to + 51 mm,\nfrom Granada Hills, passing a short distance south of\no = 25 mm, at BM S 1098 near Grapevine. The re-\nthe Olive View Sanatorium and north of Hansen\nleveling ends 4.8 km north of Grapevine, with a\nLake to Tujunga. The maximum movements occur\ngradual decrease in magnitude indicated. Again,\nat BM 03-00780 (C of LA) and BM 03-00770\nprevious leveling in the area indicates small con-\n(C of LA), having displacements of + 1,460 mm,\ntinued movements, and cause-and-effect relation with\no = 16 mm, and + 1,510 mm o = 16 mm, respec-\nthe earthquake cannot be established.\ntively. This maximum uplift area is followed within\nThe vicinity of Point Mugu-Lechusa Point (fig. 7)\n2.5 km by a zone of fairly large downthrusts which\nis an area of possible subsidence. From BM M 1099,\ndegenerate to the noise level at BM 02-03900 (C of\n10 km east of Port Hueneme, to BM F9A = 48-102,\nLA). A mark-by-mark tabulation of these displace-\nnear Lechusa Point, the apparent movement remains\nments will be found in table 3. Considering figures\nfairly constant around - 32 mm, while o varies from\n3 and 4 together gives an area of subsidence to the\n20 to 18 mm. Past levelings indicate that this may be\neast and south of the vicinity of Van Norman Lake\na moving area. If future leveling verifies this con-\nand a region of uplift to the west and north.\nclusion, it would be doubtful that the area has been\nFigure 5 shows an area of probable upheaval be-\naffected by this earthquake.\nginning at BM RV 64 (SPRR) = 208-83 (Los\nThe final section of leveling showing significant\nAngeles County-LACo) near Castaic Junction, with\nmovement lies between BM 21-03910 (C of LA),\napparent movement of + 30 mm, o = 18 mm. This\nlocated 22 km north of San Pedro, and BM 12-01329\nincreases to + 64 mm, o = 18 mm, at BM 208-89\n(C of LA), about 4 km south of the Los Angeles","Vertical Crustal Movements\n303\n1600\n1400\n1200\n1000\n800\n600\n400\n200\n55\n60\n6.5\n45\n50\n70\no\nKilometers\nFigure t.-Graph 200 displacements of apparent remains vertical a constant displacement: 16 mm. 1972 Distance free-adjusted calculated in km from 1970 BM free-adjusted P 99 Reset 1933=48-62 at\nelevation.\nStandard\ndeviation\nMonica.\nthese\nSanta\nfor","304\nSan Fernando Earthquake of 1971\n150\n40\n50\n60\n100\nKilometers\n50\n10\n20\no\n80\n90\n120\n130\n140\n150\n160\n170\nKilometers\n30\n50\n100\nFigure 7.-Graph of apparent vertical displacement: 1972 free-\n150\nadjusted elevation minus 1970 free-adjusted elevation. Standard\ndeviation for these displacements varies from 20 mm at Port\nFigure 5.-Graph of apparent vertical displacement: 1972 free-\nHueneme to 18 mm at Lechusa Point. Distance is calculated in\nadjusted elevation minus 1970 free-adjusted elevation. Standard\nkm from BM X 569 at Ventura.\ndeviation for these displacements varies from 18 mm at Saugus\nto 22 mm at Palmdale to 23 mm at Rosamond. Distance is calcu-\nlated in km from BM H 1051 at Montalvo.\n20\n30\n40\n50\n0\nKilometers\n50\n10\n40\n20\n30\n30\n20\n40\n10\nFigure 8.-Graph of apparent vertical displacement: 1972 free-\nadjusted elevation minus 1970 free-adjusted elevation. Standard\ndeviation for these displacements varies from 9 mm to 13 mm\n170\n180\n190\n200\nat Los Angeles City Hall. Distance is calculated in km from Tidal\no\nKilometers\nBench Mark 8 at San Pedro.\nFigure 6.-Graph of apparent vertical displacement: 1972 free-\nadjusted elevation minus 1970 free-adjusted elevation. Standard\ndeviation for these displacements varies from 23 mm south of\nCONCLUSIONS\nGorman to 25 mm north of Lebec. Distance is calculated in km\nfrom Tidal Bench Mark 8 at San Pedro.\nResults of the comparison of marks in the 1968-69\npreearthquake net with those in the 1971 postearth-\nCity Hall (fig. 8) . The apparent movement averages\nquake releveling indicate that earth movements defi-\nabout - 18 mm. There is one relatively large down-\nnitely caused by the disturbance fall within an\nthrust to - 40 mm, followed by a fairly rapid return\nellipse, centered on maximum displacement BM\nto the - 18-mm level. The standard deviation varies\n03-00770 (C of LA) near the Olive View Sanato-\nfrom 9 to 13 mm at the Los Angeles City Hall. This\nrium, with a major axis of 20 km oriented in a\nmovement is barely significant. Once again, slight\nnorthwest-southeast direction and a minor axis of 11\nmovements over the years have been indicated in\nkm oriented in a northeast-southwest direction. Areas\nthis area, and no definite connection with the earth-\nof movement outside this region may have been\nquake can be made.\naffected by the earthquake, but most likely these are","Vertical Crustal Movements\n305\nareas of continuing gradual movement. If so, the\n(abstract) EOS Transactions, American Geophysical Union,\nVol. 50, No. 11, Nov. 1969, p. 601.\ncomparisons are of some use for determining move-\nHoldahl, Sanford R., \"Studies of Precise Leveling at California\nment rates in these areas.\nFault Sites\" (abstract), EOS Transactions, American Geo-\nphysical Union, Vol. 51, No. 11, Nov. 1970, p. 742.\nACKNOWLEDGMENTS\nAPPENDIX-TABLES OF OBSERVED\nELEVATION DIFFERENCES\nThe author wishes to thank Allen Pope and San-\nford Holdahl for their conversations on and help\nThe following tables contain a mark-by-mark tab-\nwith the statistics.\nulation of the results of the two adjustments for each\nof the 1,162 recovered marks. A name appearing in\nREFERENCES\nthe column headed \"Location\" means \"in the vicin-\nity of.\" Each table is considered as a continuous line\nHirvonen, R. A., \"The Propagation of Errors\" and \"Matrices,\"\nof levels, and distance is calculated from the first\nAdjustment by Least Squares in Geodesy and Photogram-\nmark in the table. Apparent movement is computed\nmetry, Chs. III and XII, Frederick Ungar Publishing Co.,\nas the 1972 free-adjusted elevation minus the 1970\nNew York, N.Y., 1971, pp. 20-35 and 136-150.\nfree-adjusted elevation. o is the standard deviation\nHoldahl, Sanford R., \"Geodetic Evaluation of Land Sub-\nof the apparent movement.\nsidence in the Central San Joaquin Valley of California\"","San Fernando Earthquake of 1971\n306\nTable 1.-Line of levels, San Pedro to 4.9 km north of Grapevine\nElevation\nApparent\nLocation\nBench mark\nDistance\nmovement\na\nPreearthquake\nPostearthquake\nkm\nm\nm\nmm\nmm\nSan Pedro\n24-0010 = Tidal 8\n0.00\n3.392\n3.392\n0\n0\n24-000300\nCofLA)\n0.07\n2.045\n2.043\n-2\n24-000500\nCofLA)\n0.49\n1.969\n1.964\n-5\n1\n24-000700 CofLA)\n0.84\n3.312\n3.311\n-1\n24-000900 (CofLA)\n0.89\n2.183\n2.181\n-2\n24-00110 = Tidal 10\n0.94\n2.779\n2.776\n-3\n24-00130(CofLA)\n1.07\n4.592\n4.588\n-4\n2\n24-001500 CofLA)\n1.54\n11.514\n11.512\n-2\n24-001700 CofLA)\n1.75\n15.498\n15.499\n+1\n24-006096 (CofLA)\n2.04\n20.871\n20.870\n-1\n3\n24-006150 (CofLA)\n2.16\n21.196\n21.195\n-1\n24-00625 CofLA)\n2.25\n19.549\n19.549\n0\n24-006350 CofLA)\n2.36\n14.586\n14.585\n-1\n24-006500 CofLA)\n2.50\n8.612\n8.612\no\n24-006700 CofLA)\n2.58\n5.431\n5.430\n-1\n24-006900 CofLA)\n2.70\n5.907\n5.907\n0\n24-007100 CofLA)\n2.81\n6.515\n6.514\n-1\n24-007300 CofLA)\n3.04\n6.500\n6.498\n-2\n24-007500 CofLA)\n3.13\n6.986\n6.986\n0\n24-007550 (CofLA)\n3.24\n6.432\n6.428\n-4\n24-00771 (CofLA)\n3.45\n6.990\n6.990\n0\n24-007730 CofLA)\n3.62\n4.689\n4.689\n0\n24-00825 CofLA)\n3.70\n3.974\n3.972\n-2\n24-008456 CofLA)\n3.82\n3.467\n3.466\n-1\n24-00910( (CofLA)\n3.93\n3.018\n3.017\n-1\n24-009300 (CofLA)\n4.12\n2.788\n2.788\n0\n4\n24-009500 CofLA)\n4.24\n3.132\n3.133\n+1\n24-00970( CofLA)\n4.36\n3.134\n3.134\n0\n24-00990( CofLA)\n4.55\n3.482\n3.482\n0\n24-010100 (CofLA)\n4.62\n3.790\n3.791\n+1\n24-00490( (CofLA)\n4.65\n3.949\n3.950\n+1\n24-005100 (CofLA)\n4.68\n3.909\n3.910\n+1\n24-005900 CofLA)\n5.35\n2.855\n2.856\n+1\n24-01406 (CofLA)\n6.04\n5.742\n5.743\n+1\n24-01410(CofLA)\n6.25\n3.427\n3.430\n+3\n24-01430(CofLA)\n6.32\n3.766\n3.769\n+3\n24-014500 CofLA)\n6.66\n3.522\n3.522\n0\n24-01470 CofLA)\n7.11\n3.409\n3.406\n-3\n24-014900 CofLA)\n7.25\n3.248\n3.243\n-5\n24-01510 (CofLA)\n7.58\n2.862\n2.854\n-8\n24-01530( (CofLA)\n7.76\n2.808\n2.799\n-9\n24-01550( CofLA)\n7.94\n3.086\n3.077\n-9\n24-01570( CofLA)\n8.11\n2.760\n2.749\n-11\n24-01580( CofLA)\n8.19\n2.398\n2.383\n-15\n24-015900 (CofLA)\n8.47\n2.700\n2.685\n-15\n24-016100 (CofLA)\n8.50\n2.282\n2.267\n-15\n24-025800 CofLA)\n8.68\n4.391\n4.374\n-17\n24-025900 (CofLA)\n8.83\n6.556\n6.536\n-20\n24-02610( CofLA)\n9.02\n8.258\n8.234\n-24\n24-02640( (CofLA)\n9.23\n9.733\n9.709\n-24\n24-02650( (CofLA)\n9.34\n10.063\n10.038\n-25\n24-026600 (CofLA)\n9.45\n10.910\n10.883\n-27\n6\n21-03690(CofLA) = 5-46 C\n13.61\n13.130\n13.108\n-22\n8\n21-03693(CofLA)\n13.82\n12.587\n12.568\n-19\n21-03698( (CofLA)\n14.02\n12.480\n12.463\n-17\n21-03710(CofLA)\n14.26\n12.520\n12.505\n-15\n21-03731(CofLA)\n14.67\n11.307\n11.294\n-13\n21-03750(CofLA)\n15.50\n10.954\n10.948\n-6\n21-03770( CofLA)\n15.95\n10.976\n10.970\n-6\n21-037920 (CofLA)\n16.50\n8.765\n8.762\n-3\n21-038156 (CofLA)\n18.36\n6.516\n6.511\n-5\n21-038326 (CofLA)\n19.12\n3.927\n3.913\n-14\n21-038500 (CofLA)\n19.99\n4.585\n4.584\n-1\n21-03858( (CofLA)\n20.22\n5.409\n5.407\n-2\n21-038656 (CofLA)\n20.45\n5.757\n5.759\n+2","Vertical Crustal Movements\n307\nTable 1.-Line of levels, San Pedro to 4.9 km north of Grapevine-Continued\nElevation\nApparent\nLocation\nBench mark\nDistance\nmovement\na\nPreearthquake\nPostearthquake\nSan Pedro (continued).\nkm\nm\nm\nmm\nmm\n21-038780\nCofLA)\n20.85\n6.512\n6.507\n-5\n21-03891\nCofLA)\n21.47\n13.986\n13.980\n-6\n21-039100\nCofLA)\n22.04\n12.851\n12.841\n-10\n21-039300 CofLA)\n22.50\n15.734\n15.721\n-13\n21-039386 CofLA)\n22.77\n14.704\n14.690\n-14\n21-03951 (LACo)\n23.24\n16.372\n16.358\n-14\n21-03969 CofLA)\n23.69\n17.531\n17.515\n-16\n21-039930 CofLA)\n24.46\n23.816\n23.797\n-19\n21-04011 (CofLA)\n24.75\n26.917\n26.897\n-20\n21-04020( (CofLA)\n25.19\n30.144\n30.123\n-21\n10\n18-00012(CofLA)\n25.57\n35.489\n35.470\n-19\n18-000500 CofLA)\n26.05\n36.749\n36.729\n-20\n18-000700 (CofLA)\n26.38\n35.935\n35.917\n-18\n18-000886 CofLA)\n26.77\n36.383\n36.362\n-21\n18-001300 (LACo)\n27.21\n35.054\n35.032\n-22\n18-001400 CofLA)\n27.66\n35.543\n35.523\n-20\n18-001700 CofLA)\n28.05\n36.007\n35.987\n-20\n18-002090 CofLA)\n28.25\n36.014\n35.995\n-19\n18-002700 CofLA)\n28.88\n33.226\n33.210\n-16\n18-00289 CofLA)\n29.20\n32.899\n32.883\n-16\n18-00332 (CofLA)\n29.73\n34.533\n34.517\n-16\n18-00371 (CofLA)\n30.13\n34.663\n34.646\n-17\n18-00420 CofLA)\n30.59\n36.168\n36.151\n-17\n18-004500 CofLA)\n30.82\n36.516\n36.499\n-17\n18-00491 (CofLA)\n31.14\n37.121\n37.103\n-18\n18-00571 (CofLA)\n31.54\n37.961\n37.944\n-17\n18-006106 CofLA)\n31.85\n38.521\n38.502\n-19\n18-006500 CofLA)\n32.26\n40.043\n40.024\n-19\n18-006700 CofLA)\n32.70\n40.873\n40.833\n-40\n18-0071001 CofLA)\n33.12\n41.453\n41.421\n-32\n18-007300 CofLA)\n33.33\n41.906\n41.875\n-31\n18-007700 CofLA)\n33.93\n43.940\n43.911\n-29\n18-007900 CofLA)\n34.32\n45.134\n45.106\n-28\n18-008500 CofLA)\n34.84\n47.705\n47.681\n-24\n18-00891 (CofLA)\n35.17\n48.859\n48.839\n-20\nT 412 = 18-00930\n35.67\n50.537\n50.518\n-19\n12\n18-00969(CofLA)\n36.12\n51.128\n51.110\n-18\n18-009900 (CofLA)\n36.50\n52.594\n52.574\n-20\n18-010690 (CofLA)\n36.95\n53.905\n53.887\n-18\nA 170 = 18-01090\n37.34\n55.496\n55.475\n-21\n18-01130(CofLA)\n37.61\n55.905\n55.887\n-18\n18-01170(CofLA)\n38.24\n59.309\n59.292\n-17\n18-01197 (CofLA)\n38.53\n60.550\n60.533\n-17\n18-012050 CofLA)\n38.59\n60.794\n60.777\n-17\n18-012490 CofLA)\n39.02\n63.191\n63.173\n-18\n12-01291 (CofLA)\n39.52\n64.898\n64.883\n-15\n12-013290 (CofLA)\n39.85\n65.962\n65.950\n-12\n12-01370( CofLA)\n40.34\n68.446\n68.438\n-8\n12-057490 CofLA)\n40.60\n69.091\n69.085\n-6\n12-057600 CofLA)\n40.97\n70.885\n70.881\n-4\n12-05791 (CofLA)\n41.38\n72.820\n72.814\n-6\n12-05810(CofLA)\n41.81\n74.951\n74.945\n-6\n12-05820(CofLA)\n42.14\n76.141\n76.131\n-10\n12-05841 (CofLA)\n42.63\n78.263\n78.249\n-14\n12-05862(CofLA)\n42.81\n79.059\n79.045\n-14\n12-05866(CofLA)\n42.99\n79.662\n79.647\n-15\n12-03330(CofLA)\n43.67\n85.298\n85.287\n-11\n12-03350(CofLA)\n43.90\n87.403\n87.392\n-11\n32=338 Reset 1936 = 12-17190\n44.25\n103.397\n103.386\n-11\n13\nLos Angeles City Hall.\n12-19171(CofLA)\n44.69\n92.713\n92.698\n-15\n12-04550(CofLA)\n45.41\n87.094\n87.075\n-19\n12-04530(CofLA)\n45.61\n88.497\n88.478\n-19\nL 141 = 12-04840\n46.06\n89.805\n89.785\n-20\n12-04814(CofLA)\n46.37\n90.789\n90.769\n-20\nV 32 = 12-04790(CofLA)\n46.72\n93.273\n93.256\n-17\n12-04750(CofLA)\n46.95\n95.523\n95.507\n-16","308\nSan Fernando Earthquake of 1971\nTable 1.-Line of levels, San Pedro to 4.9 km north of Grapevine-Continued\nElevation\nApparent\nLocation\nBench mark\nDistance\nmovement\no\nPreearthquake Postearthquake\nLos Angeles City Hall\n(continued).\nkm\nm\nm\nmm\nmm\nE 769 = 12-34910(CofLA)\n47.23\n96.254\n96.239\n-15\n12-24970 = 49-1A(LACo)\n47.64\n101.477\n101.463\n-14\n12-24990 =9-25(LACo) =\n48.35\n98.856\n98.844\n-12\n12-25030(CofLA)\n48.53\n101.740\n101.729\n-11\n12-25035 (CofLA)\n49.21\n103.730\n103.719\n-11\n12-25041 (CofLA)\n49.60\n104.045\n104.032\n-13\nD 99 = 12-25050\n49.94\n104.487\n104.475\n-12\n12-25074(CofLA)\n50.36\n104.924\n104.913\n-11\nN 970 Reset 1967 = 12-25087\n50.59\n106.085\n106.074\n-11\n12-25089(CofLA)\n50.85\n107.576\n107.564\n-12\n12-25109(CofLA\n51.40\n114.096\n114.085\n-11\n12-25125(CofLA)\n51.69\n112.510\n112.500\n-10\nX 768 Reset 1948 = 12-25065\n51.81\n112.437\n112.427\n-10\n12-25135(CofLA)\n52.17\n112.417\n112.409\n-8\n12-25170(CofLA)\n52.71\n114.155\n114.154\n-1\n12-25202(CofLA)\n53.17\n119.749\n119.729\n-20\nW 768 = 12-25210\n53.53\n120.052\n120.049\n-3\n12-25250(CofLA)\n53.65\n117.720\n117.717\n-3\nV 768 = 12-25270\n54.50\n126.877\n126.864\n-13\n12-24430(CofLA)\n54.85\n127.810\n127.797\n-13\nB 52 = 12-22785\n55.62\n131.844\n131.830\n-14\nJ 32 = 432 (USGS)=12-22790\n55.70\n131.745\n131.732\n-13\nU 768 = 12-22810\n56.36\n134.590\n134.575\n-15\n09-01500(CofLA)\n56.82\n135.039\n135.026\n-13\n09-01530 (CofLA)\n56.89\n135.745\n135.732\n-13\nT 768 = 09-01560\n57.41\n138.529\n138.515\n-14\nN 1141 = 09-01605\n58.17\n141.084\n141.070\n-14\n09-01620(CofLA)\n58.27\n141.820\n141.805\n-15\n09-01650(CofLA)\n58.82\n142.690\n142.676\n-14\n99 Reset 1935 = 09-01655\n58.99\n140.552\n140.538\n-14\n09-01705(CofLA)\n59.58\n141.446\n141.433\n-13\n09-01710(CofLA)\n59.81\n141.539\n141.526\n-13\n09-017200 CofLA)\n60.76\n142.766\n142.751\n-15\n09-017500 CofLA)\n60.79\n143.096\n143.079\n-17\n09-017850 (CofLA)\n61.63\n148.953\n148.938\n-15\n09-018300 (CofLA)\n63.37\n160.559\n160.540\n-19\nB 787 = 09-01840\n63.65\n163.330\n163.310\n-20\nY 60 = 09-01860\n64.66\n172.850\n172.828\n-22\n09-01862(CofLA)\n64.71\n173.070\n173.048\n-22\nC 787 = 09-01891\n65.56\n178.559\n178.541\n-18\nH 43 Reset 1932 =09-01920\n66.02\n182.529\n182.512\n-17\n09-01950(CofLA)\n66.28\n181.568\n181.551\n-17\nR 786 = 09-01980\n66.84\n190.010\n189.994\n-16\n09-02010(CofLA)\n66.95\n190.636\n190.620\n-16\nS 786 = 09-02040\n67.37\n194.989\n194.974\n-15\n08-25525(CofLA)\n68.01\n201.645\n201.630\n-15\n38-239 = 08-25526\n68.22\n204.159\n204.143\n-16\nG 787 = 08-25530\n68.97\n213.600\n213.581\n-19\n08-25560(CofLA)\n69.44\n219.340\n219.319\n-21\nL 43 Reset 1946=08-25590\n69.71\n222.991\n222.968\n-23\n08-25620(CofLA)\n70.12\n227.544\n227.521\n-23\nU 786=08-25645\n70.31\n230.202\n230.175\n-27\n08-25650(CofLA)\n70.37\n229.669\n229.647\n-22\nSun Valley\n08-25681(CofLA)\n71.39\n241.530\n241.505\n-25\n08-25740(CofLA)\n71.67\n244.660\n244.636\n-24\n08-25750(CofLA)\n71.97\n247.168\n247.143\n-25\n08-02190(CofLA)\n72.18\n248.621\n248.595\n-26\n786=08-25800\n72.56\n252.355\n252.327\n-28\n08-25815(CofLA)\n73.05\n255.779\n255.748\n-31\n08-25830(CofLA\n73.21\n257.451\n257.420\n-31\n08-25834(CofLA)\n73.30\n258.828\n258.797\n-31\n08-258400 CofLA)\n73.84\n261.663\n261.630\n-33\n15\n08-258600 CofLA)\n74.02\n263.613\n263.579\n-34\nW 786 = 08-25870\n74.10\n264.807\n264.772\n-35\n08-25890(CofLA)\n74.47\n267.400\n267.364\n-36","Vertical Crustal Movements\n309\nTable 1.-Line of levels, San Pedro to 4.9 km north of Grapevine-Continued\nElevation\nApparent\nLocation\nBench mark\nDistance\nmovement\no\nPreearthquake\nPostearthquake\nSun Valley (continued)\nkm\nm\nm\nmm\nmm\n08-25920(CofLA)\n74.52\n267.660\n267.623\n-37\nV 7 786 = 08-25950\n74.93\n271.139\n271.098\n-41\n08-25982(CofLA)\n75.13\n272.597\n272.553\n-44\n08-26011(CofL\n75.39\n274.327\n274.280\n-47\n08-26070(CofLA)\n75.86\n276.274\n276.222\n-52\n08-26040(CofLA)\n75.88\n276.843\n276.791\n-52\n08-26060 = 34204 (LACo)\n76.10\n280.376\n280.322\n-54\nP 43=08-26130\n76.29\n279.353\n279.298\n-55\n08-26160(CofLA\n76.78\n278.878\n278.817\n-61\nY 786 =08-26190\n77.00\n281.146\n281.084\n-62\n03-01685(CofLA)\n77.38\n286.829\n286.766\n-63\n03-01687(CofLA)\n77.41\n287.182\n287.119\n-63\n03-01710(CofLA)\n77.71\n290.557\n290.494\n-63\nG 1142=03-01712\n77.79\n291.817\n291.764\n-53\n03-01755(CofLA)\n78.00\n293.568\n293.516\n-52\n03-01770( (CofLA)\n78.20\n296.398\n296.343\n-55\n03-018000 CofLA)\n78.39\n298.481\n298.426\n-55\n03-01830 CofLA)\n78.68\n301.810\n301.761\n-49\n03-018600 (CofLA)\n78.70\n301.435\n301.385\n-50\nPacoima\n03-018900 (CofLA)\n79.12\n304.822\n304.777\n-45\nN 898=03-01930\n79.46\n307.954\n307.913\n-41\n03-01950( CofLA)\n79.62\n308.611\n308.570\n-41\n03-019800 CofLA)\n79.66\n308.593\n308.549\n-44\n03-020100 CofLA)\n80.11\n311.607\n311.564\n-43\n03-02040 (CofLA)\n80.13\n311.644\n311.603\n-41\nE 1142 = 03-02068\n80.39\n314.415\n314.368\n-47\n03-02070( CofLA)\n80.43\n313.430\n313.382\n-48\n03-021000 CofLA)\n80.64\n315.296\n315.243\n-53\n03-021256 CofLA)\n81.02\n317.189\n317.135\n-54\n03-02130 (CofLA)\n81.10\n317.522\n317.468\n-54\nR 43 Reset 1955 = 03-02160\n81.27\n319.547\n319.490\n-57\n03-02190(CofLA\n81.47\n320.843\n320.780\n-63\n03-02195(CofLA)\n81.54\n320.256\n320.195\n-61\n03-02220(CofLA)\n82.08\n321.649\n321.581\n-68\nS 43 Reset 1966 = 03-02251\n82.38\n323.208\n323.139\n-69\n1066 (USGS) Reset 1966 = 03-\n82.63\n324.023\n323.960\n-63\n02254.\n03-02310(CofLA)\n82.81\n326.154\n326.090\n-64\n03-02340(CofLA)\n83.41\n328.882\n328.833\n-49\nD 1142 =03-02355\n83.55\n328.729\n328.680\n-49\n03-02370(CofLA\n83.89\n331.510\n331.483\n-27\n03-02430(CofLA)\n84.15\n336.349\n336.325\n-24\n03-02429(CofLA)\n84.27\n334.223\n334.202\n-21\n03-02440(CofLA).\n84.56\n337.819\n337.848\n+29\n03-02450(CofLA)\n85.14\n350.094\n350.366\n+272\n03-066900 (CofLA)\n85.20\n349.924\n350.184\n+260\n03-02490(CofLA)\n85.68\n354.753\n355.066\n+313\n03-025206 (CofLA)\n85.88\n357.159\n357.518\n+359\nP 53 Reset 1932 = 04-04590\n86.07\n358.225\n358.627\n+402\n04-04620(CofLA)\n86.50\n363.916\n364.438\n+522\n04-04635(CofLA)\n86.71\n366.635\n367.179\n+544\n04-046500 (CofLA)\n86.92\n369.563\n370.132\n+569\n04-046800 CofLA)\n87.15\n372.438\n373.042\n+604\n04-047100 CofLA)\n87.18\n372.727\n373.334\n+607\n04-047200 CofLA)\n87.40\n376.163\n376.778\n+615\nRS 10 (USGS) = 04-04740\n87.62\n378.871\n379.470\n+599\n04-04760(CofLA)\n87.86\n382.361\n382.933\n+572\n04-04770 CofLA)\n88.09\n387.904\n388.451\n+547\n04-04801 (CofLA)\n88.42\n385.649\n386.126\n+477\n04-048300 (CofLA)\n88.98\n387.496\n387.672\n+176\n15\n388.280\n+183\nEast of Van Norman\nO 53 Reset 1950 =04-04860\n89.05\n388.097\nLake.\n04-04890(CofLA\n89.31\n387.883\n388.103\n+220\n04-00790(CofLA)\n89.71\n386.787\n386.898\n+111\n04-008200 (CofLA)\n89.93\n388.510\n388.652\n+142\n04-008400 (CofLA)\n90.27\n390.562\n390.713\n+151\n04-00855(CofLA)\n90.41\n390.220\n390.393\n+173","310\nSan Fernando Earthquake of 1971\nTable 1.-Line of levels, San Pedro to 4.9 km north of Grapevine-Continued\nElevation\nApparent\nLocation\nBench mark\nDistance\nmovement\na\nPreearthquake Postearthquake\nEast of Van Norman\nLake (continued).\nkm\nm\nm\nmm\nmm\n04-00872(CofLA)\n90.57\n396.449\n396.657\n+208\n04-00900(CofLA\n90.88\n410.391\n410.549\n+158\n04-00930=60-7(LACo)\n91.22\n407.989\n408.050\n+61\n1142=04-00935=60-7A(LACo). =\n91.27\n407.984\n408.083\n+99\n04-07660(CofLA)\n91.97\n419.696\n419.767\n+71\n04-07690=60-8A (LACo)\n92.52\n440.627\n440.715\n+88\n898 = 60-8\n92.66\n432.417\n432.495\n+78\n=60-9\n93.01\n438.977\n439.039\n+62\n60-14A(CSDH)\n94.45\n543.991\n544.053\n+62\n60-16(CSDH)\n94.83\n526.036\n526.057\n+21\n60-19(CSDH)\n95.27\n502.873\n502.917\n+44\n60-21(CSDH)\n95.63\n486.866\n486.893\n+27\n60-22(CSDH)\n95.86\n476.923\n476.941\n+18\n60-23(CSDH)\n95.95\n473.172\n473.205\n+33\n60-23A(CSDH)\n96.15\n464.396\n464.422\n+26\n60-25A(LACo)\n96.68\n445.359\n445.378\n+19\n60-27(CSDH)\n97.27\n430.764\n430.786\n+22\n60-28(CSDH)\n97.53\n427.627\n427.640\n+13\n60-28A(LACo)\n97.56\n427.925\n427.943\n+18\n60-29(CSDH)\n97.93\n423.242\n423.258\n+16\n60-30(CSDH)\n98.09\n417.807\n417.825\n+18\n60-29A(CSDH)\n98.34\n413.260\n413.276\n+16\n60-30A(CSDH)\n98.54\n410.981\n410.995\n+14\n60-31A(CSDH)\n99.16\n407.344\n407.364\n+20\n60-32(CSDH)\n100.02\n398.138\n398.138\n0\n60-32A(LACo)\n100.04\n397.045\n397.053\n+8\n60-32B(LACo)\n100.48\n396.908\n396.921\n+13\n60-32C(CSDH)\n101.16\n414.222\n414.237\n+15\n17\n60-33A(CSDH)\n101.49\n408.861\n408.863\n+2\n60-34A(LACo)\n102.03\n384.725\n384.746\n+21\n60-35A(LACo)\n103.07\n380.067\n380.084\n+17\n60-35B(CofLA)\n103.12\n380.608\n380.624\n+16\n60-36\n103.90\n384.470\n384.499\n+29\n49(CHC) = 60-38\n105.17\n383.654\n383.683\n+29\nQ 370 = 60-39\n106.25\n370.799\n370.820\n+21\n60-40(LACo)\n107.06\n363.290\n363.322\n+32\nR 370=60-41\n107.96\n357.049\n357.104\n+55\nU 370\n114.09\n309.104\n309.105\n+1\n18\nCastaic Junction\n208-80(LACo)\n114.93\n310.803\n310.808\n+5\nM 52 Reset 1967 =205-12A\n115.62\n316.432\n316.434\n+2\n(LACo).\n208-79(LACo)\n116.55\n319.517\n319.519\n+2\nV 370 =205-13 (LACo)\n117.23\n324.841\n324.846\n+5\n208-78(LACo)\n117.72\n328.892\n328.896\n+4\nW 370 Reset 1967 = 208-77(LACo).\n118.49\n332.823\n332.832\n+9\nR 970 Reset 1967=208-76(LACo).\n119.25\n342.453\n342.465\n+12\nS 3970=208-74(LACo)\n120.76\n350.991\n351.008\n+17\nCastaic\n208-73(LACo)\n121.39\n354.987\n354.999\n+12\nX 370 = 208-72(LACo)\n122.14\n375.040\n375.073\n+33\n208-70(LACo)\n123.10\n419.758\n419.781\n+23\nP 52=208-69(LACo)\n123.52\n440.883\n440.907\n+24\n208-68(LACo)\n124.04\n467.049\n467.072\n+23\n970=208-67(LACo)\n124.81\n486.979\n486.999\n+20\n208-66(LACo)\n125.24\n498.556\n498.596\n+40\n208-65(LACo)\n125.86\n502.436\n502.459\n+23\n208-64(LACo)\n126.90\n571.015\n571.037\n+22\n208-63(LACo)\n127.42\n582.958\n582.976\n+18\n208-62(LACo)\n128.03\n618.456\n618.478\n+22\nZ 370 Reset 1967 = 208-61(LACo)\n128.67\n656.817\n656.842\n+25\n208-60(LACo)\n129.18\n671.895\n671.918\n+23\n208-59(LACo)\n129.74\n702.363\n702.380\n+17\nM 450=208-58(LACo)\n130.19\n726.924\n726.952\n+28\n208-57(LACo)\n130.57\n742.635\n742.656\n+21\n208-56(LACo)\n131.11\n774.591\n774.604\n+13","Vertical Crustal Movements\n311\nTable 1.-Line of levels, San Pedro to 4.9 km north of Grapevine-Continued\nElevation\nApparent\nDistance\nLocation\nBench mark\nmovement\na\nPreearthquake\nPostearthquake\nCastaic (continued)\nkm\nm\nm\nmm\nmm\nN 450 = 208-55(LACo)\n131.66\n808.280\n808.302\n+22\n208-54(LACo)\n132.03\n828.989\n829.005\n+16\nU 970 = 208-53(LACo)\n132.59\n853.607\n853.622\n+15\nP 450 =208-52(LACo) =\n133.70\n889.138\n889.154\n+16\n2807(USGS) = 208-50(LACo)\n135.68\n855.942\n855.962\n+20\n20\nT 2=208-49(LACo)\n136.34\n893.276\n893.291\n+15\nW 12(DWR) = 208-48(LACo)\n137.57\n950.394\n950.407\n+13\nR 450 = 208-47(LACo)\n139.89\n952.272\n952.287\n+15\nV 970 = 208-45(LACo)\n140.65\n983.469\n983.487\n+18\nW 970 = 208-44(LACo)\n141.89\n1015.323\n1015.338\n+15\nN 370 = 208-43(LACo)\n143.13\n971.016\n971.036\n+20\nL 992 = 208-42(LACo)\n143.58\n963.188\n963.202\n+14\n967.870\n+12\nM 370 = 208-41(LACo)\n144.88\n967.858\n1011.049\n+14\nK 992 = 208-40(LACo)\n145.60\n1011.035\n1030.943\n+17\nW 52 = 208-39(LACo)\n145.96\n1030.926\n1071.026\n+16\nL 370 = 208-38(LACo)\n146.74\n1071.010\n1044.217\n+16\nJ 992 = 208-37(LACo)\n147.80\n1044.201\n1071.768\n+15\nK 370 =208-36(LACo)\n148.29\n1071.753\n1111.183\n+15\nX 970 ==208-35(LACo)\n148.97\n1111.168\n1132.546\n+16\nH 992 = 208-34(LACo)\n149.31\n1132.530\n+16\nQ 53 208-33(LACo)\n150.21\n1183.520\n1183.536\n+14\nG 992=208-32(LACo)\n150.64\n1160.612\n1160.626\n+14\nR 53=208-31(LACo)\n151.27\n1130.159\n1130.173\n+17\nJ 370=208-30(LACo)\n152.28\n1088.869\n1088.886\n+11\nF 992 2=208-29(LACo)\n152.92\n1068.463\n1068.474\n+13\n153.66\n1104.423\n1104.436\n208-28A(LACo)\n+10\nS 3=208-28(LACo)\n153.69\n1104.727\n1104.737\n+12\nB 992 = 208-27(LACo)\n154.41\n1141.452\n1141.464\n1158.917\n1158.931\n+14\nH 370 = =208-26(LACo)\n154.74\n1150.689\n1150.704\n+15\nG 370 = 208-24(LACo)\n156.22\n1146.653\n1146.667\n+14\nZ 991 = 208-23(LACo)\n156.36\n1133.833\n. 1133.847\n+14\nY 991 = 208-22(LACo)\n157.28\n1124.605\n1124.620\n+15\nT 53 = 208-21(LACo)\n157.72\n1142.498\n1142.511\n+13\nX 991 = 208-20(LACo)\n158.01\n1150.130\n1150.143\n+13\nW 991 = 208-19(LACo)\n158.57\n1175.036\n1175.054\n+18\nY 970 = 208-18(LACo)\n159.20\n159.68\n1201.161\n1201.178\n+17\nF 370 =208-17(LACo)\n160.92\n1248.523\n1248.539\n+16\nV 991 = 208-16(LACo)\n161.04\n1255.670\n1255.687\n+17\nT 991 = 208-15(LACo)\n1260.865\n+18\nE 370 = 208-14(LACo)\n161.20\n1260.847\n1283.803\n+18\n161.96\n1283.785\nS 991 = 208-13(LACo)\n162.49\n1287.686\n1287.706\n+20\nV 53 = 208-12(LACo)\n1281.045\n+16\n163.33\n1281.029\nR 991 = 08-11(LACo)\n164.17\n1269.256\n1269.272\n+16\nW 53 = 208-10(LACo)\n+19\n164.93\n1222.341\n1222.360\n208-9(LACo)\n+16\n1198.686\n1198.702\nD 370 =208-8(LACo)\n165.69\n+18\n165.90\n1187.817\n1187.835\nU 991 = 208-7(LACo)\n+18\n166.22\n1165.727\n1165.745\n208-6(LACo)\n166.57\n1148.907\n1148.926\n+19\n208-5(LACo)\n+20\n167.11\n1118.177\n1118.197\n208-4(LACo)\n+22\n1095.417\n1095.439\nX 53 = 208-3(LACo)\n167.59\n+19\n168.02\n1069.943\n1069.962\n208-2(LACo)\n168.37\n1052.095\n1052.117\n+22\n(LACo)\n1015.705\n+31\nQuail F RM 1 = 102-82B(LACo).\n171.53\n1015.674\n1016.110\n+30\nQuail F = 102-82A(LACo)\n171.55\n1016.080\n1016.441\n+29\nQuail F RM = 102-82C (LACo)\n171.56\n1016.412\n1016.596\n+33\nQuail B = 102-82D(LACo)\n172.09\n1016.563\n+28\nZ 973 Reset 1965 = 102-83A\n172.51\n1015.213\n1015.241\n(LACo).\n1014.678\n+30\nY 973 Reset 1965 = 102-83B\n172.56\n1014.648\n(LACo).\n+28\n1014.896\n1014.924\nX 973 Reset 1965 = 102-83C\n172.61\n(LACo).\n+25\n23\nW 973 Reset 1965 = 102-83D\n172.66\n1014.852\n1014.877\n(LACo).","312\nSan Fernando Earthquake of 1971\nTable 1.-Line of levels, San Pedro to 4.9 km north of Grapevine-Continued\nElevation\nApparent\nLocation\nBench mark\nDistance\nmovement\nPreearthquake\nPostearthquake\nCastaic (continued)\nkm\nm\nm\nmm\nmm\nV 973 Reset 1965 = 102-83E\n172.72\n1013.879\n1013.906\n+27\n(LACo).\nU 973 = 102-84A(LACo)\n172.82\n1010.543\n1010.568\n+25\nS 973 = 102-84B(LACo)\n172.90\n1011.208\n1011.240\n+32\nR 973 = 102-84C(LACo)\n172.95\n1012.153\n1012.185\n+32\nQ 973 = 102-84D(LACo)\n173.00\n1013.080\n1013.112\n+32\nP 973 = 102-84E(LACo)\n173.05\n1014.055\n1014.086\n+31\nN 973 = 102-84F(LACo)\n173.10\n1014.962\n1014.994\n+32\nM 973 = 102-84K(LACo)\n173.15\n1015.882\n1015.913\n+31\nQ 452 = 102-85(LACo)\n173.20\n1016.761\n1016.793\n+32\nZ 53 Reset 1953 = 102-86(LACo)\n173.55\n1031.281\n1031.314\n+33\nP 452 = 102-87(LACo)\n173.75\n1036.158\n1036.190\n+32\nN 452 = 102-88(LACo)\n174.04\n1049.986\n1050.017\n+31\n102-88A(LACo)\n174.35\n1067.948\n1067.980\n+32\nB 370 = 102-89(LACo)\n174.89\n1092.898\n1092.934\n+36\nM 452 = 102-90(LACo)\n175.09\n1086.052\n1086.086\n+34\nL 452 = 102-91(LACo)\n175.62\n1061.494\n1061.529\n+35\nA 370 = 102-92(LACo)\n176.00\n1054.418\n1054.451\n+33\nK 452 = 102-93(LACo)\n176.31\n1061.383\n1061.419\n+36\nJ 452 = 102-94(LACo)\n176.85\n1062.516\n1062.551\n+35\nA 54 = 102-95(LACo)\n177.32\n1070.893\n1070.928\n+35\nH 452 = 102-96(LACo)\n177.60\n1080.398\n1080.434\n+36\nG 452 = 102-97(LACo)\n178.05\n1084.781\n1084.815\n+34\nF 452 = 102-98(LACo)\n178.55\n1097.446\n1097.479\n+33\nR 608 = 102-99(LACo)\n179.04\n1106.982\n1107.039\n+57\nE 452 = 102-100(LACo)\n179.23\n1111.551\n1111.585\n+34\n102-100A(LACo)\n179.78\n1127.100\n1127.132\n+32\nZ 368 = 102-101(LAC\n180.45\n1153.097\n1153.128\n+31\nGorman\nB 54 = 102-102(LACo)\n180.99\n1161.640\n1161.674\n+34\n102-106(LACo)\n183.57\n1248.561\n1248.589\n+28\n102-107(LACo)\n184.20\n1274.429\n1274.468\n+39\n102-108(LACo)\n184.91\n1236.127\n1236.163\n+36\n102-110(LACo)\n186.39\n1196.150\n1196.188\n+38\nBoundary Monument =102-111\n186.71\n1166.946\n1166.986\n+40\n(LACo).\n0+00(LACRD) = 102-112(LACo).\n186.73\n1166.631\n1166.671\n+40\nBoundary Monument 2 =102-13\n186.74\n1166.690\n1166.730\n+40\n(LACo).\nB 650 = 102-114(LACo)\n187.14\n1141.144\n1141.184\n+40\nH 971 = 102-115(LACo)\n187.69\n1131.207\n1131.247\n+40\nE 54\n189.07\n1097.731\n1097.772\n+41\nD 54\n189.27\n1088.436\n1088.478\n+42\nP 1059\n189.44\n1089.642\n1089.684\n+42\nLebec\nF 54\n190.82\n1055.802\n1055.850\n+48\nU 594\n192.49\n1020.122\n1020.168\n+46\nT 1098\n193.72\n997.474\n997.518\n+44\nG 54\n193.90\n985.332\n985.381\n+49\nU 974\n195.44\n954.026\n954.075\n+49\nV 974\n196.81\n887.557\n887.605\n+48\nJ 537 Reset 1960\n197.90\n827.922\n827.968\n+46\nS 1098\n198.23\n812.158\n812.209\n+51\nE 367\n198.43\n800.158\n800.205\n+47\nH 537\n198.97\n769.253\n769.303\n+50\nD 367\n199.25\n752.847\n752.896\n+49\nG 537\n199.67\n725.069\n725.117\n+48\nR 1098\n200.76\n661.638\n661.682\n+44\nT 974\n201.25\n633.836\n633.882\n+46\nZ 365\n202.12\n580.055\n580.104\n+49\nG 540\n202.77\n534.326\n534.371\n+45\nQ 1098\n203.05\n524.548\n524.592\n+44\nP 1098\n203.50\n502.218\n502.262\n+44\nT 824 Reset 1958\n204.62\n457.186\n457.228\n+42\n25","Vertical Crustal Movements\n313\nTable 2.-Line of levels, Montalvo to 6.9 km south of Rosamond\nElevation\nApparent\nLocation\nBench mark\nDistance\nmovement\no\nPreearthquake Postearthquake\nkm\nm\nm\nmm\nmm\n29.255\n-28\n20\nH 1051\n0.00\n29.283\n20\n102-6 (VCo)\n0.68\n28.927\n28.910\n-17\n1.76\n37.023\n37.010\n-13\nMontalvo\nRV 2 (SPCo)\n-16\n26 (C of V)\n2.82\n44.199\n44.183\nRV 3 (SPCo)\n2.84\n44.193\n44.176\n-17\nRV 5 (SPCo)\n4.48\n50.722\n50.704\n-18\n43.752\n-19\nRV 6 (SPCo)\n5.33\n43.771\n102-7 (VCo)\n6.28\n38.964\n38.940\n-24\n20\n43.647\n-21\nV 304\n7.05\n43.668\n149 (USGS)\n7.57\n45.941\n45.928\n-13\n56-2 (C of V)\n7.93\n48.630\n48.612\n-18\n102-8 (C of V)\n9.01\n53.494\n53.477\n-17\n102-9 (C of V)\n9.91\n57.379\n57.360\n-19\n10.79\n59.111\n59.095\n-16\nW 304\n64.883\n-18\nRV 9 (SPCo)\n11.80\n64.901\n-17\nRV 10 (SPCo)\n12.98\n64.232\n64.215\n-18\n13.62\n66.496\n66.478\nX 304\n102-10 (C of V)\n14.11\n68.349\n68.332\n-17\n71.427\n71.409\n-18\nRV 12 (SPCo)\n14.82\n68.875\n-18\n20\nRV 13 (SPCo)\n15.43\n68.893\n-13\nRV 19 (SPCo)\n20.58\n95.350\n95.337\nSanta Paula\n92.812\n92.796\n-16\n65-4 (VCo)\n21.66\n-13\n94.941\n94.928\nRV 21 (SPCo)\n22.58\n-16\n103.342\n102-13 (VCo)\n23.68\n103.358\n108.177\n-14\nRV 22 (SPCo)\n24.35\n108.191\n-12\n102-14 (VCo)\n24.91\n113.025\n113.013\n-9\n119.582\n119.573\nRV 23 (SPCo)\n25.69\n153.622\n153.622\n0\n501 (USGS)\n31.35\n31.53\n135.857\n135.854\n-3\n5-67 (VCo)\n136.280\n-4\n19\nRV 28 (SPCo)\n32.31\n136.284\n136.749\n-3\n8-81 (VCo)\n32.85\n136.752\n137.026\n-3\nRV 29 (SPCo)\n32.96\n137.029\n-6\n19-203 (VCo)\n33.63\n132.618\n132.612\n-8\n34.71\n139.040\n139.032\nRV 30 (SPCo)\n-7\n35.23\n143.056\n143.049\nFillmore\nE 305\n-7\n35.65\n146.369\n146.362\nRV 32 (SPCo)\n36.14\n145.685\n145.677\n-8\n102-15 (VCo)\n37.00\n139.213\n139.205\n-8\n102-16 (VCo)\n142.669\n-12\n38.12\n142.681\n102-17 (VCo)\n147.656\n-12\n102-18 (VCo)\n38.54\n147.668\n-14\n39.24\n152.116\n152.102\n102-19 (VCo)\n-13\n40.29\n162.866\n162.853\n102-20 (VCo)\n19\n41.40\n164.375\n164.355\n-20\nRV 35 (SPCo)\n-20\n42.22\n171.368\n171.348\n102-21 (VCo)\n-20\n42.89\n177.763\n177.743\nRV 37 (SPCo)\n183.570\n-26\n102-22 (VCo)\n43.65\n183.596\n190.326\n-23\n102-23 (VCo)\n45.38\n190.349\n-20\n46.26\n202.220\n202.200\nRV 40 (SPCo)\n-14\n47.05\n206.664\n206.650\n102-24 (VCo)\n47.47\n211.099\n211.088\n-11\nH 305\n18\n210.678\n210.668\n-10\nRV 41 (SPCo)\n47.49\n47.87\n213.750\n213.749\n-1\n102-25 (VCo)\n48.58\n209.989\n209.980\n-9\nRV 43 (SPCo)\n49.35\n209.530\n209.511\n-19\nRV 44 (SPCo)\nPiru\n50.29\n215.319\n215.306\n-13\nRV 45 (SPCo)\n220.547\n-7\nRV 46 (SPCo)\n50.99\n220.554\n222.496\n-2\nSP 30 (VCo)\n51.34\n222.498\n-1\n51.53\n225.709\n225.708\nJ 305\n+9\n231.078\n231.087\nRV 47 (SPCo)\n52.51\n231.683\n231.692\n+9\nRV 48 (SPCo)\n52.74\n231.900\n+8\n18\n53.44\n231.892\nRV 49 (SPCo)\n54.15\n238.024\n238.028\n+4\nSP 33 (VCo)\n236.816\n+8\n54.59\n236.808\nRV 50 (SPCo)\n+9\n55.05\n238.392\n238.401\nK 305\n245.701\n245.712\n+11\nRV 51 (SPCo)\n55.76","314\nSan Fernando Earthquake of 1971\nTable 2.-Line of levels, Montalvo to 6.9 km south of Rosamond-Continued\nElevation\nApparent\nLocation\nBench mark\nDistance\nmovement\na\nPreearthquake\nPostearthquake\nPiru (continued)\nkm\nm\nm\nmm\nmm\nRV 52 (SPCo)\n56.80\n253.354\n253.361\n+7\nRV 53 (SPCo) 1969 Elev\n57.30\n254.481\n254.490\n+9\nC 41\n58.41\n262.042\n262.056\n+14\nRV 55 (SPCo)\n58.60\n261.007\n261.026\n+19\n206-33 (LACo)\n59.40\n263.900\n263.914\n+14\n206-21 (LACo)\n60.49\n273.485\n273.500\n+15\nRV 57 (SPRR) = 206-22 (LACo)\n61.29\n273.092\n273.103\n+11\n206-24A (LACo)\n62.14\n281.614\n281.625\n+11\n206-24 (LACo)\n62.52\n288.173\n288.187\n+14\nRV 58 (SPRR) = 206-25 (LACo)\n63.05\n288.179\n288.192\n+13\nRV 59 (SPRR) = 206-26 (LACo)\n63.71\n287.526\n287.535\n+9\n206-27 (LACo)\n64.05\n288.893\n288.897\n+4\n206-29 (LACo)\n65.24\n297.596\n297.603\n+7\n206-30 (LACo)\n66.33\n303.305\n303.309\n+4\n206-31 (LACo)\n67.33\n307.896\n307.901\n+5\nCastaic Junction\nRV 60 (SPRR) = 206-31A (LACo)\n67.40\n307.114\n307.112\n-2\nU 370 =206-32 (LACo)\n67.83\n309.104\n309.105\n+1\n18\nRV 62 (SPRR) = 208-81 (LACo)\n68.76\n314.052\n314.062\n+10\n208-82 (LACo)\n69.20\n317.464\n317.485\n+21\nRV 64 (SPRR) = 208-83 (LACo)\n70.12\n325.542\n325.572\n+30\nQ 970 = 208-84\n70.24\n327.817\n327.863\n+46\n18\nRV 65 (SPRR) = 208-85 (LACo)\n70.42\n327.840\n327.888\n+48\nT 370 = 208-86 (LACo)\n70.93\n329.558\n329.605\n+47\n208-87 (LACo)\n71.72\n335.143\n335.194\n+51\n208-87A (LACo)\n71.73\n335.348\n335.400\n+52\nS 370 Reset 1964 = 208-88 (LACo)\n72.77\n342.609\n342.663\n+54\nSaugus\n208-89 (LACo)\n73.24\n345.843\n345.907\n+64\n208-90 (LACo) = RV 68 (SPRR)\n74.12\n350.530\n350.591\n+61\nJ 52 = 208-91 (LACo)\n74.61\n353.820\n353.880\n+60\n18\n1171 (USGS) = 60-42 (LACo)\n75.15\n356.572\n356.589\n+17\nC 1148 =60-43A (LACo)\n75.25\n351.772\n351.834\n+62\nX 898 =60-43 (LACo)\n75.31\n352.187\n352.245\n+58\n201-121A (LACo)\n76.02\n357.481\n357.535\n+54\n201-120 (LACo)\n77.00\n363.957\n364.014\n+57\nY 984 =201-118A (LACo)\n78.97\n377.630\n377.705\n+75\n201-116A (LACo)\n80.01\n388.741\n388.784\n+43\n201-115A (LACo)\n80.78\n396.995\n397.063\n+68\n201-114 (LACo)\n81.71\n409.509\n409.588\n+79\n201-113 (LACo)\n82.24\n416.320\n416.422\n+102\n18\n201-112 (LACo)\n82.62\n416.035\n416.119\n+84\n201-111A (LACo)\n83.54\n426.794\n426.935\n+141\n201-110A (LACo)\n84.34\n438.802\n438.941\n+139\n18\nBM (SCE) = 201-65 (LACo)\n122.09\n968.759\n968.805\n+46\nSEC 22-27 (LACS) = 201-64\n122.10\n968.815\n968.863\n+48\n(LACo).\nSloot = 201-63 (LACo)\n122.15\n970.517\n970.564\n+47\nW 31 Reset 1955 = 201-62 (LACo)\n122.20\n970.707\n970.756\n+49\nV 431 = 201-61 (LACo)\n122.44\n975.192\n975.238\n+46\nU 431 = 201-60 (LACo)\n122.69\n983.048\n983.093\n+45\nMont 2 =201-59 (LACo)\n122.85\n982.838\n982.883\n+45\nF 1000 = 201-58 (LACo)\n123.02\n983.269\n983.316\n+47\n3219 (USGS)=201-57 = (LACo)\n123.18\n981.399\n981.445\n+46\nS 431 = 201-56 (LACo)\n123.27\n983.541\n983.587\n+46\n21\nQ 431 = 201-54 (LACo)\n123.65\n977.125\n977.175\n+50\nH 57 = 201-53 (LACo)\n123.85\n976.345\n976.387\n+42\nQ 811 = 201-52 (LACo)\n124.10\n978.986\n979.029\n+43\nL 899 = 201-51 (LACo)\n124.27\n979.973\n980.019\n+46\nA 994 =201-50A (LACo)\n124.36\n979.765\n979.809\n+44\nM 431 Reset 1963 = 201-49A (LACo)\n124.49\n975.887\n975.932\n+45\nE 1000 =201-48 (LACo)\n124.71\n965.562\n965.607\n+45\nK 431 = 201-47 (LACo)\n124.90\n955.225\n955.267\n+42\nAtlas = 201-45 (LACo)\n125.15\n942.836\n942.876\n+40\nAtlas RM =201-44 (LACo)\n125.16\n942.973\n943.013\n+40\nM 899 = 201-43 (LACo)\n125.23\n940.365\n940.406\n+41\nN 899 = 201-42 (LACo)\n125.37\n935.064\n935.105\n+41\nP 899 = 201-41 (LACo)\n125.45\n932.334\n932.374\n+40","Vertical Crustal Movements\n315\nTable 2.-Line of levels, Montalvo to 6.9 km south of Rosamond-Continued\nElevation\nApparent\nDistance\nmovement\no\nLocation\nBench mark\nPreearthquake\nPostearthquake\nkm\nSaugus (continued)\nm\nm\nmm\nmm\n937.293\n+40\nLoft A = 201-40 (LACo)\n125.52\n937.253\n929.317\n+39\nQ 899 = 201-39 (LACo)\n125.65\n929.278\n+40\nR 899 = 201-38 (LACo)\n125.77\n924.514\n924.554\n+40\n22\nS 899 = 201-37 (LACo)\n126.05\n918.042\n918.082\n+39\nP 811 Reset 1955 = 201-36 (LACo)\n126.14\n914.738\n914.777\n+38\nT 899 =201-35 (LACo)\n126.32\n908.099\n908.137\n+38\n126.61\n902.612\n902.650\nV 899 = 201-32\n+39\n126.69\n900.706\n900.745\nW 899 = 201-31\n126.77\n898.775\n898.815\n+40\nZ 899 = 201-30\n126.85\n896.458\n896.498\n+40\nY 899 = 201-29\n126.92\n894.255\n894.299\n+44\nX 899 = 201-28\n892.434\n+38\n126.99\n892.396\nDD 487 = 201-27\n+46\n127.13\n889.369\n889.415\nT 430 = 201-25\n+40\n127.22\n887.418\n887.458\nM 811 Reset 1955=201-24\n+38\n127.39\n885.585\n885.623\nEE 487 = 201-22\n+39\n127.46\n884.929\n884.968\nP 430 = 201-21\n127.54\n883.172\n883.210\n+38\nN 430 = 201-20\n881.008\n+38\n127.68\n880.970\nG 57 = 201-18\n880.020\n+37\nL 430 Reset 1955=201-17\n127.73\n879.983\n+39\n127.81\n878.803\n878.842\nK 430 = 201-16\n+38\n22\n127.89\n877.799\n877.837\nJ 430 = 201-15\n+39\n127.97\n876.234\n876.273\nH 430 = 201-14\n+36\n128.05\n875.293\n875.329\nG 430 = 201-13\n128.21\n874.114\n874.152\n+38\nE 430 = 201-11\n128.29\n872.709\n872.747\n+38\nD 430 = 201-10\n871.677\n+36\n128.45\n871.641\nB 430 = 201-8\n870.245\n+36\n128.51\n870.209\nD 1000 = 201-7\n+37\n128.58\n869.470\n869.507\nZ 429 = 201-6\n+40\n128.63\n868.424\n868.464\n109 (USFS) = 201-5\n128.65\n867.743\n867.781\n+38\nY 429 = 201-4\n866.561\n+40\n128.69\n866.521\nX 429 = 201-3\n865.945\n+37\n128.74\n865.908\nW 429 = 201-2\n865.644\n+41\n128.79\n865.603\nV 429 = 201-1\n864.832\n+34\n128.84\n864.798\nU 429 = 101-1\n+33\n128.89\n864.085\n864.118\nT 429 = 101-2\n+36\n128.94\n863.493\n863.529\nS 429 = 101-3\n128.99\n862.852\n862.885\n+33\nR 429 = 101-4\n129.04\n862.410\n862.440\n+30\nQ 429 = 101-5\n861.704\n+36\n129.09\n861.668\nP 429 = 101-6\n863.191\n+36\n129.19\n863.155\nM 429 = 101-8\n862.238\n+33\n129.24\n862.205\nL 429 = 101-9\n862.885\n+38\n129.31\n862.847\nAlpine = 101-11\n+35\n129.40\n860.889\n860.924\nJ 429 = 101-12\n+36\n129.45\n860.706\n860.742\nH 429 = 101-13\n129.54\n860.475\n860.510\n+35\nF 429 = 101-15\n859.742\n+35\n129.59\n859.707\nE 429 = 101-16\n859.526\n+35\n129.64\n859.491\nD 429 = 101-17\n+37\n129.69\n858.595\n858.632\nC 429 = 101-18\n+31\n129.74\n857.993\n858.024\nB 429 = 101-19\n+35\n129.79\n857.208\n857.243\nA 429 = 101-20\n+38\n129.84\n856.193\n856.231\nZ 428 = 101-21\n129.89\n855.753\n855.793\n+40\nY 428 = 101-22\n22\n129.94\n855.227\n855.265\n+38\nX 428 = 101-23\n130.10\n853.788\n853.829\n+41\nU 428 = 101-26\n130.17\n854.380\n854.415\n+35\nT 487 = 101-28\n854.525\n+46\n130.20\n854.479\nV 487 = 101-29\n855.410\n+39\n130.24\n855.371\nS 428 = 101-30\n+36\n130.29\n854.887\n854.923\nX 487 = 101-32\n+35\n130.32\n854.832\n854.867\nY 487 = 101-33\n130.35\n854.866\n854.904\n+38\nZ 487 = 101-34\n854.961\n+54\n130.37\n854.907\nQ 428 = 101-35\n854.877\n+38\n130.42\n854.839\nP 428 = 101-36\n+35\n130.58\n858.046\n858.081\nVoir 2 = 101-39\n+35\n130.63\n856.760\n856.795\nJ 811 = 101-41\n130.68\n853.451\n853.486\n+35\nH 811 = 101-42","316\nSan Fernando Earthquake of 1971\nTable 2.-Line of levels, Montalvo to 6.9 km south of Rosamond-Continued\nElevation\nApparent\nLocation\nBench mark\nDistance\nmovement\no\nPreearthquake Postearthquake\nSaugus (continued)\nkm\nm\nm\nmm\nmm\nA 488 = 101-44\n130.76\n850.217\n850.244\n+27\nB 488 = 101-45\n130.79\n849.189\n849.220\n+31\nC 488 = 101-46\n130.82\n848.423\n848.453\n+30\nD 488 = 101-47\n130.85\n847.986\n848.016\n+30\nC 1000 = 101-48A\n130.88\n847.603\n847.633\n+30\nF 428 = 101-48B\n130.90\n847.310\n847.339\n+29\nF 488 = 101-49\n130.91\n847.396\n847.426\n+30\nG 488 = 101-50\n130.93\n846.606\n846.635\n+29\nG 811 = 101-51\n130.95\n846.309\n846.340\n+31\nD 428 Reset 1947 = 101-52\n131.00\n845.818\n845.849\n+31\nC 428 = 101-53\n131.05\n844.142\n844.173\n+31\nB 428 = 101-54\n131.09\n843.942\n843.973\n+31\nA 428 Reset 1964 = 101-55A\n131.14\n842.302\n842.333\n+31\nY 427 = 101-57\n131.23\n839.279\n839.309\n+30\nX 427 = 101-58\n131.28\n837.762\n837.791\n+29\nW 427 = 101-59\n131.33\n837.241\n837.269\n+28\nV 427 = 101-60\n131.38\n836.695\n836.725\n+30\n22\nJ 488 = 101-61\n131.44\n836.326\n836.356\n+30\nH 488 = 101-62\n131.49\n835.162\n835.192\n+30\nS 427 = 101-63\n131.53\n833.376\n833.406\n+30\nR 427 = 101-64\n131.58\n833.449\n833.479\n+30\nL 1147 = 101-64A\n131.59\n833.336\n833.366\n+30\nQ 427 = 101-65\n131.64\n832.955\n832.985\n+30\nP 427 = 101-66\n131.69\n831.773\n831.802\n+29\nM 427 = 101-68\n131.79\n829.689\n829.718\n+29\nL 427 = 101-69\n131.84\n829.047\n829.077\n+30\nK 427 = 101-70\n131.89\n828.292\n828.320\n+28\nJ 427 = 101-71\n131.97\n827.671\n827.699\n+28\n22\nH 427 = 101-72\n132.04\n826.339\n826.369\n+30\nF 427 = 101-74\n132.20\n822.516\n822.545\n+29\nE 427 = 101-76\n132.28\n821.884\n821.911\n+27\nA 427 = 101-80\n132.60\n816.603\n816.627\n+24\nY 426 = 101-82\n132.76\n815.728\n815.750\n+22\nX 426 = 118-1\n132.84\n814.408\n814.430\n+22\nS 487 = 101-86\n133.15\n812.395\n812.412\n+17\nR 487 = 101-87\n133.24\n812.320\n812.340\n+20\nQ 487 = 101-88\n133.35\n812.225\n812.246\n+21\nR 426 = 101-89A\n133.43\n811.351\n811.372\n+21\nC 811 = 101-89\n133.44\n811.516\n811.538\n+22\n22\nQ 426 = 101-91\n133.52\n811.338\n811.358\n+20\n2657 (USGS) = 101-93\n133.71\n810.483\n810.503\n+20\nX 811 = 101-94\n133.82\n809.928\n809.949\n+21\nB 811 = 101-95\n133.85\n810.333\n810.352\n+19\nA 811 = 101-96\n133.98\n809.248\n809.264\n+16\nPalmdale\nM 426 = 101-97\n134.11\n808.192\n808.211\n+19\nL 426 = 101-98\n134.23\n808.113\n808.133\n+20\nK 426 = 101-99\n134.36\n806.300\n806.320\n+20\nPalmdale 118-3A\n134.63\n805.272\n805.296\n+24\nG 426 = 101-101\n134.75\n803.698\n803.720\n+22\nF 426 = 101-102\n134.88\n802.691\n802.713\n+22\n22\nE 426 = 101-103\n135.01\n801.374\n801.396\n+22\nD 426 = 101-104\n135.13\n800.253\n800.276\n+23\nB 426 = 101-106\n135.45\n797.918\n797.940\n+22\nP 487 = 101-107\n135.71\n797.702\n797.722\n+20\nZ 425 = 101-108\n135.83\n796.760\n796.779\n+19\nY 425 = 101-109\n136.02\n797.263\n797.282\n+19\nX 425 = 101-110\n136.20\n797.525\n797.543\n+18\nW 425 = 101-111\n136.38\n796.710\n796.728\n+18\nA 1000 = 101-112A\n136.59\n797.308\n797.326\n+18\nV 425 = 101-113\n136.77\n796.049\n796.065\n+16\n22\nU 425 = 101-114\n137.03\n795.016\n795.031\n+15\nT 425 = 101-115\n137.29\n795.396\n795.413\n+17\nS 425 = 101-116\n137.55\n794.001\n794.018\n+17\nSahara = 101-117\n137.64\n794.452\n794.469\n+17\nSahara RM = 101-117A\n137.66\n794.569\n794.586\n+17\nSahara RM 3 = 101-117B\n137.69\n794.202\n794.219\n+17","Vertical Crustal Movements\n317\nTable 2.-Line of levels, Montalvo to 6.9 km south of Rosamond-Continued\nElevation\nApparent\nDistance\nmovement\nBench mark\no\nLocation\nPreearthquake Postearthquake\nkm\nPalmdale (continued)\nm\nm\nmm\nmm\n789.647\n+10\n101-118 (LACo)\n138.44\n789.637\n785.520\n+10\n139.13\n785.510\nW 811 = 101-119\n+9\n139.92\n779.054\n779.063\nK 1147 = 101-120A\n23\n140.70\n775.295\n775.302\n+7\nV 811 = 101-121\n142.38\n761.407\n761.404\n-3\nU 811 = 101-123\n142.66\n757.988\n757.986\n-2\nB 57 Reset 1955 = 101-124\n751.043\n-6\n2462 (USGS) = 101-124A\n143.45\n751.049\n-10\n143.92\n746.052\n746.042\nT 811 = 101-125\n144.66\n738.643\n738.623\n-20\n101-126 (LACo)\n730.786\n-37\n145.49\n730.823\nS 811 Reset 1955 = 101-127\n146.34\n725.274\n725.172\n-102\n101-128 (LACo)\n-130\n147.02\n719.709\n719.579\nG 487 = 101-130\n147.25\n717.088\n716.942\n-146\n2356 (USGS) = 101-131A\n712.603\n-135\n148.02\n712.738\n101-132 (LACo)\n-134\n23\n148.11\n712.393\n712.259\nJ 1147 = 101-132A\n711.083\n-129\n148.37\n711.212\n2335 (USGS) = 101-133\n-134\nZ 56 Reset 1965 = 101-134A\n149.19\n709.910\n709.776\n149.70\n708.810\n708.708\n-102\n101-135 (LACo)\n706.496\n706.395\n-101\n150.81\nZ 811 = 101-136\n705.424\n-95\n151.39\n705.519\n101-137 (LACo)\n-99\n152.55\n702.824\n702.725\nY 56 = 101-138\n-91\n153.27\n701.844\n701.753\n2302 (USGS) = 101-139\n701.599\n-88\n153.74\n701.687\nOban RM 1 = 101-140\n-88\n153.75\n702.494\n702.406\nOban (USGS) = 101-141\n-92\n701.652\n701.560\nOban RM 2 = 101-142\n153.77\n154.74\n701.456\n701.363\n-93\nH 487 = 101-143\n700.781\n-89\n155.42\n700.870\n101-144 (LACo)\n-81\n156.28\n701.289\n701.208\nT 1146 = 101-145A\n701.557\n701.458\n-99\n157.28\n101-146 (LACo)\n702.286\n-83\n158.04\n702.369\nJ 487 = 101-147\n-70\n159.20\n702.393\n702.323\nW 56 = 101-148\n702.841\n-54\n159.67\n702.895\nN 487 = 101-149\nRosamond\n161.22\n703.542\n703.504\n-38\nM 487 = 101-151","318\nSan Fernando Earthquake of 1971\nTable 3.-Line of levels, 0.4 km west of Bridge No. 53-35 over Topanga Creek to intersection of Foothill Blvd. and Ocean View Blvd.,\nLa Canada\nElevation\nApparent\nLocation\nBench mark\nDistance\nmovement\nPreearthquake Postearthquake\nkm\nm\nm\nmm\nSanta Monica\nmm\nP 99 Reset 1933 = 48-62\n0.00\n8.774\n8.764\n-10\n15\n56-1A (LACo)\n0.31\n11.950\n11.940\n-10\n56-1 (LACo)\n1.30\n24.544\n24.519\n-25\n56-1B (LACo)\n2.00\n35.159\n35.149\n-10\n56-2 (LACo)\n2.35\n46.811\n46.802\n-9\n17-F3 (LACFCD) = 56-3\n2.97\n67.520\n67.511\n-9\n53-143 (LACFCD) = 56-4\n3.78\n90.425\n90.415\n-10\n56-4B (LACo)\n4.17\n99.618\n99.609\n-9\n56-4C (LACo)\n4.54\n132.831\n132.822\n-9\n56-4D (LACo)\n4.92\n163.759\n163.752\n-7\n56-5 (LACo)\n5.14\n180.811\n180.806\n-5\n56-5A (LACo)\n5.59\n208.297\n208.293\n-4\n56-6 (LACo)\n6.07\n224.501\n224.490\n-11\nRS 20A (USGS) = 56-7\n6.74\n223.981\n223.977\n-4\nA 50 = 56-8\n7.41\n225.615\n225.610\n-5\n56-9 (LACo)\n8.01\n234.864\n234.858\n-6\n56-10 (LACo)\n8.91\n246.033\n246.031\n-2\n56-10A (LACo)\n9.52\n255.210\n255.211\n+1\n56-10B (LACo)\n9.81\n261.542\n261.546\n+4\n56-11A (LACo)\n10.63\n272.209\n272.209\n0\nX 1135 = 56-11B\n11.02\n277.478\n277.480\n+2\n56-12 (LACo)\n11.35\n285.835\n285.833\n-2\n56-12A (LACo)\n12.00\n306.951\n306.957\n+6\n56-13A (LACo)\n12.72\n327.352\n327.379\n+27\n56-13 (LACo)\n12.76\n329.189\n329.181\n-8\nA 10 (LACE) = 56-13B\n13.02\n341.898\n341.900\n+2\n56-13C (LACo)\n13.33\n358.502\n358.502\n0\n56-14 (LACo)\n13.80\n388.601\n388.596\n-5\n49 = 56-14A\n13.94\n388.180\n388.186\n+6\n56-15 (LACo)\n14.94\n407.106\n407.108\n+2\n56-15A (LACo)\n15.61\n433.167\n433.159\n-8\nB 1141 = 56-15B\n15.95\n451.449\n451.455\n+6\n56-16 (LACo)\n16.14\n457.140\n457.143\n+3\n1141 = 56-17A\n16.61\n439.583\n439.586\n+3\n56-17B (LACo)\n17.21\n411.827\n411.826\n-1\n56-17C (LACo)\n17.60\n394.338\n394.337\n-1\n56-18A (LACo)\n17.85\n381.353\n381.349\n-4\n56-18B (LACo)\n18.24\n358.662\n358.659\n-3\n56-19 (LACo)\n18.59\n342.628\n342.625\n-3\n56-19A (LACo)\n18.62\n341.196\n341.192\n-4\n56-19B\n18.83\n329.759\n329.759\n0\n56-20A (LACo)\n19.41\n301.970\n301.964\n-6\nY 1135 = 56-21A\n19.96\n291.088\n291.085\n-3\n56-22 (LACo) =06-02280\n20.58\n280.534\n280.523\n-11\nT 1135 = 56-22A\n21.04\n275.588\n275.580\n-8\n56-23 (LACo) = 06-02400\n21.26\n271.878\n271.869\n-9\n16\nWoodland Hills\n57-35 (LACo) =06-06330\n21.32\n268.409\n268.402\n-7\n06-02405 (CofLA)\n21.39\n269.747\n269.737\n-10\n06-02500 (CofLA)\n21.65\n266.641\n266.633\n-8\n06-02520 (CofLA)\n21.67\n266.425\n266.418\n-7\n06-02530 (CofLA)\n22.00\n262.792\n262.787\n-5\n06-02560 (CofLA)\n22.21\n260.047\n260.043\n-4\n06-02570 (CofLA)\n22.45\n256.572\n256.566\n-6\n06-02590 (CofLA)\n22.68\n252.701\n252.695\n-6\n06-02610 (CofLA)\n22.91\n249.747\n249.734\n-13\n06-02640 (CofLA)\n23.31\n246.219\n246.213\n-6\n06-02700 (CofLA)\n23.71\n244.190\n244.183\n-7\n06-02732 (CofLA)\n23.84\n244.125\n244.117\n-8\n06-02852 (CofLA)\n24.33\n242.237\n242.228\n-9\n06-02910 (CofLA)\n24.56\n241.742\n241.736\n-6\n06-02970 (CofLA)\n24.98\n243.340\n243.336\n-4\n06-03005 (CofLA)\n25.21\n244.160\n244.155\n-5\n06-03035 (CofLA)\n25.44\n245.023\n245.017\n-6\n06-03060 (CofLA)\n25.49\n244.837\n244.832\n-5\n06-03095 (CofLA)\n25.70\n246.269\n246.264\n-5","Vertical Crustal Movements\n319\nTable 3.-Line of levels, 0.4 km west of Bridge No. 53-35 over Topanga Creek to intersection of Foothill Blvd. and Ocean View Blvd.,\nLa Canada-Continued\nElevation\nApparent\nLocation\nBench mark\nDistance\nmovement\nPreearthquake Postearthquake\nWoodland Hills\n(continued).\nkm\nm\nm\nmm\nmm\n06-03150 (CofLA)\n25.92\n247.807\n247.802\n-5\n06-03180 (CofLA)\n26.34\n250.551\n250.548\n-3\n06-03210 (CofLA)\n26.74\n252.294\n252.291\n-3\n06-03242 (CofLA)\n26.77\n252.480\n252.477\n-3\n06-03272 (CofLA)\n27.01\n253.280\n253.275\n-5\n06-03300 (CofLA)\n27.23\n254.586\n254.582\n-4\n06-03332 (CofLA)\n27.38\n255.539\n255.536\n-3\n06-03362 (CofLA)\n27.75\n258.282\n258.279\n-3\n260.338\n06-03388 (CofLA)\n27.96\n260.337\n+1\n06-03422 (CofLA)\n28.23\n263.624\n263.626\n+2\n06-03450 (CofLA)\n28.45\n266.278\n266.278\n0\n06-03483 (CofLA)\n28.66\n268.455\n268.453\n-2\n06-03485 (CofLA)\n28.81\n270.996\n270.993\n-3\n271.043\n-2\n06-03510 (CofLA)\n28.95\n271.045\n271.921\n06-03541 (CofLA)\n29.15\n271.927\n-6\n272.157\n-1\n06-03600 (CofLA)\n29.36\n272.158\n273.855\n0\n06-03610 (CofLA)\n29.47\n273.855\n0\n06-03620 (CofLA)\n29.74\n276.036\n276.036\n-1\n06-03655 (CofLA)\n29.90\n276.952\n276.951\n06-03690 (CofLA)\n30.04\n275.817\n275.818\n+1\n06-03720 (CofLA)\n30.11\n275.933\n275.930\n-3\n289.554\n-7\n06-03760 (CofLA)\n30.52\n289.561\n06-03770 (CofLA)\n30.78\n284.950\n284.953\n+3\n06-03840 (CofLA)\n30.82\n283.095\n283.097\n+2\n06-03839 (CofLA)\n30.83\n283.926\n283.927\n+1\n05-00420 (CofLA)\n31.10\n284.547\n284.550\n+3\n289.983\n289.988\n+5\n05-00450 (CofLA)\n31.54\n291.227\n291.231\n+4\n05-00475 (CofLA)\n31.71\n31.97\n293.850\n293.850\n0\n16\nRS 17 = 05-00535\n05-00540 (CofLA)\n32.03\n292.719\n292.721\n+2\n294.706\n+2\n05-00830 (CofLA)\n32.24\n294.704\n295.962\n+3\n05-00825 (CofLA)\n32.38\n295.959\n32.69\n297.701\n297.705\n+4\nQ 31 = 05-00330\n297.832\n+3\n05-00360 (CofLA)\n32.91\n297.829\n+2\n05-00781 (CofLA)\n33.32\n296.420\n296.422\n-3\n05-00770 (CofLA)\n33.54\n293.314\n293.311\n290.686\n290.689\n+3\n05-00060 (CofLA)\n33.78\n291.516\n291.519\n+3\n05-00760 (CofLA)\n34.01\n289.272\n+3\n05-00740 (CofLA)\n34.20\n289.269\n05-00730 (CofLA)\n34.23\n289.092\n289.093\n+1\n04-02910 (CofLA)\n34.63\n291.398\n291.401\n+3\n290.651\n+3\n04-02810 (CofLA)\n34.95\n290.648\n+2\n35.08\n290.917\n290.919\n04-02787 (CofLA)\n289.641\n289.645\n+4\n04-02760 (CofLA)\n35.47\n293.138\n293.143\n+5\n04-02700 (CofLA)\n35.85\n36.32\n294.759\n294.764\n+5\n04-01860 (CofLA)\n295.871\n+3\n36.70\n295.868\n04-02640 (CofLA)\n+1\n37.12\n287.963\n287.964\n04-02580 (CofLA)\n-7\n37.43\n285.227\n285.220\n04-02549 (CofLA)\n-3\n04-02542 (CofLA)\n37.56\n286.977\n286.974\n+1\n04-02520 (CofLA)\n37.98\n293.831\n293.832\n300.840\n300.836\n-4\n04-02490 (CofLA)\n38.53\n299.093\n299.086\n-7\n04-01800 (CofLA)\n38.82\n302.687\n-4\n04-02460 (CofLA)\n39.05\n302.691\n299.250\n-6\n04-02445 (CofLA)\n39.23\n299.256\n-4\n04-02430 (CofLA)\n39.66\n298.064\n298.060\n298.073\n298.066\n-7\n04-02399 (CofLA)\n39.85\n296.599\n296.598\n-1\n04-02340 (CofLA)\n40.58\n294.566\n-3\n04-02321 (CofLA)\n40.76\n294.569\n292.492\n-1\n04-02315 (CofLA)\n40.99\n292.493\n-2\n04-02310 (CofLA)\n41.18\n290.861\n290.859\n-2\n41.21\n290.996\n290.994\n04-02309 (CofLA)\n41.60\n289.124\n289.122\n-2\n04-02302 (CofLA)\n288.100\n288.098\n-2\n04-01180 (CofLA)\n41.78\n285.213\n285.208\n-5\n04-01171 (CofLA)\n42.01\nGranada Hills","320\nSan Fernando Earthquake of 1971\nTable 3.-Line of levels, 0.4 km west of Bridge No. 53-35 over Topanga Creek to intersection of Foothill Blvd. and Ocean View Blvd.,\nLa Canada-Continued\nElevation\nApparent\nLocation\nBench mark\nDistance\nmovement\na\nPreearthquake Postearthquake\nGranada Hills\n(continued).\nkm\nm\nm\nmm\nmm\n04-01205 (CofLA)\n42.25\n284.788\n284.782\n-6\n04-01261 (CofLA)\n42.47\n287.673\n287.664\n-9\n04-01270 (CofLA)\n42.50\n287.843\n287.837\n-6\n04-01290 (CofLA)\n42.65\n288.880\n288.872\n-8\n04-01322 (CofLA)\n42.92\n290.645\n290.640\n-5\n04-05468 (CofLA)\n43.01\n291.416\n291.411\n-5\n04-04120 (CofLA)\n43.78\n300.865\n300.862\n-3\n04-05490 (CofLA)\n43.82\n301.232\n301.231\n-1\n04-05510 (CofLA)\n44.28\n309.814\n309.812\n-2\n04-05520 (CofLA)\n44.51\n315.245\n315.243\n-2\n04-04438 (CofLA)\n44.65\n318.559\n318.562\n+3\n04-04440 (CofLA)\n44.70\n319.287\n319.290\n+3\n04-05550 (CofLA)\n44.90\n323.917\n323.913\n-4\n04-05570 (CofLA)\n45.14\n328.919\n328.921\n+2\n04-05590 (CofLA)\n45.28\n332.508\n332.513\n+5\n04-05610 (CofLA)\n45.63\n341.497\n341.534\n+37\n04-05612 (CofLA)\n45.67\n342.583\n342.624\n+41\n04-05660 (CofLA)\n46.30\n361.579\n361.681\n+102\n04-05662 (CofLA)\n46.34\n363.144\n363.249\n+105\n04-05690 (CofLA)\n46.74\n376.693\n376.802\n+109\n04-05720 (CofLA)\n47.06\n388.018\n388.112\n+94\n04-05761 (CofLA)\n47.56\n397.111\n397.248\n+137\n04-06200 (CofLA)\n47.66\n393.935\n394.055\n+120\n04-07400 (CofLA)\n47.95\n386.357\n386.320\n-37\n04-07410 (CofLA)\n48.12\n388.565\n388.579\n+14\n04-07425 (CofLA)\n48.31\n392.391\n392.380\n-11\n04-07455 (CofLA)\n48.75\n406.705\n406.822\n+117\n04-07465 (CofLA)\n49.05\n420.038\n420.124\n+86\n04-07475 (CofLA)\n49.22\n420.989\n421.185\n+196\n04-07485 (CofLA)\n49.43\n414.162\n414.395\n+233\n04-07495 (CofLA)\n49.54\n409.994\n410.137\n+143\n04-00872 (CofLA)\n49.83\n396.449\n396.657\n+208\n15\n04-04950 (CofLA)\n53.96\n426.368\n426.838\n+470\n03-00995 (CofLA)\n55.94\n420.725\n421.285\n+560\nOlive View\n03-00990 (CofLA)\n56.39\n414.448\n415.093\n+645\n03-00962 (CofLA)\n56.84\n407.008\n407.776\n+768\n03-00930 (CofLA)\n57.29\n399.321\n400.310\n+989\n03-00900 (CofLA)\n57.74\n394.783\n396.027\n+1244\n03-00850 (CofLA)\n57.96\n394.758\n396.040\n+1282\n03-00840 (CofLA)\n58.19\n393.248\n394.573\n+1325\n03-00820 (CofLA)\n58.74\n379.485\n380.879\n+1394\n03-00810 (CofLA)\n58.97\n378.803\n380.255\n+1452\n03-00780 (CofLA)\n58.99\n378.991\n380.451\n+1460\n03-00771 (CofLA)\n59.01\n369.895\n371.314\n+1419\n03-00770 (CofLA)\n59.03\n370.556\n372.066\n+1510\n03-00751 (CofLA)\n59.44\n363.763\n364.037\n+274\n03-00750 (CofLA)\n59.85\n363.817\n364.072\n+255\n03-00720 (CofLA)\n60.10\n363.155\n363.356\n+201\n03-00670 (CofLA)\n60.19\n363.616\n363.760\n+144\n03-00657 (CofLA)\n60.69\n357.541\n357.618\n+77\n03-00631 (CofLA)\n61.16\n352.248\n352.311\n+63\n03-00630 (CofLA)\n61.20\n352.002\n352.070\n+68\n03-00620 (CofLA)\n61.50\n348.842\n349.022\n+180\n03-00607 (CofLA)\n61.67\n350.781\n350.882\n+101\n03-00547 (CofLA)\n61.89\n354.269\n354.204\n-65\n03-00542 (CofLA)\n62.13\n353.731\n353.649\n-82\n03-00540 (CofLA)\n62.22\n354.790\n354.722\n-68\n03-05010 (CofLA)\n62.59\n352.752\n352.685\n-67\n03-00480 (CofLA)\n63.04\n348.146\n348.082\n-64\nHansen Lake\n03-00421 (CofLA)\n63.49\n339.057\n338.992\n-65\n03-00391 (CofLA)\n63.73\n333.337\n333.282\n-55\n03-00360 (CofLA)\n63.85\n329.477\n329.423\n-54\n03-00330 (CofLA)\n64.28\n327.590\n327.535\n-55","Vertical Crustal Movements\n321\nTable 3.-Line of levels, 0.4 km west of Bridge No. 53-35 over Topanga Creek to intersection of Foothill Blvd. and Ocean View Blvd.,\nLa Canada-Continued\nElevation\nApparent\nLocation\nBench mark\nDistance\nmovement\na\nPreearthquake Postearthquake\nHansen Lake\n(continued).\nkm\nm\nm\nmm\nmm\n03-00300 (CofLA)\n64.86\n327.102\n327.043\n-59\n03-00270 (CofLA)\n65.36\n333.784\n333.708\n-76\n03-00244 (CofLA)\n65.72\n329.155\n329.092\n-63\n03-00238 (CofLA)\n65.81\n329.858\n329.794\n-64\n03-00210 (CofLA)\n66.24\n333.865\n333.807\n-58\n339.070\n-43\n03-00160 (CofLA)\n66.70\n339.113\n03-00150 (CofLA)\n66.88\n343.695\n343.651\n-44\n03-00120 (CofLA)\n67.05\n345.243\n345.199\n-44\n-51\n03-00061 (CofLA)\n67.73\n351.297\n351.246\n-54\n03-00060 (CofLA)\n67.75\n351.397\n351.343\n351.608\n351.569\n-39\n03-00030 (CofLA)\n68.16\n351.207\n351.181\n-26\n03-00025 (CofLA)\n68.22\n368.125\n-45\n03-00010 (CofLA)\n68.68\n368.170\n02-04080 (CofLA)\n69.23\n365.997\n365.962\n-35\n02-04079 (CofLA)\n69.25\n366.638\n366.605\n-33\n02-04046 (CofLA)\n70.40\n377.018\n376.922\n-96\n-20\n02-04020 (CofLA)\n70.88\n402.899\n402.879\n02-03980 (CofLA)\n70.98\n405.510\n405.493\n-17\n02-03961 (CofLA)\n71.26\n406.233\n406.196\n-37\n02-03959 (CofLA)\n71.33\n406.129\n406.096\n-33\n02-02310 (CofLA)\n71.59\n409.509\n409.481\n-28\n411.167\n-25\n02-02340 (CofLA)\n71.81\n411.192\n411.447\n-15\n02-03930 (CofLA)\n71.85\n411.462\n415.689\n-14\n02-03900 (CofLA)\n72.06\n415.703\n415.237\n-12\n02-03899 (CofLA)\n72.09\n415.249\n-13\n02-03870 (CofLA)\n72.22\n418.267\n418.254\n-12\n02-03840 (CofLA)\n72.32\n420.484\n420.472\n422.182\n422.172\n-10\n02-03811 (CofLA)\n72.40\n422.644\n422.635\n-9\n02-03780 (CofLA)\n72.51\n427.883\n-8\n02-02010 (CofLA)\n72.73\n427.891\n02-03750 (CofLA)\n72.82\n429.421\n429.416\n-5\n02-03720 (CofLA)\n72.98\n435.290\n435.287\n-3\n02-03661 (CofLA)\n73.14\n442.357\n442.353\n-4\n-2\n02-03660 (CofLA)\n73.17\n442.496\n442.494\n-4\n02-03630 (CofLA)\n73.29\n446.932\n446.928\n-6\n448.992\n448.986\n02-03601 (CofLA)\n73.34\n-7\n454.036\n454.029\n02-03530 (CofLA)\n73.45\n456.034\n456.027\n-7\n02-03510 (CofLA)\n73.51\n457.792\n-10\n02-03480 (CofLA)\n73.56\n457.802\n460.420\n-6\n02-03420 (CofLA)\n73.62\n460.426\n464.233\n-7\n02-03410 (CofLA)\n73.72\n464.240\n468.448\n-7\n02-03390 (CofLA)\n73.87\n468.455\n-9\n02-03360 (CofLA)\n74.01\n473.208\n473.199\n-8\n02-03329 (CofLA)\n74.16\n478.934\n478.926\n483.659\n483.648\n-11\n02-03300 (CofLA)\n74.33\n486.021\n486.013\n-8\n02-03270 (CofLA)\n74.40\n495.557\n-8\n02-03210 (CofLA)\n74.67\n495.565\n02-03179 (CofLA)\n74.78\n498.212\n498.204\n-8\n02-03150 (CofLA)\n74.99\n506.655\n506.638\n-17\n509.221\n509.214\n-7\n02-01260 (CofLA)\n75.07\nTujunga\n515.792\n-10\n02-03119 (CofLA)\n75.36\n515.802\nRS 6 (USGS) = 09-01110\n75.51\n521.815\n521.810\n-5\n09-01080 (CofLA)\n75.57\n521.965\n521.954\n-11\n09-01050 (CofLA)\n75.78\n530.851\n530.844\n-7\n-6\n09-01046 (CofLA)\n75.83\n533.462\n533.456\n549.688\n549.683\n-5\n09-01030 (CofLA)\n76.24\n-6\n554.819\n554.813\n09-01020 (CofLA)\n76.41\n556.423\n556.415\n-8\n09-01017 (CofLA)\n76.46\n560.092\n560.088\n-4\n09-00991 (CofLA)\n76.80\n560.581\n-3\n09-00967 (CofLA)\n77.07\n560.584\n559.876\n-4\n09-00931 (CofLA)\n77.17\n559.880\n0\n09-00895 (CofLA)\n77.52\n562.700\n562.700\n0\n09-00870 (CofLA)\n77.64\n564.003\n564.003\n563.081\n563.081\n0\n09-00830 (CofLA)\n77.77","322\nSan Fernando Earthquake of 1971\nTable 3.-Line of levels, 0.4 km west of Bridge No. 53-35 over Topanga Creek to intersection of Foothill Blvd. and Ocean View Blvd.,\nLa Canada-Continued\nElevation\nApparent\nLocation\nBench mark\nDistance\nmovement\nPreearthquake Postearthquake\nTujunga (continued).\nkm\nm\nm\nmm\nmm\n09-00812 (CofLA)\n78.06\n558.405\n558.405\n0\n09-00811 (CofLA)\n78.10\n558.223\n558.223\n0\n09-00800 (CofLA)\n78.35\n547.538\n547.538\n0\n09-00790 (CofLA)\n78.57\n540.853\n540.855\n+2\n09-00781 (CofLA)\n78.82\n531.017\n531.018\n+1\n09-00750 (CofLA)\n78.98\n523.090\n523.092\n+2\n09-00721 (CofLA)\n79.42\n516.333\n516.335\n+2\n09-00661 (CofLA)\n80.32\n481.651\n481.652\n+1\n09-00629 (CofLA)\n80.61\n476.440\n476.438\n-2\n09-00600 (CofLA)\n81.02\n477.945\n477.949\n+4\n09-00570 (CofLA)\n81.40\n477.215\n477.220\n+5\n09-00557 (CofLA)\n81.68\n475.714\n475.719\n+5\n09-00540 (CofLA)\n82.10\n469.262\n469.266\n+4\n09-00530 (CofLA)\n82.44\n464.819\n464.821\n+2\n09-00511 (CofLA)\n82.79\n457.121\n457.125\n+4\n47-11 (LACo) = 09-00509\n82.81\n456.766\n456.769\n+3\n16","Vertical Crustal Movements\n323\nTable 4.-Line of levels, 6.5 km southeast of Ventura to San Pedro\nElevation\nApparent\nLocation\nBench mark\nDistance\nmovement\no\nPreearthquake Postearthquake\nkm\nm\nm\nmm\nmm\nVentura\nX 569\n0.00\n25.172\n25.143\n-29\nY 569\n0.95\n24.850\n24.828\n-22\nH 1051\n2.44\n29.283\n29.255\n-28\n20\nR 30\n5.03\n24.033\n24.016\n-17\nA 570\n6.11\n23.470\n23.447\n-23\nD 174\n7.77\n21.852\n21.823\n-29\nX 318\n7.80\n22.084\n22.052\n-32\nB 570\n9.42\n17.560\n17.534\n-26\nU 318\n10.87\n16.934\n16.914\n-20\nB 31\n11.19\n15.313\n15.294\n-19\nV 318\n10.29\n17.077\n17.055\n-22\nW 1100\n11.47\n12.998\n12.983\n-15\nY 901\n12.74\n10.956\n10.945\n-11\nJ 1051\n13.38\n9.292\n9.284\n-8\nV 1100\n14.72\n7.324\n7.319\n-5\nU 1100\n15.37\n6.340\n6.335\n-5\nPort Hueneme\nL 1099\n16.33\n3.630\n3.629\n-1\nH 584\n17.76\n4.411\n4.397\n-14\nG 584\n19.14\n4.902\n4.885\n-17\n-20\nF 584 Reset 1962\n20.91\n4.701\n4.681\n-33\nM 1099\n21.94\n4.205\n4.172\nE 584\n22.69\n4.861\n4.822\n-39\nK 1051\n23.80\n4.462\n4.435\n-27\nPass RM 1\n26.28\n8.451\n8.422\n-29\nPass RM 2\n26.30\n7.446\n7.418\n-28\n8.168\n-29\nPass\n26.31\n8.197\nB 584\n27.49\n3.644\n3.612\n-32\nLaguna 2 AZI\n27.53\n3.632\n3.599\n-33\nA 584\n28.54\n2.114\n2.082\n-32\nTidal 4A\n29.90\n1.550\n1.518\n-32\n3.333\n-34\nZ 583\n30.06\n3.367\n3.988\n-33\nR 1051\n30.21\n4.021\n14.304\n-30\nH 1099\n31.80\n14.334\n17.787\n-30\nPoint Mugu RM 9.635\n31.99\n17.817\n-29\nG 1099\n32.66\n9.417\n9.388\n-28\nQ 1051\n33.96\n6.159\n6.131\n4.456\n4.427\n-29\nX 583\n34.04\n10.514\n10.480\n-34\nShale RM\n36.09\n7.719\n-29\nW 583\n36.50\n7.748\nP 1051\n37.70\n18.392\n18.361\n-31\n38.43\n12.412\n12.380\n-32\nM 1051\nU 583\n38.66\n12.679\n12.646\n-33\n-31\n40.14\n13.175\n13.144\nN 1051\nT 583\n40.70\n8.959\n8.925\n-34\nS 583\n41.99\n9.138\n9.104\n-34\n31.072\n-32\nG 7 B (VCo) Reset 1957\n43.50\n31.104\n22.931\n-34\n19\nU 1051\n44.16\n22.965\n5.591\n-34\nQ 583 Reset 1954\n44.99\n5.625\n44.030\n-30\nV 1051 = 48-150C\n46.75\n44.060\n29.591\n-33\nW 1051 = 48-149B\n48.52\n29.624\nR 50(USGS) = 48-149\n48.80\n29.625\n29.602\n-23\n-35\nX 1051 = 48-147B\n50.33\n52.886\n52.851\n-32\nL 583 = 48-142\n52.21\n31.434\n31.402\nR 49(USGS) Reset 1938 = 48-136\n54.13\n5.714\n5.682\n-32\nK 583=48-131C\n55.58\n5.012\n4.977\n-35\n9.113\n-32\nJ 583 = 48-126\n57.00\n9.145\nR 48(USGS) Reset 1937 = 48-122\n58.03\n62.801\n62.772\n-29\nH 583 = 48-119\n58.61\n49.220\n49.195\n-25\n39.126\n39.102\n-24\nZ 576 = 112A\n60.52\nY 576 = 48-107\n62.23\n5.323\n5.301\n-22\n5.298\n-22\n1307 Reset 1938=48-106\n62.28\n5.320\n41.179\n-18\nF 9A =48-102\n63.07\n41.197\n-18\nG 9A = 48-100\n63.94\n14.190\n14.172\n-13\nF 1052 = 48-95A\n65.43\n5.169\n5.156\n5.171\n5.156\n-15\n1303 Reset 1938=48-95\n65.45","324\nSan Fernando Earthquake of 1971\nTable 4.-Line of levels, 6.5 km southeast of Ventura to San Pedro-Continued\nElevation\nApparent\nLocation\nBench mark\nDistance\nmovement\na\nPreearthquake Postearthquake\nPort Hueneme\n(continued).\nkm\nm\nm\nmm\nmm\nE 1052 = 48-89A\n66.88\n48.737\n48.724\n-13\nD 1052 = 48-85A\n68.26\n60.340\n60.329\n-11\n48-83A (LACo)\n68.95\n27.790\n27.728\n-62\nC 1052 = 48-80A\n70.18\n6.799\n6.785\n-14\nR 576 = 48-78\n70.95\n5.476\n5.463\n-13\n48-77A (LACo)\n71.49\n4.573\n4.560\n-13\nS 576 = 48-76\n72.30\n4.222\n4.208\n-14\nB 1052 = 48-75A\n73.62\n5.735\n5.724\n-11\nN 576 = 48-73\n74.84\n5.425\n5.411\n-14\nM 576 = 48-70A\n76.31\n6.632\n6.638\n+6\nL 576 = 48-67\n78.31\n6.623\n6.616\n-7\n48-66 (LACo)\n78.63\n6.663\n6.654\n-9\nP 99 Reset 1933 = 48-62\n79.96\n8.774\n8.764\n-10\n15\nJ 576 = 48-56\n82.21\n6.826\n6.817\n-9\nH 576 = 48-50\n83.60\n6.302\n6.296\n-6\nG 50 = 48-31\n86.83\n5.111\n5.101\n-10\nSanta Monica\nF 576 = 48-33\n87.97\n5.731\n5.723\n-8\nH 767 = 48-34\n88.84\n5.936\n5.928\n-8\n39 (CofLA) = 48-35\n89.32\n5.089\n5.078\n-11\nTidal Sta. 44 Tidal 4=48-36\n89.47\n7.851\n7.842\n-9\nTidal Sta. 44 Tidal ==48-38\n89.60\n7.042\n7.032\n-10\nTidal Sta. 44 Tidal 2 2=48-20\n89.82\n17.954\n17.946\n-8\n14\nTidal Sta. 44 Tidal 5=48-18\n90.13\n19.585\n19.579\n-6\nL 767 = 48-17\n91.46\n7.047\n7.038\n-9\nK 767 = 48-14\n92.63\n6.373\n6.362\n-11\nE 776 = 48-11\n93.49\n3.959\n3.952\n-7\nM 767 = 48-9\n94.48\n4.097\n4.090\n-7\nN 17(CofLA) = 48-8 (LACo)\n94.58\n3.282\n3.275\n-7\nP 50 = 27-13\n101.62\n5.794\n5.781\n-13\nS 767 = 27-12\n102.37\n16.659\n16.648\n-11\nR 767 = 27-10\n103.46\n15.162\n15.155\n-7\n56.328 (CofLA) =27-9A(LACo)\n103.83\n17.024\n17.017\n-7\nT 767 = 27-9\n104.27\n15.722\n15.711\n-11\nH 1052 = 27-5A\n105.93\n12.062\n12.053\n-9\nB 768 = 27-4\n106.92\n7.432\n7.429\n-3\n27-3 (LACo) = Tidal 2\n107.29\n4.986\n4.981\n-5\nR 50 = 27-2\n107.43\n4.033\n4.030\n-3\n12\nV 767 = 27-1\n108.50\n7.230\n7.223\n-7\nY 614 = 21-24\n108.96\n8.365\n8.358\n-7\nJ 1052 = 21-26A\n110.06\n10.633\n10.624\n-9\nTorrance C2 = 21-28\n110.88\n6.693\n6.680\n-13\n20 (USGS) = 21-29\n110.89\n7.180\n7.165\n-15\nS 50 = 21-30\n110.91\n7.282\n7.268\n-14\nC 768 = 21-31\n111.34\n8.267\n8.239\n-28\nZ 767 = 21-33\n112.56\n7.115\n7.097\n-18\nT 50 = 21-35\n113.63\n4.693\n4.675\n-18\nTorrance E7A = 21-40\n115.46\n2.560\n2.526\n-34\nTorrance F7 = 21-42\n116.14\n5.312\n5.279\n-33\nRS 28A (USGS) = 21-45\n116.45\n13.429\n13.397\n-32\nRedondo Beach\nRedondo = 21-50\n118.24\n21.181\n21.160\n-21\nRedondo RM = 21-50A\n118.28\n20.964\n20.945\n-19\nD 768 =21-51B\n119.19\n15.050\n15.034\n-16\nE 768 Reset 1962 = 21-52C\n119.82\n25.977\n25.962\n-15\n10","Strong-Motion Accelerograph Records\nAt the time of the San Fernando earthquake, the\nSeismological Field Survey of the National Oceanic\nand Atmospheric Administration (NOAA) was oper-\nating, in cooperation with numerous other organiza-\ntions, a dense network of strong-motion accelero-\ngraphs in southern California. As a result, 241\naccelerograms were recorded during the shock, in-\nCONTENTS\ncluding more than 175 from the Los Angeles area\nPage\nwhere a large number of instruments are installed at\n326\nACCELEROGRAPH NETWORK\nSTRONG-MOTION RESULTS\nvarious levels of high-rise buildings, 21 to 50 km\n326\n347 SUMMARY\nfrom the epicenter.\n348 ACKNOWLEDGMENTS\nEvaluation of these data will be relevant particu-\n348\nREFERENCES\nlarly to the investigation of dynamic behavior of in-\nstrumented buildings under moderate seismic forces.\nAlso, in a related aspect, it may provide the best\nmeasure of intensity of ground motion in noninstru-\nmented areas where destruction was the heaviest.\nPerhaps information from other stations may prove\nto be equally important in completing the total pat-\ntern of strong shaking, for accelerations were re-\ncorded at several dams, near aqueducts and pumping\nfacilities, and at numerous free-field locations-all es-\nsentially outside Los Angeles. In any event, the total\ncollection of strong-motion records, the largest ever\ncompiled from a single earthquake, has provided\nmore significant data than had been accumulated\nduring the 39-year history of the program. The ulti-\nmate benefit derived from application of the strong-\nmotion data program is a highly rewarding payoff\nfor the long-range investment in engineering seismol-\nogy investigations made by the Seismological Field\nSurvey under the National Ocean Survey and the\nformer U.S. Coast and Geodetic Survey. The Seismo-\nR. P. MALEY\nlogical Field Survey was transferred to NOAA's En-\nSeismological Field Survey\nvironmental Research Laboratories in 1972.\nEarth Sciences Laboratories\nEnvironmental Research Laboratories, NOAA\nEditors' note.-This paper is adapted from the report: Hudson,\nW. K. CLOUD 1\nDonald E. (ed.), Strong-Motion Instrumental Data on the San\nBerkeley Seismograph Station\nFernando Earthquake of Feb. 9, 1971, Earthquake Engineering\nUniversity of California\nResearch Laboratory, California Institute of Technology, Pasadena,\nBerkeley, Calif.\nand Seismological Field Survey, National Oceanic and Atmospheric\nAdministration, San Francisco, Sept. 1971, 260 pp.\n1 Former Chief of Seismological Field Survey\n325","326\nSan Fernando Earthquake of 1971\nACCELEROGRAPH NETWORK\nnumber or numbers indicate the presence of one or\nmore instruments at that particular site.\nSince late 1932, the Seismological Field Survey has\nThe earthquake was recorded by five different\noperated a strong-motion accelerograph network in\ntypes of strong-motion accelerographs, possessing a\nthe Western United States to record damaging mo-\nvariety of natural periods, sensitivities, and recording\ntions of earthquakes. Following the establishment of\nmedia (table 1) Four of the five models have been\na group of stations in the early and middle 1930s,\ndeveloped and marketed since 1963 and are, in a\nthe number of instruments in southern California,\nsense, largely responsible for the substantial growth\nsome 15 to 20, remained relatively constant until\nin the network because previous instrumentation\n1963, at which time the first modern accelerograph\nwas bulky, difficult to maintain, more expensive, and\nwas designed and produced by United Electro-Dy-\nrequired special housing. Reproductions of typical\nnamics (later absorbed by Teledyne-Geotech) The\nseismograms are shown as follows: on 12-inch paper\nintroduction of this new instrument stimulated the\nrecords from the AR-240 in figures 4, 5, and 6; on\ndevelopment of an extensive cooperative network by\n70-mm film records from the SMA-1 in figure 7; and\nthe U.S. Coast and Geodetic Survey and other orga-\non 35-mm film records from the MO-2 in figure 8.\nnizations-such as the California State Department\nRepresentative recordings from the RFT-250 are\nof Water Resources, U.S. Army Corps of Engineers,\nshown in a paper in Volume III by Hudson,\nand California Institute of Technology-private\n\"Strong-Motion Accelerogram Processing.\" Almost\nbuilding owners subject to seismic provisions of local\n90 percent of the acceleration data were recorded on\nbuilding codes, and various other public and private\nthe newer models, including all data obtained from\ninstitutions. From 1963 to the present, the size of the\nthe 68 multiple-instrumented buildings. For more\nnetwork increased at an accelerating pace-particu-\ndetailed information concerning characteristics of\nlarly since 1965 when the city of Los Angeles passed\nvarious models, refer to Hudson (1970) and Halver-\nan ordinance requiring three accelerographs in new\nson (1969 and 1971).\nstructures taller than six stories. This requirement\nA total of 241 records were recovered from sta-\nbecame more widespread when it was adopted by\ntions located between 8 and 369 km of the epicenter,\nmany other cities as a result of being included in the\nthe majority of records being obtained from sites\nappendix of the 1970 Uniform Building Code. Con-\ncloser than 75 km, primarily in the Los Angeles re-\nsequently, at the time of the San Fernando earth-\ngion. Table 2 lists maximum accelerations for the\nquake of February 9, 1971, there were over 200 accel-\nthree components at each station. It includes station\nerographs in and near Los Angeles, 185 of which\nname and locator coordinates for figures 1, 2, and 3,\nwere in Los Angeles and Beverly Hills.\nepicentral distances, instrument identification num-\nbers referenced to the annual strong-motion data\nSTRONG-MOTION RESULTS\ntable, type of structure at each site, specific location\nof instruments within multistory buildings and\nLocations of strong-motion accelerograph stations\nin central and southern California at the time of the\nupon dams, and general geology for each site. Where\nSan Fernando earthquake, whether or not the instru-\nthe notation NR appears in the data column, no\nrecord was obtained because of battery failure or\nment was triggered by ground shaking, are shown in\nsuccessively greater geographic detail for the region\nequipment malfunction. Where the notation PR ap-\nsouth of Fresno (fig. 1), the extended Los Angeles\npears, only a partial record was obtained and, con-\narea (fig. 2), and the zone of heaviest concentration\nsequently, the earliest and strongest motions of the\nin central Los Angeles (fig. 3)\nearthquake were not recorded. All instruments\nEach instrument site is coded with a permanent\nwithin 250 km are included in the table, whether or\nidentification number; thus, one may go directly to\nnot they were triggered by the earthquake, because\nthe listing of strong-motion instrumental data, issued\nthe mere fact that the instrument did not receive\nannually by the Seismological Field Survey, to find\nsufficient ground motion to activate its starter is, by\nthe geographic coordinates, instrument type, and op-\nitself, of some importance. Figures 9, 10, and 11\nerating characteristics of that particular accelero-\nshow the maximum horizontal and vertical ground\ngraph. Note that each point on the map refers only\naccelerations plotted on maps at their respective\nto the station location, whereas the accompanying\nstation locations.","5\n4\n2\n3\n+\nHOOVER DAM\nBLYTHE\n295\nG\n115°00'\n292-\n+\n+\nAS VEGAS\n+\n+\n464\n296-313\n124\nearthquake.\n117.\n412\nF\n10\n66\n286\n15\n116°00'\n8\n+\n+\n+\n+\n1.-Accelerograph 119°00' stations in central 118°00' and southern California during San Fernando\nPALM SPRINGS\nBAKER C\n105\nE\n103\n10\nOSAN BERNARDINO\n117°00'\no\n123\nBARSTOW\n-275-7\n+\n+\n+\nRIVERSIDE\n270\n395\n274\n129\n5\n66\nSAN DIEGO\n012\nIII\n116\n0\n113°\na\n280\nD\nOLANCASTER\nOSAN FERNANDO\nMOJAVE\n+\nSEE ENLARGEMENT OF THIS AREA\n+\n+\nLOS ANGELES\nB\n35-39\nC\nBAKERSFIELD\n27\n96\n98-100\n02\n+\n+\n+\n4\n0 5 10 20 20 30 40 40\nOXNARDO\n8 16 32 48 64\nD\n272\nSCALE IN KILOMETERS\n44\n94-95 all\nSCALE IN MILES\n43\n42.\nFigure\n410\nB\nBARBARA\n282 SANTA\n283\n5\n0\n106-7-46\n120°00'\n+\n+\nUSAN LUTS OBISPO\n15\n101\nA\n271\n064\n35°00'\n34°00'\n33°00\n36°00'","328\nSan Fernando Earthquake of 1971\nA\nB\nC\nD\nE\nF\n52\n1\n34°45'\n+\n+\n+\n+\n+\n121\nLANCASTER\n125\n580\n126\n127\n2\n128\n262\nPALMDALE\n110\n269\n34°30'\n+\n+\n284-5\nLAKE PIRU\nANTELOPE\n3\nNEWHALL\n290\n279\nVAN\nSIMI VALLEY\nNORMAN\nRESERVOIR\n34°15'\n+\n+\n+\n+\nSAN FERNANDO\n241-3\n267-8\n104\n259-61\n458-60\n466-8\n118-20\n266\nFOOTHILL BLVD\n461-3\n122\n287\n220-2\n253.5\nVENTURA\n475\nGLENDAIE\n256-8\nFOOTHILL\nHOLLYWOOD\n141°\n264-5\n4\n482-4\nPASADENA\n278\nSAN\nBERNARDINO\nFREEWAY\n190-2\n250-\n181-3\nPOMONA\nMALIBU\n2894\nSEE ENLARGEMENT OF THIS AREA\n34°00'\n+\n288\n+\n+\nFREEWAY\n244-6\n229-31\n247-9\n108\nARTESIA FREE WAY\nRIVERSIDE FREEWAY\n5\n476-8\nANAHEIM\n411\n472-4\n130\n132.\nIRVINE LAKE\n131\nD\n33°45'\n+\n+\n+\n2810\nLONG\nBEACH\nSANTA ANA\ns\nSCALE IN MILES\n114\n0\n2\n10\n6\nSCALE IN KILOMETERS\n16\n33°30'\n+\n+\n+\n+\n465\nSANTA CATALINA\nISLAND\n7\n118°45'\n118°30'\n118°15'\n118°00'\n117°45'\nFigure 2.-Accelerograph stations in extended Los Angeles area during San Fernando earthquake.","DODGER\nSTADIUM\nLOS ANGELES\n118°15'00\"\n137-39\n172-74\n145-47\n157-59\n17'30\"\n211-13\n217-19\nJEFFERSON BLVD\n20' 00\"\nBLVD\nHOLLYWOOD\n+\nSCALE IN KILOMETERS\nSCALE IN MILES\n1-14-24\n452-54\n3.-\n1434-36\nFigure\n455-57\n422-24\n193-95\nBEVERLY\nHILLS\n118°25'00\"\n425-27\n187-8\n34° 01'\n34° 03'\n34° 07'\n34°05'","330\nSan Fernando Earthquake of 1971\nTable 1.-Different accelerograph models triggered by the San Fernando earthquake\nEarth-\nYear\nInstrument\nquake\nSensitivity\nPeriod\nRecording medium\nManufacturer\nintro-\nrecords\nduced\ncm/g\nSecond\nC&GS Standard\n28\n6 to 17\n0.04\n6- or 12-inch photo paper\nCoast and Geodetic Survey\n1932\n.08\nAR-240\n75\n7.5\n.06\n12-inch photo paper\nTeledyne-Geotech, Inc\n1963\nRFT-250\n58\n1.9\n.05\n70-mm film\nTeledyne-Geotech, Inc\n1967\nMO-2\n45\n1.5 horizontal,\n.03 35-mm film\nVictorial Engineering, Ltd.,\n1967\n2.2 vertical.\nNew Zealand.\n(to\nU.S.)\nSMA-1\n35\n1.9\n.04 70-mm film\nKinemetrics, Inc\n1970\nThe highest earthquake accelerations ever instru-\nIII by Trifunac and Hudson, \"Analysis of Pa-\nmentally measured, high-frequency horizontal pulses\ncoima Dam Accelerogram\") A peak vertical acceler-\nin the 1g+ range, were recorded on the east abut-\nation of 0.72g was recorded at the same time during\nment of the Los Angeles County Flood Control Dis-\nan average background level of 0.4 to 0.5g. The\ntrict's Pacoima Dam, 8 km south of the epicenter\nhighest ground accelerations measured in the past\nand 4 km north of the surface faulting in the Syl-\nwere: 0.3g, recorded at El Centro, 8 km from the\nmar-San Fernando area. The station is located on a\nImperial fault, during the magnitude 7.1 earth-\njointed and fractured granitic ridge, part of a large\nquake of 1940 and 0.5g, recorded only 75 m from\nblock of the San Gabriel Mountains that was\nbreakage that occurred on the San Andreas fault\nthrusted up and left laterally at least 2 m during the\nduring the magnitude 5.3 Parkfield earthquake of\nearthquake. Maximum horizontal accelerations of\n1966. A comprehensive analysis of the Pacoima Dam\n1.25g occurred 6 to 8 seconds after instrumental trig-\nrecord is included in the paper by Trifunac and\ngering, within a 7-second envelope of the heaviest\nHudson, cited above.\nground shaking, where acceleration values generally\nThe next highest horizontal accelerations meas-\nranged from 0.50 to 0.75g (see the paper in Volume\nured during the earthquake were slightly less than\n8244 ORION BLVD., LOS ANGELES\n1st FI. North\nIst\nFI.\nDown\nIst FI. West\nIO seconds\nFigure 4.-AR-240 accelerograph record from Holiday Inn, 8244 Orion Boulevard, Los Angeles.","Strong-Motion Accelerograph Records\n331\n3710 WILSHIRE, , LOS ANGELES\nBSMT West\nBSMT\nDown\nBSMT\nSouth\n10 seconds\nFigure 5.-AR-240 accelerograph record from 3710 Wilshire Boulevard, Los Angeles.\nSANTA FELICIA DAM , CREST\nS 75°1 W\nDOWN\nS 15°E E\n10 seconds\nFigure 6.-AR-240 accelerograph record from Santa Felicia Dam, crest.\n0.4g, recorded at two stations 25 to 29 km northwest to 31 km, recorded maximum accelerations of 0.16 to\nof the epicenter in the Castaic area. By contrast, 0.19g, one-half or less than those at Castaic (refer to\nnearby instruments of the Lake Hughes array, at 29 Nos. 4, 12, 13, 14, and 16 in table 2) . A superficial","332\nSan Fernando Earthquake of 1971\n420 NO. ROXBURY DRIVE, BEVERLY HILLS\n10th FI. N 50°E\n10th FI. Down\n10th FI. N 40°W\n5th FI. N 50°E\n5th FI. Down\n5th FI. N 40°W\nIst FI. N 50°E\nIst FI. Down\nIst FI. N 40°W\n10 seconds\nFigure 7.-SMA-1 accelerograph record from 420 North Roxbury Drive, Beverly Hills.\n5260 CENTURY, LOS ANGELES\nRoof East\nRoof North\nRoof Up\n4th FI. East\n4th FI. North\n4th FI. Up\nIst FI. East\n1st FI. North\nIst FI. Up\nI second\nFigure 8.-MO-2 accelerograph record from 5260 Century Boulevard, Los Angeles.\ninspection of these results suggests that geological\nUnited Water Conservation District's Santa Felicia\nconditions had a considerable effect upon the ampli-\nDam located on Piru Creek, 33 km northwest of the\ntudes because the lower values were recorded on\nepicenter, where two accelerographs and six seismo-\ncrystalline rock and the higher values on Tertiary\nscopes were installed on the crest and at various sur-\nsandstones. Perhaps future examination of spectra\nrounding sites. The dam is an earthfill structure\nwill cast more light upon the character of this appar-\nwith a 1,260-foot-long crest rising 200 feet above the\nent amplification.\nstreambed. Figure 6 shows the accelerograph record\nAn interesting set of records was obtained at\nfrom the crest station where the maximum accelera-","Strong-Motion Accelerograph Records\n333\nTable 2.-Maximum accelerations recorded during the San Fernando earthquake\nMaximum acceleration (g)\nLocation\nDis-\nStructure\nIdentifi-\nCom-\ntance\nComments\nGround\nOther\nGeology\ntype\nStation name\ncation\nfrom\nponent\nnumber*\nMap\nKey\nepi-\nlevel\nFloors/Levels\ncenter\nkm\nSmall build-\n4 km from\n1 Pacoima\n279\n2\nC-3\n8\nDown\n0.72\nHighly\nS.74°W\n1.25\njointed dio-\ning.\nsurface\nDam.\nfaulting.\nS.16°E\n1.24\nrite gneiss.\n4th\n8-roof\n7-story RC\n8 km from\n20\nDown\n0.17\n0.23\n0.22\nAlluvium\n2 Los Angeles,\n241-3\n2\nC-4\nbuilding.\nsurface\nNorth\n.27\n.18\n.39\n8244\nfaulting.\nWest\n.14\n.24\n.31\nOrion.\n4th\n8-roof\nCircular 7-\n13 km from\n.19\n17\nAlluvium\n3 Los Angeles,\n458-60\n2\nC-4\n24\n.12\nDown\n.34\n500'; water\nstory RC\nsurface\nWest\n.11\n.23\n15107\ntable at 70'.\nbuilding.\nfaulting.\nSouth\n.12\n.26\n.38\nVanowen.\nSmall build-\n25 Down\n.18\nEocene sand-\n4 Lake\n128\n2 B-2\nstone below\nN.21°F\n.37\ning.\nHughes,\nN.69°W\n.28\na shallow\nNo. 12.\n(10' ) )\nlayer of\nalluvium.\n6th\n13-roof\n28\nUp\n.09\n.11\nNR\nAlluvium\n12-story RC\n5 Los Angeles,\n253-5\n2 C-4\nbuilding.\nN.78°W\n.19\n.27\n.21\n14724\nS.12°W\n.26\n.36\n.32\nVentura.\n7th\n13-roof\n.13\nAlluvium;\n12-story RC\n6 Los Angeles, 466-8\n2\nC-4\n28\nDown\n.10\n.18\nbuilding.\nS.09°W\n.23\n.25\n.26\nwater table\n15250\nat 55'.\nS.81 °E\n.14\n.21\n.18\nVentura.\n7th\n13th\nNR **\nC-4\n28\nUp\n.15\n.07\nAlluvium\n13-story RC\n7 Los Angeles,\n256-8\n2\nN.12°E\nNR\n.24\n.27\nbuilding.\n15433\n.23\nN.78°W\nNR\n.17\nVentura.\n9th\n18-roof\n17-story St. **\nAlluvium;\n.11\n.22\n.21\n8 Los Angeles,\n461-3\n2\nC-4\n28\nDown\n.22\nwater table\nbuilding.\nS.09°W\n.13\n.18\n15910\nS.81 E\n.15\n.13\n.23\nat 35'\nVentura.\nMidlevel ac-\nNR\n35' of allu-\n12-story RC\n9. Los Angeles, 259-61\n2\nC-4\n28\nNR\nNR\nvium over\nbuilding.\ncelerograph\n16055\nout for\nsiltstone\nVentura.\nand sand-\nrepair.\nstone;\nwater table\nat 50'.\nOwner did\nAlluvium\n9-story RC\n10\nLos Angeles,\n118-20\n2\nC-4\n28\nbuilding.\nnot supply\n16661\nbatteries.\nVentura.\n10-roof\n9-story St.\n2 D-4\n29\nDown\n.13\n.26\nSandy-gravel\n11 Pasadena,\n267-8\nbuilding.\nS.08°\nW\n.17\n.21\nJet Pro-\nS.82°E\n.21\n.38\npulsion\nLaboratory.\nWeathered\nSmall build-\n.16\n12 Lake\n126\n2\nC-2\n29\nDown\ngranitic.\ning.\nS.21°W\n.16\nHughes,\nS.69°E\n.19\nNo. 4.\nSmall build-\nDown\n.12\nGneiss\n13 Lake\n127\n2 B-2\n29\ning.\nN.21°E\n.15\nHughes,\nN.69°W\n.16\nNo. 9.\nSandstone\nSmall build-\n29\nDown\n.18\n14 Castaic\n110\n2\nB-2\ning.\nN.21°E\n.39\nN.69°W\n.32\n11th\n20th\nPR\n**\n.23\nInterlayered\n20-story RC\n15 Los Angeles,\n220-2\n2\nC-4\n30\nDown\n.09\nbuilding.\nPR\n.10\nsoft sand-\nNorth\n.18\n3838\nstone and\nWest\n.13\nPR\n.21\nLanker-\nshale.\nshim.\nSmall build-\n31 Down\n.12\nGranitic\n16 Lake\n125\n2 C-2\ning.\nN.21°E\n.17\nHughes,\nN.69°W\n.13\nNo. 1.\n3-story build-\nDown\n.14\nAlluvium\n17. Glendale,\n122\n2 D-4\n32\ning.\nS.70°E\n.28\n633 East\nS.20°W\n.23\nBroadway.\nSee footnotes at end of table.","334\nSan Fernando Earthquake of 1971\nTable 2.-Maximum accelerations recorded during the San Fernando earthquake-Continued\nLocation\nDis-\nMaximum acceleration (g)\nIdentifi-\ntance\nCom-\nStructure\nStation name\ncation\nfrom\nGround\nponent\nOther\nGeology\ntype\nComments\nnumber*\nMap\nKey\nepi-\nlevel\ncenter\nFloors/Levels\nkm\n18. Los Angeles,\n141\n2 C-4\n33\nDown\n0.12\nGranitic\nConcrete pier\nGriffith\nSouth\n.18\non bed-\nPark Ob-\nWest\n.16\nrock.\nservatory.\n19 Palmdale\n262\n2 D-2\n33\nDown\n.08\nAlluvium\nSmall build-\nS.60°E\n.11\ning.\nS.30°W\n.13\nAbutment\ncrest\n20 Santa Felicia 284-5\n2 A-3\n33\nDown\n.09\nSandstone-\nEarthfill\n6 seismoscope\nDam.\nS.82°W\n.24\nshale com-\ndam; height\nrecords\nS.08°E\n.23\nplex.\n200', crest\nalso ob-\nDown\n0.07\nlength\ntained on\nS.75°W\n.18\n1,260'.\nand near\nS.15°E\n.22\nthe dam.\n21. Pasadena,\n266\n2\nD-4\n34\nDown\n.08\nWeathered\n2-story build-\nSeismo-\nEast\n.19\ngranitic.\ning.\nlogical Lab-\nSouth\n.11\noratory.\n6th\n12-roof\n22. Los Angeles, 238-40\n3\nC-1\n34 Down\n.06\n.16\n0.22\nAlluvium\n11-story RC\n7080\nEast\n.11\n.19\n.21\nbuilding.\nHollywood.\nNorth\n.10\n.12\n.12\n12th\n22₫\n23 Los Angeles, 446-8\n3\nC-1\n34\nUp\n.08\n.14\n.19\nAlluvium\n22-story RC\n1760 North\nSouth\n.16\n.08\n.11\nbuilding.\nOrchid.\nEast\n.13\n.14\n.20\n7th\n14th\n24 Los Angeles, 232-4\n3 D-1\n34\nUp\n.09\nNR\nNR\nAlluvium;\n14-story St.\n6430\nSouth\n.19\nNR\nNR\nwater table\nbuilding.\nSunset.\nEast\n.14\nNR\nNR\nat 55'.\n6th\n12-roof\n25 Los Angeles, 235-7\n3 D-1\n34\nUp\n.08\nPR\n.29\nAlluvium;\n11-story St.\n6464\nSouth\n.11\nPR\n.24\nwater table\nbuilding.\nSunset.\nEast\n.12\nPR\n.28\nat 55'.\nP.E. lot\nBase.\nRoof\n26 Los Angeles,\n133-5\n3\nC-1\n35\nUp\n.12\n.06\nNR\n700' of\n14-story RC\nHollywood\nEast\n.22\n.15\nNR\nalluvium.\nbuilding.\nStorage.\nSouth\n.19\n.11\nNR\n3d\n8th\nlevel\nlevel\n27. Los Angeles, 226-8\n3 D-1\n35\nDown\n.13\n.13\n.20\nShallow\n8-story RC\nAccelero-\n4867\nS.89°W\n.17\n.30\n.45\nalluvium\nbuilding.\ngraphs on\nSunset.\nS.01°E\n.17\n.22\n.46\nover Mio-\nB and 2 in\ncene silt-\nnorth wing;\nstone.\non 8 in\neast wing.\n28 Fairmont\n121\n2 C-2\n36\nUp\n.05\nGranitic\nReservoir.\nN.34°W\n.10\nN.56°E\n.07\n5th\n11-roof\n29 Beverly Hills, 452-4\n3\nB-2\n36\nDown\n.04\n.05\n.10\nAlluvium;\n10-story RC\n435 North\nNorth\n.06\n.13\n.24\nwater table\nbuilding.\nOakhurst.\nWest\n.09\n.14\n.25\nat 22'.\n4th\n9th\n30. Los Angeles, 142-4\n3\nB-2\n36\nDown\n.03\nNR\n.12\nAlluvium\n9-story RC\n120\nS.02°W\n.09\n.18\n.33\nbuilding.\nRobertson.\nS.88°E\n.09\n.18\n.28\n5th\n10th\n31 Beverly Hills, 455-7\n3\nB-2\n37\nDown\n.04\n.10\n.12\nAlluvium\n10-story RC\n450 North\nN.50°E\n.20\n.22\n.30\nbuilding.\nRoxbury.\nN.40°W\n.17\n.21\n.22\n5th\n11-roof\n32. Beverly Hills, 416-8\n3\nB-2\n37\nUp\n.04\n.08\nPR\nAlluvium;\n10-story RC\n9100\nEast\n.16\n.13\nPR\nwater table\nbuilding.\nWilshire.\nSouth\n.12\n.15\nPR\nat 40'.\n33. Beverly Hills, 434-6\n3\nB-2\n37\nNR\nNR\nNR\nAlluvium;\n10-story RC\n9450\nwater table\nbuilding.\nWilshire.\nat 40' +.\nSee footnotes at end of table.","Strong-Molion Accelerograph Records\n335\nTable 2.-Maximum accelerations recorded during the San Fernando earthquake-Continued\nLocation\nDis-\nMaximum acceleration (g)\nIdentifi-\nCom-\ntance\nStructure\nStation name\ncation\nfrom\nGround\nOther\nponent\nGeology\nComments\ntype\nnumber*\nMap\nKey\nepi-\nlevel\nFloors/Levels\ncenter\nkm\n34 Los Angeles,\n140\n3 A-2\n37\nUp\n0.07\n70' of allu-\n7-story build-\nInstrument\nU.C.L.A.\nNorth\n.10\nvium over\ning.\nadjacent to\nWest\n.09\n5,000' of\nU.C.L.A.\nsedimen-\nreactor.\ntary rock.\n35 Pasadena,\n475\n2 D-4\n37 Down\n.10\nApproxi-\n2-story build-\nC.I.T.\nEast\n.11\nmately\ning.\nAthenaeum.\nNorth\n.10\n1,000 of\nalluvium\nupon\ngranite.\n10-roof\n36\nPasadena,\n264-5\n2 D-4\n37 Down\n.12\n0.14\nApproxi-\n9-story RC\nMillikan\nEast\n.18\n.34\nmately\nbuilding.\nLibrary,\nNorth\n.22\n.33\n1,000 of\nC.I.T.\nalluvium\nupon\ngranite.\n37\nCentury City, 410\n3\nB-2\n38\nNR\nAlluvium\nSmall build-\nGround\ning.\nStation.\n16th\n28-roof\n38\nLos Angeles,\n184-6\n3\nB-2\n38\nUp\n.06\nPR\n0.35\nSilt and sand\n27-story St.\n1900\nS.46°E\n.08\nPR\n.15\nlayers;\nbuilding.\nAvenue of\nN.44°E\n.10\nPR\n.12\nwater level\nStars.\nat 70'.\n9th\n21-roof\n39 Los Angeles,\n187-9\n3\nB-2\n38\nDown\n.07\n.14\nPR\nSilt and sand\n19-story St.\n1901\nN.46°W\n.12\n.18\nPR\nlayers;\nbuilding.\nAvenue of\nS.44°W\n.17\n.11\nPR\nwater table\nat 70'-80'.\nStars.\n5th\n16-roof\n40 Los Angeles, 425-7\n3 B-2\n38\nDown\n.08\n.16\n.31\nSilt and sand\n15-story\nS.36°E\n1800\n.08\n.21\n.28\nlayers;\nbuilding.\nN.54°E\nCentury\n.10\n.22\n.28\nwater table\nPark East.\nat 70'-80'.\n7th\n17-roof\n41 Los Angeles, 440-2\n3\nB-2\n38\nDown\n.07\n.12\n.27\nSilt and sand\n16-story St.\nN.54°E\n1880\n.11\n.10\n.10\nlayers;\nbuilding.\nN.36°W\nCentury\n.13\n.14\n.12\nwater table\nat 70'-80'.\nPark East.\n14th\n20th\n42\nLos Angeles,\n419-21\n3 B-2\n38 Down\nNR\n.19\n.35\nSilt and sand\n20-story St.\n1888\nN.54°E\nNR\n.14\n.15\nlayers;\nbuilding.\nN.36°W\nCentury\nNR\n.06\n.08\nwater table\nPark East\nat 70'-80'.\nBuilding.\n5th\n9th\nlevel\nlevel\n43 Los Angeles,\n422-4\n3\nB-2\n38 Down\nNR\n.09\n.11\nSilt and sand\n6-story (9-\nBasement\n1888\nS.36°E\nNR\n.18\n.38\nlayers;\nlevel) RC\naccelero-\nCentury\nN.54°E\nNR\n.12\n.31\nwater table\nparking\ngraph out\nat 70'-80'.\nPark East\nfor repair.\nramp.\nRamp 43.\n10th\n19-roof\n44 Los Angeles,\n193-5\n3\nB-2\n38\nUp\nNR\nNR\n.23\nAlluvium\n17-story RC\n2080\nN.50°E\nNR\nNR\n.35\nbuilding.\nCentury\nN.40°W\nNR\nNR\n.18\nPark East.\n8th\n15th\n45 Los Angeles, 407-9\n3 A-2\n38\nUp\nPR\nPR\n.16\nAlluvium.\n15-story RC\nUpper 2\nN.76°W\n930\nPR\nPR\n.15\nWater table\nbuilding.\ninstruments\nN.14°E\nat 55'.\nHilgard.\nPR\nPR\n.20\nin elevator\ntower,\nstructur-\nally separ-\nated from\nthe north\nand south\nresidential\ntowers.\nSee footnotes at end of table.","San Fernando Earthquake of 1971\n336\nTable 2.-Maximum accelerations recorded during the San Fernando earthquake-Continued\nLocation\nDis-\nMaximum acceleration (g)\nIdentifi-\nCom-\nStructure\ntance\nGround\nOther\nGeology\nComments\nStation name\ncation\nfrom\nponent\ntype\nnumber*\nMap\nKey\nepi-\nlevel\nFloors/Levels\ncenter\nkm\n8th\n14th\nAlluvium\n14-story RC\n46\nLos Angeles,\n178-80\n3\nA-2\n38\nDown\nNR\n0.10\n0.15\nN.78°W\nNR\n.12\n.14\nbuilding.\n945\nS.12°W\nTiverton.\nNR\n.23\n.18\n3d\n6th\n47 Los Angeles,\n223-5\n3\nD-2\n38\nDown\n0.08\n.13\n.16\nAlluvium\n7-story RC\nN.15°E\n.12\n.22\n.24\nbuilding.\n4680\n.18\n.30\nWilshire.\nN.75°W\n.09\n16th\n33-roof\n48. Los Angeles, 428-30\n3\nC-2\n38\nUp\n.03\n.08\n.15\nAlluvium-\n31-story St.\n.12\n.17\nasphaltic\nbuilding.\n5900\nN.83°W\n.07\nS.07°W\n.10\n.14\nWilshire.\n.07\nsands.\n10th\n17th\n49 Los Angeles,\n443-5\n3\nC-2\n38\nUp\n.04\n.07\n.07\nThin layer of\n17-story RC\n.13\n.28\n.30\nalluvium\nbuilding.\n6200\nN.08°E\nN.82°W\n.15\n.26\nWilshire.\n.13\nover\nasphaltic\nsands.\n3d\n7th\nUp\n.07\nNR\nNR\nAlluvium\nArcuate-\nAccelero-\n50\nLos Angeles,\n413-5\n3\nB-2\n39\nNR\nNR\nshaped 7-\ngraph on 7\n1177\nN.31°W\n.12\nN.59°E\nNR\nNR\nstory RC\nBeverly\n.11\nwas out\nbuilding.\nfor repair.\nDrive.\n8th\n17-roof\n51 Los Angeles,\n431-3\n3\nD-2\n39\nDown\n.05\n.10\n.20\nAlluvium,\n16-story RC\n616 South\nNorth\n.10\n.22\n.31\nsiltstone at\nbuilding.\nNormandie.\nWest\n.11\n.14\n.23\n25'.\n4th\n8-roof\n52 Los Angeles,\n199-201\n3\nD-2\n39\nDown\n.06\n.10\n.26\nAlluvium\n7 stories; 2\n3407 West\nSouth\n.17\n.21\n.29\nSt. and 5\nRC.\nSixth.\nEast\n.19\n.21\n.21\n2d\n12th\n53 Los Angeles, 196-8\n3\nD-2\n39\nDown\n.07\nNR\n.12\nAlluvium\n12-story RC\n3345\nSouth\n.12\n.17\n.21\nbuilding.\nWilshire.\nEast\n.09\n.11\n.26\n13th\n31st\n54. Los Angeles, 202-4\n3\nD-2\n39\nUp\n.07\nPR\nPR\nSiltstone;\n31-story St.\nPR\nPR\nwater table\nbuilding.\n3411\nSouth\n.11\nPR\nPR\nat basement\nWilshire.\nWest\n.14\nlevel.\n5th\n11th\n16\nAlluvium\n11-story RC\n55 Los Angeles, 208-10\n3\nD-2\n39\nDown\n.05\n.10\n.12\n.24\n.22\nbuilding.\n3470\nEast\n.23\nWilshire.\nNorth\n.15\n.21\n11th\n21st\n56 Los Angeles, 211-3\n3\nD-2\n39\nUp\n.06\nNR\nNR\nAlluvium;\n21-story St.\nNR\nNR\nwater table\nbuilding.\n3550\nNorth\n.18\nWilshire.\nWest\n.12\nNR\nNR\nat 35'.\n5th\n11th\n57. Los Angeles, 217-9\n3\nD-2\n39\nDown\n.08\n10\n.17\nAlluvium\n11-story RC\n.17\n.27\n.37\nbuilding.\n3710\nWest\nWilshire.\nSouth\n.16\n.16\n.22\n8th\n14-roof\n13-story RC\n58 Los Angeles, 449-51\n3\nE-2\n40\nDown\n.04\n.07\n14\nAlluvium;\nN.29°E\n.10\n.13\n.20\nsiltstone at\nbuilding.\n2500\nN.61°W\n20'-30';\nWilshire.\n.10\n.16\n.19\nand water\ntable at 35'\n7th\n15th\n.17\nMiocene silt-\n15-story St.\n59.\nLos Angeles,\n137-9\n3\nF-2\n41\nDown\n.08\n.10\nN.50°W\nWater and\n.14\n.17\n.16\nbuilding.\nstone.\nPower\nS.40°W\n.20\n.13\n.12\nBuilding.\n12th\n18-roof\n60. Los Angeles,\n145-7\n3\nE-2\n41\nUp\n.04\nPR\n.09\n25' of allu-\n17-story RC\nInstruments\n222 South\nN.53°W\n.15\nPR\n.40\nvium over\nbuilding.\nin different\nFigueroa.\nS.37°W\n.12\nPR\n.31\nshale;\nbldg. sec-\nwater table\ntions; G-\nat 20'.\nnorth tower\nand 18-\nsouth\ntower.\nSee footnotes at end of table.","Strong-Motion Accelerograph Records\n337\nTable 2.-Maximum accelerations recorded during the San Fernando earthquake-Continued\nLocation\nDis-\nMaximum acceleration (g)\nIdentifi-\nCom-\nStructure\ntance\nStation name\ncation\nfrom\nGround\nOther\nGeology\nponent\nComments\ntype\nnumber*\nMap\nKey\nepi-\nlevel\nFloors/Levels\ncenter\nkm\n12th\n18-roof\n61\nLos Angeles,\n148-50\n3\nE-2\n41\nUp\n0.06\nNR\n0.17\n25' of allu-\n17-story RC\nInstruments\n234 South\nS.53°E\n.17\nNR\n.50\nvium over\nbuilding.\nin different\nFigueroa.\nN.37°E\n.20\nNR\n.44\nshale;\nsections;\nwater table\nC-west\nat 20'.\ntower, 12-\nelevator\ntower, and\n18-east\ntower.\n19th\n39th\n62 Los Angeles,\n157-9\n3\nE-2\n41\nDown\n.06\n0.12\nNR\nShale\n39-story St.\n445 South\nN.52°W\n.14\n.21\nNR\nbuilding.\nFigueroa.\nS.38°W\n.13\n.13\nNR\n8th\n17-roof\n63. Los Angeles,\n151-3\n3\nF-2\n41\nDown\n.04\n.07\n.21\nAlluvium\n15-story St.\n250 East\nN.36°E\n.09\n.21\n.16\nbuilding.\nFirst.\nN.54°W\n.13\n.17\n.18\n16th\n32-roof\n64. Los Angeles,\n172-4\n3\nE-2\n41\nUp\n.06\n.15\n.22\nPliocene\n31-story St.\n800 West\nN.53°W\n.15\n.18\n.28\nsiltstone.\nbuilding.\nFirst.\nN.37°E\n.09\n.11\n.18\n6th\n11-roof\n65 Los Angeles,\n160-2\n3 E-2\n41\nUp\n.08\n.16\nPR\nAlluvium\n10-story RC\n533 South\nN.30°W\n.25\n.34\nPR\nbuilding.\nS.60°W\nFremont.\n.22\n.31\nPR\n2d\n8th\n66 Los Angeles,\n169-71\n3\nE-2\n41\nDown\nPR\n.10\n.15\nAlluvium\n8-story RC\nS.30°W\nPR\n.22\n.30\nbuilding.\n750 South\nN.60°W\nGarland.\nPR\n.16\n.23\n2d\n10th\n17th\n.07\nPR\n.23\nShale and\n16-story St.\nSecond floor\n67. Los Angeles,\n154-6\n3\nE-2\n41\nDown\nS.37°W\n420 South\n.12\nPR\n.23\nsiltstone,\nbuilding;\nis ground\nGrand.\nS.53°E\n.17\nPR\n.32\nseveral\nlevel; floor\nnote com-\n1,000'.\nnumbers\nment.\nfrom ad-\njoining\nbuilding.\n6th\n10th\n68. Los Angeles,\n469-71\n3\nE-3\n41 Down\n.16\n14\n.23\nAlluvium\n10-story RC\n.23\nbuilding.\n1625\nN.28°E\n.14\n.18\nN.62°W\n.28\nOlympic.\n.27\n.22\n24th\n43d\n69\nLos Angeles,\n163-5\n3 E-3\n41\n43-story St.\nDown\n.06\nNR\n.11\nAlluvium\n.10\nNR\n.11\nbuilding.\n611 West\nN.52°W\nN.38°E\nSixth.\n.11\nNR\n.18\n70. Santa Anita\n104\n2 D-4\n42 Down\n.07\nGranite dio-\nSmall build-\nN.03°E\n.18\nrite com-\ning.\nDam.\nN.87°W\n.24\nplex.\n6th\n12th\n71. Alhambra,\n482-4\n2 D-4\n42\nDown\n.09\n.11\n17\nFew 100' of\n12-story St.\n.13\n.15\n.18\nalluvium\nbuilding.\n900 South\nWest\n.11\n.14\n.15\nover silt-\nFremont.\nSouth\nstone.\n5th\n10th\n500' of\n72 Los Angeles, 437-9\n3\nE-3\n42\nDown\n.05\n.09\n.15\n10-story St.\ngravelly\nbuilding.\n1150 South\nS.53°E\n.12\n.11\n.14\nN.37°E\n.09\n.10\n.11\nsand over\nHill.\nshale.\n7-story RC\n73 Los Angeles,\n214-6\n3\nE-3\n42\nNR\nNR\nNR\n400' of\nalluvium.\nbuilding.\n3663\nHoover.\n4th\n7th\nlevel\nlevel\n8-level RC\n74 Los Angeles,\n166-8\n3\nE-3\n42\nDown\n.08\n.12\n.26\nAlluvium\n.22\n.25\n.38\nparking\n646 South\nS.37°W\nS.53°W\n.25\n.26\n.48\nOlive.\nramp.\n4th\n8th\nlevel\nlevel\n75 Los Angeles, 175-7\n3\nE-3\n42 Down\n.09\n.19\n.24\nAlluvium\n8-level RC\nS.37°W\n.16\n.25\nparking\n808 South\n.14\nS.53°E\n.13\n.26\n.44\nOlive.\nramp.\nSee footnotes at end of table.","San Fernando Earthquake of 1971\n338\nTable 2.-Maximum accelerations recorded during the San Fernando earthquake-Continued\nLocation\nDis-\nMaximum acceleration (g)\nIdentifi-\nCom-\nStructure\ntance\nfrom\nGround\nOther\nGeology\nComments\nStation name\ncation\nponent\ntype\nnumber*\nMap\nKey\nepi-\nlevel\nFloors/Levels\ncenter\nkm\n4th\n8-roof\n76\nLos Angeles,\n181-3\n2\nD-4\n42\nDown\n0.08\n0.12\n0.13\nPleistocene\n7-story RC\nN.38°W\n1640\n.14\n.20\n.24\nalluvium;\nbuilding.\nS.52°W\n.44\nwater table\nMarengo.\n.14\n.26\nat 35'.\n5th\n11-roof\n2 C-4\n42\nUp\nNR\n.11\n.16\nAlluvium;\n10-story RC\n77\nLos Angeles,\n250-2\nwater table\nbuilding.\n11661 San\nN.35°W\nNR\n.08\n.10\nS.55°W\nNR\n.09\n.11\nat 57'.\nVicente.\n5th\n13-roof\n12-story RC\nRoof ac-\n78\nLos Angeles,\n205-7\n3\nE-3\n42\nUp\n.05\n.08\n.09\n400' of allu-\nS.61°E\n3440 Uni-\n.08\n.13\n.24\nvium over\nbuilding.\ncelerograph\nN.29°E\n.06\n.14\n.26\nclay and\nis in top of\nversity,\nU.S.C.\nshale; water\nsmall\ntable at\nelevated\n275'.\npenthouse.\n5th\n9th\n42\nDown\n.06\n.08\n.12\nShale at east\n9-story RC\n79 Los Angeles,\n190-2\n2 D-4\nS.28°W\n.08\n.16\n.20\nend of\nbuilding.\n2011\nS.62°E\n.07\n.18\n.21\nbuilding; 8'\nZonal.\nof fill at\nwest end.\n80\nPyramid\n58\n2\nA-2\n44\nNR\nShale\nSmall build-\ning.\n2 E-2\n46 Down\n.06\n400' of allu-\nSmall build-\n81\nPearblossom. 269\nNorth\n.10\nvium over\ning.\nWest\n.15\n14,000' of\nsedimentary\nrock.\n6-story build-\n2 D-4\n46\nUp\n.05\n>1,000' of\n82 Vernon\n288\nS.07°W\n.09\nalluvium;\ning.\nN.83°W\n.11\nwater table\nat > 300'.\n6th\n12th\n2 C-5\n48 Down\n.04\n.05\n.06\nTerrace\n12-story RC\n83 Los Angeles,\n244-6\nS.45°W\n.04\n.10\n.12\ndeposits-\nbuilding.\n8639\nS.45°E\n.04\n.10\n.12\nsand.\nLincoln.\n7th\n14th\nNR\n.05\nAlluvium\n14-story RC\n84 Los Angeles,\n247-9\n2\nC-5\n49\nUp\n.01\nNorth\n.03\nNR\n.10\nbuilding.\n9841\nWest\n.03\nNR\n.09\nAirport\nBoulevard.\n4th\n8-roof\n85 Los Angeles,\n229-31\n2\nC-5\n49\nUp\n.02\n.04\n.08\nAlluvium\n7-story St.\nEast\n.06\n.04\n.09\nbuilding.\n5260\nNorth\n.06\n.07\n.06\nCentury.\n2 D-4\n52\nDown\n.05\nMore than\nEarthfill dam;\nAccelero-\n86 Whittier\n289\nS.53°W\n.10\n1,000' of\nheight 56',\ngraph on\nNarrows\nS.37°E\n.10\nalluvium.\ncrest length\ncrest of\nDam.\n14,960'.\ndam.\n55\nAlluvium\nSmall build-\nDown\n.06\n87\nOso Pump-\n52\n2\nB-1\ning Plant.\nNorth\n.05\ning.\nWest\n.05\nVolcanic\nSmall build-\n88 Puddingstone 278\n2 E-4\n62\nDown\n.05\nN.55°E\n.09\nclastics and\ning.\nDam.\nN.35°W\n.05\nintrusions\nwith asso-\nciated\nshales.\n89 Palos Verdes 411\n2\nC-5\n67\nDown\n.01\nShallow\n2-story build-\nS.25°E\n.04\nPleistocene\ning.\nEstates.\nN.65°E\n.02\nsands over\nshale-vol-\ncanic com-\nplex.\nSee footnotes at end of table.","Strong-Motion Accelerograph Records\n339\nTable 2.-Maximum accelerations recorded during the San Fernando earthquake-Continued\nLocation\nDis-\nMaximum acceleration (g)\nIdentifi-\nCom-\ntance\nStructure\nStation name\ncation\nfrom\nGround\nOther\nGeology\nponent\nComments\ntype\nnumber*\nMap\nKey\nepi-\nlevel\nFloors/Levels\ncenter\nkm\n#1\n#2\n90 Wrightwood 290\n2\nF-3\n70\nDown\n0.02\n0.02\nAlluvium\nSmall build-\nBoth accelero-\nS.25°W\n.05\n.06\ning.\ngraphs at\nveneer on\nS.65°E\n.04\n.04\nigneous\nground\nmetamor-\nlevel.\nphic com-\nplex.\n91 Tejon\n96\n1\nC-3\n71\nDown\n.02\nGranitic\nSmall build-\nEast\n.02\ning.\nNorth\n.03\n92 Long Beach,\n130\n2 D-5\n71\nUp\n.02\nAlluvium;\nSmall build-\nTerminal\nS.69°W\n.03\nwater table\ning.\nIsland.\nN.21°W\n.03\nat 20'.\n93 San Antonio\n287\n2 F-4\n71\nUp\n.03\nUp to 150' of\nEarthfill dam;\nAccelero-\nDam.\nN.15°E\n.08\nalluvium\nheight 160',\ngraph on\nN.75°W\n.06\ncrest length\ncrest of\nover\ngranitics.\n3,850'.\ndam.\n94 Long Beach,\n131\n2 D-5\n72\nUp\n.02\nAlluvium;\n3-story build-\nUtility\nNorth\n.03\nwater table\ning.\nBuilding.\nEast\n.02\nat 15'.\n95. Long Beach,\n132\n2\nD-5\n73\nDown\n.02\nUncon-\n9-story build-\nN.76°W\nState\n.04\nsolidated\ning.\nCollege.\nS.14°W\n.02\nsilt-sand-\nclay.\n96 Grapevine,\n27\n1\nC-3\n73\nDown\n.02\n15' of allu-\nSmall build-\nTehachapi\nSouth\n.05\nvium over\ning.\nPumping\nEast\n.07\ngneiss.\nPlant.\n97 Carbon\n108\n2 E-5\n74\nDown\n.04\nThin allu-\nEarthfill dam,\nAccelero-\nS.40°W\nheight 99',\nCanyon\n.07\nvium over\ngraph on\nS.50°E\nDam.\n.07\npoorly\ncrest length\ncrest of\ncemented\n2,610'.\ndam.\nsiltstone.\n10-\n10-\nwest\ncenter\n98 Fullerton,\n476-78\n2 E-5\n74 Down\n.02\n.04\n0.02\nAlluvium\n10-story RC\nBoth upper\nbuilding.\n2600\nWest\n.04\n.11\n.09\naccelero-\nNutwood.\nSouth\n.04\n.13\n.15\ngraphs on\ntop (10th)\nfloor.\n99 Port\n272\n1\nB-3\n78\nUp\n.01\nAlluvium\nSmall build-\nHueneme.\nSouth\n.03\n> 1,000'.\ning.\nWest\n.02\n10th\n19th\nAlluvium\n19-story RC\n100\nOrange,\n472-4\n2\nE-5\n83\nDown\n.01\n.04\n.08\n4000 West\nWest\n.02\n.09\n.15\n> 300' over\nbuilding.\nChapman.\nSouth\n.02\n.08\n.11\nshale.\nUp\n.02\nAlluvium\n3-story build-\n101\nSanta Ana\n281\n2\nE-5\n86\nN.04°E\n.03\ning.\nS.86°W\n.03\n102\nWheeler\n102\n1\nC-2\n89\nDown\n.01\nAlluvium\nSmall build-\nSouth\n200'-300'.\nRidge.\n.02\ning.\nEast\n.03\nTerrace de-\n18-story RC\n103\nCosta Mesa\n114\n2 E-6\n96\nDown\n.01\nSouth\n.02\nposits.\nbuilding.\nEast\n.04\n104\nCedar\n111\n1\nD-3\n98\nDown\n.01\nGranitic\nSmall build-\nSprings,\nS.05°W\n.02\ning.\nS.85°E\nAllen\n.02\nRanch.\nLimestone-\nSmall build-\nTwo accelero-\n105\nDevils\n116\n1\nD-3\n99\nCanyon.\ngneiss com-\ning.\ngraphs\nplex.\nwere not\ntriggered.\nSee footnotes at end of table.","340\nSan Fernando Earthquake of 1971\nTable 2.-Maximum accelerations recorded during the San Fernando earthquake-Continued\nLocation\nDis-\nMaximum acceleration (g)\nIdentifi-\nCom-\nStructure\ntance\nGround\nOther\nGeology\nStation name\ncation\nfrom\nComments\nponent\ntype\nnumber*\nMap\nKey\nepi-\nlevel\nFloors/Levels\ncenter\nkm\n106\nCedar\n112\n1\nD-3\n101\nDown\n0.01\nShallow\nSmall build-\nSprings\nS.36°W\n.03\ngravelly\ning.\nS.54°E\nPumping\n.03\nalluvium.\nPlant.\n107 Colton\n113\n1\nD-3\n104\nUp\n.03\nAlluvium\nSmall build-\nEast\n.04\n> 500'.\ning.\nSouth\n.04\n108\nSan\n274\n1\nD-3\n104\nDown\n.02\nAlluvium\n6-story build-\nBernar-\nEast\n.05\n1,000';\ning.\ndino.\nNorth\n.04\nwater table\nat 30'.\n109 Loma Linda. 129\n1\nD-3\n111\nPR\nAlluvium\n10-story build-\ning.\nBoulder\n2-story build-\nRecord not\n110\nSanta\n283\n1\nB-3\n119\nDown\nalluvium\ning.\navailable\nBarbara\nEast\n700' deep.\nfor scaling.\nCourt\nNorth\nHouse.\n#1\n#2\n#3\n#4\nSmall build-\n111\nMaricopa\n41-4\n1\nB-2\n119\nDown\n<.01\n<0.01\n0.01\n0.01\nPoorly\nS.40°W\n<.01\n<.01\n.01\n.01\ncemented\nings.\nArray.\nS.50°E\n<.01\n<.01\n.01\n.01\nsandstone.\nDown\n.02\nAlluvium\nSmall build-\n112\nSan Juan\n465\n2 F-7\n120\nN.33°E\n.04\ning.\nCapistrano.\nN.57°W\n.03\n113 Bakersfield\n4\n1\nB-2\n122\nUp\n<.01\nAlluvium\nLarge 1-story\nSouth\n.01\n> 500'.\nbuilding.\nWest\n<.01\n114\nBuena Vista\n11\n1\nB-2\n122\nDown\n<.01\nAlluvium\nSmall build-\nSouth\n.01\ning.\nEast\n.01\n115. Perris\n270\n1\nD-4\n127\nAlluvium\nSmall build-\nWas not\ning.\ntriggered.\nveneer over\ngranitic.\n2-roof\n40' of allu-\n116 Taft\n94-5\n1\nB-2\n128\nDown\n.01\n1-story school\nVertical com-\nN.21°E\n.02\n.02\nvium over\nbuilding.\nponent on\nS.69°E\n.01\n.01\npoorly\nroof is\ncemented\nunreadable.\nsandstone.\n117 Santa\n282\n1\nB-3\n133\nDown\n.01\nAlluvium\n2-story build-\nBarbara,\nEast\n.02\ning.\nveneer over\nUniversity\nNorth\n.01\nsandstone.\nof Cali-\nfornia.\n118\nSan Onofre\n280\n1\nD-4\n135\nDown\n.01\nLightly\nSmall build-\nN.33°E\n.01\ncemented\ning.\nN.57°W\n.02\nPliocene\nsandstone\n> 325'\ndepth.\n119 Hemet\n123\n1\nE-4\n139 Down\n.03\nAlluvium\nSmall build-\nS.45°W\n.05\ning.\nS.45°E\n.04\nSpillway\nCrest\nAux. crest\n120 Isabella\n35-9\n1\nC-2\n140\nDown\n<.01\n<.01\n<.01\nMain dam on\nEarthfill dam.\nDam.\nN.14°E\n.01\n.01\n.01\ngranite;\nN.76°W\n.01\n.01\n.01\nAux. on\ngranite and\nalluvium.\nCont. tower\nAux. abut.\n<.01\n< .01\n.01\n.01\n.01\n.01\nSee footnotes at end of table.","Strong-Motion Accelerograph Records\n341\nTable 2.-Maximum accelerations recorded during the San Fernando earthquake-Continued\nLocation\nDis-\nMaximum acceleration (g)\nIdentifi-\ntance\nCom-\nStructure\nStation name\ncation\nfrom\nGround\nponent\nOther\nGeology\nComments\ntype\nnumber*\nMap\nKey\nepi-\nlevel\ncenter\nFloors/Levels\nkm\nAbut.\nCrest\n121\nCachuma\n106-7\n1\nB-3\n147\nNR\nNR\nShale\nEarthfill dam.\nDam.\n122\nAnza\n103\n1\nE-4\n178\nDown\n0.01\nAlluvium\nSmall build-\nN.45°E\n.03\ning.\nN.45°W\n.04\n123\nPoint Con-\n271\n1\nA-3\n188\nShale\nSmall build-\nWas not\ncepcion.\ning.\ntriggered.\n124\nSalinas Dam\n64\n1\nA-2\n209\nSedimentary\nConcrete dam. Was not\nrock.\ntriggered.\n125\nSan Diego\n277\n1\nD-5\n216\nUp\n< .01\nShallow\n4-story build-\nEast\n.01\nalluvium\ning.\nSouth\n.01\n(50'-100')\nover sedi-\nmentary\nrock.\n22d\n126\nSan Diego\n275-6\n1\nD-5\n216\nDown\n<\n.01\nNR\nShallow\n22-story St.\nGas and\nEast\n.01\nbuilding.\nterrace\nElectric\nNorth\n.01\ndeposits.\nCompany.\n127\nSan Luis\n83\n1\nA-2\n219\n5' of clay\nSmall build-\nWas not\nObispo.\nloam over\ning.\ntriggered.\nFranciscan\nshale.\n128 Temblor\n97\n1\nA-2\n225\nSerpentine\nSmall build-\nWas not\ning.\ntriggered.\n#5\n#8\n129\nCholame-\n13-16\n1\nA-2\n227\nDown\n<.01\n<0.01\nAlluvium\nSmall build-\nNos. 2 & 12\nShandon\nN.51°E\n.01\n.01\nings.\nwere not\nArray.\nN.39°W\n.01\n.01\ntriggered.\nCrest\nAbut.\nCont. tower\n130 Terminus\n98-100\n1\nB-1\n229\nDown\n<.01\n<.01\n0.01\nMetamorphic\nEarthfill dam.\nDam.\nS.81°E\n.01\n<.01\n<.01\ncomplex.\nN.09°E\n<.01\n<.01\n.01\n131\nBorrego\n105\n1\nE-4\n230\nDown\n<.01\nAlluvium\nSprings.\nS.45°W\n<.01\nS.45°E\n< .01\n132 Superstition\n286\n1\nF-5\n286\nGranitic\nSmall build-\nWas not\nMountain.\ning.\ntriggered.\n133\nImperial\n124\n1\nF-5\n308\nAlluvium\nSmall build-\nWas not\ning.\ntriggered.\nHospital\n134\nEl Centro\n117,\n1\nF-5\n318-\nDown\n< .01\nAlluvium\nSmall build-\nAccelero-\n412,\n324\nS.52°W\n.01\nseveral\ning.\ngraphs at\n464\nS.38°E\n.01\n1,000'.\nUnion\nMeadows\nSchool and\nthe Irriga-\ntion Dis-\ntrict sub-\nstation\nwere not\ntriggered.\n135\nLas Vegas,\n296\n1\nF-1\n348\nVertical\n<.01\nAlluvium\nLandmark\nN.-S\n.01\nTower.\nE.-W\n.01\n136 Las Vegas,\n302\n1\nF-1\n348 +\nVertical\n<.01\nAlluvium\nInter-\nN.-S\n.01\nnational\nE.-W\n.01\nHotel.\nSee footnotes at end of table.","San Fernando Earthquake of 1971\n342\nTable 2.-Maximum accelerations recorded during the San Fernando earthquake-Continued\nMaximum acceleration (g)\nLocation\nDis-\nStructure\nIdentifi-\nCom-\ntance\nGround\nOther\nGeology\nComments\nStation name\ncation\nfrom\nponent\ntype\nnumber*\nMap\nKey\nepi-\nlevel\nFloors/Levels\ncenter\nkm\nTop\n137 Las Vegas,\n305\n1\nF-1\n348 +\nUp\n<0.01\nAlluvium\nBank of\nN.27EE\n.01\nS.63°E\n.01\nNevada.\n138 Las Vegas,\n309\n1\nF-1\n348 £\nVertical\n<0.01\nAlluvium\nN.-S\n.01\nUniv. of\nE.-W\n.01\nNevada.\nTop\n139 Las Vegas,\n327\n1\nF-1\n348 +\nVertical\n<.01\nAlluvium\nN.-S\n.01\nRoyal Inn.\nE.-W\n.01\nTop\n140 Las Vegas,\n311\n1\nF-1\n348\nVertical\n<.01\nAlluvium\nStardust.\nN.-S\n.01\nE.-W\n.01\nTop\nAlluvium\n141 Las Vegas,\n312\n1\nF-1\n348 #\nVertical\n.01\n.01\nDesert Inn.\nN.-S\nE.-W\n.02\nTop\n.01\nAlluvium\n142 Las Vegas,\n299\n1\nF-1\n348 ₺\nVertical\n.01\nN.-S\n.01\n.02\nDunes\nE.-W\n.02\n.02\nHotel.\nTop(200)\nTop (400)\n<0.01\nAlluvium\n143 Las Vegas,\n302\n1\nF-1\n348 ₺\nVertical\n<.01\nN.-S\n.03\n.02\nSahara.\nE.-W\n.02\n.02\nAlluvium\n348 +\nVertical\n<.01\n144 Las Vegas,\n308\n1\nF-1\nN.-S\n.01\nGround\nE.-W\n.01\nStation.\nOil\nIntake\nhouse\nGallery\ntower\nConcrete dam. Oilhouse is\n145 Hoover Dam, 292-4\n1 G-1\n369\nUp\nAll traces show amplitudes\nSeveral 100'\nS.45°E\n<.01.\nof volcanic\non abut-\nNev.\nS.45°W\nbreccia\nment.\nover basalt.\nRefers to list in \"Strong-Motion Station Instrumental Data,\" issued annually by the Seismological Field Survey.\n*\nAbbreviations: PR =partial record; NR = no record; RC=reinforced concrete; and St. = steel.\ntion was slightly greater than 0.2g, approximately the\nthat occurred between 1933 and 1969. It is evident\nsame as that measured at the outlet structure below\nthe more conservative attenuation curve, log\nthat\nthe dam. The relatively long-period waves recorded\n(a/g) = 3.5 - 2 log (D + 80) where D is the dis-\nat the crest, 0.6 to 0.9 second, caused the adjacent\ntance to the epicenter or to the observed faulting,\nseismoscope with a natural period of 0.75 second to\nagrees well with the data from this earthquake, ex-\ngo off scale, while at the outlet structure, the domi-\ncept for the unexpectedly high values at Pacoima\nnant period was near 0.1 second. Consequently, com-\nDam and smaller deviations noted at distances of 25\nparatively small amplitudes were recorded on the\nand 29 km in the Castaic area. The Pacoima Dam\nseismoscope at that site (see the paper in Volume III\nanomaly may be difficult to assess because the instru-\nby Morrill, \"Seismoscope Results\") The difference\nment is located on a fractured granitic ridge, part of\nin frequencies is attributed to the longer period re-\na regional block that was thrust up and laterally a\nsponse of the earthfill dam in contrast to that of a\nfew meters during the earthquake. Note that the\nsmall concrete structure with an integral 30-foot still-\ndata at distances greater than 45 km are consistent\nwith the less conservative of the two curves, log\ning well embedded in a sandstone and shale complex.\n(a/g) = 2 log (D + 43) ; although some of the val-\nMaximum horizontal ground accelerations re-\nues between 30 and 45 km do fall above that limit,\ncorded during the San Fernando earthquake are\nplotted against epicentral distance in figure 12. Su-\nthese represent only 10 percent of the large number\nperimposed on the graph are the acceleration atten-\nof points in that interval.\nuation curves developed by Cloud and Perez (1969),\nThe ground accelerations recorded in various lo-\ncalities throughout the Los Angeles area, between 21\nusing data gathered from 19 different earthquakes","2\n3\n4\n5\n+\nHOOVER DAM\nBLYTHE\nG\nearthquake.\n<.01,<.01\n115°00'\n+\n+\nLAS VEGAS\n+\n<.01,<.01\n+\n120°00' 9.-Maximum horizontal 119°00' and vertical ground-acceleration 118°00' values in central and southern California during San Fernando\n<.01,<.01\nF\n66\n10\n15\n8\n116°00'\n+\n+\n+\n+\nPALM SPRINGS\nBAKER O\n<.01,<.01\n.04,.01\nE\n10\n05, 02 NISAN BERNARDINO\n117°00'\nBARSTOW\n05,.03\n+\nSAN DIEGO, 01,<.01\n+\n+\nDRIVERSIDE\n395\n02,.01\n.03,.01\n66\n5\no\na\n.02,.01\nD\nOLANCASTER\nOSAN FERNANDO\nMOJAVE\n+\nSEE ENLARGEMENT OF THIS AREA\n+\n+\nLOS ANGELES\nB\nC\n.01,<.01\nBAKERSFIELD\nD\n.07,.02\n.03,.02\n01,<.01\n.03,.01\n.01,.01\n+\n+\n+\n.03,.01\nOXNARDO\n40\n64\n<.01,<.01\nD\nSCALE IN KILOMETERS\n30\nSCALE IN MILES\n48\nB\n20\n32\nBARBARA\nSANTA\n02,.01\n5\n10\n16\n0\n0\n+\n+\nOSAN LUIS OBISPO\n<.01,<.01\nFigure\n101\nA\n33°00'\n34°00'\n35°00'\n36°00'","San Fernando Earthquake of 1971\n344\nC\nD\nE\nF\nA\nB\n.05,.06\n1\n+\n34°45\n+\n+\n+\n+\n.10,.05\nLANCASTER\n.17,.12\n.19,.16\n2\n.13,.08\n.16,.12\nPALMDALE\n.37,.18\n39,.18\n15,.06\n+\n34°30'\n+\nLAKE PIRU\n.23,.09\n.06,.02\n3\nNEWHALL\n1.25,.72\nVAN\nNORMAN\nSIMI VALLEY\nRESERVOIR\n+\n+\n+\n34°15'\n+\nSAN FERNANDO\n27,.17\n21,.13\n12,.12\n.24,.07\n23,.10\n19,.08\n15,. 11\nFOOTHILL BLVD\n28, 14\n26,.09\n18,.09\n22, FOOTHILL\n12\nGLENDALE\nVENTURA\n4\nHOLLYWOOD\n18,.12\nPASADENA\n13,.09\n.09,.05\nSAN\nBERNARDINO\nFREEWAY\n08,.06\nPOMONA\n14,.08\nMALIBU\nSEE ENLARGEMENT OF THIS AREA\n+\n34°00\n+\n+\nT\nFREEWAY\n11,.05\n04, 04\n.03,.01\n.06,.02\nRIVERSIDE FREEWAY\nARTESIA FREE WAY\n5\n.04,.02\nANAHEIM\n04,.01\n02,.01\n/\n.04,.02\nD'RVINE\n03 02\nLAKE\n+\n03,.02\n33°45'\n+\n+\nLONG\nBEACH\nSANTA ANA\n.04,.01\nSCALE IN MILES\n0\n2\n6\n10\n6\nSCALE IN KILOMETERS\n16\n+\n+\n+\n+\n33°30'\n.04,.02\nSANTA CATALINA\nISLAND\n7\n118°45'\n118°30'\n118°15'\n118°00\n117°45'\nFigure 10.-Maximum horizontal and vertical ground-acceleration values in extended Los Angeles area during San Fernando earthquake.","DODGER\nSTADIUM\n13,.0\nANGELES\nVERNON AVE\n11.00\n118°15'00\"\n25,.08\n14,.06\n17,.07\n+\n25..08\n14,.09\nearthquake.\n12..05\nFernando\n10,.04\n08,.05\n17,.13\n15 .05\n11..05\n19,.06\n12.07\n14,.07\n18,.06\n17,.08\nJEFFERSON BLVD\nSANTA MONICA BLVD.\n12..08\n07..03\n22..12\n13,.04\nBLVD\nSCALE IN KILOMETERS\nCULVER CITY\n0\n20,.04\nBEVERLY\nHILLS\n118° 25'00\"\nMONICA\nFigure\n34° 03'\n34°01'\n34° 07'\n34° 05'","346\nSan Fernando Earthquake of 1971\n1.00\nlog (a/g) = 3.0 2 log (D+43)\nLOS ANGELES AREA\nO\nlog (a/g) = 3.5-2 log (D+80)\nX\n10\nMAXIMUM ACCELERATION VALUES\nThree Stations Nearest The Epicenter\nDistance from the epicenter\nDistance from surface faulting\nAll Other Stations\nDistance from the epicenter\n62\nMiles\n62\n6.2\n620\n1\n10\nKilometers\n100\n1000\nDISTANCE FROM THE EPICENTER OR FAULT\nFigure 12.-Maximum horizontal ground accelerations recorded during San Fernando earthquake (values > 0.01g).\nand 42 km of the epicenter, show a surprisingly simi-\ndicated by the highest values near Los Angeles air-\nlar range of values regardless of where the individual\nport (in the 48- to 49-km distance range) of only\ninstrument clusters were located (table 3) For in-\n0.03 to 0.06g, and at Long Beach (nominally 70-km\nstance, the maximum ground accelerations in San\ndistant) where the maximum accelerations were 0.02\nFernando Valley, at 21 to 28 km of the epicenter,\nto 0.04g.\nranged from 0.11 to 0.27g, while those in downtown\nStrong-motion seismograms were recorded on the\nLos Angeles, at 41 to 42 km of the epicenter, ranged\ntop floors of 57 high-rise buildings in the Los Ange-\nfrom 0.09 to 0.27g. Although there are considerably\nTable 3.-Range of maximum horizontal ground accelerations at\nmore records available from downtown Los Angeles,\nvarious Los Angeles localities\nit should be pointed out that the average of all maxi-\nDistance\nMaximum\nNumber\nmum ground accelerations was 0.17g in the San Fer-\nLocality\nfrom\nhorizontal\nof\nthe\nground\nnando Valley compared to 0.15g in the downtown\nmeasure-\nepicenter\nacceleration\nments\narea. Of additional interest, the highest amplitudes\nkm\ng\nin the San Fernando Valley were predominantly in a\nSan Fernando Valley\n21-28\n0.11-0.27\n10\nHollywood\n34\n.10-\n.22\n12\nnorth-south direction, nearly 90° to the trend of\nPasadena (C.I.T.)\n37\n.10-\n.22\n4\nfaulting. Similar strongly polarized amplitudes were\nBeverly Hills-West Los Angeles\n36-38\n.06-\n.20\n24\nWilshire District\n38-39\n.09-\n.19\n18\nobserved on some seismoscope records recovered\nDowntown Los Angeles\n41-42\n.09-\n.27\n26\nLos Angeles International\nfrom the same area. Beyond 45 km, the apparent at-\nAirport\n48-49\n.03- .06\n6\ntenuation of peak acceleration fell off sharply as in-\nLong Beach\n67-72\n.02- .04\n8","Strong-Motion Accelerograph Records\n347\nTable 4.-Types of structures where records were obtained\nles area, including six reinforced concrete structures\nwhere upper level accelerations exceeded 0.4g-an\nNumber of records from\nLarge buildings*\ndifferent levels\neight-story hospital in Hollywood, two eight-level\nNumber of stories\nparking ramps and two 16-story towers in downtown\nLowest\nMiddle\nTop\nLos Angeles, and a seven-story hotel 3 km east of\n2\n0\n1\nLarge 1\n8\n0\n0\n2-4\ndowntown (Nos. 27, 60, 61, 74, 75, and 76 in table\n24\n22\n23\n5-10\n2) A maximum acceleration of 0.50g, the highest\n28\n22\n29\n11-20\n21-30\n4\n1\n2\nobserved in any building during the San Fernando\n3\n3\n>30\n5\nearthquake, was measured in one of the 16-story\n71\n48\n58\nTotals\ntowers. Horizontal accelerations greater than 0.3g OC-\nHydraulic structures\ncurred in 14 other structures, all but two of rein-\n7\nCrest of earthfill dams\n1\nIn concrete dam\nforced concrete frame construction. Vertical accelera-\n3\nIntake towers\ntions exceeded 0.3g on the top floor of only three\n12\nAbutments or near dams\n6\nOther existing or planned structures\nbuildings, all located in Century City adjacent to\n29\nTotal\nBeverly Hills (Nos. 38, 40, and 42 in table 2)\nWhere ground amplitudes in buildings were equal\nOther sites\n10\nArrays across the San Andreas fault\nto or greater than 0.10g, the ratio of peak horizontal\n7\nOther faultline stations\n6\nMiscellaneous\naccelerations, top to bottom, ranged from 1.1 to 2.3\n23\nin 80 percent of the comparisons. A few buildings\nTotal\nshowed ratios as high as 3.5, and, at five other sites,\nExcludes 12 Las Vegas stations.\nratios were less than 1.0 (0.6 to 0.9), thus showing\nin the Los Angeles area, that is, there were only\nan apparent reduction of seismic forces at the tops of\nthree operating accelerographs in buildings small\nthe structures. These latter buildings were all 15 to\nenough to be called free-field stations, and just one\n22 stories in height, with fundamental periods of vi-\nof these was near the major clusters of tall buildings\nbration between 1.5 and 2.7 seconds (Nos. 15, 23, 41\n(Hollywood Storage, No. 26 in table 2) In an\n(both directions) and 59 in table 2)\nengineering sense, the distribution of accelerographs\nAs in past earthquakes, accelerograms from the\nwas relatively inequitable because there were no re-\nupper floors of high-rise buildings showed the struc-\ncorders in single-family residential dwellings, in\ntures responded in a manner related to their funda-\nmoderate-size apartment units, at bridges or along\nmental and other modes of vibration (figs. 4, 5, 7,\nfreeways, in industrial plants or major utility sites\nand 8) Ambient vibrations were measured in nu-\n(other than high-rise buildings) , or at the numerous\nmerous buildings before the San Fernando earth-\nharbors and marinas.\nquake, thus making it possible to compare these val-\nues with the periods induced by seismic forces and\nSUMMARY\nwith the natural periods following the earthquake\nStrong-motion accelerograph records were ob-\n(see Volume I paper by Mulhern and Maley, \"Build-\ntained from 241 instruments operated as part of the\ning Period Measurements Before, During, and After\nNOAA cooperative network between 8 and 369 km\nthe San Fernando Earthquake\")\nof the San Fernando earthquake epicenter. More\nA summary of the types of structures existing at\nthan 175 of these records came from the Los Angeles\naccelerograph sites reveals that nearly 80 percent\narea where building codes in a number of cities have\n(189) of the 241 records were obtained at various\nrequired the installation of accelerographs at three\nlevels of taller buildings (table 4) Another 29 rec-\nords were from hydraulic structures, principally\nlevels in new buildings taller than six stories.\nAmong the more significant results are the follow-\ndams, where one to five accelerographs had been in-\nstalled in various configurations on the dam and its\ning:\nappurtenances and at the abutments. The remaining\n1 The highest earthquake accelerations ever\n23 records are from accelerographs in small build-\nmeasured, 1.25g horizontally and 0.72g vertically,\nwere recorded on the abutment of Pacoima Dam, 8\nings, chiefly along the San Andreas and San Jacinto\nfault zones. Perhaps the most notable deficiency in\nkm from the epicenter.\n2 Except for the anomalously high Pacoima\nnetwork coverage is the lack of free-field instruments","348\nSan Fernando Earthquake of 1971\nDam results, attenuation of maximum horizontal\nlogical Field Survey-NOAA in the collection and\nground accelerations from all recording sites is, for\nhandling of records, including C. F. Knudson, B. J.\nthe most part, consistent with the equation, log\nMorrill, E. C. Etheredge, P. N. Mork, L. J. Foote,\n(a/g) = 3.5 - 2 log (D + 80), calculated by\nand B. L. Silverstein; and special thanks to V. Perez\nCloud and Perez for past earthquakes.\nwho completed the painstaking task of scaling the\n3 The range of maximum ground accelerations\nrecords. R. J. Dielman of the California Institute of\nrecorded at different localities in the Los Angeles\nTechnology supplied extensive assistance during the\narea was relatively similar, generally about 0.10 to\nfield investigations, in the recovery and processing of\n0.25g, although the measured values fell off rapidly\nrecords, and in the production of maps and tables\nbeyond 45 km.\nused in this report. J. West of the Environmental\n4 Peak accelerations exceeding 0.3g were re-\nResearch Laboratories' Special Projects Party in Las\ncorded on the top floors of 20 different high-rise\nVegas, Nev., participated in the collection of records\nbuildings, including a 17-story tower 41 km from the\nand directed the postearthquake building period\nepicenter where a maximum of 0.5g was observed.\nmeasurements. J. D. Patterson of the Jet Propulsion\n5 In 80 percent of the buildings where the\nLaboratory, California Institute of Technology,\nbase accelerations were 0.10g or greater, the top-floor\ndrafted the instrument location maps.\naccelerations were 1.1 to 2.3 times those recorded at\nthe ground level.\nREFERENCES\n6 It is apparent that the distribution of ac-\ncelerographs in southern California is far from equi-\nAllen, Clarence R., Engen, G. R., Hanks, Thomas C., Nord-\ntable, both geographically and in an engineering\nquist, J. M., and Thatcher, W. R., \"Main Shock and Larger\nsense, because about 85 percent of the instruments\nAftershocks of the San Fernando Earthquake, February 9\nare in the Los Angeles area and nearly all of these\nThrough March 1, 1971,\" The San Fernando, California,\nEarthquake of February 9, 1971, Geological Survey Profes-\nare in high-rise buildings.\nsional Paper 733, U.S. Geological Survey and the National\nThe unprecedented number of accelerograph rec-\nOceanic and Atmospheric Administration, U.S. Department\nords obtained from the San Fernando earthquake\nof the Interior and U.S. Department of Commerce, Wash-\nprovides such a large volume of instrumental strong-\nington, D.C., 1971, pp. 17-20.\nmotion data that scientists and engineers will require\nCloud, W. K., and Perez, V., \"Strong Motion-Records and\nmany years of investigation and research to utilize\nAcceleration,\" Proceedings of the Fourth World Conference\non Earthquake Engineering, Santiago, Chile, January 13-18,\nthe data in their entirety. Since 1940, the El Centro\n1969, Vol. I A-2, Impeso en Editurial Univesitaria, Santiago,\nrecord, with a maximum acceleration of 0.3g, has\nChile, 1969, pp. 119-132.\nbeen a prime tool for use in earthquake engineering.\nHalverson, H. T., Some Recent Developments in Strong- Motion\nNow ground accelerations have been recorded in ex-\nSeismographs, Geotech-A Teledyne Co., Monrovia, Calif.,\ncess of 1.0g at a site near Los Angeles and from 0.2\n1969, 18 pp. and tables and figs.\nto 0.4g at 14 other nearby stations. The ultimate\nHalverson, H. T., \"The SMA-1 Strong-Motion Accelerograph,\"\nevaluation of these data unquestionably will have a\nFourth Symposium on Earthquake Engineering, November\nlarge influence upon the design and construction of\n14-16, 1970, Roorkee, India, Sarita Prakashan Nauchandi\nGrounds, Meerut, India, 1971, pp. 45-50.\nbuildings and other critical facilities, on the zoning\nHudson, Donald E., \"Ground Motion Measurements,\" Earth-\nof potentially high seismic risk areas, and on a host\nquake Engineering, Prentice-Hall, Inc., Englewood Cliffs,\nof other related problems. The saturation of strong-\nN.J., 1970, pp. 107-125.\nmotion accelerographs in the Los Angeles area,\nKamb, Barclay, Silver, L. T., Abrams, M. J., Carter, B. A.,\nthough far from optimum, has resulted in excellent\nJordan, Thomas H., and Minster, J. Bernard, \"Pattern of\ndividends, particularly in view of the short-term ex-\nFaulting and Nature of Fault Movement in the San Fer-\nistence of this concentrated network.\nnando Earthquake,\" The San Fernando, California, Earth-\nquake of February 9, 1971, Geological Survey Professional\nACKNOWLEDGMENTS\nPaper 733, U.S. Geological Survey and the National Oceanic\nand Atmospheric Administration, U.S. Department of the\nThe authors appreciate the substantial contribu-\nInterior and U.S. Department of Commerce, Washington,\ntions provided by their coworkers from the Seismo-\nD.C., 1971, pp. 41-54.","Statistical Summary\nAccelerograph Performance\nThe magnitude 6.4 San Fernando earthquake of\nFebruary 9, 1971, triggered 272 accelerographs in\nCalifornia and Nevada. Thus, it provided an authen-\ntic test for a large portion of the strong-motion net-\nwork that is operated cooperatively by the Seismolog-\nical Field Survey and other organizations in the\nWestern United States. Because this earthquake was\nthe first to be recorded by such a large number of in-\nstruments, it is particularly relevant to examine the\nsuccess achieved in maintaining the dense network of\ninstruments that now exists in southern California.\nTable 1 shows that of the 272 accelerographs trig-\ngered by the earthquake, 229 records were obtained\nand 43 records (or approximately 16 percent) were\nlost. Table 1 also shows that the number of lost rec-\nords was greater at code stations (19 percent) , where\nTable 1.-General accelerograph performance\nCode\nNoncode\nTotal\nstations\nstations\nAccelerographs triggered\n186\n86\n272\nRecords obtained\n150\n79\n229\nRecords lost\n36\n7\n43\nPercent lost\n19\n8\n16\naccelerographs were installed because of building\ncode requirements, than at noncode stations (8 per-\ncent) Reasons for the disproportionately higher loss\nof records at code stations in relation to noncode sta-\ntions are: (1) the existence of a large number of\nslightly less reliable accelerographs in the code net-\nwork; and (2) the greater attention, in terms of\nservice interval and comprehensive maintenance,\nEditors' note.-This paper is adapted from the report: Hudson,\nDonald E. (ed.) Strong-Motion Instrumental Data on the San\nR. P. MALEY\nFernando Earthquake of Feb. 9, 1971, Earthquake Engineering\nResearch Laboratory, California Institute of Technology, Pasadena,\nSeismological Field Survey\nand Seismological Field Survey, National Oceanic and Atmospheric\nEarth Sciences Laboratories\nAdministration, San Francisco, Sept. 1971, 260 pp.\nEnvironmental Research Laboratories, NOAA\n349","350\nSan Fernando Earthquake of 1971\ngiven to the instruments at noncode stations. For\ntrickle charger or periodic battery recharging. It is\nresults of accelerograph performance at individual\neasily serviced and maintained.\nstations refer to \"Strong-Motion Instrumental Data\n5 MO-2 is a compact unit with no charger\non the San Fernando Earthquake of Feb. 9, 1971\"\nneeded, but cannot be calibrated after installation. It\nis difficult to service effectively and therefore oper-\n(Hudson 1971)\nThere was a greater emphasis on maintenance at\nates with a reduced reliability.\nnoncode stations because this portion of the network,\nTable 3 summarizes the performance of the var-\nalthough geographically far less dense, supplies data\nious accelerograph models during the San Fernando\nat key structures and free-field ground sites, including\nearthquake.\nthose along important faultlines. These noncode sta-\nTable 3.-Accelerograph performance by instrument type\ntions generally provide the seismic information\nneeded to interpret variations in strong-motion re-\nType of\nAccelero-Records Records\nLoss\naccelerograph\nsponse characteristics over a broad range of geologic\ngraphs\nlost\nrate\nPercent\nenvironments.\nC&GS Standard\n19\n16\n3\n16\nThe accelerographs at Las Vegas, Nev., were ex-\nAR-240\n82\n75\n7\n9\nRFT-250\n66\n58\n8\n12\ncluded from consideration in this report because\nMO-2\n67\n45\n22\n33\nthey are operated by the Environmental Research\nSMA-1\n38\n35\n3\n8\nLaboratories' Special Projects Party primarily to\nTotals\n272\n229\n43\n16\nmonitor nuclear detonations at the Nevada Test Site.\nTable 2, listing the specific reasons for instru-\nIt is readily apparent that the failure rate is rela-\nmental failures, shows that more than two-thirds of\ntively low for four types of accelerographs and inor-\nthese failures resulted from inadequacies of the power\ndinately high for the fifth type, the MO-2. Although\nthe MO-2 is generally somewhat less reliable than\nsupply.\nthe other instruments, it is only fair to point out\nTable 2.-Cause and number of accelerograph failures\nthat its failures more often were marked by longer\nintervals between inspections (table 4) The MO-2s\nNumber\nCause of failure\nof\nwere relegated by a priority system to the least\nfailures\nimportant of the current instrumentation because of\n30\nBattery discharged\n6\na number of recurring, and as yet unsolved, func-\nFilm transport failure\n3\nRelay failure\ntional problems as well as the lack of calibration ca-\n4\nMiscellaneous\npability after installation. Table 4 shows that the\nTotal\n43\nMO-2 inspection interval averaged 7 months and\nIncludes normal battery degradation (23), trickle charger plug\nthat the code stations generally had a much longer\npulled out (1), battery disconnected (1), battery case broken (1),\nwrong-type batteries (3), and corrosion (1).\ninspection interval than the noncode stations. Under\nFive types of accelerographs operating in southern\noptimum conditions, the accelerographs should be\nCalifornia at the time of the San Fernando earth-\nserviced every 2 months; in any event, servicing\nquake briefly are described as follows:\nshould occur at a maximum of every 3 months if\n1 Standard Coast and Geodetic Survey strong-\nnominal success is to be achieved in obtaining earth-\nmotion seismograph, developed in 1931, is operat-\nquake records.\ning today with some modifications. It requires a\nThe second section of table 4 shows why the rela-\ntrickle charger and greater maintenance than any\ntively large loss ratio occurred among the MO-2 ac-\nmodern accelerograph.\ncelerographs; that is, the replaceable batteries had\n2 AR-240 is a compact accelerograph, devel-\nbeen in use on an average of 81/2 months, 21/2\noped with external calibration capability, that is sim-\nmonths longer than desirable. Neglecting the\nple to maintain but still requires a trickle charger.\nSMA-1s that had short-term batteries because of re-\n3 RFT-250, which followed the AR-240, is\ncent installations, it may be noted the average age of\nmore compact, is easily maintained, and contains re-\nreplaceable batteries in the code stations was nearly\nchargeable batteries without a trickle charger.\ndouble that of noncode stations.\n4 SMA-1 is a very compact unit that operates\n1 Subsequent SMA-1 accelerographs have rechargeable batteries with\nwith disposable batteries, thereby eliminating a\ntrickle chargers.","Summary of Accelerograph Performance\n351\nTable 4.-Inspection interval before the earthquake\n3 Seventy percent of the 43 records lost re-\nsulted from power supply failures-in most instances\nMonths\nCode stations\nMO-2\n7\ncaused by the normal degradation of rechargeable\n6\nAR-240\nbatteries. With this fact in mind, it is recommended\nRFT-250\n4\n21/2\nSMA-1\nthat all future instrumentations include trickle\n51/2\nchargers to maintain the batteries whenever a con-\nAverage for all four\nNoncode stations\nvenient 110-volt supply is available at the station.3\n31/2\nAverage of all stations\nAlthough there appears to be a large differ-\n4\nReplaceable battery age on February 9, 1971\nence in the performance of the various accelerograph\nCode stations\n81/2\nMO-2\nmodels, this difference, more than likely, is the con-\n41/2\nRFT-250\n21/2\nsequence of the priority system of maintenance.\nSMA-1\nNoncode stations\n5\nRedundancy of time and starting systems\n31/2\nAverage of all stations\namong accelerographs in multiple installations is\nhighly desirable because it provides individual tim-\ning and starting capabilities to each instrument in\nNo reference was made to the standard accelero-\nevent of the malfunction of one or more accelero-\ngraphs or AR-240s because both instruments have\ngraphs within the group. A few total failures and nu-\ntrickle chargers; consequently, batteries are not ex-\nmerous records without a time base were observed\nchanged on a routine basis.\nduring the San Fernando event because of the lack\nThe following comments summarize the general\nof such compensating systems. The Seismological\nresults of strong-motion accelerograph performance\nField Survey has for a number of years recom-\nduring the San Fernando earthquake:\nmended inclusion of alternate time systems on all in-\n1 Approximately 16 percent of the potential\nstruments and backup starters in multiple installa-\ndata from 272 instruments was lost. In contrast, dur-\ntions. Had there been no redundant starters in Los\ning the Borrego Mountain earthquake of April\nAngeles buildings, an additional 14 records would\n1968, less than 1 percent of the data from 115 accel-\nhave been lost.\nerographs was lost.\nBecause future earthquakes in California in the\n2 Because a greater importance was attached to\nmagnitude 6 to 7 range will probably trigger several\nthe inspection and upkeep of the noncode instru-\nhundred strong-motion accelerographs, it is hoped\nments, a considerably larger percentage of records\nthat these comments will provide some beneficial\nwas obtained from them than from the code instru-\ncontribution to the cooperative network.\nments.2\n2 The priority system of maintenance is no longer in effect. All\n3 Trickle chargers have since been installed on all network\ninstruments are now being inspected on a routine basis.\ninstruments.","","Seismoscope Results\nINTRODUCTION\nAt the time of the San Fernando earthquake, the\nSeismological Field Survey was operating 150 seismo-\nscopes and over 250 strong-motion accelerographs in\nthe affected area.\nThe seismoscope network was established in 1960\nCONTENTS\nwhen a number of instruments were purchased by\nPage\ndifferent agencies, both private and governmental,\n353 INTRODUCTION\nand were installed and subsequently maintained by\n353\nDESCRIPTION OF SEISMOSCOPE\nthe Seismological Field Survey.\n354\nSEISMOSCOPE RECORD RECOVERY\n354\nSEISMOSCOPE DATA\nAll but six of the 150 seismoscopes in the shaken\n354 RECORDS OF SPECIAL INTEREST\narea recorded data useful to earthquake engineers.\n364 ACKNOWLEDGMENTS\nThis report presents the basic data from the seismo-\n364 REFERENCE\nscopes.\nDESCRIPTION OF SEISMOSCOPE\nThe seismoscope was designed by the U.S. Coast\nand Geodetic Survey and developed by the Califor-\nnia Institute of Technology in the late 1950s, and\nthe first 200 were installed in 1960. At present, there\nare 375 in the field, scattered from Fairbanks,\nAlaska, to El Centro, Calif. The seismoscope was de-\nsigned as a simplified, low-cost instrument to supple-\nment the more expensive strong-motion accelero-\ngraph.\nThe seismoscope consists of a free conical\npendulum that can move in any horizontal direction.\nThe wire-flexure pivot support of the pendulum\nmoves with the ground, and the resulting angular\ndeflections-relative to the instrument frame-are\nrecorded by a scriber on a smoked spherical watch\nglass. Eddy current damping is provided by an alu-\nminum disk in the form of a segment of a spherical\nEditors' note.-This paper is adapted from the report: Hudson,\nDonald E. (ed.), Strong-Motion Instrumental Data on the San\nB. J. MORRILL\nFernando Earthquake of Feb. 9, 1971, Earthquake Engineering\nResearch Laboratory, California Institute of Technology, Pasadena,\nSeismological Field Survey\nand Seismological Field Survey, National Oceanic and Atmospheric\nEarth Sciences Laboratories\nAdministration, San Francisco, Sept. 1971, 260 pp.\nEnvironmental Research Laboratories, NOAA\n353","354\nSan Fernando Earthquake of 1971\nshell, which moves between the poles of a permanent\nmagnet system. This aluminum segment is the prin-\ncipal contributor to the moment of inertia of the\ncompound pendulum. Because the motion in a hori-\nzontal plane is traced as a permanent record, the se-\nquence of events can be followed even though there\nis no time-recording device. This instrument, using a\nsimple recording technique, is superior to one that\nindicates maximum displacements.\nThe instrument is shown in figure 1, and a typical\ninstallation is shown in figure 2. Two types of\nseismoscopes now in use are the Wilmot and the\nSprengnether, which have the characteristics given in\ntable 1.\nSEISMOSCOPE RECORD RECOVERY\nFigure 2.-Typical seismoscope field installation showing\nconcrete base and external protective cover.\nOf the 150 possible records, 144 usable records\nwere obtained. Six records were lost because of mois-\nTable 1.-Seismoscope characteristics\nture and vandalism. Two records (Pacoima and Dry\nWilmot\nSpreng-\nCanyon) were partially destroyed when the earth-\nnether\nquake motion exceeded the design limits of the in-\nSerial number\n100,200,\n2,800\nand 500\nstruments and the recording plates were dislodged.\nSensitivity (cm/rad)\n5.45\n6.00\nPeriod (seconds)\n0.75\n0.78\nDamping (percent of critical)\n8.22\n8.22\nHowever, some useful information on these records\nwas obtained during the first few seconds.\nSEISMOSCOPE DATA\nFigure 3 is a map showing the seismoscope sites in\nsouthern California. The site location numbers\nshown on the map are listed in table 2. The map in\nfigure 4 shows the largest vectors of each seismo-\nscope response. For each record, the maximum dis-\nplacement of the trace from the initial zero point\nwas measured. From the sensitivity of the seismo-\nscope in cm/rad, the maximum relative displacement\nresponse-spectrum value Sa was calculated from:\nSa-8T Omax 10\n(Hudson and Cloud 1967)\nwhere\nT = period (second)\nn = damping (percent of critical)\nOmax = trace amplitude/sensitivity.\nRECORDS OF SPECIAL INTEREST\nThe records in figure 5, Nos. 213 and 210 from\nFigure 1.-The seismoscope is a relatively low-cost instrument that\nthe east abutment and crest of the San Fernando\nmeasures directly one point on the response spectrum.","","San Fernando Earthquake of 1971\n356\nTable 2.-Southern California seismoscope stations and data from San Fernando earthquake\nLocation from\nMaximum\nepicenter\nrelative\nInstru- Map\ndisplacement\nCity\nBuilding or site\nSite\nloca-\nment\nno. 1\ntion\nDirec-\nDirec-\nno.\ntion\nDis-\ntion\nSd\n(N-C.W.)2\n(N-C.W.)2\ntance\nO\nkm\no\ncm\nAltadena:\nDevils Gate Reservoir (crest)\n146\n566\nE-1\n135\n31.4\n047\n1.22\nDevils Gate Reservoir (left bank)\n147\n568\nE-1\n139\n31.4\n074\n1.29\nResidence, 1972 Skyview Drive\n232\n117\nE-1\n131\n35.0\n359\n2.72\nArcadia:\nSanta Anita Reservoir\n148\n565\nC-3\n124\n42.1\n230\n0.66\nArrowhead:\nU.S. Forest Service\n149\n107\nD-3\n103\n105.9\n360\n0.78\nAzusa:\nCogswell Reservoir (crest)\n150\n507\nD-3\n113\n43.6\n088\n1.12\nCogswell Reservoir (right bank)\n151\n530\nD-3\n113\n43.6\n303\n0.79\nSan Gabriel Reservoir (crest)\n152\n506\nD-3\n114\n54.4\n331\n3.27\nSan Gabriel Reservoir (left bank)\n153\n545\nD-3\n114\n54.4\n358\n0.16\nBeverly Hills:\nLower Franklin Canyon Reservoir (west abutment)\n154\n207\nD-2\n182\n33.4\n172\n1.06\nLower Franklin Canyon Reservoir (main crest)\n155\n206\nD-2\n182\n33.4\n174\n2.63\nBurbank:\nBurbank High School\n156\n125\nD-1\n164\n24.9\n278\n4.85\nCastaic:\nNorth Station\n157\n229\nC-3\n310\n23.3\n195\n3.72\nOld Ridge Route\n158\n2874\nC-3\n306\n29.8\n360\n3.88\nCedar Springs:\nStrong-Motion Station\n159\n2867\nD-3\n098\n99.6\n022\n0.29\nCholame:\nCholame Array No. 2\n15\n2855\nA-2\n310\n208.1\n240\n0.08\nCholame Array No. 5\n18\n2858\nA-2\n310\n208.1\n315\n0.08\nCholame Array No. 8\n21\n2896\nA-2\n310\n208.1\n115\n0.16\nClaremont:\nLive Oak Reservoir (crest)\n161\n524\nD-3\n115\n68.0\n010\n0.24\nLive Oak Reservoir (left bank)\n162\n514\nD-3\n115\n68.0\n232\n0.38\nThompson Creek Reservoir (crest)\n163\n560\nD-3\n114\n69.6\n026\n0.75\nThompson Creek Reservoir (left bank)\n164\n515\nD-3\n114\n69.6\n030\n0.35\nEagle Rock:\nEagle Rock Reservoir (west abutment)\n173\n208\nE-2\n147\n36.2\n276\n4.17\nEagle Rock Reservoir (main dam crest)\n174\n209\nE-2\n147\n36.2\n300\n4.93\nEl Centro:\nImperial Valley Irrigation District (accelerograph site)\n168\n132\nF-5\nNegligible\nEl Centro High School\n169\n158\nF-5\nNegligible\nEl Centro Steamplant\n170\n164\nF-5\nNegligible\nEl Centro Water Works\n171\n124\nF-5\nNegligible\nEl Segundo:\nHyperion Treatment Plant\n172\n102\nC-4\n183\n52.6\n090\n0.62\nEncino:\nEncino Reservoir (crest)\n165\n199\nC-3\n201\n30.2\n185\n1.59\nEncino Reservoir (west abutment)\n166\n217\nC-3\n201\n30.2\n178\n0.51\nEncino Reservoir (tower)\n167\n200\nC-3\n201\n30.2\n140\n1.94\nGlendale:\nHerbert Hoover High School\n177\n141\nE-1\n156\n28.2\nOff\ncenter\n(vandal-\nized)\nGlendora:\nBig Dalton Reservoir (crest)\n178\n520\nD-3\n115\n60.0\n100\n0.35\nBig Dalton Reservoir (left bank)\n179\n567\nD-3\n115\n60.0\n174\n0.32\nGrapevine:\nTehachapi Pumping Plant (north site)\n35\n2851\nC-3\n327\n72.7\n187\n0.35\nTehachapi Pumping Plant (accelerograph site)\n36\n2954\nC-3\n327\n72.7\n240\n0.51\nHollywood:\nHollywood Reservoir (west abutment)\n182\n205\nD-2\n168\n31.8\n320\n1.05\nHollywood Reservoir (main dam crest)\n183\n198\nD-2\n169\n31.8\n275\n0.66\nHollywood Reservoir (crest)\n221\nD-2\n160\n36.6\n112\n3.44\nHollywood Reservoir (right abutment)\n212\nD-2\n168\n36.6\n360\n2.40\nLake Hughes:\nLake Hughes Array:\nNo. 1 (never installed)\nC-3\nNo. 2\n186\n2824\nC-3\n349\n30.5\n160\n1.56\nNo. 3\n187\n2887\nC-3\n347\n29.4\n080\n1.44\nNo. 4\n188\n2891\nC-3\n345\n29.1\n326\n1.91\nNo. 4a\n189\n2889\nC-3\n343\n29.2\n330\n2.37\nSee footnotes at end of table.","Seismoscope Results\n357\nTable 2.-Southern California seismoscope stations and data from San Fernando earthquake-Continued\nLocation from\nMaximum\nepicenter\nrelative\nInstru- Map\ndisplacement\nSite\nloca-\nBuilding or site\nment\nCity\nno. 1\ntion\nDirec-\nDirec-\nno.\ntion\nDis-\nSa\ntion\n(N-C.W.)2\n(N-C.W.)\n2\ntance\nO\nkm\nO\ncm\nLake Hughes-continued:\nLake Hughes Array-continued:\n1.32\n190\n2894\nC-3\n347\n29.6\n338\nNo. 5\nC-3\nNo. 6 (station removed)\n191\n2822\nC-3\n331\n29.3\n313\n1.13\nNo. 7\n192\n2890\nC-3\n329\n29.0\nVandal-\nNo. 8\nized\n193\n2892\nC-3\n326\n28.0\n160\n0.91\nNo. 9\nC-3\nNo. 10 (never installed)\n25.0\n134\n1.04\n194\n2819\nC-3\n324\nNo. 11\n195\n2893\nC-3\n322\n24.4\n120\n1.82\nNo. 12\nLancaster:\n175\n211\nC-3\n356\n34.2\n218\n1.46\nFairmont Reservoir (south abutment)\n176\n216\nC-3\n356\n34.2\n010\n2.04\nFairmont Reservoir (main dam crest)\nLong Beach:\n146\n0.64\n196\n147\nC-4\n164\n72.6\nMunicipal Building (accelerograph site)\n197\n122\nC-4\n174\n71.8\n350\n1.83\nSan Pedro High School\n198\n149\nC-4\n167\n73.0\n095\n0.66\nTerminal Island (accelerograph site)\nLos Angeles:\n176\n43.4\n140\n3.52\n199\n192\nD-3\nBaldwin Hills Reservoir (east abutment)\n2.92\n200\n104\nF-2\n150\n46.5\n278\nEast Los Angeles Junior College\nVandal-\n201\n140\nD-2\nHancock Park\nized\n2.10\n202\n110\nF-2\n144\n44.2\n357\nTaylor Residence\n004\n0.35\n203\n143\nD-4\n121\n107.0\nColton (accelerograph site)\n170\n35.4\n345\n3.08\n204\n146\nD-2\nHollywood Storage (accelerograph site)\n205\n156\nC-4\n196\n42.3\n015\n2.29\nTauxe Residence\n41.0\n280\n3.10\n206\n150\nE-2\n160\nEdison Building (accelerograph site)\n158\n48.2\n138\n2.17\n207\n148\nE-3\nVernon (accelerograph site)\n1.02\n208\n123\nC-4\n179\n48.5\n146\nLeeds Residence\n080\n1.29\n209\n137\nF-2\n187\n37.8\nU.C.L.A. (accelerograph site)\n24.1\n220\n0.73\n210\n109\nC-3\n197\nDuke Residence\n212\n113\nC-2\n181\n39.2\n203\n1.39\nWest Los Angeles Public Library\n24.1\n060\n3.35\n213\n139\nC-1\n192\nVan Nuys High School\n160\n52.8\n037\n1.10\n214\n129\nC-4\nSouthgate High School\n1.46\n215\n162\nE-2\n144\n42.6\n070\nElysian Heights School\n049\n2.06\n216\n127\nC-4\n181\n46.5\nPlaya Del Rey School\n45.4\n081\n2.06\n217\n154\nC-4\n174\nWindsor Hills School\n166\n43.9\n152\n2.17\n218\n157\nE-2\nMuseum of Science and Industry\n58.3\n110\n2.04\n219\n163\nC-4\n166\nCompton School Administration Building\n160\n49.6\n198\n1.39\n220\n120\nC-4\nHuntington Park City Hall\n0.35\n221\n134\nC-4\n173\n67.8\n090\nNarbonne High School\nMaricopa:\n117.8 Negligible\n63\n629\nB-3\n309\nStation B\nMonrovia:\n45.0\n040\n1.00\n222\n505\nD-3\n123\nSawpit Canyon Reservoir (right bank)\n123\n45.0\n043\n0.81\n223\n569\nD-3\nSawpit Canyon Reservoir (crest)\nMount Wilson:\n37.0\n1.06\n224\n114\nC-3\n121\nCaltech Seismograph Station\nPacoima:\n227\n525\nC-3\n180\n6.9\nPlate\nPacoima Dam\nthrown off\nPasadena:\n38.2\n008\n2.10\n228\n508\nF-1\n131\nEaton Wash Reservoir (base)\n2.76\n131\n38.2\n122\n229\n517\nF-1\nEaton Wash Reservoir (crest)\n226\n2.24\n230\n133\nF-1\n134\n31.0\nGilman Residence\n38.4\n214\n2.40\n166\nF-2\n140\nCaltech Campus, Millikan Library (accelerograph site)\n231\n139\n38.6\n247\n1.94\n240\n138\nF-2\nCaltech Campus, Athenaeum\n32.2\n015\n2.69\n233\n151\nE-1\n141\nMotta Residence\n33.0\n255\n3.77\n234\n108\nF-1\n139\nMuir High School\n1.22\n138\n34.6\n205\n235\n100\nF-1\nWashington Junior High School\n083\n2.24\n236\n152\nF-2\n143\n35.0\nSeismological Laboratory\n35.4 Damaged\n237\n126\nF-2\n144\nSan Raphael School\nby water\n2.42\n35.9\n136\n238\n124\nF-2\n141\nGarfield School\n134\n38.3 Damaged\n239\n128\nF-1\nHale School\nby water\nSee footnotes at end of table.","358\nSan Fernando Earthquake of 1971\nTable 2.-Southern California seismoscope stations and data from San Fernando earthquake-Continued\nLocation from\nMaximum\nepicenter\nrelative\nInstru-\nMap\ndisplacement\nCity\nBuilding or site\nSite\nment\nloca-\n1\ntion\nDirec-\nno.\nno.\nDirec-\ntion\nDis-\ntion\nSa\n(N-C.W.)2\ntance\n(N-C.W.)2\nO\nkm\no\ncm\nPearblossom:\nPearblossom Pumping Plant\n241\n2847\nD-3\n074\n47.4\n072\n0.82\nPerris:\nAccelerograph Station\n242\n249\nD-4\n118\n129.0\n016\n0.08\nPiru:\nSanta Felicia Dam:\n(toe, S-1)\n262\n590\nC-3\n282\n33.4\n290\n2.10\n(outlet works, S-2)\n263\n588\nC-3\n282\n33.4\n295\n1.24\n(right abutment, S-3)\n264\n586\nC-3\n282\n33.4\n288\n1.82\n(right crest, S-4)\n265\n589\nC-3\n282\n33.4\n302\n5.63\n(dam crest, S-5)\n266\n587\nC-3\n282\n33.4\n305\n6.28\n(left abutment, S-6)\n267\n585\nC-3\n282\n33.4\n303\n2.30\nRiverside:\nCaltech Seismograph Station\n243\n142\nD-4\n114\n105.0 Negligible\nSan Bernardino:\nPost Office\n244\n144\nD-3\n108\n106.0\n004\n0.35\nDevils Canyon:\nSite No. 1\n245\n233\nD-3\n102\n100.0\n340\n0.44\nSite No. 2\n246\n231\nD-3\n102\n100.0\n157\n0.46\nSite No. 3 (removed)\nSite No. 4\n247\n227\nD-3\n102\n100.0\n355\n0.29\nSite No. 5\n248\n241\nD-3\n102\n100.0\n009\n0.38\nSite No. 6\n249\n237\nD-3\n102\n100.0\n017\n0.16\nSite No. 7\n250\n232\nD-3\n102\n100.0\n345\n0.65\nSan Dimas:\nPuddingstone Reservoir (crest)\n251\n529\nD-3\n122\n64.4\n318\n4.17\nPuddingstone Reservoir (accelerograph site)\n254\n521\nD-3\n122\n64.4\n136\n1.29\nSan Dimas Reservoir (crest)\n252\n531\nD-3\n115\n63.4\n270\n0.41\nSan Dimas Reservoir (left bank)\n253\n509\nD-3\n115\n63.4\n200\n0.58\nSan Fernando:\nLower San Fernando Dam (east abutment)\n255\n213\nC-3\n208\n14.9\n287\n6.70\nLower San Fernando Dam (main dam crest)\n256\n210\nC-3\n208\n14.9\n110\n7.72\nSan Marino:\nSan Marino City Hall\n211\n115\nF-2\n138\n41.4\n248\n3.08\nCrotty Residence, Shenandoah Road\n651\nF-2\n140\n41.9\n150\n2.58\nSanta Ana:\nAccelerograph Site\n258\n159\nD-4\n145\n87.6\n260\n0.62\nSanta Barbara:\nAccelerograph Site\n259\n500\nB-3\nNegligible\nUniversity of California\n260\n145\nB-3\n271\n143.8\n335\n0.35\nSanta Barbara Museum\n261\n116\nB-3\nNegligible\nGoleta, Food Fair Market\n180\n135\nB-3\n271\n143.8\n048\n0.57\nGoleta, Sylvester Residence\n181\n155\nB-3\n271\n143.8\n270\n0.19\nSanta Monica:\nSanta Ynez Dam (right abutment)\n193\nC-3\n279\n144.9\n360\n0.66\nSanta Ynez Dam (crest)\n195\nC-3\n279\n144.9\n269\n0.95\nSaugus:\nBouquet Canyon Reservoir (west abutment)\n184\n201\nC-3\n008\n20.6 Damaged\nby water\nBouquet Canyon Reservoir (main dam crest)\n185\n202\nC-3\n008\n20.6\n080\n3.84\nDry Canyon Reservoir (east abutment)\n268\n194\nC-3\n307\n14.9\n268\n4.75\nDry Canyon Reservoir (main dam crest)\n269\n196\nC-3\n307\n14.9\nPlate\nthrown\noff\nSunland:\nBig Tujunga Reservoir (crest)\n270\n528\nC-3\n119\n22.5\n275\n2.78\nBig Tujunga Reservoir (left bank)\n271\n513\nC-3\n119\n22.5\n317\n2.17\nTable Mountain:\nTiltmeter Station\n272\n131\nD-3\n091\n70.4\n188\n0.29\nTaft:\nBuena Vista Accelerograph Site\n130\n260\nB-2\n309\n117.8 Negligible\nBuena Vista North\n131\n235\nB-2\n309\n117.8 Negligible\nBuena Vista South\n132\n228\nB-2\n309\n117.8 Negligible\nWestwood:\nLower Stone Canyon Reservoir (east abutment)\n273\n204\nC-3\n189\n32.2\n162\n0.73\nLower Stone Canyon Reservoir (main dam crest)\n274\n203\nC-3\n189\n32.2\n190\n1.47\nWheeler Ridge:\nAccelerograph Station\n138\n2955\nC-2\n319\n90.4\n065\n0.22\nWheeler Ridge Pumping Plant\n139\n2897\nC-2\n319\n90.4\n162\n0.29\nWind Gap Pumping Plant\n140\n2850\nC-3\n319\n90.4\n107\n0.32\nTiltmeter No. 2\n141\n2849\nC-3\n319\n90.4\n080\n0.48\n1\nPermanent identification number in annual list of stations issued by Seismological Field Survey, NOAA.\n2 North-clockwise.","Seismoscope Results\n359\n02850\n2887 2824\n2884\n2849\n18851\n2890\n2022\n28920\n2819\n2893\n2874\nSAN\nLAKE HUGHES ARRAY\n229\nFairmont\n211\n216\nKilometers\nArray\nANDREAS\n2887\no\nHughes\n&\n2892\n202\nO2893\n2874\nFAULT\nP229\n2847\n587\na\n194\nDry Canyon\n590\nSanta Felicia\nZONE\nEPICENTER\nPacoima\nO 525\n528\n513\nA\n210\n507\n530\n0114\nISS\n506\n545\n125\nQ139\n568\n3319\n101\n569\nGlendale\nPasadena\n524\n199\n514\n200\n205\nOTS\n217\n212\n208\n203\n209\n204\n529\n206\n521\n207\n1626\n109\nLos\n150\n137g\nAngeles\nSanta\n157\n148\n192\nMonica\n1270\n154\nP120\n0129\nPASADENA AREA\n1108\nKilometers\n163\n151\n100\nPasadena\n134\no\nQ147\n149c\nSEISMOSCOPE STATIONS\n152\n1220\nHighway 66\nSAN FERNANDO EARTHQUAKE OF\nSeis Lab. CIT\n9 FEBRUARY 1971\n166\nMaintained By Seismological Field Survey\n0\n188\nScale basic\n30\n0\n124\nKilometer\nS\nLagand:\nThrust Fault\nEpicenter\n@ est\nMax. Relative Displacement (Ca)\n11\nAzimuth (Dog True )\nD565\nScope Serial No.\nSouth Pasadena\n110\nFigure 4.-Two largest vectors of each seismoscope response.","360\nSan Fernando Earthquake of 1971\nBurbank High School S/N 125\nSanta Felicia Dam Crest S/N 587\nSan Fernando Dam Crest S/N 210\nSan Fernando Dam Abutment S/N 213\n5 CM\nFigure 5.-Selected seismoscope records from San Fernando earthquake.\nDam at the Lower Van Norman Reservoir, have spe-\nafter the earthquake when the level of the reservoir\ncial interest because they show the motion before\nhad been lowered. Figure 7 shows the maximum\nand during the failure of the dam. The crest instru-\nheight of the water inside the outer protective cover\nment escaped damage as it sank under the water\nduring submergence, indicating how air trapped\nwhen the face of the dam slipped. Figure 6 (a) shows\nunder the instrument cover protected the seismo-\nthe instrument housing at San Fernando Dam as it\nscope itself from submergence. Figure 8 shows the\nappeared before the earthquake and figure 6 (b)\nseismoscope on its tilted foundation after the protec-","Seismoscope Results\n361\nOUTER PROTECTIVE COVER\nSEISMOSCOPE COVER\nENTRAPPED AIR\nWATERLINE\n37°\n(a)\nFigure 7.-Schematic of seismoscope showing height of water\ninside cover during submergence.\n(b)\nFigure 6.-Seismoscope Serial No. 210 at site number 256, (a) at\ncrest of Lower San Fernando Dam before earthquake, and (b)\nafter earthquake and lowering of reservoir level. The instrument\nat left in (b) is a Peak Recording Accelerometer installed after\nphotograph (a).\ntive cover was removed. The position of the stylus\non the record plate while the instrument was tilted\nis shown by the straight line in the lower part of\nfigure 5, No. 210. The small transverse line and the\nportion of the record between that position and the\nFigure 8.-Seismoscope Serial No. 210 in final position\nblack blob probably represent motion of the scope\nafter earthquake and lowering of water level.\nnear the end of the sliding, and the black blob per-\nHardsite: Crystalline rock, shales, and well-\nhaps represents the motion during the initial part of\nconsolidated sedimentary rock with sometimes minor\nthe sliding. The remainder of the record represents\nmotion of the crest of the dam before failure. Fig-\namounts of overburden.\nures 9 and 10 show damping and tilt test records\nmade on the instruments (Nos. 210 and 213) im-\nTable 3.-Seismoscope characteristics at Lower\nVan Norman Reservoir\nmediately after recovery. Table 3 gives the instru-\nmental constants of both instruments.\nCrest\nAbutment\nAll data for figure 11 were taken from ground-\n210\n213\nSerial number\nfloor locations. The seismoscope sites were classified\n5.52\n5.52\nSensitivity (cm/rad)\n0.75\n0.75\nPeriod (seconds)\neither as hard (black circles) or soft (open circles)\nSingle amplitude at 10 percent of damping\n0.73\n1.27\n(cm)\naccording to the following definitions.","2.2\nLOWER SAN FERNANDO DAM CREST\n2.0\nSEISMOSCOPE SERIAL NO. 210\n<<<\n1.8\n1.6\nFigure 9.-Damping and tilting test records after earthquake.\nSTANDARD SEISMOSCOPE\nSINGLE AMPLITUDE - CM\n1.4\n0\n1.2\nCURVE\n1.0\n0.8\n0.6\nEXPERIMENTAL\n0.4\nPOINTS\n0.2\no\n24\n20\n16\n12\n8\n4\no","2.2\nLOWER SAN FERNANDO DAM ABUTMENT\n2.0\nSEISMOSCOPE SERIAL NO. 213\n1.8\nAbutment\n3\nTTIT\no\n1.6\nSTANDARD SEISMOSCOPE\nSINGLE AMPLITUDE - CM\nFigure 10.-Damping and tilt test records after earthquake.\n1.4\n1.2\nCURVE\n1.0\n0.8\n0.6\n0.4\nEXPERIMENTAL\n0.2\nPOINTS\nO\no\n8\n4\n16\n12\n24\n20","364\nSan Fernando Earthquake of 1971\nSoftsite: Unconsolidated sedimentary rock, mod-\n10.0\nerate to great depths of alluvium, and highly frac-\nLower San Fernando Dam\ntured sedimentary rock along with any depth of\nalluvium.\nThree curves are shown on the plot, representing\nonly the hardsites, only the softsites, and a combina-\ntion of both. Attenuation formulas for all three cate-\ngories are as follows:\n1.0\nHardsites\nSa=102 = D-1.227\nSoftsites\nSa=990 D-1.702\nAll sites (101 points)\nSa=280 D-1.437\nwhere\nSa = maximum relative displacement (cm) and\nD = distance (km),\nACKNOWLEDGMENTS\nCholame Array\nSpecial recognition is given Leroy Foote, Pete\n0.1\nMork, and Barry Silverstein, Seismological Field Sur-\nHardsites\nvey, for recovering seismoscope records and for con-\nSoftsites\nducting special instrument tests. Virgilio Perez, Seis-\nCombination\nmological Field Survey, provided most of the\ncomputer analysis. Appreciation is extended to Rich-\nSeismoscope Results: San Fernando\nard Delman, California Institute of Technology,\nEarthquake 9 February 1971\nfor assistance in preparing figures 3 and 7.\nSeismological Field Survey, NOAA\nLegend:\nHardsite\no Softsite\nREFERENCE\n.01\n10\n100\n1000\nHudson, Donald E., and Cloud, W. K., \"An Analysis of Seis-\nDistance (Km)\nmoscope Data From the Parkfield Earthquake of June 27,\n1966,\" Bulletin of the Seismological Society of America,\nFigure 11.-Seismoscope results for hardsites, softsites,\nand a combination of both.\nVol. 57, No. 6, Dec. 1967, pp. 1143-1159.","Strong-Motion Accelerogram Processing\nACCELEROGRAM COLLECTION AND\nREPRODUCTION\nThe simultaneous triggering of 272 strong-motion\naccelerographs in the southern California region\nover distances of several hundred miles presented an\nunprecedented problem of record collection and data\nCONTENTS\nhandling.\nPage\nAfter the earthquake, an immediate decision was\n365\nACCELEROGRAM COLLECTION AND\nmade in the Los Angeles office of the Seismological\nREPRODUCTION\nField Survey of the National Oceanic and Atmos-\n366\nACCELEROGRAM PROCESSING AND\nANALYSIS PROGRAM\npheric Administration (NOAA) that, in the interest\n366\nRECORD REPRODUCTION\nof minimizing the risk of losing records, only the\n367\nDIGITIZATION PROGRAM\nregular experienced staff members connected with\n368\nSAMPLE ACCELEROGRAMS\n369\nMILLIKAN LIBRARY RESPONSE\nthe office would pick up the photographic records\n370\nPACOIMA DAM ACCELEROGRAM\nfrom the field instruments. It was felt that the exist-\n370\nRESPONSE SPECTRUM CALCULATIONS\ning film supplies in the accelerographs would be ade-\n371\nACKNOWLEDGMENTS\nquate to record the important aftershocks and that\n374\nREFERENCES\nthe time delay in collecting the records would entail\nno practical disadvantage because preliminary re-\nports had indicated that there had been no signifi-\ncant structural damage in any of the buildings hous-\ning the accelerographs.\nBy February 10, 1971, the day after the\nearthquake, the first group of accelerograms had\nbeen collected from the buildings nearest the epicen-\ntral region and had been developed and scaled for\napproximate peak acceleration values. The Los An-\ngeles Department of Building and Safety was notified\nimmediately of the availability of these records for\ninspection by engineers and building owners. By this\ntime, it was also evident that there, in fact, had been\nno significant structural damage to any of the build-\nings housing the strong-motion accelerographs SO\nthat no special system was necessary for the rapid\nEditors' note.-This paper is adapted from the report: Hudson,\nD. E. HUDSON\nDonald E. (ed.) Strong-Motion Instrumental Data on the San\nFernando Earthquake of Feb. 9, 1971, Earthquake Engineering\nEarthquake Engineering Research\nResearch Laboratory, California Institute of Technology, Pasadena,\nLaboratory\nand Seismological Field Survey, National Oceanic and Atmospheric\nCalifornia Institute of Technology\nAdministration, San Francisco, Sept. 1971, 260 pp.\nPasadena, Calif.\n365","366\nSan Fernando Earthquake of 1971\ncommunication of accelerograph readings to build-\n1\nTo produce accurate archival copies of all\ning owners. The large values of acceleration mea-\nrecords as well as copies suitable for digitization and\nsured on the first records, however, made it clear that\ndata processing.\na major effort should be made to insure a rapid and\n2 To produce multiple copies of a form suita-\nwide distribution of the results.\nble for immediate display and distribution to all in-\nDuring a period from 2 to 3 weeks after the earth-\nterested parties and to arrange for such distribution.\nquake, all photographic records were brought into\n3 To carry out an accurate digitization of all\nthe Los Angeles office of the Seismological Field Sur-\nusable records in a form compatible with past accel-\nvey where they were developed and preliminary la-\nerogram analysis.\nbeling and scaling of peak accelerations were carried\n4. To prepare for all records corrected accel-\nout. This was done on a priority basis, with the rec-\nerogram data, integrated velocity and displacement\nords nearest the epicentral region being collected\ncurves, and Fourier and response spectrum curves\nand processed first because of the intense interest of\nin various standard forms.\nall earthquake investigators. The accelerographs\nthemselves were all checked for proper operation\nRECORD REPRODUCTION\nand were left with a full film supply in readiness for\nthe next earthquake.\nAfter preliminary labeling and checking in the\nThe Pacoima Dam accelerograph, located virtually\nLos Angeles office of the Seismological Field Survey,\nat the epicenter of the earthquake, could not be\nall originals were taken to the C.I.T. Jet Propulsion\nreached for several days after the earthquake because\nLaboratory in Pasadena where permanent photo-\nof large rockslides which blocked the access road,\ngraphic labels were made for each record, including\nrendering visits to the sites on foot hazardous. The\nall pertinent instrumental information. These labels\nprecipitous nature of the steep canyon location pre-\nwere spliced on all records for future reproduction.\ncluded the use of helicopters.\nAn accurate 1-to-1 film copy of the initial strong-\nThe records from the five accelerograph types that\nmotion portion of each record was then made by the\ncomprise the network were in the following forms:\nPhotographic Department at the Jet Propulsion Lab-\nthe Standard U.S. Coast and Geodetic Survey and\noratory. A standard grid was photographed along\nAR-240, 12-inch-wide photographic paper; the\nwith each record to check any distortions in the\nRFT-250 and SMA-1, 70-mm film; and the MO-2,\nprocessing. One negative and one positive were made\n35-mm film. The record lengths varied from a few\nof each record on a stable film base. These short film\nfeet to 30 feet, with several records as long as 80 feet.\ncopies then became the basis for reproduction of\nThe total set of 229 usable records from the 241\nmultiple copies for immediate distribution.\ntotal records obtained consisted of 103 12-inch paper\nFor distribution copies of the 12-inch paper accel-\nrecords, 93 70-mm records, and 45 35-mm records.\nerograms, the short-film positive was used in a regu-\nlar black-line print machine. In this way, records\nACCELEROGRAM PROCESSING AND\ncould be reproduced economically in numbers of a\nANALYSIS PROGRAM\ndozen or SO to follow demand. Part of this copying\nwas done at the Jet Propulsion Laboratory.\nTo render assistance to the Seismological Field\nFor distribution copies of the 70- and 35-mm\nSurvey for its immediate problems of record repro-\nshort-film records, the short-negative copies were sent\nduction and dissemination and to provide for even-\nto the Rapid Blue Print Company in Los Angeles\ntual complete data analysis, the Engineering Division\nfor full-size photographic prints. This resulted in ac-\nof the National Science Foundation (NSF) and the\ncurate black-line-on-white copies for distribution,\nEarthquake Engineering Research Laboratory at the\nwhich were also suitable for direct duplicating for\nCalifornia Institute of Technology (C.I.T.) devel-\npreliminary work. The duplicating was carried out\noped a data handling and processing program imme-\nin the Mechanical Engineering Department at C.I.T.\ndiately following the earthquake. The main objec-\nTo make the records available for public inspec-\ntives of this special NSF program in the data\ntion as soon as possible, a room was established on\nprocessing phase were:\nthe campus of C.I.T. where copies of all accelero-","Strong-Motion Accelerogram Processing\n367\ngrams were posted as soon as available, along with\ntechnicians to the C.I.T. campus for assistance with\nadditional information such as instrument location\nrecord processing and digitization. With this assist-\nance, the accelerograph constants were checked from\nand aftershock epicenter. Wide publicity was given\nthe calibration runs included on the accelerograms.\nto the availability of this information through press\nand television coverage. In the weeks following the\nearthquake, several thousand visitors availed them-\nDIGITIZATION PROGRAM\nselves of this opportunity, including more than a\nBecause of the large number of accelerograms, it\nhundred earthquake experts from Japan. Sets of\nwas realized immediately that record digitization\nmultiple copies also were delivered to the Los Ange-\nwould be a major task. Because a good deal of experi-\nles office of the Seismological Field Survey for distri-\nence with accuracy evaluation and with the training\nbution to building owners, through the Los Angeles\nof operators had been obtained on the Benson-\nDepartment of Building and Safety, and to the\nLehner 099D Datareducer (Hudson et al. 1969a and\nNOAA/EERI San Fernando Earthquake Investiga-\nTrifunac 1970), it was decided that this semiauto-\ntion Committee located at the University of Califor-\nmatic method of digitization would be started im-\nnia, Los Angeles (U.C.L.A.).\nmediately; in addition, an intensive investigation of\nTo produce archival copies of the complete 12-\nmore automatic systems, based on digital-imaging\ninch paper records, original records were taken in\nprocessing techniques, would also be initiated.\nsmall lots to the Continental Graphics Company in\nDuring the past few years, several digital-imaging\nLos Angeles where one negative and two positives\nprocesses have been developed for special applica-\nwere produced of the entire length of each original\ntions. Such systems have been applied to the digitiza-\nrecord. Because many of the records were 20 feet\ntion of space photographs and to the digitization of\nlong and several were as long as 80 feet, this in-\nbubble-chamber tracks for particle physics investiga-\nvolved special processing facilities. As an additional\ntions. It appeared that several of these systems would\ncontrol on the accuracy of the reproductions, techni-\nbe directly applicable to accelerograph digitization,\ncians from the Jet Propulsion Laboratory measured\nbut that a considerable computer programing job\nand recorded a set of standard lengths on the origi-\nwould be involved. In addition, it was clear that the\nnal records and on the photographic copies.\nproblem of accuracy evaluation would take a differ-\nTo produce the archival full-length copies of the\nent form and would require a detailed investigation.\n35- and 70-mm records, a negative and two positives\nBecause all available automatic systems required that\nwere produced by Yale Laboratories in Los Angeles.\nthe record be in the form of a 35- or 70-mm film\nSpecial control of this process was required to pro-\nstrip, it was decided that the 12-inch paper records\nduce suitable records for automatic image-processing\nwould be digitized semiautomatically with the hope\ndigitization.\nthat by the time they were finished, the automatic\nIn addition to the above standard records, certain\nsystem would be in successful operation.\nextra editions were produced of several accelero-\nTo assist with the semiautomatic digitization, time\ngrams having special interest. Three hundred copies\nwas made available on a second 099D Datareducer\nwere printed in accurate full-scale format of the Pa-\nthrough the courtesy of the Shell Oil Company in\ncoima Dam accelerogram; a similar set was produced\nLos Angeles. A staff of some 12 operators, consisting\nfor the basement and roof records at the C.I.T. Mil-\nof Jet Propulsion Laboratory technicians and part-\nlikan Library as an example of building-response\ntime students from C.I.T., was trained and checked\nmeasurements. Considering all of the above proc-\nfor accuracy. With this staff and the two 099D Data-\nesses, within a few weeks of the earthquake, several\nreducers, all 90 paper accelerograms were digitized\nthousand accelerograms had been distributed very\nand made compatible with past accuracy standards\nwidely around the world.\nwithin 3 months of the earthquake.\nAlong with the above record-reproduction process,\nAt the time of completion of the paper records, it\nthe Jet Propulsion Laboratory staff prepared a code\nwas evident that the automatic digitization process\nnumber and tabulation listing for all accelerograms\nwould be feasible and that the bulk of the film accel-\nas well as location maps for the instrument installa-\nerograms could be digitized in this new way. It was\ntions. In addition, the Laboratory arranged for trans-\nalso clear that some of the film records were not of a\nfer of a number of professional data processors and","368\nSan Fernando Earthquake of 1971\nquality for automatic digitization, but would require\nwide paper may be seen in figures 4 and 5 of the\nthe individual attention possible with the semiauto-\npaper in Volume III by Maley and Cloud, \"Strong-\nmatic method. It was accordingly decided to perform\nMotion Accelerograph Records.\" Examples of AR-\nautomatic processing on all suitable records and to\n240 records of ground sites are shown in figure 6\nfinish the others on the 099D Datareducer.\nof that same paper. Typical building records ob-\nIn retrospect, it appears that the system of semiau-\ntained on 70-mm film with the SMA-1 accelerograph\ntomatic digitization used on the paper accelerograms\nare shown in figure 7, and those obtained on 35-mm\nwas an effective way of dealing with the problem.\nfilm with the MO-2 accelerograph are in figure 8\nThe success of the approach depended on the availa-\nin the paper by Maley and Cloud. A ground-station\nbility of a group of experienced part-time operators\nrecord from an SMA-1 accelerograph is included as\nfrom the Jet Propulsion Laboratory and from the\nfigure 1 of the present paper.\nC.I.T. student group. This is an essential feature be-\nThe records of figures 2a, 2b, and 2c are from a\ncause no one person can engage in the digitization\ntelephone-line-interconnected accelerograph system\nfor more than 2 or 3 hours without an inevitable\njoining the C.I.T. campus, the Seismological Labora-\ndegradation of accuracy. Given the relatively infre-\ntory, and the Jet Propulsion Laboratory over a dis-\nquent nature of strong earthquakes, such automatic\ntance of some 6 miles. These five RFT-250 accelero-\ndigitization is a feasible, though laborious, approach.\ngraphs are SO arranged that the first one to trigger\nAs a check on the fully automatic digitization\nfrom earthquake ground motion will start simultane-\nprocess, a 35-mm record of average quality was sent\nously the other instruments in the network (Keight-\nto Information International, Inc., in Los Angeles\nley 1970) For the San Fernando earthquake, the\nwhere the digitization was accomplished and sup-\nSeismological Laboratory and the Jet Propulsion\nplied on magnetic tape. This tape was then processed\nLaboratory accelerographs should trigger about the\nat the C.I.T. Computing Center, and a large-scale\nsame time, some 1 to 2 seconds before the initial\n8X plot of a selected portion of the record was plot-\nearthquake waves would reach the Millikan Library\nted on the Calcomp plotter. This computer-plotted\naccelerograph on the C.I.T. campus. A comparison\naccelerogram was then superimposed directly on an\nof the records of figures 2a, 2b, and 2c shows that the\n8X enlargement of the original 35-mm accelerogram.\nMillikan Library recording was started in advance of\nThe excellent agreement obtained for this direct\nthe main earthquake ground motions as indicated at\ncomparison indicated that a satisfactory accuracy had\nthe other stations. A comparison of the Millikan Li-\nbeen achieved in the automatic digitization process.\nbrary record with that obtained at another campus\nbuilding-the Athenaeum-which was not on the\nSAMPLE ACCELEROGRAMS\ninterconnected network, indicates that the self-trig-\nExamples of sets of three building accelerograms\ngered Athenaeum accelerograph started before the\nobtained with AR-240 accelerographs on 12-inch-\ndistant-triggered Library instrument. This occurred\nC.I.T. ATHENAEUM, PASADENA\nEast\nDown\nNorth\n10 seconds\nFigure 1.-SMA-1 accelerograph record from Athenaeum station, California Institute of Technology, Pasadena.","Strong-Motion Accelerogram Processing\n369\nC.I.T. MILLIKAN LIBRARY, PASADENA\n10th FI. East\n10th FI. Down\n10th FI. North\nBsmt East\nBsmt Down\nBsmt North\n10 seconds\nFigure 2a.-Accelerograph record from interconnected instrument system station at C.I.T. Millikan Library, Pasadena.\nC.I.T. SEISMOLOGICAL LAB, PASADENA\nWest\nDown\nSouth\n10 seconds\nFigure 2b.-Accelerograph record from interconnected instrument system station at C.I.T. Seismological Laboratory, Pasadena.\nbecause the SMA-1 accelerograph in the Athenaeum\nground motion was preceded by smaller shaking that\nis triggered by a vertical starter. The arrival of the\nserved to start the accelerograph in enough time to\nvertical waves preceded the arrival of the horizontal\nrecord a relatively complete picture of significant\nwaves which triggered the RFT-250 accelerographs\nground motion. The telephone-interconnected sys-\nin the network by an amount more than enough to\ntem or an accelerograph with a memory, therefore,\ncompensate for the gain in triggering time in the in-\nwas not required. This is probably also likely to be\nterconnected network. In this case, the vertical\ntrue for most damaging earthquakes, although the\nstarter was evidently a simpler way to insure an early\npossibility certainly exists that, in some cases, infor-\nstart than the interconnected network.\nmation might be lost for an abrupt beginning.\nIt is also evident that the additional complexity of\nMILLIKAN LIBRARY RESPONSE\nthe interconnected system has not reduced the relia-\nbility of the system, which operated correctly in all\nThe accelerogram (fig. 2a) recorded on the roof of\nrespects. For this particular earthquake, the main\nthe nine-story Millikan Library on the C.I.T. cam-","370\nSan Fernando Earthquake of 1971\nJ.P.L., PASADENA\n9th FI. S 8°W\n9th FI. Down\n9th FI. S 82°E\nBsmt S 8°W\nBsmt Down\nBsmt S 82°E\n10 seconds\nFigure 2c.-Accelerograph record from interconnected instrument system station at C.I.T. Jet Propulsion Laboratory, Pasadena.\npus is of unusual interest because of the complete\nently no significant structural damage to the build-\ndynamic investigations made on this building before\ning, and the period change can probably be at-\nthe earthquake (Kuroiwa 1967 and Blandford et al.\ntributed to alterations in the attachment of\n1968).\nprecast concrete window-panel sections that made up\nFigure 3 (a) is the record of a man-excited low-\nthe north-south faces of the building.\nlevel vibration, indicating that the fundamental\nSuch permanent period changes have been noted\neast-west lateral natural period of vibration at small\nin past earthquakes (Esteva and Nieto 1967) and\namplitudes of motion was 0.66 second before the\nhave been observed in numerous buildings after the\nearthquake. This value also was confirmed by\nSan Fernando earthquake.\nforced vibration resonance tests at a considerably\nhigher force level and by ambient vibration tests in-\nPACOIMA DAM ACCELEROGRAM\nvolving wind and microtremor excitations. The\nBecause of the very special interest and impor-\nearthquake accelerogram of figure 3 (b) shows that\ntance of the Pacoima Dam accelerogram record,\nduring the earthquake vibrations, which reached a\nwhich was obtained virtually on top of the epicenter,\npeak acceleration of 0.37g, the period of fundamen-\na special effort was made for a prompt analysis of the\ntal mode was 1.01 seconds. This considerable length-\nrecord and dissemination of the results. Because the\nening of the period is attributed to the much higher\nsite conditions under which the record was obtained\nlevels of the building motion and to the nonlinear\nwere unusual, a special investigation was made of the\ncharacter of the structure.\nsite and of the condition of the accelerograph after\nThe accelerogram of figure 3 (c) shows that for\nthe earthquake. This investigation and analysis of\nthe small building motions excited by a small earth-\nthe accelerogram are discussed in detail in a paper\nquake aftershock, the fundamental period was 0.76\nin Volume III by Trifunac and Hudson, \"Analysis\nsecond. A low-level wind-excited test was then run to\nof Pacoima Dam Accelerogram.\"\ncheck the final postearthquake state of the building,\nand the period was found to be 0.77 second, as in\nRESPONSE SPECTRUM CALCULATIONS\nfigure 3 (d) It is evident that, after the earthquake,\nthe small-amplitude motion had been lengthened\nThe response spectrum of the Pacoima Dam rec-\npermanently by some 15 percent. There was appar-\nord, along with integrated ground velocity and","Strong-Motion Accelerogram Processing\n371\nONE SECOND\n0.65 SEC. = T\nRANGER SEISMOMETER\nAMPLITUDE LEVELS 22 0.00lg\n(a) MAN-EXCITED VIBRATIONS BEFORE EARTHQUAKE\n0.19g\nEAST\nONE SECOND\n1.01 SEC. = T\n0.37 g\nVERTICAL\n10th FLOOR, MILLIKAN LIBRARY\n0.5 g ACCELERATION\nNORTH\nRFT-250 ACCELEROGRAPH\n(b) SAN FERNANDO EARTHQUAKE OF FEBRUARY 9, 1971\nONE\n= 0.76 Ska\nT\nSECOND\nVM-1 VIBRATION MONITOR\nAMPLITUDE LEVELS 22 0.00l g\n(c) EARTHQUAKE AFTERSHOCK, MARCH 8, 1971\nONE\n0.77 SEC.\nSECOND\nVM- VIBRATION MONITOR\nAMPLITUDE LEVELS z 0.0001 g\n(d) LOW-LEVEL WIND EXCITATION, MARCH 17, 1971\nVIBRATION MEASUREMENTS AT TOP OF MILLIKAN LIBRARY\nFigure 3.-Instrument records from C.I.T. Millikan Library, Pasadena.\ndisplacement curves, is given in a paper in Volume\nneering applications. In figures 4a through 7c, the\nIII by Trifunac and Hudson cited previously. Be-\ntop curve is for zero percent of critical damping and\ncause of the special interest in response spectra from\nthe lower three curves are for 2, 5, and 10 percent of\nother key stations in the region, preliminary spectra\ncritical damping, respectively.\nhave been computed from the uncorrected accelero-\nACKNOWLEDGMENTS\ngram data for several additional records (figs. 4a, 4b,\n4c, 5a, 5b, 5c, 6a, 6b, 6c, 7a, 7b, and 7c). These pre-\nThe above data handling and processing program\nliminary spectra will be superseded by slightly more\ninvolved the cooperation of a large number of orga-\naccurate curves calculated according to standard pro-\nnizations and individuals, many of whom made\ncedures (Hudson et al. 1969b and 1971, Trifunac\nmajor contributions of time under difficult circum-\n1970, and Trifunac et al. 1971), , but the small differ-\nstances. We particularly appreciate the fine coopera-\nences involved will not be significant for most engi-\ntion that we have always received from the Seismo-","372\nSan Fernando Earthquake of 1971\nTO\nRELATIVE VELOCITY RESPONSE SPECTRUM\nRELATIVE VELOCITY RESPONSE SPECTRUM\n50\n71.007 CASTAIC OLD RIDGE ROUTE 2/9/71 0600 PST N69W\n71.008 2/9/71 0600PST L.A. 8244 ORION BLVD. 1ST FLOOR WEST\n50\nOh\n10\n20\n0\n1\n0\n1\n2\n3\n4\n5\n6\n7\n8\n9\n10\n0\n2\n3\n4\n5\n6\n7\n8\n9\n10\nPERIOD IN SECONDS\nPERIOD IN SECONDS\nFigure 4a.-Preliminary relative velocity response spectrum for\nFigure 5a.-Preliminary relative velocity response spectrum for 8244\nCastaic, Old Ridge Route station-horizontal component, N.69° W.,\nOrion Boulevard station-horizontal component, west, 20 km\n29 km from epicenter.\nfrom epicenter.\n70\nRELATIVE VELOCITY RESPONSE SPECTRUM\n200\nRELATIVE VELOCITY RESPONSE SPECTRUM\n50\n71.007 CASTAIC OLD RIDGE ROUTE 2/9/71 0600 PST N21E\n71.008 2/9/71 0600PST L.A. 8244 ORION BLVD. 1ST FLOOR NORTH\n59\nOn\n20\n20\n10\n0\n0\n0\n1\n2\n3\n.4\n5\n6\n7\n8\n9\n10\n0\n1\n2\n3\n4\n5\n6\n7\n8\n9\n10\nPERIOD IN SECONDS\nPERIOD IN SECONDS\nFigure 4b.-Preliminary relative velocity response spectrum for\nFigure 5b.-Preliminary relative velocity response spectrum for 8244\nCastaic, Old Ridge Route station-horizontal component, N.21°E.,\nOrion Boulevard station-horizontal component, north, 20 km\n29 km from epicenter.\nfrom epicenter.\n20\nRELATIVE VELOCITY RESPONSE SPECTRUM\n20\nRELATIVE VELOCITY RESPONSE SPECTRUM\n50\n71.007 CASTAIC OLD RIDGE ROUTE 2/9/71 0600 PST DOWN\n71.008 2/9/71 0600PST L.A. 8244 ORION BLVD. 1ST FLOOR DOWN\n100\n80\n50\n4b\n20\n10\n0\n0\n1\n2\n3\n4\n5\n6\n7\n8\n9\n10\n0\n1\n2\n3\n4\n5\n6\n7\n8\n9\n10\nPERIOD IN SECONDS\nPERIOD IN SECONDS\nFigure 4c.-Preliminary relative velocity response spectrum for\nFigure 5c.-Preliminary relative velocity response spectrum for 8244\nCastaic, Old Ridge Route station-vertical component, 29 km\nOrion Boulevard station-vertical component, 20 km from\nfrom epicenter.\nepicenter.","Strong-Motion Accelerogram Processing\n373\n06\n70\nRELATIVE VELOCITY RESPONSE SPECTRUM\nRELATIVE VELOCITY RESPONSE SPECTRUM\n50\n50\n71.060 2/9/71 0600PST 445 FIGUEROA. SUBBASEMENT N52W\n71.005 2/9/71 0600PST L.A. 250 E. 1ST STREET N54W\n50\n50\nOh\n20\n20\n10\n10\n0\n0\n3\n4\n5\n6\n7\n8\n9\n10\n0\n1\n2\n3\n4\n5\n6\n7\n8\n9\n10\n0\n1\n2\nPERIOD IN SECONDS\nPERIOD IN SECONDS\nFigure 6a.-Preliminary relative velocity response spectrum for 445\nFigure 7a.-Preliminary relative velocity response spectrum for 250\nSouth Figueroa Street station-horizontal component, N.52°W.,\nEast First Street station--horizontal component, N.54°W., 41 km\nfrom epicenter.\n41 km from epicenter.\nTO\n10\nRELATIVE VELOCITY RESPONSE SPECTRUM\nRELATIVE VELOCITY RESPONSE SPECTRUM\n60\n60\n71.005 2/9/71 0600PST L.A. 250 E. 1ST STREET N36E\n71.060 2/9/71 0600PST 445 FIGUEROA. SUBBASEMENT S38W\n50\n9h\n4b\n30\n20\n20\n10\n10\n0\n4\n5\n6\n7\n8\n9\n10\n6\n7\nB\n9\n10\n0\n2\n3\n0\n1\n2\n3\n4\nS\nPERIOD IN SECONDS\nPERIOD IN SECONDS\nFigure 7b.-Preliminary relative velocity response spectrum for 250\nFigure 6b.-Preliminary relative velocity response spectrum for 445\nEast First Street station-horizontal component, N.36°E., 41 km\nSouth Figueroa Street station-horizontal component, S.38°W.,\nfrom epicenter.\n41 km from epicenter.\n28\nRELATIVE VELOCITY RESPONSE SPECTRUM\nRELATIVE VELOCITY RESPONSE SPECTRUM\n24\n24\n71.005 2/9/71 0600PST L.A. 250 E. 1ST STREET DOWN\n71.060 2/9/71 0600PST 445 FIGUEROA. SUBBASEMENT DOWN\n20\n0\n0\n2\n4\n3\n5\n6\n7\n8\n9\n10\n0\n1\n2\n3\n4\n5\n6\n7\n8\n9\n10\nPERIOD IN SECONDS\nPERIOD IN SECONDS\nFigure 7c.-Preliminary relative velocity response spectrum for 250\nFigure 6c.-Preliminary relative velocity response spectrum for 445\nEast First Street station-vertical component, 41 km from\nSouth Figueroa Street station-vertical component, 41 km from\nepicenter.\nepicenter.","374\nSan Fernando Earthquake of 1971\nlogical Field Survey (NOAA) including: W. K.\nREFERENCES\nCloud (now at the Berkeley Seismograph Station at\nBlandford, R. R., McLamore, V. R., and Aunon, J., \"Struc-\nthe University of California), former chief; W. R.\ntural Analysis of Millikan Library From Ambient Vibra-\nMaley, head of the Los Angeles office; and E. C. Eth-\ntions,\" Teledyne Earth Sciences Report No. 616-0268-2107.\nPasadena, 1968, 24 pp.\neridge of the Los Angeles staff. From the San Fran-\nEsteva, L., and Nieto, J. A., \"El Temblor de Lima, Peru,\ncisco office of the Seismological Field Survey, C. F.\noctubre 17, 1966\" (Earthquake of Lima, Peru, October 17,\nKnudson, B. J. Morrill, and their staff of technicians\n1966), Revista Ingenieria, Vol. 37, Mexico D. F., Mexico,\nrendered great assistance. V. Perez of the San\nJan. 1967, pp. 45-62.\nFrancisco office carried out the exacting job of pre-\nHudson, Donald E., Brady, A. Gerald, Trifunac, Mihailo D.,\nliminary checking and scaling of the records and as-\nand Vijayaraghavan, A., \"Strong-Motion Earthquake Acceler-\nsisted with record digitization. A key member of the\nograms-Digitized and Plotted Data, Vol. II-Corrected\nC.I.T. staff was R. J. Dielman who has been assist-\nAccelerograms and Integrated Ground Velocity and Dis-\nplacement Curves, Part A-Accelerograms IIA001 Through\ning the Seismological Field Survey with field installa-\nIIA020,\" Earthquake Engineering Research Laboratory Re-\ntion and servicing and who rendered great service\nport EERL 71-50, California Institute of Technology, Pasa-\nafter the earthquake in the recovery of records, in\ndena, July 1971, 324 pp.\nthe accelerograph site investigations, and in the\nHudson, Donald E., Nigam, N. C., and Trifunac, Mihailo D.,\nhandling of the records for processing. We are very\n\"Analysis of Strong-Motion Accelerograph Records,\" Pro-\nfortunate in being able to obtain from the Lamont-\nceedings of the Fourth World Conference on Earthquake\nDoherty Geological Observatory of Columbia Uni-\nEngineering, Santiago, Chile, January 13-18, 1969, Vol. I,\nAsociacion Chilena de Sismologia e Ingenieria Antisismica,\nversity, Palisades, N.Y., the services of M. D. Tri-\nSantiago, Chile, 1969a, pp. A2-1-17.\nfunac whose past experience in accelerograph data\nHudson, Donald E., Brady, A. Gerald, and Trifunac, Mihailo\nprocessing proved invaluable to us. In a remarkably\nD., \"Strong-Motion Earthquake Accelerograms-Digitized\nshort time, A. G. Brady, with the assistance of A. Vi-\nand Plotted Data, Vol. I-Uncorrected Accelerograms, Part\njayaraghavan, trained a very effective team of digitiz-\nA-Accelerograms IA1 Through IA20,\" Earthquake Engi-\ning operators and accomplished the complicated pro-\nneering Research Laboratory Report EERL 69-20, Cali-\ngraming details necessary for computer processing of\nfornia Institute of Technology, Pasadena, July 1969b,\n204 pp.\nthe accelerograms. At the Jet Propulsion Laboratory,\nKeightley, W. O., \"A Strong-Motion Accelerograph Array With\nwe received very quick cooperation from W. H.\nTelephone Line Interconnections,\" Earthquake Engineering\nPickering, director, and from M. E. Alper, our main\nResearch Laboratory Report EERL 70-05, California Insti-\ncoordinating link. R. B. Ford and R. D. Windmiller\ntute of Technology, Pasadena, Sept. 1970, 35 pp.\nof the photographic processing laboratory were of\nKuroiwa, J. H., \"Vibration Test of a Multistory Building,\"\ngreat assistance in the reproduction of the records,\nEarthquake Engineering Research Laboratory Report, Cali-\nand M. R. Trubert offered very useful advice in lay-\nfornia Institute of Technology, Pasadena, June 1967, 113 pp.\ning the groundwork for the automatic digitizing\nTrifunac, Mihailo D., \"Low Frequency Digitization Errors and\nprocess. The aid of J. D. Patterson in preparing\na New Method for Zero Baseline Correction of Strong-\nbasic maps is also appreciated.\nMotion Accelerograms,\" Earthquake Engineering Research\nLaboratory Report EERL 70-07, California Institute of\nThe program was made possible and its prompt\nTechnology, Pasadena, Sept. 1970, 55 pp.\nimplementation after the earthquake was assured by\nTrifunac, Mihailo D., Udwadia, F. E., and Brady, A. Gerald,\nthe special efforts of C. C. Thiel, C. A. Babendreier,\n\"High Frequency Errors and Instrument Corrections of\nand M. P. Gaus of the Engineering Mechanics De-\nStrong-Motion Accelerograms,\" Earthquake Engineering Re-\npartment, Engineering Division, National Science\nsearch Laboratory Report EERL 71-05, California Institute\nFoundation.\nof Technology, Pasadena, July 1971, 49 pp.","Analysis of Pacoima Dam Accelerogram\nINTRODUCTION\nThe Pacoima Dam accelerogram, recorded vir-\ntually in the center of the epicentral region, is of\nunique importance for earthquake engineering and\nfor strong-motion seismology. Not only are the accel-\neration levels considerably higher than have ever\nCONTENTS\nbeen recorded for any past earthquake, but the se-\nPage\nquence of initial aftershocks as revealed on the com-\n375 INTRODUCTION\nplete record gives an unprecedented picture of the\n375\nACCELEROGRAPH SITE\nearly stages of seismic energy release.\n376\nACCELEROGRAPH PERFORMANCE\n383\nRESPONSE SPECTRA\nBecause of the special interest in this record and\n386 ENGINEERING SIGNIFICANCE OF PACOIMA\nbecause the local site conditions required some spe-\nRESULTS\ncial studies and explanations, the Pacoima Dam rec-\n388 COMPLETE PACOIMA RECORD\n388 ACKNOWLEDGMENTS\nord was studied very carefully immediately following\n390\nREFERENCES\nthe earthquake. The present section, based on a\npaper which appeared in the Bulletin of the Seismo-\nlogical Society of America (Trifunac and Hudson\n1971), is included in this volume to indicate the\nkind of analysis to which all accelerograms will ulti-\nmately be subjected and to complete the picture of\nthe overall scope of the cooperative program be-\ntween the Seismological Field Survey of the National\nOceanic and Atmospheric Administration (NOAA)\nand the California Institute of Technology (C.I.T.).\nAlthough this 6.4 magnitude earthquake is not\nlarge from the seismological point of view, it was as-\nsociated with very severe ground motions and must\nbe ranked as a major event from the standpoint of\ndamage and of general engineering implications.\nACCELEROGRAPH SITE\nFigure 1 shows the location of the main shock and\nrepresentative aftershocks, indicating the position of\nPacoima Dam near to the center of energy release.\nM. D. TRIFUNAC\nEditors' note.-This paper is adapted from the report: Hudson,\nD. E. HUDSON\nDonald E. (ed.) Strong-Motion Instrumental Data on the San\nFernando Earthquake of Feb. 9, 1971, Earthquake Engineering\nEarthquake Engineering Research\nResearch Laboratory, California Institute of Technology, Pasadena,\nLaboratory\nand Seismological Field Survey, National Oceanic and Atmospheric\nCalifornia Institute of Technology\nAdministration, San Francisco, Sept. 1971, 260 pp.\nPasadena, Calif.\n375","376\nSan Fernando Earthquake of 1971\nextent to which presently unknown details of the\nN\n3.0-3.4\nridge structure may influence the recorded motions\n3.5-3.9\n4.0 4.4\nis, for the time being, a matter for speculation.\no\n5\n10 km\n4.5 5.1\nAs depicted in figure 4, about 5 m to the west of\n34°30\nCastaic\nthe accelerograph, a small rockslide occurred (about\nMain Shock\nActon\n5 to 10 cu m) during the earthquake. Fortunately,\nSolemint\nit was not large enough to disturb the accelerograph\nPacoima Dam\nSaugus\nfoundation. One of the cracks penetrated into the\nAccelerograph\nfoundation of the instrument house (fig. 6) although\nNewhall\nthe instrument pier itself, which was separated by an\ninch or SO from the foundation of the circular house,\nwas not cracked. Two months after the earthquake,\nfault traces\nchanges in the configuration of these foundation\nSylmar\nGranada\ncracks indicate that long-term motion of some kind\nHills\nSunland\nis continuing. After the earthquake, the instrument\nSan Fernando\n34°15'\nChatsworth\nmounting pier was still attached solidly to the foun-\n7118\ndation rock, and the mounting bolts that attach the\nLa Canada\nVan Nuys\naccelerograph to the pier were tight and undisturbed.\nBurbank\nThe only sign of disturbance was a small, permanent\nGlendale\ntilt of the instrument during the earthquake, esti-\nLos Angeles\nmated to be on the order of 0.5° in the northwest\ndirection. The amount of this permanent tilt can be\nestimated with fair accuracy from the adjustments\nFigure 1.-Map of epicenters of main shock and representative\nrequired to relevel the accelerograph after the earth-\naftershocks of San Fernando earthquake, magnitude 3.0 and\ngreater, through February 23, 1971 (reproduced by permission\nquake (Dielman 1971) A view of the accelerograph\nfrom the California Institute of Technology, Division of Geo-\nmounted on its concrete pedestal within the circular\nlogical and Planetary Sciences 1971).\nhouse after the earthquake is shown in figure 7.\nA plan view of the dam and its abutment area,\nFigure 2 shows an oblique aerial photograph look-\nwith the instrument locations indicated, is shown in\ning southwest over the Pacoima Dam site, with the\nfigure 8. The locations of the SR-100 Wilmot Seis-\nSan Fernando Valley in the distance. The location of\nmoscope on the crest of the dam near the tower and\nthe AR-240 accelerograph at Pacoima Dam is\nthe AR-240 strong-motion recorder near the foot\nshown, and the locations of the two heavily damaged\nbridge between the shelter house and the spillway\nhospitals are indicated in the background. Figure 3\ntunnel are shown. During the first few seconds of\nshows a closeup view of the dam, and the location of\nearthquake motion, the motion of the crest of the\nthe accelerograph on a rocky spine adjacent to the\ndam was SO severe that the seismoscope glass record\ndam abutment is indicated. Figure 4 shows a view of\nplate was dislodged from its retaining ring, prevent-\nthe circular instrument house seen from below on\ning any usable seismoscope record from being ob-\nthe dam, and figure 5 is a view of the dam and the\ntained.\ninstrument house from above, looking north. In\nFigure 1 shows the setting of the site within the af-\nboth of these figures, extensive cracking of the gneis-\ntershock region. The site is approximately 8 km\nsic granite-diorite rock can be noted. Many cracks\nsouth of the instrumentally determined epicenter\npenetrate through the smooth gunite coating into\nand is nearly in the center and above the tentative\nthe rock below.\nfault dislocation surface, striking N.72°W. and drop-\nHowever, the extent to which the surface fractures\nping about 45° toward the north (Kamb et al.\nof the gunite coating reflect the conditions of the\n1971)\nmajor rock mass below is not known. Relatively\nsmall cracks of the dimensions of the gunite fractures\nACCELEROGRAPH PERFORMANCE\nwould be associated with higher frequencies than\nthose involved in the approximately 10-Hz motions\nThe AR-240 strong-motion accelerograph at the\nobserved on the record (figs. 10, 11, and 12) The\nPacoima Dam site records two horizontal and one","Pacoima Dam Accelerogram\n377\nvertical component of acceleration on 12-inch-wide the Los Angeles County Flood Control District and\nis a part of the southern California strong-motion ac-\nphotographic paper. The accelerograph transducers\ncelerograph network maintained by the Seismologi-\nhave natural frequencies of about 19 Hz and critical\ncal Field Survey, NOAA.\ndamping of approximately 60 percent (Hudson\nAs mentioned previously, the accelerograph foun-\n1970). The instrument is one of several owned by\nSYLMAR FAULT\nVETERANS FAULT\nOLIVE VIEW\nVETERANS\nHOSPITAL\nHOSPITAL\nACCELEROGRAPH SITE\nFigure 2.-Oblique aerial view, looking southwest over Pacoima Dam site.","ACCELEROGRAPH SITE\nSEISMOSCOPE SITE\nFigure 3.-View of Pacoima Dam.","Pacoima Dam Accelerogram\n379\nINSTRUMENT HOUSE\nINSTRUMENT\nPIER\nCRACK\nFigure 6.-Cracks in foundation of instrument house.\nFigure 4.-Strong-motion AR-240 accelerograph site\nand small rockslide.\nFigure 7.-AR-240 accelerograph after earthquake.\nFigure 5.-View of dam and instrument site, looking north.","50\n1800\nmeters\n1825\n1850\n1875\n1900\n1925\nMOTION RECORDER\no\nAR-240 - STRONG\n1975\nFigure 8.-Pacoima Dam site map with AR-240 accelerograph and SR-100 Wilmot Seismoscope.\nSHELTER\nHOUSE\n1900\n226\nWILMOT SEISMOSCOPE\n2000\nN\nSR 100\nTOWER","Pacoima Dam Accelerogram\n381\nTable 1.-Accelerograph baseline shift-lower bounds\ndation remained tilted through a small angle,\nestimated to be about 0.5°, after the earthquake.\nDirection of baseline shift\nBaseline shift\nfor tilt in northwest direction\nThis small angle was sufficient to actuate the starting\npendulum, and the instrument recorded continously\ncm/sec2\n13.3\nN.74°E\nfor some 6 minutes until it ran out of paper. During\n7.7\nDown\n2.6\nN.16°W\nthis interval, at least 30 aftershocks were recorded.\nIn one sense, the small permanent tilt of the founda-\nThe integration of the digitized accelerograms\ntion can be considered to be a fortunate occurrence,\n(fig. 9) including the first aftershock (about 42 sec-\nbecause it permitted the recording of the beginning\nonds), indicates that the tilt must have occurred\nof the aftershock sequence and indicated the exact\nwithin the first 10 to 15 seconds of the strong mo-\nsequence of aftershock events in the epicentral re-\ntion. This can be concluded from the behavior of\ngion. These details of the aftershock sequence are of\nthe integrated velocity curves. If a straight line fitted\nimportance in investigating the mechanism of energy\nto the velocity curves (Trifunac 1970) over the in-\nrelease (Trifunac 1972),\nterval between 12 and 42 seconds is extrapolated\nTo check the instrument performance, tilt, free\nback to zero time, the resulting displacement curves\nvibration, and damping tests were performed after\nindicate the following permanent displacement\nthe earthquake. The tilt test showed that the sensi-\namplitudes after the earthquake (table 2)\ntivity of the accelerograph had not changed sig-\nnificantly. The alignment of the transducer axes in\nTable 2.-Permanent displacement amplitudes\nrelation to the instrument base also was checked dur-\ning the tilt test (Trifunac and Hudson 1970) It was\nPermanent\nfound that the two horizontal transducers were well\nPermanent displacement in direction\ndisplacement\namplitudes\nwithin a 1° alignment. The vertical transducer sensi-\nm\ntivity vector was about 5° from the vertical in the\n1.0\nN.74°E\n1.3\nUp\nlongitudinal direction.\n1.7\nS.16°E\nJudging from the accuracy of the typical strong-\nmotion accelerograph (Trifunac and Hudson 1970)\nIt might be tempting to interpret these results in\nit may be concluded that the AR-240 accelerograph\nterms of the observed surface fault displacements\nat the Pacoima Dam site performed essentially to\n(Kamb et al. 1971, fig. 1) However, if it is assumed\nspecifications and that the recorded acceleration\nthat the tilting indeed took place during the first 10\ntraces may be adopted as representative of the actual\nseconds, the lower bounds for the \"permanent dis-\nmotion of the instrument foundation. The peak ac-\nplacements\" obtained only from the tilt would be\nceleration values remained on-scale on the photo-\n(based on data in table 1) as shown in table 3.\ngraphic paper; there is no evidence of appreciable\nnonlinear response at the maximum amplitudes in-\nTable 3.-Permanent displacement amplitudes-lower bounds\nvolved.\nLower bounds on\nAfter the earthquake, the instrument base was\npermanent displacement\nPermanent displacement in\namplitudes\ndirection\ntilted in approximately the northwest direction in\ncaused by tilt\nrelation to its position before the earthquake. Be\nm\ncause the preliminary calculations of the ground dis-\n4\nS.74°W\n3\nUp\nplacement indicated a significant shift in the acceler-\n1\nS.16°E\nograph baseline, clearly a consequence of such tilt,\ntests were conducted to ascertain likely limits for\nFor this calculation, it was assumed that the accel-\nsuch displacements. The accelerograph was tilted in\neration zero baseline is determined by its fixed posi-\nthe northwest direction through an angle that just\ntion after the tilt is completed-10 seconds after the\ninstrument has triggered-and that the tilt occurred\nclosed the starter pendulum gap. In this way, a lower\nuniformly over the 10-second interval. Comparing\nbounds estimate of the acceleration baseline shift\nthe amplitudes given in tables 2 and 3, it may be\ncould be determined. The results of this test are\nconcluded that the tilt was large enough to prevent\ngiven in table 1.","382\nSan Fernando Earthquake of 1971\nGROUND ACCELERATION\n2/9/71 0600 PST PACOIMA DAM, CALIFORNIA\n1000\nS 74°W COMPONENT\no\n1000\no\n10\n20\n30\n40\nSECONDS\nGROUND ACCELERATION\n2/9/71 0600 PST PACOIMA DAM, CALIFORNIA\n1000\nDOWN COMPONENT\n1000\no\n10\n20\n30\n40\nSECONDS\nGROUND ACCELERATION\n2/9/71 0600 PST PACOIMA DAM, CALIFORNIA\n1000\nS16°E COMPONENT\no\n1000\nO\n10\n20\n30\n40\nSECONDS\nFigure 9.-Plot of digitized accelerograms recorded at Pacoima Dam.","Pacoima Dam Accelerogram\n383\nany estimation of the permanent displacements asso-\nmotion. Thus, the displacements in figures 10, 11,\nciated with the earthquake.\nand 12 may contain an unknown contribution from\nthe tilting of the instrument in addition to the ac-\nData Processing and Ground-Motion Calculations.-\ntual ground motion. Nevertheless, the computed\nFigure 9 is a plot of the first 42 seconds of the digi-\nground motion indicates that the biggest displace-\ntized accelerograms, including the first aftershock.\nments were vertical and in the north-south direction,\nThe strong motion representing the main energy re-\nin general agreement with observed surface faulting\nlease lasted about 7 seconds, and the first aftershock\n(fig. 1)\nwas recorded about 29 seconds after the instrument\nwas triggered. The first 15-second portion of the ac-\nIn terms of acceleration amplitude, the ground\nceleration was chosen for the analysis of ground mo-\nmotions recorded at the Pacoima Dam site are the\ntion.\nlargest measured during any earthquake. The rela-\ntively short duration of the severe shaking is a conse-\nThe AR-240 accelerogram was digitized at C.I.T.\nquence of the short fault rupture.\non a Benson-Lehner 099D Datareducer and was\nprocessed by the standard methods developed in re-\ncent years for strong-motion accelerogram analysis\nRESPONSE SPECTRA\n(Hudson et al. 1969). The quality of the original\nrecord was excellent. The trace was clear and contin-\nThe computed relative velocity and S response\nuous, with the exception of one 1.25g peak on the\nspectra (Sa = displacement spectrum and T = pe-\nS.16°E. component at 7.6 seconds. At this point, the\nriod) are shown in figures 13 and 14. For each\ntrace was lost above the 1g level and had to be\nacceleration component, the response spectrum curves\nextrapolated. Because of the excellent photographic\nwere calculated for 0, 2, 5, 10, and 20 percent of\nquality of the trace, this extrapolation could be car-\ncritical damping. As expected, the relative velocity\nried out with confidence. The error in the peak is\nbelieved to be less than 0.1g, which would not ap-\nand S spectra are very similar for short periods,\npreciably influence any calculations based on the ac-\ncelerogram. This digitization of the Pacoima Dam\nwhile the spectrum falls off more rapidly for\naccelerogram is believed to be as accurate as may be\nlonger periods. It may be recalled that the zero-\nachieved by presently available techniques and equip-\ndamped relative velocity response spectrum is an ap-\nment.\nproximate representative of the Fourier amplitude\nThe baseline correction was performed by high-\nspectrum of the accelerogram.\npass filtering of the uncorrected data above the 0.07-\nThe spectrum curves for the horizontal S.16°E.\nHz frequency. This means that all periods longer\nand S.74°W components show peaks at about 0.4-\nthan approximately 16 seconds have been removed\nand 1.4-second periods, while the spectra for the ver-\nfrom the record; hence, no information on perma-\ntical component indicate predominant periods near\nnent displacements is to be expected from the analy-\n0.3 and 2 seconds. The short duration of the strong\nsis. This filtering procedure and the least squares fit-\nmotion is reflected in the nature of the response\nting of a straight line to the ground velocity, which\ngives an estimate of the initial velocity, constitute a\nspectra of figure 13, which shows a relatively flat\nnew method recently proposed for standard baseline\ncharacter for periods longer than 5 or 6 seconds. In\ncorrection of the strong-motion accelerograms (Tri-\nthe period range from 0.5 to about 3 seconds, the\nfunac 1970) The resulting acceleration, velocity,\nspectral amplitudes are similar to those calculated\nand displacement curves for the three recorded com-\nfor the El Centro 1940 accelerogram (Alford et al.\nponents are shown in figures 10, 11, and 12. As\n1951) The high-frequency spectral amplitudes in\nshown in these figures, the maximum acceleration is\nthe Pacoima Dam record are not incompatible with\n1.25g for both horizontal components and 0.70g for\npast experience. Similar high-frequency characteris-\nthe vertical component, and the peak velocity is 115\ntics can be noted on records from the Parkfield,\ncm/sec.\nCalif., earthquake of June 27, 1966 (Housner and\nThe tilting of the instrument base must have\nTrifunac 1967), and for the Koyna, India, earth-\ntaken place during the first 15 seconds of the strong\nquake of December 10, 1967 (Gupta et al. 1971).","San Fernando Earthquake of 1971\n384\nDirect comparisons with these earthquakes are diffi-\nThe strong earthquake ground motion recorded\ncult because of significant differences in the locations\nduring the 1966 Parkfield, Calif., earthquake (Hous-\nof the accelerographs, with respect to the pattern of\nner and Trifunac 1967) may be considered as a typi-\nfaulting, and in the sizes of the events. Table 4 gives\ncal example of a short, impulsive-type ground mo-\ntion. On the other hand, the motion recorded at El\nan approximate idea of such comparisons.\nGROUND ACCELERATION\n1000\no\n1000\nI\nI\nI\no\n5\n10\n15\n100\nGROUND VELOCITY\n50\no\n50\n100\nI\nI\nI\no\n5\n10\n15\n50\nGROUND DISPLACEMENT\no\n50\no\n5\n10\n15\nSECONDS\nFigure 10.-S.74°W. motion, Pacoima Dam.","Pacoima Dam Accelerogram\n385\n1000\nGROUND ACCELERATION\no\n1000\nI\nI\nI\no\n5\n10\n15\n100\nGROUND VELOCITY\n50\no\n50\n100\nI\nI\nI\nO\n5\n10\n15\n50\nGROUND DISPLACEMENT\no\n50\nI\nI\no\n5\n10\n15\nSECONDS\nFigure 11.-Down motion, Pacoima Dam.\ndisplacement curves, plotted in figures 10, 11, and\nCentro during the 1940 Imperial Valley, Calif.,\n12, show that from the engineering point of view,\nearthquake (Trifunac and Brune 1970) is an exam-\nple of the relatively long shaking produced by multi-\nthe duration of the energy release during the San\nple events successively occurring along a fault about\nFernando earthquake is somewhere between that re-\n40 miles long. The ground acceleration, velocity, and\nleased at Parkfield and that at El Centro.","San Fernando Earthquake of 1971\n386\nGROUND ACCELERATION\n1000\no\n1000\no\n5\n10\n15\n100\nGROUND VELOCITY\n50\no\n50\n100\no\n5\n10\n15\n50\nGROUND DISPLACEMENT\no\n50\nI\nI\no\n5\n10\n15\nSECONDS\nFigure 12.-S.16°E. motion, Pacoima Dam.\nENGINEERING SIGNIFICANCE OF PACOIMA that indicate high spectral The accelerations response spectrum do not curves of alone the\nsevere damage to structures. It always is also tell clear the\nRESULTS\nfacts about strong earth- cannot whole story. give a complete acceleration picture of history. the effects These facts\nquake One amplitudes ground of the motion important in themselves is that large do ground not necessarily accelera- time duration of the\ntion","Pacoima Dam Accelerogram\n387\nhave been clearly demonstrated by the spectra calcu-\nlated for the Parkfield earthquake (Housner and\nTrifunac 1967) and for the El Centro earthquake\nSd\nRESPONSE SPECTRUM\n2h2\n(Alford et al. 1951) . Thus, the high spectral ampli-\n71.001 2/9/71 0600 PST PACOIMA DAM, CALIFORNIA\nS 74°W COMPONENT\n200\ntudes in figures 13 and 14 do not necessarily mean\n160\n20\nRELATIVE VELOCITY RESPONSE SPECTRUM\nOh2\n71.001 2/9/71 0600PST PACOIMA DAM. CAL S74W\n80\n200\n0h\n10\n5\n6\n7\n8\n9\n0\n2\nPERIOD IN SECONDS\n20\n80\nRESPONSE SPECTRUM\nSd\n120\n71.001 2/9/71 0600 PST PACOIMA DAM, CALIFORNIA\n0h\nDOWN COMPONENT\n8\n0\n0\n2\n3\n4\n5\n6\n7\n8\n9\n10\n80\nPERIOD IN SECONDS\nOhl\n50\nRELATIVE VELOCITY RESPONSE SPECTRUM\n120\n0th\n71.001 2/9/71 0600PST PACOIMA DAM. CAL DOWN\n100\n20\nZip\n7\n8\n9\n10\n2\n5\n6\nPERIOD IN SECONDS\n50\nOh\nRESPONSE SPECTRUM\nSd\nOh2\n71.001 2/9/71 0600 PST PACOIMA DAM, CALIFORNIA\n20\nS16° E COMPONENT\n200\n160\n0\n2\n3\n5\n6\n7\n8\n9\n10\nPERIOD IN SECONDS\n20\nRELATIVE VELOCITY RESPONSE SPECTRUM\nOho\n80\n71.001 2/9/71 0600PST PACOIMA DAM. CAL S16E\n0th\n5\n6\n7\n8\n9\n10\n0\n1\n2\n3\n4\nPERIOD IN SECONDS\nFigure 14.-Sd (2/T) response spectra. Pacoima Dam. Curves are\nfor 0, 2, 5, 10, and 20 percent of critical damping.\n80\nthat this motion was very destructive for structures\n9th\nof all types. Pacoima Dam, for example, apparently\nsuffered no significant damage.\n0\n2\n3\n4\nS\n6\n7\n8\n9\n10\nPERIOD IN SECONDS\nThe San Fernando earthquake, with strong mo-\nFigure 13.-Relative velocity response spectra, Pacoima Dam.\ntion lasting about 7 seconds, now becomes an excel-\nCurves are for 0, 2, 5, 10, and 20 percent of critical damping.","388\nSan Fernando Earthquake of 1971\nTable 4.-Comparison of high-frequency spectral amplitudes from four earthquakes\nPeak\nPeak\nApprox. Sv\nEarthquake\nMagnitude\nDistance*\nacceleration\nvelocity\nfor T> 3\nsec\nkm\nin./sec\nin./sec\ng\nSan Fernando, 1971\n6.6\n5\n1.25\n45\n50\nEl Centro, 1940\n6.4\n10\n0.33\n17\n30\nParkfield, 1966\n5.5\n0.2\n0.50\n28\n30\nKoyna, India, 1967\n6.0-6.3\n5\n0.63\n9\n15\n*\nEstimated distance from accelerograph to portion of fault surface\nHousner and Trifunac (1967).\nassociated with maximum energy release.\nGupta et al. (1971).\nCalifornia Institute of Technology (1971).\nAki (1968).\nb Trifunac and Brunc (1970).\nf\nKrishna et al. (1969).\nlent example of a strong ground acceleration of short\ndulum kept the accelerograph running to record a\nto moderately long duration. If the shaking had con-\nwhole initial sequence of aftershocks in exact time\ntinued for another few seconds, much greater\nscale. Because of the special interest of this complete\ndamage would have resulted; many buildings and\naccelerogram for earthquake mechanism studies\nbridges, only partially damaged, would have col-\n(Trifunac 1972) and for strong-motion seismology\nlapsed. It is mainly this effect of the duration of\nin general, the complete 360 seconds of the accelero-\nshaking on structural damage that calls for detailed\ngram are reproduced to scale in figure 15 (a, b, C, d)\ninvestigations of the pattern of earthquake energy re-\nlease in time.\nACKNOWLEDGMENTS\nCOMPLETE PACOIMA RECORD\nWe are indebted to the Los Angeles County Flood\nThe Pacoima Dam record is unique in that a\nControl District for their forward-looking program\nsmall permanent tilt of the horizontal starter pen-\nof instrumentation and, in particular, to E. J. Ziel-\nS 74° W\nDOWN\nS 16° E\n1g\nSECONDS\no\n10\n20\n30\n40\no\nS 74° W\nDOWN\nS 16° E\nSECONDS\n50\n60\n70\n80\n90\nFigure 15a.-Pacoima Dam accelerograph record, sheet 1.","Pacoima Dam Accelerogram\n389\nS 74° W\nDOWN\nS 16° E\nSECONDS\n1g\n100\n110\n120\n130\no\nS 74° W\nDOWN\nS 16° E\nSECONDS\n140\n150\n160\n170\n180\nFigure 15b. - Pacoima Dam accelerograph record, sheet 2.\nS 74° W\nDOWN\nS 16° E\nSECONDS\n1g\n190\n200\n210\n220\n230\no\nS 74° W\nDOWN\nS 16° E\nSECONDS\n230\n240\n250\n260\n270\nFigure 15c. - Pacoima Dam accelerograph record, sheet 3.","390\nSan Fernando Earthquake of 1971\nS 74° W\nDOWN\nS 16° E\nSECONDS\n1g\n280\n290\n300\n310\n320\no\nS 74° W\nDOWN\nS 16° E\nSECONDS\n330\n340\n350\n360\nFigure 15d.-Pacoima Dam accelerograph record, sheet 4.\nbauer of that organization for cooperation with in-\nratory, California Institute of Technology, Pasadena, 1971\n(personal communication)\nstrument siting, for site visits after the earthquake,\nGupta, H. K., Rastogi, B. K., and Narain, H., \"The Koyna\nand for providing maps and information on the site\nEarthquake of December 10, 1967: a Multiple Seismic\nand the dam.\nEvent,\" Bulletin of the Seismological Society of America,\nThe work was done while the senior author M. D.\nVol. 61, No. 1, Feb. 1971, pp. 167-176.\nTrifunac was a member of the staff of the Lamont-\nHanks, Thomas C., Jordan, Thomas H., and Minster, J. Ber-\nnard, \"Precise Locations of Aftershocks of the San Fernando\nDoherty Geological Observatory of Columbia Uni-\nEarthquake 2300 (GMT) February 10-1700 February 11,\nversity and was completed at the Earthquake En-\n1971,\" The San Fernando, California, Earthquake of\ngineering Research Laboratory of the California\nFebruary 9, 1971, Geological Survey Professional Paper 733,\nInstitute of Technology.\nU.S. Geological Survey and the National Oceanic and\nAtmospheric Administration, U.S. Department of the In-\nterior and U.S. Department of Commerce, Washington,\nREFERENCES\nD.C., 1971, pp. 21-23.\nHousner, G. W., \"Strong Ground Motion,\" Earthquake Engi-\nAki, K., \"Seismic Displacements Near a Fault,\" Journal of Geo-\nneering, Prentice-Hall, Inc., Englewood Cliffs, N.J., 1970,\nphysical Research, Vol. 73, No. 16, Aug. 1968, pp. 5359-5376.\npp. 75-91.\nAlford, J. L., Housner, G. W., and Martel, R. R., \"Spectrum\nHousner, G. W., and Trifunac, Mihailo D., \"Analysis of Accel-\nAnalysis of Strong-Motion Earthquakes,\" Earthquake Engi-\nprograms-Parkfield Earthquake,\" Bulletin of the Seismo-\nneering Research Laboratory Report, California Institute of\nlogical Society of America, Vol. 57, No. 6, Dec. 1967,\nTechnology, Pasadena, 1951, 129 pp.\npp. 1193-1220.\nCalifornia Institute of Technology, Division of Geological and\nHudson, Donald E., \"Ground Motion Measurements,\" Earth-\nPlanetary Sciences, \"Preliminary Seismological and Geologi-\nquake Engineering, Prentice-Hall, Inc., Englewood Cliffs,\ncal Studies of the San Fernando, California, Earthquake of\nN.J., 1970, pp. 107-125.\n9 February 1971,\" Bulletin of the Seismological Society of\nHudson, Donald E., Brady, A. Gerald, and Trifunac, Mihailo\nAmerica, Vol. 61, No. 2, Apr. 1971, pp. 491-495.\nD., \"Strong Motion Earthquake Accelerograms-Digitized\nDielman, Richard J., Earthquake Engineering Research Labo-\nand Plotted Data, Vol. I-Uncorrected Accelerograms, Part","Pacoima Dam Accelerogram\n391\nLaboratory Report EERL 70-07, California Institute of\nA-Accelerogram IAI Through IA20,\" Earthquake En-\ngineering Research Laboratory Report EERL 69-20, Cali-\nTechnology, Pasadena, Sept. 1970, 55 pp.\nTrifunac, Mihailo D., \"Stress Estimates for the San Fernando,\nfornia Institute of Technology, Pasadena, July 1969, 204 pp.\nCalifornia, Earthquake of February 9, 1971: Main Event\nKamb, Barclay, Silver, L. T., Abrams, M. J., Carter, B. A.,\nand Thirteen Aftershocks,\" Bulletin of the Seismological\nJordan, Thomas H., and Minster, J. Bernard, \"Pattern of\nSociety of America, Vol. 62, No. 3, June 1972, pp. 721-750.\nFaulting and Nature of Fault Movement in the San Fer-\nTrifunac, Mihailo D., and Brune, James N., \"Complexity of\nnando Earthquake,\" The San Fernando, California, Earth-\nEnergy Release During the Imperial Valley, California,\nquake of February 9, 1971, Geological Survey Professional\nEarthquake of 1940,\" Bulletin of the Seismological Society\nPaper 733, U.S. Geological Survey and the National Oceanic\nand Atmospheric Administration, U.S. Department of the\nof America, Vol. 60, No. 1, Feb. 1970, pp. 137-160.\nTrifunac, Mihailo D., and Hudson, Donald E., \"Laboratory\nInterior and U.S. Department of Commerce, Washington,\nEvaluations and Instrument Corrections of Strong-Motion\nD.C., 1971, pp. 41-54.\nAccelerograms,\" Earthquake Engineering Research Labora-\nKrishna, Jai, Chandrasekaran, A. R., and Saini, S. S., \"Analysis\ntory Report EERL 70-04, California Institute of Tech-\nof the Koyna Accelerogram of December 11, 1967,\" Bulletin\nof the Seismological Society of America, Vol. 59, No. 4, Aug.\nnology, Pasadena, Aug. 1970, 113 pp.\nTrifunac, Mihailo D., and Hudson, Donald E., \"Analysis of\n1969, pp. 1719-1731.\nthe Pacoima Dam Accelerogram-San Fernando, California,\nTrifunac, Mihailo D., \"Low Frequency Digitization Errors and\nEarthquake of 1971,\" Bulletin of the Seismological Society\na New Method for Zero Baseline Correction of Strong\nMotion Accelerograms,\" Earthquake Engineering Research\nof America, Vol. 61, No. 5. Oct. 1971, pp. 1393-1411.","","Velocity Response Envelope Spectrum\nas a Function of Time\nINTRODUCTION\nBecause of their special interest to engineering\nseismology, five important accelerograms from the\nFebruary 9, 1971, San Fernando earthquake were\nchosen for more detailed spectral analysis. The spec-\ntrum of the velocity response envelope as a function\nCONTENTS\nof time for 5 percent of critical damping is calcu-\nPage\nlated for the horizontal component of these five rec-\n393\nINTRODUCTION\nords. The stations from which these records were ob-\n393\nVELOCITY RESPONSE ENVELOPE\ntained range from 6.9 to 41 km in distance from the\nSPECTRUM (VRES)\n394\nCOMMENTS ON VRES, SAN FERNANDO\nepicenter of the earthquake. The records are those\nEARTHQUAKE\nfor Pacoima Dam, Castaic (Old Ridge Route), 8244\n395 CONCLUSIONS\nOrion Boulevard, 250 East First Street, and 445\n395 ACKNOWLEDGMENTS\n395\nREFERENCES\nSouth Figueroa Street. Because of the high accelera-\ntions experienced at the Pacoima Dam site, it be-\ncame of great interest to study the effect of peak ac-\ncelerations on the velocity response and its time\nduration.\nVELOCITY RESPONSE ENVELOPE\nSPECTRUM (VRES)\nThe digital data used to calculate the response\nspectrum are uncorrected accelerogram data digitized\nat the California Institute of Technology (C.I.T.).\nThe difference in the results for response spectra,\nusing uncorrected data, corrected data for instru-\nment constants, and a more exacting baseline correc-\ntion, is of minor significance for most engineering\napplications and is not considered in this paper.\nThe velocity response spectrum has been calcu-\nlated previously for these five sites by Hudson\n(1971) and by Trifunac and Hudson (1971) As\nVIRGILIO PEREZ\npointed out by Trifunac (1971) and Arms (1971),\nSeismological Field Survey\nmuch detailed information can be obtained by study-\nEarth Sciences Laboratories\ning the response spectrum as a function of time.\nEnvironmental Research Laboratories, NOAA\n393","San Fernando Earthquake of 1971\n394\nThe velocity response spectrum is obtained from\nseconds at every 0.2 second. This scheme was chosen\nthe well-known equation of motion given by the sin-\nto obtain a good distribution density of the higher\ngle-degree-of-freedom, viscously damped linear oscil-\nfrequencies that are of a more oscillatory nature. For\nlator expressed by the differential equation:\neach period, the envelope of single-degree-of-freedom\noscillator response was approximated by connecting\nthe absolute values of all the peaks of the response\nwhere\ncurve. The envelope curve was then interpolated at\nX = relative motion of the mass of the oscillator;\nequal time intervals of 0.1 second for Pacoima Dam,\n1 = fraction of critical viscous damping;\nw = natural frequency of vibration; and\n250 East First Street, and 445 South Figueroa Street\na(t) = absolute ground acceleration.\nand at 0.2-second intervals for Castaic (Old Ridge\nTrifunac (1971) has shown that the single-degree-\nRoute) and 8244 Orion Boulevard.\nof-freedom, viscously damped linear oscillator acts as\nThese 40 periods, with their respective VRES cal-\na narrow-band filter which amplifies the input fre-\nculated at equal time intervals, generate a rectangu-\nquencies, centered around the testing frequency,\nlar grid of spectral values. For visual ease, contours\nwith a /2 delay of the response. Thus, it would be\nof equal amplitude can then be produced by plotting\nexpected that the maximum response of a lightly\ninterpolated values from the grid, giving a topo-\ndamped oscillator, induced by a peak ground acceler-\ngraphical map of VRES amplitude values as a func-\nation, would come soon after the peak, with the lag\ntion of time and period. In the examples that follow\nin time approximated by one-fourth the length of\n(figs. 1 through 10), contour maps are shown with\nthe period of the oscillator used. For short periods,\neach amplitude level identified by different shading.\nthe response as a function of time of the single-\nTo the right of each topographical map, the maxi-\ndegree-of-freedom oscillator would be highly oscilla-\nmum relative velocity response spectrum is plotted in\ntory, with the frequency components of the response\nthe usual manner and is drawn to the same scale as\ncentered around the period of the oscillator. A\nthe graph to the left. Below the topographical map,\nsmoother curve that lends itself to analysis can be\nthe acceleration is plotted to the same scale. In es-\ngenerated by calculating the envelope of the relative\nsence, the topographical map shows the peaks and\nvelocity response as a function of time. The envelope\nvalleys of VRES as a function of time and period; on\nof the response includes all the information required\nthe right side, the maximum velocity response spec-\nto calculate the maximum relative velocity response\ntrum shows the silhouette of the peaks.\nspectrum as it is normally defined. It also retains a\nhistory of the response peaks as they vary in time.\nCOMMENTS ON VRES, SAN FERNANDO\nFor a given amplitude level, the significance of study-\nEARTHQUAKE\ning the time duration of the envelope curve means\nFigures 1 through 10 show the contour maps of\nthat the oscillatory motion of the response lasted that\nVRES as a function of time. The different amplitude\nlength of time, with amplitudes equal to or higher\nlevels of VRES are illustrated clearly, and one can\nthan the given amplitude. For brevity, the relative\neasily compute the duration of any given level and\nvelocity response envelope spectrum will be referred\nthe range of periods for which this level is reached\nto as VRES.\nor exceeded. A summary of some of the highlights is\nIn most engineering structures, the equivalent vis-\ngiven in tables 1, 2, and 3. For example, table 1 lists\ncous damping is found in the range from 1 to 5 per-\nthe five stations chosen for analysis, the directions of\ncent of critical damping. For this study, a 5 percent\nthe horizontal components, the epicentral distances,\nof critical damping factor was chosen in calculating\nthe length of records used in calculating the re-\nVRES.\nsponse, and the maximum ground accelerations and\nFollowing is an explanation of the method by\nVRESs and their respective times of occurrence.\nwhich VRES as a function of time was produced.\nFirst, the single-degree-of-freedom oscillator re-\nTable 2 shows the direction and the period at\nsponse was calculated for 40 different undamped nat-\nwhich maximum values of VRES were experienced\nural periods. The periods selected were from 0.2 to\nand the time increment before, soon after, or long\n1.5 seconds at intervals of 0.05 second, from 1.5 to\nafter the maximum ground-acceleration input OC-\n2.0 seconds at every 0.1 second, and from 2.0 to 3.6\ncurred. Of the 10 components analyzed, seven can be","Velocity Response Envelope Spectrum\n395\nconsidered independent of maximum acceleration.\nAlthough the response spectrum as presented in\nThe other three components lag within a cycle of\nthis paper gives a great amount of detailed informa-\nthe time of maximum acceleration. For example, the\ntion about the time history of the response, more\nlargest ground-acceleration peak of frequencies that\ngeneral statements about time duration of response\ninduced maximum VRES levels in the Pacoima\nwill have to wait until a greater number of accelero-\nS.16°E. direction had a value of 0.75g. This peak OC-\ngrams have been studied in a similar manner.\ncurred 3.1 seconds before maximum acceleration,\nand it had only 60 percent of that maximum value.\nACKNOWLEDGMENTS\nFor the 8244 Orion Boulevard site, west direction,\nthe peak amplitude preceding the maximum VRES\nI am indebted to Glenn Converse, Charles F.\nvalues was 53 percent of maximum ground accelera-\nKnudson, and Christopher Rojahn for their critical\ntion. In this case, the maximum VRES peak OC-\nreading of this manuscript and their most helpful\ncurred more than 13 seconds after maximum ground\nsuggestions.\nacceleration.\nTable 3 lists the direction, the maximum ground\naccelerations, the maximum VRES values, the time\nREFERENCES\ndurations of different VRES amplitude levels, and\nArms, R. A., Seismological Observatory, Geophysics Division,\nthe period range for which the time duration holds\nDepartment of Scientific and Industrial Research, P.O. Box\ntrue. The time durations of high VRES values vary\n8005, Wellington, New Zealand, 1971 (personal communica-\nin relation to the duration of the strong motion that\ntion).\ninduced them, but, for these five stations, they are\nHousner, G. W., Martel, R. R., and Alford, J. L., \"Spectrum\nshorter in length. For example, the Pacoima Dam ac-\nAnalysis of Strong-Motion Earthquakes,\" Bulletin of the\nSeismological Society of America, Vol. 43, No. 2, Apr. 1953,\ncelerogram had a strong acceleration motion dura-\npp. 97-119.\ntion of about 7 seconds in both horizontal directions.\nHudson, Donald E., \"Response Spectrum Techniques in Engi-\nThe S.16°E. component has the relative velocity\nneering Seismology,\" Proceedings of the World Conference\nlevel of 150 cm/sec, which is 66 percent of the maxi-\non Earthquake Engineering, Berkeley, California, June 1956,\nmum response experienced in that direction, lasting\nEarthquake Engineering Research Institute and the Univer-\n4.3 seconds; the S.74°W component has a VRES\nsity of California, Berkeley, June 1956, pp. 4-1-4-12.\nvalue of 150 cm/sec, which is 72 percent of the maxi-\nHudson, Donald E. (ed.), \"Strong-Motion Accelerogram Proc-\nessing,\" Strong-Motion Instrumental Data on the San Fer-\nmum response, lasting 0.8 second. A comparison of\nando Earthquake of Feb. 9, 1971, Earthquake Engineering\nthe 100-cm/sec amplitude level areas for these two\nResearch Laboratory, California Institute of Technology,\ncomponents reveals the S.16°E. component is five\nPasadena, and the Seismological Field Survey, National\ntimes as great as the S.74°W. component. This ac-\nOceanic and Atmospheric Administration, U.S. Department\ncelerogram clearly illustrates that maximum ground\nof Commerce, San Francisco, Calif., Sept. 1971, pp. 157-204.\nacceleration is not necessarily proportional to either\nJenscke, V., Clough, R. W., and Penzien, J., Analysis of Earth\nmaximum VRES values or to its duration.\nMotion Accelerograms, University of California, Berkeley,\nJan. 1964, 162 pp.\nCONCLUSIONS\nMaley, R. P., and Cloud, W. K., \"Strong-Motion Accelerograph\nRecords,\" Strong-Motion Instrumental Data on the San Fer-\nAnalysis of the records from five sites in the San\nnando Earthquake of Feb. 9, 1971, Earthquake Engineering\nFernando earthquake indicates that: (1) The maxi-\nResearch Laboratory, California Institute of Technology,\nmum relative velocity response spectrum for 5 per-\nPasadena, and the Seismological Field Survey, National\ncent of critical damping is not necessarily caused by\nOceanic and Atmospheric Administration, U.S. Department\nthe maximum ground acceleration; and (2) maxi-\nof Commerce, San Francisco, Calif., Sept. 1971, pp. 1-53.\nmum velocity response is not necessarily propor-\nTrifunac, Mihailo D., \"Response Envelope Spectrum and In-\nterpretation of Strong Earthquake Ground Motion,\" Bulletin\ntional to maximum acceleration.\nof the Seismological Society of America, Vol. 61, No. 2, Apr.\nThe time durations of high VRES levels are much\n1971, pp. 343-356.\nless than the time durations of the portion of high\nTrifunac, Mihailo D., and Hudson, Donald E., \"Analysis of\naccelerations that induced them. Perhaps this may\nthe Pacoima Dam Accelerogram-San Fernando, California,\nshed some light on the slight damage experienced at\nEarthquake of 1971,\" Bulletin of the Seismological Society\nPacoima Dam.\nof America, Vol. 61, No. 5, Oct. 1971, pp. 1393-1411.","396\nSan Fernando Earthquake of 1971\nTable 1.-Maximum accelerations for five San Fernando earthquake accelerograms\nMaximum\nEpicentral\nLength\nMaximum\nTime\nvelocity\nTime\nStation\nDirection\ndistance\nof record\nacceler-\nof OC-\nof OC-\nresponse\nused\nation\nenvelope\ncurrence\ncurrence\nspectrum\nkm\nSeconds\nSeconds\ncm/sec\nSeconds\ng\n1\nPacoima Dam\nS.16°E\n6.9\n12\n1.240\n7.748\n226\n4.602\nS.74°W\n12\n1.250\n8.510\n208\n8.730\n2 8244 Orion Boulevard, 1st floor, Los Angeles\nNorth\n20\n24\n0.258\n12.525\n112\n12.624\nWest\n24\n.138\n7.025\n112\n20.654\n3 Castaic (Old Ridge Route)\nN.21°E\n30\n24\n.336\n2.613\n54\n3.125\nN.69°W\n24\n.289\n1.073\n63\n3.250\n4 250 East First Street, basement, Los Angeles\nN.36°E\n41\n12\n.107\n3.200\n41\n11.766\nN.54°W\n12\n.132\n2.825\n36\n6.341\n5. 445 South Figueroa Street, subbasement, Los\nN.52°W\n41\n14\n.148\n4.738\n49\n7.696\nAngeles.\nS.38°W\n14\n.130\n5.091\n51\n13.831\nTable 2.-Maximum velocity response and time of occurrence in reference to maximum acceleration\nMaximum VRES\nMaximum VRES\nMaximum VRES\nPeriod at which\nStation\nDirection\noccurring before\noccurring soon\noccurring long\nmaximum\nmaximum\nafter maximum\nafter maximum\nVRES occurs\nacceleration\nacceleration\nacceleration\nSeconds\nSeconds\nSeconds\nSeconds\n1. Pacoima Dam\nS.16°E\n-3.15\n1.30\n:\nS.74°W\n+0.22\n0.50\n. .\n2 8244 Orion Boulevard\nNorth\n+0.10\n1.70\nWest\n+13.63\n3.00\n3 Castaic (Old Ridge Route)\nN.21°E\n+0.51\n0.50\nN.69°W\n+2.18\n0.90\n4 250 East First Street\nN.36°E\n+8.57\n3.40\nN.54°W\n+3.52\n1.35\n:\n5. 445 South Figueroa Street\nN.52°W\n+2.96\n1.05\nS.38°W\n+8.74\n3.60\nTable 3.-Time duration of different amplitude levels of response\nStation\nDirection\nMaximum\nMaximum\nTime duration\nPeriod range\nacceleration\nVRES\ncm/sec\ncm/sec\nSeconds\nSeconds\ng\n1. Pacoima Dam\nS.16°E\n1.240\n226\nVRES>200: 1.2\n1.10-1.60\nVRES> 150: 4.3\n0.90-2.50\nS.74°W\n1.250\n208\nVRES 150: 0.8\n0.50\nVRES 100: 1.8\n0.35-0.70\n2 8244 Orion Boulevard\nNorth\n0.258\n112\nVRES 100: 1.0\n1.65-1.80\nVRES 60: 7.0\n1.10-2.20\nWest\n.138\n112\nVRES 100: 4.3\n2.65-3.25\nVRES\n60:\n8.0\n1.90-3.60\n3. Castaic (Old Ridge Route)\nN.21°E\n.336\n54\nVRES\n40:\n0.8\n0.45-0.55\nN.69°W\n.289\n63\nVRES\n40:\n3.2\n0.60-1.30\n4. 250 East First Street\nN.36°E\n.107\n41\nVRES\n30:\n2.2*\n2.70-3.60\nN.54°W\n.132\n36\nVRES\n30:\n1.3\n1.0 and 1.4\n5. 445 South Figueroa Street\nN.52°W\n.148\n49\nVRES\n40:\n1.5\n0.95-1.10\nS.38°W\n.130\n51\nVRES\n40:\n1.5*\n2.60-3.60\n*\nTime duration of VRES was limited by the length of the accelerogram chosen.","Velocity Response Envelope Spectrum\n397\nVELOCITY RESPONSE 5 PERCENT CRITICAL DAMPING\nSEISMOLOGICAL FIELD SURVEY\n4.0\n4.0\nunits=cm/sec\n050-100; 100-150; 150-200;\n200-250\n3.0\n3.0\n2.0\n2.0\n1.0\n1.0\n0\n0\n10.0\n11.0\n12.0\n0\n100. 0 200.0 300.0\n0\n1.0\n2.0\n3.0\n4.0\n5.0\n6.0\n7.0\n8.0\n9.0\nTIME - SECONDS\nVELOCITY RESPONSE-CM/SE\n13.0\n0\n-13.0\nFigure 1.-Velocity response envelope spectrum (VRES) for Pacoima Dam, S.16°E. direction.\nVELOCITY RESPONSE, 5 PERCENT CRITICAL DAMPING\nSEISMOLOGICAL FIELD SURVEY\n4.0\n4.0\nunits=cm/sec\n50-100;\n100-150;\n150-200\n3.0\n3.0\n2.0\n2.0\n1.0\n1.0\n0\n0\n0\n1.0\n2.0\n3.0\n4.0\n5.0\n6.0\n7.0\n8.0\n9.0\n10.0\n11.0\n12.0\n0\n100. 0 200.0 300.0\nTIME - SECONDS\nVELOCITY RESPONSE-CM/SEC\n13.0\n0\n-13.0\nFigure 2.-Velocity response envelope spectrum (VRES) for Pacoima Dam, S.74°W. direction.","398\nSan Fernando Earthquake of 1971\nVELOCITY RESPONSE. 5 PERCENT CRITICAL DAMPING\nSEISMOLOGICAL FIELD SURVEY\n4.0\n4.0\nunits=cm/sec\n20-40\n40-60\n60-80\n80-100\n100+\n3.0\n3.0\n2.0\n2.0\n1.0\n1.0\n0\n0\n0\n2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 0\n50.0\n100.0\n150.0\nTIME SECONDS\nVELOCITY RESPONSE-CM/SEC\n3.0\n0\n-3.0\nFigure 3.-Velocity response envelope spectrum (VRES) for 8244 Orion Boulevard, 1st floor, north direction.\nVELOCITY RESPONSE 5 PERCENT CRITICAL DAMPING\nSEISMOLOGICAL FIELD SURVEY\n4.0\n4.0\nunits=cm/sec\n20-40\n40-60\n60-80\n80-100\n100+\n3.0\n3.0\n2.0\n2.0\n0\n1.0\n1.0\n0\n0\n0\n2.0\n4.0\n6.0\n8.0\n10.0\n12.0\n14.0\n16.0\n18.0\n20.0\n22.0\n24.\n0\n0\n50.0\n100. 0 150.0\nTIME SECONDS\nVELOCITY RESPONSE-CM/SED\n2.0\n0\n-2.0\nFigure 4.-Velocity response envelope spectrum (VRES) for 8244 Orion Boulevard, 1st floor, west direction.","Velocity Response Envelope Spectrum\n399\nVELOCITY RESPONSE 5 PERCENT CRITICAL DAMPING\nSEISMOLOGICAL FIELD SURVEY\n4.0\n4.0\nunits=cm/sec\n-\n10-20;\n20-30:\n30-40;\n40-50\n50+\n3.0\n3.0\n2.0\n2.0\nwy\n1.0\n1.0\n0\n0\n4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0\n0\n20.0\n40.0\n60.0\n0\n2.0\nTIME SECONDS\nVELOCITY RESPONSE-CM/SEC\n4.0\n0\nMy\n-4.0\nFigure 5.-Velocity response envelope spectrum (VRES) for Castaic, Old Ridge Route, N.21°E. direction.\nVELOCITY RESPONSE. 5 PERCENT CRITICAL DAMPING\nSEISMOLOGICAL FIELD SURVEY\n4.0\n4.0\nunits=cm/sec\n10-20:\n20-30;\n30-40;\n40-50;\n50+\n3.0\n3.0\n(\n2.0\n2.0\n0\nUNIVERSITY\n1.0\n1.0\no\n0\n0\n0\n2.0\n4.0\n6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0\n0\n50.0\n100.0\nTIME SECONDS\nVELOCITY RESPONSE CM/SEC\n3.0\n0\n-3.0\nFigure 6.-Velocity response envelope spectrum (VRES) for Castaic, Old Ridge Route, N.69°W. direction.","San Fernando Earthquake of 1971\n400\nVELOCITY RESPONSE 5 PERCENT CRITICAL DAMPING\nSEISMOLOGICAL FIELD SURVEY\n4.0\n4.0\nunits=cm/sec\n10-20;\n20-30;\n30-40;\n40+\n3.0\n3.0\n2.0\n2.0\n1.0\n1.0\n0\n0\n0\n1.0\n2.0\n3.0\n4.0\n5.0\n6.0\n7.0\n8.0\n9.0\n10.0\n11.0\n12.0\n0\n20.0\n40.0\n60.0\nTIME SECONDS\nVELOCITY RESPONSE-CM/SEC\n2.0\n0\n-2.0\nFigure .Velocity response envelope spectrum (VRES) for 250 East First Street, basement, N36°E. direction.\nVELOCITY RESPONSE, 5 PERCENT CRITICAL DAMPING\nSEISMOLOGICAL FIELD SURVEY\n4.0\n4.0\nunits=cm/sec\n10-20\n20-30:\n30+\n3.0\n3.0\n2.0\n2.0\n1.0\n1.0\n0\n0\n12.0\n0\n1.0\n2.0\n3.0\n4.0\n5.0\n6.0\n7.0\n8.0\n9.0\n10.0\n11.0\n0\n20.0\n40.0\nVELOCITY RESPONSE CM/SEC\nTIME - SECONDS\n2.0\n0\n-2.1 0\nFigure 8.-Velocity response envelope spectrum (VRES) for 250 East First Street, basement, N 54°W. direction.","Velocity Response Envelope Spectrum\n401\nVELOCITY RESPONSE. 5 PERCENT CRITICAL DAMPING\nSEISMOLOGICAL FIELD SURVEY\n4.0\n4.0\nunits=cm/sec\nthe 30-40;\n10-20;\n20-30;\n40-50\n3.0\n3 0\n2.0\n2.0\n1.0\n1.0\n0\n0\n0\n2.0\n4.0\n6.0\n8.0\n10.0\n12.0\n14.0 0\n20.0\n40.0\n60.0\nTIME SECONDS\nVELOCITY RESPONSE-CM/SEC\n2.0\n0\n-2 0\nFigure -Velocity response envelope spectrum (VRES) for 445 South Figueroa Street, subbasement, N.52°W. direction.\nVELOCITY RESPONSE. 5 PERCENT CRITICAL DAMPING\nSEISMOLOGICAL FIELD SURVEY\n4.0\n4.0\nunits=cm/sec\n0 20;\n20 30;\n30 40;\n40 50;\n50+\n3.0\n3.0\n2.0\n2.0\n1.0\n1.0\n0\n0\n0\n2.0\n4.0\n6.0\n8.0\n10.0\n12.0\n14.0 0\n20.0\n40.0\n60.0\nTIME SECONDS\nVELOCITY RESPONSE-CM/SEC\n2.0\n0\n-2. 0\nFigure 10. - -Velocity response envelope spectrum (VRES) for 445 South Figueroa Street, subbasement, S.38°W. direction.","","Response of Pacoima Dam to Aftershocks\nof San Fernando Earthquake\nThe large strong motions recorded at Pacoima\nDam from the San Fernando earthquake of February\n9, 1971, have been discussed in a large number of ar-\nticles, some of which have questioned the importance\nof the 1.25g measurement, the largest recorded from\nan earthquake (Boore 1972, Duke et al. 1972, Mur-\nphy et al. 1972, Reimer et al. 1972, and Trifunac\nCONTENTS\nand Hudson 1971). Earth-transmitted shocks exceed-\nPage\n404\nPROCEDURES\ning 1g have frequently been recorded from large ex-\n404\nFrequency-Domain Amplification\nplosions.\n405\nTime-Domain Amplification\nThe strong-motion station was located near the\n405\nRESULTS\n405\nFrequency Domain\nsouth dam abutment on a narrow rocky ridge of\n413\nTime Domain\ngneissic granite-diorite. Many nearby surface frac-\n414\nSUMMARY\ntures were produced by the earthquake, which was\n415\nREFERENCES\naccompanied by a small rockslide about 5 m to the\nwest of the strong-motion site and numerous rock-\nslides in the valley below the 113-m-high arch-con-\nstant angle dam that was completed in 1929.\nShortly after the high accelerations were observed\nfrom the Pacoima Dam station, a team was fielded\nfrom National Oceanic and Atmospheric Administra-\ntion/Earth Sciences Laboratories (NOAA/ESL) Spe-\ncial Projects Field Party. Three stations were installed\nto record aftershocks. Each station had three com-\nponents of 1-Hz L7 geophone recording on magnetic\ntape. The first station was located downstream in the\nvalley floor at a sufficient distance to assure that there\nwould be no feedback from the dam which would be\ninduced to vibrate in its own characteristic modes.\nStation A was on the center crest of the dam next to\nthe location of the seismoscope, which had sufficient\nW. V. MICKEY\nmotion from the primary shock to dislodge the re-\nV. PEREZ\ncording plate. Station B was near the south abutment\nEarth Sciences Laboratories\nadjacent to the strong-motion recording shelter.\nEnvironmental Research Laboratories, NOAA\nThe primary objective of this study was to deter-\nW. K. CLOUD\nmine if amplification was present at the strong-mo-\nBerkeley Seismograph Station\ntion seismograph site, that is, to synthesize ground-\nUniversity of California\nmotion characteristics, maximum motions, and\nBerkeley, Calif.\n403","San Fernando Earthquake of 1971\n404\nresponse spectra which would have been recorded if\nthe dam was not there and if the station was not in-\nfluenced by the possible effects of the narrow rocky\nridge.\nFigure 1 shows the locations of the primary shock\nCOUNTY\n8\nCITY\n(star), Pacoima Dam (triangle) , and the eight after-\nshocks (circles) used in this study. Table 1 describes\n5\nthe aftershocks with date, time, location, depth, mag-\n4\nnitude (ML) and approximate distance and direc-\n3\n5\n6\ntion from the dam.\nPacoima\nRes.\nPROCEDURES\n2\n7\nSeveral techniques were used to compare the\nseismic signals recorded from the eight aftershocks at\nCO.\nCITY\nthe three stations in the time and in the frequency\ndomains.\nFigure 1.-February 9, 1971, earthquake, star; Pacoima Dam, tri-\nFrequency-Domain Amplification\nangle; and eight aftershocks numbered in order of occurrence,\ncircles.\nPseudo-relative velocity response spectra (5 per-\ncent of critical damping) were calculated for each\nacceleration pattern as influenced with fault-plane\ncomponent resulting in 72 spectra. Using the nota-\nmechanism. Because the recording sites are closely\ntions and rationale developed by Murphy et al. 1972,\nspaced, the subscript j will not be used, making pos-\nthe following approach to determining site amplifi-\nsible spectral ratios:\ncation in the frequency domain was used:\nTii(w)_Ais(w)\n(2)\nAij(w) = Tij(w)Sis(w)\n(1)\nTio(w) Aio(w)\nwhere A (w) is the ground-motion spectrum at sta-\nwhere subscript o is reference station 24 (free-field)\ntion j for aftershock i; Tij (w) is the transfer func-\nand j is station 25A-the Pacoima Dam crest-or\ntion defining the transmission path and recording site\n25B-the strong-motion site. This assumes the same\nconditions, which could also be a function of the\nsource function at all stations for a particular after-\nsource if the medium responds nonlinearly; and\nshock. The ratios of equation (2) will approximate\nSij (w) is the source function, which also would be a\nthe effects at the recording site of geological differ-\nfunction of the recording site due to the asymmetrical\nTable 1.-Aftershocks of the San Fernando earthquake\nDepth\nMagnitude\nDistance and\nDate\nTime\nAftershock\ndirection\nlocations\no\nML\nh m S\nkm\n8 km NW.\n05 53 27.4\n34 23.8 N.\n7.4\n3.3\n3-6-71\n118 26.5 W.\n07 07 36.2\n34 17.4 N.\n7.3\n2.7\n4.5 km S.\n3-7-71\n118 23.2 W.\n7 km NW.\n07 11 15.5\n34 22.7 N.\n5.1\n3.1\n3-7-71\n118 26.7 N.\n8 km NNW.\n07 52 30.4\n34 24.3 N.\n11.4\n3.2\n3-7-71\n118 24.6 W.\n08 10 38.7\n34 22.9 N.\n6.4\n2.8\n5.5 km NNW.\n3-7-71\n118 24.4 W.\n1.4(?)\n3.6\n9 km WNW.\n11 26 41.4\n34 21.7 N.\n3-7-71\n118 29.4 W.\n4.5 km S.\n8.7\n2.9\n3-8-71\n03 16 37.2\n34 17.5 N.\n118 23.8 W.\n22 27 28.4\n34 37.5 N.\n20\n3.7\n30 km NW.\n4-18-71\n118 40.9 W.\nNOTE: The first seven earthquake data were provided by the U.S. Geological Survey, Menlo Park, Calif. The April 18 earthquake was\non the NOAA/ERL/ESL Preliminary Determination of Epicenters No. 35-71, June 9, 1971.","Response of Pacoima Dam to Aftershocks\n405\nences that influence the recorded signal. If linearity\nwhere Is is the Arias intensity, V is the particle ve-\nof site response can be assumed, the spectral ratios\nlocity of the ground motion, to is the total duration\nfor a given station pair should be similar. Average\nof the motion, and T is the variable time.\nspectral ratios were computed to reconstruct a modi-\nForty-eight plots were computer plotted but are\nfication of the response spectra derived from the\nnot included in this report because of space limita-\ntions. The total summation of V2 (T) was used for\nstrong-motion record that recorded the large ac-\nratios of stations 25B/24, 25A/24, and 25B/25A as an\ncelerations,\nadditional test. This parameter is proportional to\n(3)\ntotal energy recorded at the station, and the ratios\nrepresent energy amplification.\nwhere n is 8, i is 1.\n8, j is station 25A or 25B,\nand o is station 24 (free-field).\nRESULTS\nThe modified response spectra for the three com-\nFrequency Domain\nponents of the original Pacoima Dam strong-motion\nSeventy-two response spectra were calculated by\nseismogram can then be calculated, which grossly re-\nthe Environmental Research Corporation, Las Vegas,\nmoves the effects of the dam and narrow rocky ridge.\nNev. Space limitations preclude presentation of all\nThis modified response spectra would then be that\nthe spectra in this report. Figures 2 through 7\nderived if the strong-motion stations had been on\nshow three components on each figure for events\n\"bedrock\" in the valley floor.\n66:0707 and 66:0711.\nThe response spectra from the two events are dis-\nTime-Domain Amplification\ntinctly different on station 24, the free-field, and on\nSeveral approaches were used to evaluate amplifi-\nstation 25B, the strong-motion station site. The\ncation in the time domain: (1) Total time duration\nspectra for the three components for both events at\nthat particle velocity was above certain levels; (2)\nstation 24 are similar, in contrast to stations 25A and\nnumber of occurrences or peaks contributing to the\n25B. There were two characteristics that were repeti-\ntotal duration; (3) maximum motion for each of the\ntious for station 25A, which was on the top of the\n72 seismograms and the ratio of this motion for sta-\ndam in the center. The east-west component, which\ntions 25A/24, 25A/25B, and 25B/24; and (4) Arias\nwas normal to the dam face, was higher (larger spec-\nintensity and the above ratios of the total cumulative\ntral components) for all eight shocks and had spec-\nsummation of the particle velocity squared.\ntral peaks at 0.1 and 0.2 second. The dam was not re-\nThe computer facilities of the University of Cali-\nstrained in the east-west direction and, as a result,\nfornia, Berkeley, were used to process the digital\ntended to vibrate in its own normal modes, although\ntapes. All components were used for the frequency-\nthe energy input differed in spectral content.\ndomain analysis. In the interest of economy and\nSpectral ratios were calculated and plotted for sta-\ncomputer time, only the horizontal components were\ntions 25A/24 and 25B/24 for all components and all\nprocessed for the real-time analysis. Fifteen to 20 lev-\nevents. Representative samples are shown for the\nels for testing with incremental factors of 6, 7, 8, 10,\nhorizontal components of events 66:0707 and\n12, 15, 20, 25, 30, and 40 X 10n were used for the du-\n66:0711 in figures 8 through 15. In general, the spec-\nration and number of occurrences. The original ana-\ntral ratios for stations 25A North/24 North were low\nlog tape was converted to digital tape at 160 samples\nfor the two events, in contrast to high ratios for sta-\nper second. For this analysis, 40 points per second\ntions 25A East/24 East. The stations 25B North/24\nwere used. The envelope of the analog record was\nNorth ratio was low for the first event and high for\ncalculated and used for duration and occurrence sta-\nthe second, and high for the east component ratios\ntistics. This analysis is not presented because there\nfor both events. This is an indication of the data\nwas no significant change.\nscatter or lack of uniformity between events that, as\nstated in the previous section, were of necessity con-\n(4)\nTherefore,\nsidered homogenous.","San Fernando Earthquake of 1971\n406\n10\n10\n-2\n102\n10\n-3\n10\n10\n-3\nNorth Component\nComponent\nNorth\nComponent\nComponent\nEast\nEast\nVertical Component\nComponent\nVertical\n104\n4\n4\n10\n10\n0.1\n10\n0.1\nPeriod in Seconds\nPeriod in Seconds\nspectra for station 2 showing 24. three components\nFigure 2.-Response\n3.-Response\ncomponents\nshowing\nFigure\nspectra\nevent\nthree\nfor\n2\nfor free-field\nstation\npeaks\nfor\ndam\nthe\nand\nhigh\nvalues\ntwo\ncharacteristic\ncomponent,\nwhich\nstation.\nthis\nfor\neast\nwas\nfor","Response of Pacoima Dam to Aftershocks\n407\n102\n10\n10\n102\n102\n103\n-3\n10\nNorth Component\nNorth Component\nEast Component\nEast Component\nVertical Component\nVertical Component\n104\n-4\n104\n0.1\n10\n0.1\n10\nPeriod in Seconds\nPeriod in Seconds\nFigure 5.-Response spectra for event 3 showing 24. three components\n4.-Response spectra for event 2 station showing 25B. three components\nFigure\nfor strong-motion site\nfor free-field station","San Fernando Earthquake of 1971\n408\nI\n10%\n10%\n-I\n-I\n10\n10\n-2\n102\n-2\n10\n10\n-3\n3\n10\nNorth Component\nNorth Component\nEast Component\nEast Component\nVertical Component\nVertical Component\n4\n-4\n10\n10\n10\n0.1\n0.1\n10\nPeriod in Seconds\nPeriod in Seconds\nFigure 7.-Response spectra for event 3 station showing 25B. three components\nspectra for event 3 showing three components similarities\nFigure the 6.-Response dam crest station 25A. Note characteristic\nfor strong-motion site\nfor\nbetween figures 3 and 6.","Response of Pacoima Dam to Aftershocks\n409\n10\n10\nEvent 66:0707\nEvent : 66:0707\nComponent : NORTH\nComponent : NORTH\n0.1\n0.1\n0.1\n10\n0.1\n10\nPeriod in Seconds\nPeriod in Seconds\nFigure 10.-Response spectra ratios for strong-motion site station\nFigure 8.-Response spectra ratios for dam crest station 25A and\n25B and free-field station 24 for north component, event 2.\nfree-field station 24 for north component, event 2.\n10\n10\nEvent : 66:0707\nEvent : 66:0707\nEAST\nComponent :\nComponent : EAST\n0.1\n0.1\n10\n0.1\n10\n0.1\nPeriod in Seconds\nPeriod in Seconds\nFigure 11.-Response spectra ratios for strong-motion site station\nFigure 9.-Response spectra ratios for dam crest station 25A and\n25B and free-field station 24 for east component, event 2.\nfree-field station 24 for east component, event 2.","410\nSan Fernando Earthquake of 1971\n10\n10\nEvent : 66:07 II\nEvent : 66:0711\nComponent : NORTH\nComponent : NORTH\n0.1\n0.1\n0.1\n10\n0.1\n10\nPeriod in Seconds\nPeriod in Seconds\nFigure 12.-Response spectra ratios for dam crest station 25A and\nFigure 14.-Response spectra ratios for strong-motion site station\nfree-field station 24 for north component, event 3.\n25B and free-field station 24 for north component, event 3.\n10\n10\nEvent : 66:07 11\nEvent: 66:0711\nComponent : EAST\nComponent : EAST\n0.1\n0.1\n0.1\n10\n0.1\n10\nPeriod in Seconds\nPeriod in Seconds\nFigure 13.-Response spectra ratios for dam crest station 25A and\nFigure 15.-Response spectra ratios for strong-motion site station\nfree-field station 24 for east component, event 3.\n25B and free-field station 24 for east component, event 3.","Response of Pacoima Dam to Aftershocks\n411\n10\n10\nSPECTRA RATIOS VERTICAL\nSPECTRA RATIOS EAST\n25B/24\n25B/25A\nAvg\nAvg.\n25B/25A\n25A/24\n25B/24\n25A/24\n0.1\n0.1\n10\n0.1\n10\n0.1\nPeriod in Seconds\nPeriod in Seconds\nFigure 18.-Overall average response spectra ratios, strong-motion\nFigure 16.-Overall average response spectra ratios, strong-motion\nsite to free-field, strong-motion site to dam crest, and dam crest\nsite to free-field, strong-motion site to dam crest, and dam crest\nto free-field for the eight aftershocks, vertical component.\nto free-field for the eight aftershocks, east component.\n100\n10\nS 74°W\nSPECTRA RATIOS NORTH\nOriginal\nSpectra\n25B/24\nAvg\nModified Spectra\n10\nfrom Aftershocks\n25A/24\n25B/25A\n5 %\nDamping\n0.1\n10\n0.1\n10\n0.1\nPeriod in Seconds\nPeriod in Seconds\nFigure 17.-Overall average response spectra ratios, strong-motion\nFigure 19.-Original response spectra (February 9, 1971) and\nsite to free-field, strong-motion site to dam crest, and dam crest\nmodified spectra for east component.\nto free-field for the eight aftershocks, north component.","412\nSan Fernando Earthquake of 1971\nThe ratios were averaged (geometric means) for\n0.032\nthe three components of each of the three stations\n# 2 EAST\n0.028\n2A\nand for all eight events. A standard error of estimate\n2B\nof 1.5 was used to the reconstructed spectra as an es-\n0.024\ntimate of the uncertainty in the mean values. These\n0.020\naverage spectral ratios are shown in figures 16, 17,\nand 18 and are used to reconstruct the original\n0.016\n2\nstrong-motion spectra of the primary shock in figures\n19, 20, and 21 (stations 25B/24)\n0.012\n100\n0.008\nOriginal Spectro\nS 16° E\n0.004\n0\n0.014\n2\n#2 NORTH\n2B\n0.012\nModified Spectra\n10\nfrom Aftershocks\n0010\n0.008\n2A\n0.006\n5%\nDamping\n0.004\n0.002\n0.1\n10\nPeriod in Seconds\n0\n0.001\n0.002\n0.005\n0.01\n0.02\n0.05\n0.1\n0.2\n0.5\nI\n2\n5\n10\nTime Duration, Seconds\nFigure 20.-Original response spectra (February 9, 1971) and\nmodified spectra for north component.\nFigure 22.-Time duration for particle velocity on east and north\ncomponents of stations 24, 25A, and 25B, event 2.\n100\nModified Spectra\nThe greater modification is in the shorter periods;\nVERTICAL\nfrom Aftershocks\nand for the S.16°E. component, the least change is in\nthe vertical component.\nAn overall average ratio for all frequencies for the\neight components was determined to be 1.4 for the\nnorth component, 1.65 for the east component, and\nOriginal\n0.85 for the vertical component. Applying these aver-\n10\nSpectra\nage ratios to the recorded maximum acceleration\nyields 0.89g S.16°E., 0.76g S.74°W., and 0.85g verti-\ncal.\nThe overall average ratios for all frequencies for\n5%\nthe aftershocks are as follows:\nDamping\nRatios\nI\nStation combinations\n0.1\n10\nNorth\nEast\nVertical\nPeriod in Seconds\n25B/24\n1.40\n1.65\n0.85\n25A/24\n1.20\nFigure 21.-Original response spectra (February 9, 1971) and\n1.27\n0.76\n25B/25A\n1.16\nmodified spectra for vertical component.\n1.32\n1.12","Response of Pacoima Dam to Aftershocks\n413\n0.032\n0.110\n# 3 EAST\n0.100\n0.028\n# 2 EAST\n0.090\n3A\n3B\n0.080\n0.024\n0.070\n0.020\n0.060\n2A\n2B\n0.050\n2\n0.016\n0.040\n0.012\n0.030\n3\n0.008\n0.060\n0.010\n0.050\n0.004\n3B\n0.040\n# 3 NORTH\n0\n0.014\n0.030\n3\n3A\n0.020\n0.012\n0.010\n# 2 NORTH\n0\n0.010\n2\n5\n10\n0,02\n0.05\n0.1\n0.2\n0.5\n0.001\n0.002\n0.005\n0.01\n2\nTime Duration, Seconds\nFigure 23.-Time duration for particle velocity on east and north\n0.008\ncomponents of stations 24, 25A, and 25B, event 3.\n2B\n2A\nTime Domain\n0.006\nPlots were prepared showing the time duration of\nground motion at various levels for the horizontal\n0.004\ncomponents for the eight events. Figures 22, 23, 24,\nand 25 show the time duration and the number of\n0.002\nevents which contribute to the duration for events\n66:0707 and 66:0711.\nThe station on the dam crest had larger motions\n0\n20\n50\n100\n200\nI\n2\n5\n10\nfor the east component for both events, while the\nNumber of Occurrences\nother components were less consistent. The number\nof occurrence plots was similar to the duration plots,\nFigure 24. -Number of occurrences for particle velocities on east\nand north components of stations 24, 25A, and 25B, event 2.\nbut the relative few events contributing to the large\nmotions are more apparent.\nRatios of maximum motion for the horizontal\ncomponents were calculated for the eight events and\naverages (geometric means) were obtained.","San Fernando Earthquake of 1971\n414\n0.110\nRatios\nStation combinations\n# 3 EAST\nNorth-range\nEast-range\n0.090\n25B/24\n1.74 0.86-4.58\n2.86\n1.48-4.45\n0.76 0.42-3.24\n25A/24\n1.67\n1.51-6.28\n1.78 0.72-4.22\n25B/25A\n0.73 0.43-1.08\n0.080\nThe Arias intensities were determined and plot-\nted, but are not used for this report. The terminal\nvalue of the cumulative earth motion squared was\n0.070\nused to obtain ratios which should be factors repre-\nsenting energy amplification.\n0.060\nArias intensity maximum ratios\nStation combinations\n0.050\nNorth-range\nEast-range\n25B/24\n3.58 1.38-9.9\n5.65\n2.27-12.51\n1.54 0.83-7.33\n25A/24\n7.72\n1.43-19.00\n0.73 0.24- 2.44\n25B/25A\n1.33 0.48-4.86\n0.040\nThe data in the frequency and time domains indi-\ncate amplification of the strong-motion site over the\n3A\n0.030\nfree field, and the large standard error of the esti-\n3B\nmate indicates the data scatter for the frequency do-\nmain. The number of occurrences where the individ-\n0.020\nual largest motions are distributed is of interest.\n3\n0.060\nMaximum motion\nComponent\n25A >\n25A <\n25A\n25A\n25B >\n>\n<\n25B\n25B\n25B\n24\n24\n24\n24\n0.050\n0\nNorth\n2\n6\n4\n4\n5\n3\nEast\n7\n1\n8\n0\n8\n0\n3B\nArias intensity maxima\n0.040\n# 3 NORTH\nNorth\n2\n6\n7\n1\n8\n0\nEast\n6\n2\n8\n0\n8\n0\nThe average ratios are consistently high for sta-\n0.030\ntions 25B/24, yet, for the maximum motion, there\nwere three out of five instances where station 24 was\nlarger than station 25B and four out of eight in-\n3A\n0.020\nstances where the maximum motion recorded at sta-\n3\ntion 24 was larger than at station 25A for north-\nsouth motion. The east-west maximum motion was\n0.010\nmore consistent with the ratio averages, with station\n27A being larger than station 25B for seven out of\n0\neight times and with both stations 25A and 25B\nI\n2\n5\n10\n20\n50\n100\n200\nNumber of Occurrences\nbeing larger than station 24 for all events.\nFigure 25.-Number of occurrences for particle velocities on 3. east\nand north components of stations 24, 25A, and 25B, event\nSUMMARY\nThere was amplification in both the frequency\nand time domain for the strong-motion station site as\ncompared to a free-field station for eight aftershocks,\nvarying in magnitude (ML) of 2.7 to 3.7 and occur-","Response of Pacoima Dam to Aftershocks\n415\nEarthquake Engineering (investigation of the San Fernando\nring at epicentral distances of 4.5 to 30 km from the\nearthquake), Los Angeles, Calif., Feb. 7-9, 1972.\ndam. The average spectral ratios, which could be\nDuke, C. M., Hayes, W. H., Murphy, J. R., and O'Brien,\nconsidered amplification, varied from 4.2 at 0.2-sec-\nL. J., \"Effects of Site Conditions on Ground Motions,\"\nond period for the stations 25B/24 north component\npaper presented at the National Conference on Earthquake\nEngineering (investigation of the San Fernando earth-\nto 0.52 deamplification at 0.8-second period for the\nquake) Los Angeles, Calif., Feb. 7-9, 1972.\nstations 25A/24 vertical component.\nMurphy, J. R., Lynch, R. D., and O'Brien, L. J., \"Calculated\nThe maximum motion ratio, time duration, num-\nSan Fernando Earthquake Response Spectra,\" paper pre-\nber of occurrences, and Arias intensity maximum ra-\nsented at the National Conference on Earthquake Engineer-\ning (investigation of the San Fernando earthquake), Los\ntios in general indicate amplification of the horizon-\nAngeles, Calif., Feb. 7-9, 1972.\ntal motion for the strong-motion site as compared to\nReimer, R. B., Clough, R. W., and Raphael, J. M., \"Seismic\nthe free-field motions.\nResponse of Pacoima Dam,\" paper presented at the National\nExtrapolation of time-amplification data from af-\nConference on Earthquake Engineering (investigation of the\nSan Fernando earthquake), Los Angeles, Calif., Feb. 7-9,\ntershocks as low as magnitude 2.7 to the magnitude\n1972.\n6.4 of the primary shock is speculation at best. If lin-\nTrifunac, Mihailo D., and Hudson, Donald E., \"Analyses of\nearity exists in scaling from the low to higher magni-\nthe Pacoima Dam Accelerogram,\" Strong-Motion Instru-\ntudes, the amplification is real.\nmental Data on the San Fernando Earthquake of Feb.\n9, 1971, Earthquake Engineering Research Laboratory, Cali-\nfornia Institute of Technology, Pasadena, and the Seismo-\nREFERENCES\nlogical Field Survey, National Oceanic and Atmospheric Ad-\nBoore, David M., \"Effect of Simple Topography on Seis-\nministration, U.S. Department of Commerce, San Francisco,\nmic Waves,\" paper presented at the National Conference on\nCalif., Sept. 1971, pp. 205-258.","","Repeat Magnetic Field Survey\nof San Fernando\nEarthquake Epicentral Area\nSEISMOMAGNETIC EFFECT\nBoth repeat magnetic field surveys and continuous\nrecordings indicate that magnetic field changes are\nrelated to earthquakes. Kato (1940) conducted a\nmagnetic field survey after a Japanese earthquake,\nrepeated it a year later, and found a 100-gamma\nchange. He attributed the change to seismic activity.\nCONTENTS\nRecently, the Japanese (Rikitake 1968) and the\nPage\n417\nSEISMOMAGNETIC EFFECT\nRussians (Golovkov 1969), studying seismic areas\n417\nDESCRIPTION OF FIELD SURVEYS\nby repeat field surveys, suggested that moderate\n418\nDISCUSSION AND CONCLUSIONS\nchanges (1 to 10 gammas) could be related to earth-\nREFERENCES\n421\nquakes. Hasbrouck and Allen (1972) have reported\na 13-gamma change 1.5 km from the underground\nnuclear explosion on Amchitka Island, Alaska. How-\never, more thorough surveys, by continuous record-\nings over a period of years along the San Andreas\nfault, found only small changes could be correlated\nwith creep events and occasional small earthquakes\n(Briener and Kovach 1968) Furthermore, theoreti-\ncal calculations by Talwani and Kovach (1971) and\nShamsi and Stacey (1969) show that only small mag-\nnetic field changes (1 to 2 gammas) accompany\nearthquakes or creep events along the San Andreas\nfault system.\nThis report compares the magnetic field survey\nmade after the San Fernando earthquake (magni-\ntude 6.4) of February 9, 1971 (O'Donnell and Kauf-\nmann 1971), and the repeat survey of April 1 to 7,\n1972.\nDESCRIPTION OF FIELD SURVEYS\nThe 1971 postearthquake survey consisted of set-\nting up a base station to continuously monitor the\nJ. E. O'DONNELL\ntotal magnetic field and 32 sites to be used as repeat\nH. E. KAUFMANN\nstations (O'Donnell and Kaufmann 1971) . This sur-\nGeomagnetic Investigations Group\nvey also measured the horizontal gradient at the four\nEarth Sciences Laboratories\ncardinal points located 20 feet from each station and\nEnvironmental Research Laboratories, NOAA\n417","418\nSan Fernando Earthquake of 1971\na low gradient was one of the criteria for selecting\nthe typical error is, including relocation errors, one\nthe repeat stations.\nstation was reoccupied seven times, and two others\nThe vertical gradient also was observed at the cen-\nwere reoccupied three times during the repeat sur-\nter point of each station during the repeat survey of\nvey. Table 1 shows the values as station differences-\n1972. The vertical gradient observations were made\nthe difference between the base and repeat station.\n18 inches above and below the normal 60-inch obser-\nThe standard deviations are about 2 gammas.\nvation height. The repeat observations could be\nmade to within +2 inches of the height of the origi-\nDISCUSSION AND CONCLUSIONS\nnal observations. Even so, the vertical gradient at\nThe three possible primary sources of errors in the\ntwo-thirds of the 32 sites was large enough that the\nrepeat measurements were high vertical gradients, a\nexpected error was sufficiently high to reject these\nnonuniform diurnal field, and ambient magnetic\nsites. Several other stations could not be relocated ac-\nfields caused by HVDC (High-Voltage Direct Cur-\ncurately enough to be used in the repeat survey.\nrent) lines.\nThe base station could not be reoccupied pre-\nThe vertical gradient measurements were used to\ncisely, but was relocated within several feet. Because\nreevaluate the sites which were initially chosen be-\nthe station is in a high-gradient area, this could\ncause of their low horizontal gradients. The vertical\nmean a difference of 10 or 20 gammas. However, the\ngradients actually proved to be better criteria for\nvalue would remain constant and would not inter-\nselecting sites because' the magnetic material in the\nfere with survey results, which depend on differences\nmonument or reference marker affected the local\nbetween repeat stations.\nvertical gradient. The multiple reoccupation of three\nThe magnetometer at the base station for the ini-\ndifferent sites during the second survey gives a typical\ntial survey was a fluxgate type (Schonstedt HMS-1),\nerror of less than +2 gammas and a maximum differ-\nwhich exhibited drift caused by temperature or tilt\nence of 5 gammas between the observed low and high\nchanges. The repeat survey used a proton precession\nvalues (table 1)\ntype (Varian-M50) that eliminated the drift prob-\nRikitake (1971) has shown that conductivity\nlem. This system's sensitivity was 0.9 gamma/mm,\nanomalies cause anomalous magnetic field values\nthe chart speed was 1.2 mm/min, and the sampling\nduring magnetic variations. Our observations were\nrate was once per minute. The magnetometer was\ntaken almost entirely during quiet periods, and the\ntested at the Boulder Magnetic Observatory in Boul-\ncorrections were primarily for the diurnal variation.\nder, Colo., before the survey. The test compared val-\nBut Elvers et al. (1970) have reported on an anoma-\nues computed from the normal magnetograms and\nlous diurnal variation between stations 15 miles\nanalog recordings from the proton precession. The\napart. We operated only one base station and cannot\nrecords also were checked with two other manufac-\nbe sure the diurnal variation is uniform over the 10-\nturers' proton precession magnetometers (Elsec and\nby 15-mile area. However, it is probably uniform for\nGeoMetrics) all magnetometers agreed within + 1\nthe closely spaced sites.\ngamma. The repeat stations on both surveys also had\nAnother possibility for error that can be neglected\nthe same proton precession magnetometer (Elsec)\nis the HVDC lines which run N.10°W. and are lo-\nIn the first survey, the sensitivity was 1.2 gamma;\ncated 5 miles west of the base station. The lines were\nin the second survey, it was changed to -0.6 gamma.\ndisabled during the earthquake (Moran 1971) and\nThe base station magnetometer was compared with\nwere not in operation during the first survey, but be-\nthe repeat station magnetometer during the survey\ncame operational before the repeat survey. These\nand always agreed within gamma.\nlines were spaced 40 feet apart and carried 1,300 am-\nThe estimated maximum measurement error in\nperes of current in opposite directions. We should\noccupying a repeat station twice is 6 gammas for the\nfirst survey and 4 gammas for the second survey, as-\nnot observe a magnetic field from these lines, as the\nsuming that there is no relocation error and that the\nopposite polarity of the current enables the magnetic\ndiurnal change is the same over the whole area as it\nfield to be canceled. The power transmission was in-\nis at the base station. It should be emphasized that\nterrupted once during the repeat survey, and no\nthis is a maximum error estimation and implies a\nchange was observed on the continuous recording at\nstandard deviation of 2 gammas. To determine what\nthe base station. Occasionally, one of the lines is re-","Repeat Magnetic Field Survey\n419\nTable 1.-Differences between base station and three stations during 1972 repeat survey\nStation difference\nVertical gradient\nDate\nStation\ngammas/feet\nUT\ngammas\nApril 4\nSand Canyon Fire Station\n78\n15:15\n118°24'48.0\"W\n34°23'05.4\"N\nApril 5\n02:15\n78\n15:43\n77\nApril 6\n3\n14:49\n77\nApril 7\n01:57\n78\n02:05\n78\n14:58\n82\nApril 5\nVasquez Rocks\n16:20\n485\n118°19'16.5\"W\n34°29'20.0\"N.\nApril 6\n2\n15:31\n487\nApril 7\n15:46\n489\nVasquez Rocks (East)\nApril 5\n502\n15:14\n118°19'15.5\"W\n34°29'20.1\"N\nApril 6\n8\n15:37\n504\nApril 7\n15:51\n505\nmagnetic field differences between the two surveys\nBASE LINE 49865 Gammas\n(table 2) range from -7 to - 26 gammas and indi-\n49860\ncate that at least a 19-gamma change occurred. Fur-\n50\nthermore, during the first survey, the Sand Canyon\nMARCH 1971\nFire Station had a 14-gamma change in less than 1\n40\nweek. This site is only 2,000 feet from the base sta-\n30\ntion, SO we can safely assume a uniform diurnal vari-\nation for this case. The standard deviation between\n20\n6 APRIL 1972\ntwo such difference observations is 4 gammas, SO the\n10\n19- and 14-gamma differences are significantly high.\nConsequently, we feel a seismomagnetic effect was\n49800\nobserved during the first survey, which was 2 to 3\n90\nweeks after the earthquake, and was confirmed by\n1200\n1200UT\n1600\n2000\n2400\n0400\n0800\nother sites during the repeat survey.\nFigure .Typical magnetic field diurnal curves from base station\nfor 1971 and 1972; values plotted every 30 minutes from analog\nA correlation between site location and geology\nrecordings.\nwas not significant. Most of the sites were located on\nigneous rocks-from granites to gabbro-with the\nplaced by a ground return (Lessing 1965) which\ngabbro containing a very high percentage of mag-\nwould enable a single line to give a sizable magnetic\nnetic minerals (Oakeshott 1958) . It is interesting to\nfield. The Los Angeles Department of Water and\nnote that the base station and Sand Canyon Fire Sta-\nPower records of the power transmission showed\ntion were located on sediments that have an esti-\nonly the one interruption on the lines.\nmated thickness of at least 500 feet and that overlie\nThe secular and diurnal changes were removed by\ngabbroic rock (Oakeshott 1958 and Duke et al.\ncomputing all observations back to a common base\n1971) The two stations lie approximately 2 miles\nsouthwest of the epicenter of the main earthquake.\nline as given in figure 1. A constant change may\nFrom the results of our survey, we recommend\nexist at all sites occupied in the repeat survey be-\nthat future studies include the following:\ncause of the slight relocation of the base station. The","420\nSan Fernando Earthquake of 1971\nTable 2.-Magnetic field values and differences for 1971 and 1972 surveys for stations with small vertical and\nhorizontal gradients\nStation\nDate\nObserved\nValue corrected\nDifference\nVertical\nvalue\nto baseline 49865\ngradient\nUT\ngammas/feet\ngammas\ngammas\nDillon Divide\n2-24-71\n118°20'55.0\"W\n18:56\n50333\n50359\n34°20'37.5\"N\n-9\n10\n4-5-72\n23:32\n50307\n50350\nLittle Tujunga\n2-25-71\n118°21'34.5\"W.\n19:31\n50233\n50274\n34°17'45.0\"N.\n-14\n5\n4-6-72\n00:41\n50221\n50260\nPort\n2-26-71\n118°19'44.0\"W\n19:50\n49970\n50009\n34°23'11.0\"N.\n-13\n1\n4-4-72\n23:04\n49953\n49996\nIndian\n2-28-71\n118°15'19.0\"W\n20:23\n50201\n50256\n34°23'39.5\"N.\n-21\n8\n4-4-72\n20:32\n50177\n50235\nSoledad Camp\n2-28-71\n118°16'39.0\"W\n23:31\n49979\n50011\n34°26'17.0\"N.\n-23\n2\n4-7-72\n16:37\n49945\n49988\nAgua Dulce\n2-29-71\n118°20'07.5\"W\n00:04\n50118\n50146\n34°26'18.0\"N.\n-26\n2\n4-7-72\n16:10\n50082\n50120\nPlacerita Canyon State Park\n3-1-71\n118°28'11.0\"W.\n17:33\n50200\n50224\n34°22'40.0\"N.\n-13\n5\n4-4-72\n16:50\n50174\n50211\nNorman Reservoir\n3-3-71\n118°29'15.0\"W\n00:08\n50089\n50112\n34°17'30.0\"N\n-7\n6\n4-6-72\n20:47\n50044\n50105\nSand Canyon Fire Station\n2-24-71\n118°24'48.0\"W\n17:04\n49942\n49951\n34°23'05.4\"N\n3-3-71\n21:44\n49901\n49965\n3-4-71\n18:26\n49930\n49966\n4-4-72\n15:15\n49911\n49943\n18:15\n49898\n49943\n4-5-72\n15:43\n49899\n49942\n-23\n3\n4-6-72\n14:49\n49903\n49942\n4-7-72\n01:57\n49904\n49943\n4-8-72\n02:05\n49905\n49943\n14:58\n49912\n49947\n4-10-72\n20:22\n49884\n49942\n21:29\n49889\n49941","Repeat Magnetic Field Survey\n421\n1 Because of the high local vertical gradients,\nHasbrouck, W., and Allen, J. H., \"Quasi-Static Magnetic Field\nChanges Associated With the Cannikin Nuclear Explosion,\"\nobservations should be made 10 feet or more above\npaper presented at the meeting of the Seismological Society\neach reference marker.\nof America, Honolulu, Hawaii, Mar. 28-Apr. 1, 1972.\n2 Each station and its four cardinal points\nKato, Y., \"Investigation of the Changes in the Earth's Mag-\nshould be staked with nonmagnetic markers. This\nnetic Field Accompanying Earthquake or Volcanic Erup-\nwill enable precise relocation and will avoid affecting\ntions,\" Tôhoku University Scientific Report, Ser. 1, Vol. 29,\nthe natural gradient. These stakes can be placed near\nNo. 3, Sendai, Japan, Nov. 1940, pp. 315-326.\nexisting monuments SO they can be easily relocated.\nLessing, Lawrence, \"D.C. Power's Big Comeback,\" Fortune,\n3 Two and three continuously recording base\nVol. 72, No. 3, Sept. 1965, pp. 174-196.\nstations in the area will facilitate the identification\nMoran, D. F., \"Damage to Energy and Communication Sys-\nitems,\" The San Fernando, California, Earthquake of Febru-\nof conductivity anomalies and ambient fields caused\nary 9, 1971, Geological Survey Professional Paper 733, U.S.\nby HVDC lines. One station also can be placed out-\nGeological Survey and the National Oceanic and Atmos-\nside the area and be used as a possible reference that\npheric Administration, U.S. Department of the Interior\nis not affected by the seismomagnetic effect.\nand U.S. Department of Commerce, Washington, D.C., 1971,\n4 A survey made before an earthquake and\npp. 245-250.\nthen repeated after the event would most likely show\nOakeshott, Gordon B., \"Geology and Mineral Deposits of San\nFernando Quadrangle, Los Angeles County, California,\"\na larger change than we observed. Repeat surveys\nCalifornia Division of Mines Bulletin 172, Feb. 1958, 147 pp.\ncan be interpreted quantitatively, if enough sites are\nO'Donnell, J. E., and Kaufmann, H. E., \"Magnetic Field Sur-\nused, but would probably be more useful in deter-\nvey of the San Fernando Earthquake Epicentral Area,\" The\nmining where the magnetic field should be continu-\nSan Fernando, California, Earthquake of February 9, 1971,\nously recorded to observe the empirical relation be-\nGeological Survey Professional Paper 733, U.S. Geological\ntween earthquakes and magnetic field changes.\nSurvey and the National Oceanic and Atmospheric Admin-\nistration, U.S. Department of the Interior and U.S. Depart-\nment of Commerce, Washington, D.C., 1971, pp. 157-160.\nREFERENCES\nRikitake, T., \"Geomagnetism and Earthquake Prediction,\"\nBriener, S., and Kovach, R. L., \"Local Magnetic Events\nTectonophysics, Vol. 6, No. 1, Elsevier Publishing Co.,\nAssociated With Displacement Along the San Andreas Fault\nAmsterdam, Netherlands, July 1968, pp. 59-68.\n(California), Tectonophysics, Vol. 6, No. 1, Elsevier Pub-\nRikitake, T., \"Electrical Conductivity Anomaly in the Earth's\nlishing Co., Amsterdam, Netherlands, July 1968, pp. 69-73.\nCrust and Mantle,\" Earth Science Reviews, Vol. 7, No. 1,\nDuke, C. M., Johnson, J. A., Kharraz, Y., Campbell, K. W.,\nElsevier Publishing Co., Amsterdam, Netherlands, Mar.\nand Molpiede, N. A., Subsurface Site Conditions and\n1971, pp. 35-65.\nGeology in the San Fernando Earthquake Area, UCLA-\nShamsi, S., and Stacey, F. D., \"Dislocation Models and Seismo-\nENG-7206, University of California, Los Angeles, Dec.\nmagnetic Calculations for California 1906 and Alaska 1964\n1971, 118 pp.\nEarthquakes,\" Bulletin of the Seismological Society of\nElvers, D., Perkins, D., and Holbrook, R., \"A Survey of\nAmerica, Vol. 59, No. 4, Aug. 1969, pp. 1435-1448.\nAnomalous Geomagnetic Variations in Puerto Rico,\" Oper-\nTalwani, P., and Kovach, R. L., \"Theoretical Studies and\national Data Report C&GS DR 9, U.S. Coast and Geodetic\nAnalysis of Data From the San Andreas Magnetometer\nSurvey, U.S. Department of Commerce, Washington, D.C.,\nArray,\" Final Report, Grant NU: E22-85-70G, Environ-\nSept. 1970, 44 pp.\nmental Research Laboratories, National Oceanic and At-\nGolovkov, V. P., \"Anomalous Geomagnetic Field Variations\nmospheric Administration, U.S. Department of Commerce,\nin a Seismically Active Region,\" Geomagnetism and\nBoulder, Colo., Aug. 1971, pp. 1-14.\nAeronomy, Vol. 9, No. 6, Dec. 1969, pp. 912-913.","","Index\nBalboa Boulevard bridge 128\nAirport:\nA\nHollywood-Burbank 43\nBalboa Inlet Tunnel 28, 214\nBalboa Outlet Tunnel 218\nAbbey Hotel 41\nSan Fernando 31\nAccelerogram processing 365-374\nVan Nuys 47\nBallona Creek 163\nBambi Place 35\nAccelerogram records of largest\nAlabama Hills 7\nBank of California Building 46\naftershocks 81\nAlameda 42\nAccelerograms selected for spectral\nAlaska 353, 417\nBanning 7\nBarrett 17, 18\nanalysis 393-401\nAlaska earthquake of 1964: 126\nBartholomaus Canyon 27, 131\nAccelerograph performance,\nAlemany High School 132\nBartholomaus Ranch trenches\nstatistical summary of 349-351\nAlhambra 26, 38\nAliso Canyon oilfield 29\n173-178, 181\nAccelerograph record at Pacoima\nBear Canyon area 34\nDam 16\nAlluvial fans 191\nBear Divide Ranger Station 34\nAlta Mesa Convalescent Hospital\nAccelerograph records, strong-\nmotion 325-348\n129\nBear Divide seismometer\nrecording site 71, 72, 78, 80\nAccelerograph site and\nAltadena 38\nBee Canyon 26, 128, 134\nperformance, Pacoima Dam\nAmchitka Island, Alaska 417\nBenson-Lehner 099D Datareducer\nAntelope Valley 229\n375-391\nAntelope Valley Freeway 27\n367, 368, 383\nActon 10\nAerial view over Pacoima Dam\nApartment buildings damaged\nBerkeley 6, 18, 405\nBerkeley network 18\nsite 377\nby earthquake 26\nBerkeley Seismograph Station, U.\nAerospace Charting and Geodetic\nAqueduct, California 243\nService, USGS 234\nAqueduct, CDWR 228\nof C. 374\nAftershock activity 17\nAquifers, effects on 220\nBeryl, Utah 23\nBeverly Hills 26, 38, 160, 326, 347\nAftershock area 13\nArias intensity 405, 414\nBig Pine fault 6\nArleta district 44\nAftershock area of San Fernando\nBig Tujunga Canyon 27, 128, 142,\nArroyo Street 29\nearthquake 14 (map)\nAR-240 accelerogram 383\n147\nAftershock depths 13\nAR-240 accelerograph 350, 351,\nBig Tujunga Dam 230\nAftershock epicenters,\nBig Tujunga Wash 128, 130, 134,\n366, 368, 376, 381\ndistribution of 18\nAR-240 accelerograph records 326\n166, 220\nAftershock focal mechanisms 13\nAssam, India, earthquake of 1897:\nBill Lane Camp 130\nAftershock records of March 30,\nBircher Street 35\n126\n31, 1971: 218\nBlackhawk Street 35\nAstoria Street 219\nAftershock zone 17, 18\nAthenaeum, C.I.T. 368, 369\nBledsoe area 29\nAftershocks, epicentral\nBledsoe Street 29\nAvenida Jolita 37\ndistribution of 13\nBlue Star Trailer Court 133, 134\nAvenue of the Oaks 36\nAftershocks of 1968 Borrego\nBody-wave focal plane solutions 49\nMountain earthquake 82\nBody-wave magnitude 50\nAftershocks of San Fernando\nBorden Avenue 26, 29, 31\nB\nearthquake 1\nBorrego Mountain 14\nAftershocks of strike-slip character\nBorrego Mountain earthquake of\nB. S. Fischer Engineering\n19\n1968: 82, 141, 351\nCompany 183\nBouguer gravity gradients 139\nAftershocks, Richter magnitude\nBackhoe trenches 165, 208\nBoulder Magnetic Observatory 418\nBakersfield 10\nof 69\nBouquet Canyon Road 27\nBakersfield earthquake 10\nAftershocks, seismograms, S-wave\nBalboa Boulevard 27, 47, 133, 200,\nBoys Market 129, 183\nspectra, and source parameters\nBradley 31\n202\nfor 69-121\n423","424\nSan Fernando Earthquake of 1971\nBradley area 29\nCarl Street 133\nContinental Graphics Company\nBradley Avenue 132, 200\nCarnegie Institution of\n367\nBridge damage 27\nWashington 6\nConverse, Davis & Associates 218\nBridgeport 23\nCarrizo Plain 7\nConverse Foundation Engineers\nBrown Trench 178, 179, 182\nCascade oilfield 29, 144\n204\nBrown's contracting yard 31, 178\nCassara Canyon 129, 130, 131\nCoop Lines 226, 228, 230\nBuenaventura 47\nCast triangulation net 243\nCoop Net 226, 235, 240, 241\nBuildings and dwellings damaged:\nCastac (Castaic) 9\nCottonwood 17, 18\nSan Fernando, Sylmar, and\nCastac Hills 8\nCounty of Los Angeles 3, 26\nenvirons 29\nCastac Mountains 8\nCourbet Street 35\nSan Fernando Valley Juvenile\nCastaic 5, 8, 9, 11, 228, 240, 331,\nCoyote Creek fault 141\nHall 189, 190\n342\nCretaceous 159, 160-162\nBullocks, Pasadena 38\nCastaic Junction 302\nCrustal movements:\nBurbank 6, 26, 38, 39\nCastaic oilfield 29\nhorizontal 230-235, 243-293\nBurnet Avenue 45\nCastaic (Old Ridge Route) 393,\nvertical 235-240, 295-324\nBurton Street 44\n394\nCatalina schist 159, 162\nCatalog of Earthquakes on the\nD\nC\nPacific Coast, 1769-1806: 7\nCDH-VII (see California Division\nDamage estimates 26\nCalifornia 6, 7, 9, 14, 23, 50, 183,\nof Highways District VII)\nDams:\n230, 298, 349, 351, 353, 383,\nCDMG (see California Division of\nLower Van Norman earthfill\n385\nMines and Geology)\ndam 27\nCalifornia Aqueduct 243\nCDWR (see California\nUpper Van Norman earthfill\nCalifornia Coordinate System 226\nDepartment of Water\ndam 27\nCalifornia Department of Water\nResources)\nDaveric Drive 45\nResources (CDWR) 20, 228,\nCenozoic 159\nDevonshire fault zone 133\n241\nCentral America low-magnification\nDewdrop 37\nCalifornia Division of Highways\nstations 50\nDilatational observations from\n190, 194, 201, 206, 228\nCentury City 347\nMexico 55\nDistrict VII (CDH-VII) 228, 235\nChase Street 44\nDillon Ranch seismometer\nCalifornia Division of Mines and\nChatsworth 1, 10, 11, 17, 18, 19,\nrecording site 71, 72, 77, 80\nGeology (CDMG) 127, 133,\n20, 43\nDisplacements along San Andreas\n165, 166, 173, 179, 193, 230\nChatsworth Reservoir 10\nfault 7\nCalifornia earthquake history 6\nChatsworth Street 35\nDivision of Mines and Geology,\nCalifornia Highway 14: 36\nChico Formation 162\nCalifornia 2\nCalifornia Highway Route 14: 228\nChimney damage 28, 38\nDomengine Formation 162\nCalifornia Institute of Technology\nChivers Street 30\nDowntown Los Angeles 26, 41, 346,\n(C.I.T.) 6, 13, 14, 15, 16, 17,\nC.I.T. (see California Institute\n347\n18, 20, 41, 44, 45, 50, 71, 72,\nof Technology)\nDry Canyon 10, 354\n120, 133, 326, 348, 353, 364,\nCity of Los Angeles, Bureau of\nDuarte 7\n366-369, 374, 375, 383, 390, 393\nEngineering (see Los Angeles\nDuration of strong shaking 23\nCalifornia Plane Coordinate\nCity Bureau of Engineering)\nDwellings, damage and losses 151\nSystem 250\nCity of Los Angeles, Department\nDwellings, damage to 29, 30\nCalifornia State College 43\nof Water and Power (see\nDwellings in area of heavy\nCalifornia State Department of\nLos Angeles Department of\nshaking 138\nWater Resources 326\nWater and Power)\nCaltech Earthquake Research\nCivic Center 42\nAffiliates 20\nCoast Ranges 138\nCamp Holton rupture 147\nE\nCoastal California 14\nCamp Holton slope failures 148\nCobalt 31\nCamp Karl Holton 133\nEagle Rock 41, 43\nCody Road 46\nCamp Karl Holton Juvenile\nEarth movements:\nCollege View Avenue 43\nFacilities 147, 148\nhorizontal 230-235, 243-293\nColumbia University 374, 390\nCamp Plenty Road 37\nvertical 235-240, 295-324\nColven Road 35\nCanoga Park 6, 10, 39, 40\nEarth ruptures in North Sylmar\nCantara Street 44\nCommercial-industrial buildings\nhousing development 207-212\nCarewell Convalescent Hospital\ndamaged by earthquake 26\nEarth Sciences Laboratories\n129\nComputing Center, C.I.T. 368\n(ESL), NOAA 403","425\nIndex\nGeologic section of:\nFarmdale 43\nEarthfill dam 332\nBartholomaus Ranch Trench A\nFatalities caused by earthquake 26\nEarthquake effects (catalog of)\n175\nFaulting and ground effects:\n2, 23\nBartholomaus Ranch Trench B\nSan Fernando, Sylmar, and\nEarthquake Engineering Research\n177\nenvirons 26\nLaboratory, C.I.T. 366, 390\nBrown Trench 178\nFaulting, predicting 152, 153\nEarthquake events of the past 5\nElysian Park Hills area 158\nFaulting, surface and subsurface\nEarthquake hazard region 14\nJuvenile Hall Trench 192\nevidence of 174-181\nEarthquake Mechanism Laboratory\nNorth Olive View, Olive View,\nFaultline-crossing geodetic\n(EML), NOAA 16, 20\nand Sylmar faults 216\nnetworks 226\nEarthquake questionnaire card\nOak Hill Trench 180\nFault-line scarp 129\ncanvass 23, 30\nPalos Verdes-San Gabriel\nFault-plane solutions for main\nEarthquakes caused by thrust fault\nMountains 157\nshock 18\nmovement 126\nSan Fernando Tunnel facing 214\nFeather River 213\nEast Andover Drive 38\nSan Fernando Valley 141\nFelt area of earthquake 23-48\nEast First Street 393, 394\nSylmar area 158\nFernando Formation 162, 163\nEbey Canyon 130\nGeological setting of earthquake\nFifth Street 30\nEighth Street 28\n138-141, 155-164\nFillmore 40\nEl Centro 330, 348, 353\nGeoMetrics magnetometer 418\nFills, damage to 208\nEl Centro earthquake of 1940:\nGladstone Avenue 31, 134\nFilmore 31\n330, 383-385, 387\nGladstone Street 129\nFirst Methodist Church 41\nEl Dorado Avenue School 132\nGlen Haven Cemetery 34\nFirst Owens River Aqueduct 28\nElastic-strain release and seismic\nGlendale 6, 26, 40, 43\nFirst Street 26\nwave energy 124\nGlendale Presbyterian Church 40\nFlintridge 40\nElectrotape 214\nGlenoaks Boulevard 27, 28, 29, 30,\nFocal mechanism of main shock 49\nElevations, measurement of 183\n31, 129, 183, 214\nFocal mechanisms and tectonic\nElizabeth Lake Canyon 11\nGlenoaks Boulevard Drain 28\ninterpretations 18-20\nElsec magnetometer 418\nGloria Avenue 46\nFocal mechanisms of aftershocks 13\nElsinore fault 6\nGolden State Freeway 27, 37, 43,\nFoothill Boulevard 3, 27, 29, 30,\nElysian Hills 159-161\n128, 131, 132, 194, 198, 201,\n31, 45, 129, 198, 214, 241\nEncino 40, 183\n214\nEncino Avenue 35\nFoothill Freeway 27, 129, 132, 134,\nGorman 302\nEngineering Geology Branch of\n148, 171, 219\nGould 230\nMWD 213\nFoothill Nursing Home 27, 29, 30\nGranada Hills 1, 17, 18, 19, 20, 27,\nEnvironmental Data Service\nFort Tejon earthquake of 1857: 7,\n28, 29, 34, 35, 133, 302\n(EDS), NOAA 49\n138, 153\nGranada Hills aftershock of March\nEnvironmental Research\nFresno 326\n31, 1971: 127\nCorporation 405\nFUGRO, Inc. 176, 206\nGranada trunkline 28\nEnvironmental Research\nGrapevine 240, 302\nLaboratories (ERL), NOAA\nGrapevine Canyon 27, 191, 217,\n31, 49, 325, 348, 350\n220\nEocene 159, 162, 163\nGrapevine Creek 148\nG\nEpicenter 137\nGriffith Park 42, 43\nEpicenter, location of 23\nGround acceleration, maximum\nEpicentral locations of southern\nGas transmission line damage 29\nmeasured 143\nCalifornia earthquakes 14\nGasline damage 29\nGround-acceleration values 343-345\nEpicentral region accelerogram 375\nGaspar de Portolá 6\nEpicentral region of San Fernando\nGround accelerations 152\nGeneral Telephone Company 29\nearthquake 14\nGround displacement at San\nGeodetic networks, fault line-\nEtiwanda Avenue 43\nFernando Valley Juvenile\ncrossing 226\nEvacuation of endangered area\nHall 189-196\nGeodetic programs in metropolitan\nbelow dam 28\nGround movements in Van\narea 223, 226\nNorman Lake vicinity 197-206\nGeodimeter 244, 246, 247\nGround rupture in North Sylmar\nGeodolite 232\nF\nhousing development 207-212\nGeologic column:\nGround rupturing, subsurface\nLos Angeles Basin 161\nF. Beach Leighton & Associates\ninvestigation of 165-172\nSan Fernando Valley 160\n133, 173, 179\nGround, shattered 149\nGeologic pit logs and sections\nFairbanks, Alaska 353\nGround water 140, 141\n168-172, 211\nFairport Avenue 37","426\nSan Fernando Earthquake of 1971\nGround-water levels 191, 215, 220\nHypocentral locations 13, 15-17\nKirkcolm Lane 44\nGunite coating, surface fractures\nof main shock 18\nKoyna, India, earthquake of 1967:\nof 376\nof aftershocks 18\n383\nH\nI\nL\nHaiwee 6\nImperial fault 330\nLa Canada 40, 41\nHansen Dam 28, 214, 220\nImperial Valley 141, 385\nLa Crescenta 41, 159\nHansen Lake 302\nIndia 126, 383\nLa Crescenta Valley fault 159\nHarding School 129\nIndian Hills Medical Center 132\nLa Glorita Circle 37\nHarding Street 28\nInformation International, Inc. 368\nLa Jolla 6, 10, 240\nHaskell Canyon 228\nInglewood fault 9, 10\nLABE (see Los Angeles City\nHead Road, Iron Canyon 38\nIntensity VII 38, 142\nBureau of Engineering)\nHerrick Avenue 132, 134\nIntensity VIII 34, 189\nLAC (see Los Angeles City net)\nHighland Park 41\nIntensity VIII-XI 23, 142, 218\nLACBE (see Los Angeles City\nHighland Sanitarium 129\nIntensity IX-XI 26\nBureau of Engineering)\nHighway 14: 33\nIntensity XII 123\nLACE (see Los Angeles County\nHighways and roads damaged by\nIntensity of shaking 123\nEngineer)\nearthquake: San Fernando,\nLACFCD (see Los Angeles County\nIntensity zones and felt area 23-48\nSylmar, and environs 27\nFlood Control)\nInterstate Highway 5: 228, 230\nHistory of earthquake events 5\nLACO (see Los Angeles County\nInterstate Highway 405: 228\nHoliday Inn (Orion) 45\nEngineer)\nInterstate 210: 219, 228\nHollywood 42, 347\nLADWP (see City of Los Angeles,\nIron Canyon 38\nHollywood fault system 161\nDepartment of Water and\nHollywood fault zone 159\nPower; Los Angeles\nHollywood-Burbank Airport 43\nDepartment of Water and\nHolocene 166, 171, 181, 191, 194\nJ\nPower)\nHolocene fault movement 129\nLake Avenue 38\nJapan 367\nHoly Cross Hospital 29, 35, 36, 132\nLake Hughes 331\nHomes damaged by earthquake 26\nJensen Filtration Plant 132\nLakeview segment 128, 130-131\nHonby 36, 37, 38, 146\nJessup Park 132\nLakeview thrust fault 128, 143\nHonby ruptures 146\nJet Propulsion Laboratory, C.I.T.\nLamont-Doherty Geological\nHonby School 37\n45, 348, 366-368, 374\nObservatory 374, 390\nHorizontal crustal movements 243-\nJoseph Jensen Filtration Plant\nLanark Street 44\n293\n27, 28, 198, 204, 217, 218, 230\nLand movement studies 223-242\nHorizontal earth movements 230-\nJurassic 161-163\nhorizontal crustal movements\n235\nJuvenile Hall 27, 127, 131, 132,\n243-293\nHospital fault 209\n189-196, 198, 200, 204, 217, 218\nvertical crustal movements\nHot Springs Avenue 37\nsee also San Fernando Valley\n295-324\nHouses, damage to 208, 211\nJuvenile Hall\nLand surveyor, implications of\nHousing development in northern\nland movement to 223\nJuvenile Hall landslide 147, 215\nSylmar 207\nLandslide origin of ruptures and\nJuvenile Hall slide 27, 132\nHubbard Street 3, 27, 28, 29, 30,\ndisplacements 197\n31, 32, 129, 183, 241\nLandslides 27, 128\nHubbard-Glenoaks Shopping\nat Juvenile Hall 147\nCenter 183\nat Kagel Mountain 148\nK\nHugo Reid adobe 7\nat Olive View Hospital 148\nat San Fernando Reservoirs 147\nHumboldt-Mendocino region 9\nKagel Canyon 27, 33, 34, 129, 130,\nLankershim 6\nHuntington Beach 10\n133, 220\nLas Vegas, Nev. 348, 350, 405\nHypocenter of San Fernando\nKagel Canyon Civic Association 34\nLe Berthon Street 46\nearthquake 1\nKagel fault 131, 220\nLechusa Point 302\nHypocenters-categories of accu-\nKagel Mountain 27, 131, 148\nLeRoy Crandall & Associates 204\nracy 17\nKaiser Foundation Hospital 44\nLesner Avenue 47\nHypocenters (vertical cross sec-\nKarl Holton Boys Camp 34\nLick Observatory 66\ntion) 19\nKern County 10, 228, 240\nLinda Vista Avenue 45\nHypocentral depth of main shock\nKern County earthquake of 1952:\nLinnet Street 47\n17\n138, 153\nLiquefaction of hydraulic fill 147","Index\n427\nMagnitude of main shock 13, 17\nLos Angeles County Engineer\nLiquefaction of soil 27, 196, 217,\nMagnitude of surface wave 50\n(LACE) 244, 246\n218\nMagnitudes of earthquakes 5\nLos Angeles County Engineer\n\"Little Tokyo\" 41\nMain Street 41\n(LACO) 226, 228-230, 232-\nLittle Tujunga Canyon 128-130,\nMaltman Avenue 42\n235, 242\n133, 144, 147, 148, 149\nMansfield Avenue Storm Drain 28\nLos Angeles County Engineer's\nLittle Tujunga Canyon Road 34\nMap of:\nOffice 205, 206\nLittle Tujunga Ranger Station 34\naccelerograph stations in central\nLos Angeles County Flood Control\nLittle Tujunga Road 130\nand southern California 327\nDistrict (LACFCD) 228, 229,\nLittle Tujunga syncline 149, 159,\naccelerograph stations in central\n230, 330, 377, 388\n208\nLos Angeles 329\nLos Angeles County Road\nLockwood Valley 6\naccelerograph stations in\nDepartment 230\nLompoc 6, 9\nextended Los Angeles area 328\nLos Angeles Department of\nLone Pine 7\naftershock area of earthquake 14\nBuilding and Safety 365, 367\nLong Beach 10, 159, 346\narea affected by earthquake 24\nLos Angeles Department of Water\nLong Beach earthquake of March\nearthquake study area 231\nand Power (LADWP) 132,\n10, 1933: 10\nelevation changes in northern\n190, 198, 200, 206, 215, 217,\nLopez 27\nSan Fernando Valley area 146\n228, 419\nLopez Canyon 27, 29, 129, 131,\nepicenters of aftershocks of \"A\"\nLos Angeles Fire Station No. 74:\n133, 134, 142, 166, 181, 214, 230\nand \"B\" hypocentral accuracy\n33\nLopez Canyon Channel 28\n18\nLos Angeles Flood Control\nLopez Dam 28, 129\nepicenters-main shock and\nDistrict 206\nLopez Debris Basin 28\naftershocks 71, 376\nLos Angeles flood control\nLorne Street 44\nepicentral area 25\nfacilities 28\nLos Angeles 3, 6, 7, 8, 9, 10, 14,\ngeological setting northern\nLos Angeles Harbor 228\n26, 28, 33, 41, 43, 49, 137, 141,\nSylmar 209\nLos Angeles High School 41\n142, 149, 153, 295, 325, 326,\ngeology of Los Angeles-San\nLos Angeles Outer Harbor 240\n342, 346, 347, 348, 351, 365,\nFernando Valley area 140\nLos Angeles River 162\n366, 367, 368, 374\nground surface ruptures at San\nLos Angeles Street 41\nLos Angeles airport 346\nFernando Valley Juvenile\nLos Feliz Boulevard 42\nLos Angeles Basin 2, 10, 138, 142,\nHall 191\nLower Van Norman Dam 131\n152, 153, 155, 159, 161-163,\nground-acceleration values in\nLower Van Norman earthfill dam\n234, 240\ncentral and southern\nLos Angeles city 10, 183, 226, 295,\n27, 28\nCalifornia 343\nLower Van Norman Lake 27, 29,\n297\nground-acceleration values in\n44, 132, 133, 198\nLos Angeles City Bureau of\ncentral Los Angeles 345\nLower Van Norman Reservoir 28,\nEngineering (LABE) 198, 200,\nground-acceleration values in\n35, 45, 360\n206, 228, 230, 232, 234, 235,\nextended Los Angeles area 344\nLow-gain instrumental records 17\n240\nhorizontal geodetic control in\nLowry Road 43\nLos Angeles City Bureau of\nSylmar-San Fernando area 224\nLuana Lane 43\nEngineering (LACBE)\n242,\nhorizontal movement of survey\nLyons Avenue 36, 37\n244\ncontrol stations 236\nLos Angeles City College 42\nhousing development northern\nLos Angeles City Hall 302, 304\nSylmar 210\nM\nLos Angeles City (LAC) net 244-\nHubbard-Glenoaks Shopping\n246\nCenter parking lot 185, 186,\nMaclay Aqueduct 132\nLos Angeles city ordinance 326\n187\nMaclay Avenue 30, 134\nintensity zones 24\nLos Angeles City School District\nMaclay High Line 28\nland movement (uplift or\n149, 150\nMaclay Reservoir 28\nsubsidence) 300\nLos Angeles Civic Center, County\nMaclay trunkline 28\nlevel net for earthquake study\nHall of Justice 240\nMagazine Canyon 28, 214\n296, 297\nLos Angeles County 10, 150, 189,\nMagnetic field repeat survey 417-\nleveling lines along which\n215, 226, 228, 235, 243, 295,\n421\nmovement occurred 299\nMagnitude 4.0 and greater shocks\n297, 302\nline-length changes 232\nLos Angeles County Assessor 151\n15, 16\nLos Angeles area (geologic) 156\nMagnitude of aftershocks 69\nLos Angeles County Earthquake\nmagnitude 4.0 and greater\nMagnitude of body wave 50\nCommission 26\nearthquakes in San Fernando\nMagnitude of earthquake events\nLos Angeles County Engineer 190,\nseries 15\n138, 141\n223","428\nSan Fernando Earthquake of 1971\nMap of: (continued)\nMechanical Engineering\nN\nmajor faults in southern\nDepartment, C.I.T. 366\nCalifornia 138\nMedical Examiner-Coroner, reports\nNassau 46\nmeasured maximum horizontal\nof 26\nNational Center for Earthquake\naccelerations 143\nMenlo Park 230\nResearch, USGS 20, 230\nPacoima Dam region and\nMerrick syncline 218\nNational Earthquake Information\naftershocks 404\nMesozoic 159, 160, 162\nCenter (NEIC) NOAA 18,\nPacoima Dam site 380\nMetropolitan Water District 14\n49, 50, 55, 64, 65\npostearthquake leveling nets in\nMetropolitan Water District\nNational Geodetic survey (NGS),\nsouthern California 229\nfacilities, damage to 213-222\nNOAA, 198, 199, 226, 228-230,\npostearthquake triangulation\nMetropolitan Water District of\n232-235, 240-242, 295, 297\nnet 252\nSouthern California (MWD)\nNational Geophysical Data Center,\npreearthquake triangulation\n28, 197, 200, 202, 204, 206,\nNOAA 50\nnet 248\n213-215, 218, 220, 228, 230\nNational Ocean Survey (NOS)\nprimary triangulation net 233\nMexico City station 55\nNOAA 198, 226, 243-246, 325\nrelative ground movement at\nMexico, dilatational observations\nNational Oceanic and Atmospheric\nSan Fernando Valley\nfrom 55\nAdministration (NOAA) 37,\nJuvenile Hall 192\nMexico stations 50, 55\n50, 226, 243, 295, 325, 365, 374,\nrupture zone northeast of Van\nMiddle Ranch 129\n375, 377, 403,\nNorman Lake 201\nMigrations in aftershock activity 17\nNational Science Foundation\nrupture zone west of Van\nMillikan Library, C.I.T. 45, 367-369\n(NSF) 20, 120, 366, 374\nNorman Lake 202\nMintryville 8, 9\nNEIC (see National Earthquake\nruptures, distortion, and\nMiocene 129, 139, 144, 159, 160-\nInformation Center)\nlandslides in Sylmar-San\n163, 166, 171\nNeon Way 35\nFernando area 145\nMission Hills 35, 191\nNevada 23, 82, 152, 348-350, 405\nSan Fernando earthquake area\nMission Hills fault 132, 139\nNevada microearthquakes 82\n(general) 223\nMission Hills syncline 131, 191,\nNevada Test Site 350\nSan Fernando Tunnel area\n218\nNew Zealand Geological Survey\ngeology facing 214\nMission Hills thrust fault 11\n173, 179\nseismoscope response vectors 359\nMission Inn 26, 41\nNewhall 5-7, 8, 9, 11, 29, 36, 37,\nseismoscope site locations 355\nMission San Fernando Rey 36\n234, 251, 254\nshattered earth localities and\nMission Wells 142\nNewhall Highway 27\nsurface fault traces 125\nMission Wells fault 132\nNewhall oilfield 29\nsouthern California Cooperative\nMission Wells segment 128, 131,\nNewhall Post Office 36\nLeveling Program 227\n142\nNewhall-Potrero oilfield 29\nstructural contours on fault\nMobile homes damaged 26\nNewhall Ranger Station 36\nplane 19\nModelo Formation 129, 130, 131,\nNewhall refinery 36\nstructural damage relative to\n133, 162, 163, 171, 173, 177\nNewhall telephone plant 36\ngeology 149,150\nModelo strata 130, 134, 166\nNewport Beach 10\nsurface breaks resulting from\nModified Mercalli intensities 123,\nNewport-Inglewood fault zone\nearthquake, (pocket insert)\n142\n159, 160, 162\nsurface ruptures, lateral\nModified Mercalli Intensity Scale\nNewport-Inglewood uplift 159, 160\ndistortion, and slope failures\n5, 26\nNewton Street 133, 166\n144\nMojave 7, 9\nNGS (see National Geodetic\nSylmar ground water basin 195\nMonterey County 7\nSurvey)\ntest pit locations 167\nMonterey Formation 163\ntopography as shown on 1935\nNOAA (see National Oceanic and\nMonterey Park 43\nSylmar Quadrangle 193\nAtmospheric Administration)\nMonterey Road 46\ntrench locations 174\nNOAA Earth Sciences Laboratories\nMontrose 43\nVan Norman Lake vicinity 199\n403\nMorningside School 30\nvertical movements resulting\nMO-2 accelerograph 350, 366, 368\nNOAA Earthquake Mechanism\nfrom earthquake 225\nMO-2 accelerograph records 326\nLaboratory 16, 20\nMarek Canyon 34,133\nMount Hamilton 6\nNOAA Environmental Data\nMarklein Avenue 46\nMt. Gleason 234\nService 49\nMartinez Formation 162\nMt. Wilson 234\nNOAA Environmental Research\nMay Company Store 39, 41\nMunsell system 175\nLaboratories 49, 325, 348, 350\nMcBroom Street 46\nMWD (see Metropolitan Water\nNOAA National Earthquake\nMean Sea Level Datum of 1929:\nDistrict of Southern\nInformation Center 18, 49, 50,\n226\nCalifornia)\n55, 64, 65","Index\n429\nParkfield earthquake of 1966:\nOlive View facility 151\nNOAA National Geodetic Survey\n330, 383-385, 387\nOlive View Hospital 23, 27, 29, 30,\n198, 199, 226, 228-230, 232-235,\nParking lot damage 183-187\n31, 32, 132, 148, 192, 193, 218,\n240-242, 295, 297\nPasadena 6, 9, 15, 17, 18, 38, 45,\n219, 229\nNOAA National Geophysical Data\n137, 139, 152, 366\nOlive View landslides 148\nCenter 50\nPasadena network, instruments of\nOlive View medical facilities 151\nNOAA National Ocean Survey\n15\nOlive View Powerplant 29\n198, 226, 243-246, 325\nPatrick Henry Junior High School\nOlive View Sanatorium 302, 304\nNOAA Seismological Field Survey\n34\nOliver Canyon 27, 130, 143\n23, 30, 325, 326, 348, 349, 351,\nPavement damage 183\nOlvera Street 41\n353, 364, 367, 374, 375, 377\nPaxton Street 133\nOlympic 42\nNOAA Seismological Research\nPDE (see Preliminary\nOrange County 10, 226, 295\nGroup 49\nDetermination of Epicenters)\nOrion Avenue 45\nNOAA/EERI San Fernando\nPearblossom 240\nOrion Boulevard 393-395\nEarthquake Investigation\nPenetrometer survey 194\nOro Vista Avenue 130\nCommittee 367\nPeninsular Ranges 138\nOsceola School 128\nNOAA/EERI Subcommittee on\nPhillippi Avenue 31\nOsceola Street 128, 129\nGeodesy 242\nPhillippi Street 30\nOswego Street 46\nNordhoff 7\nPico Canyon 7, 8\nOwens River Aqueducts 28\nNordhoff Street 44\nPico Canyon earthquake of 1893:\nOwens Valley 6, 7\nNorth American Datum of 1927:\n7, 14\nOwensmouth 6, 10\n226, 235, 247\nPico Formation 162, 163\nNorth Avenida Ronanda 37\nPine Glen Road 41\nNorth Dexter Park Road 33\nPine Valley Avenue 44\nP\nNorth Heliotrope Drive 42\nPipeline damage 29\nNorth Hollywood 6, 43\nPiru Creek 332\nPacific Coast companies, oil wells\nNorth Kagel Canyon Road 34\nPiru Mountains 8\nof 8\nNorth Little Tujunga Canyon\nPlacerita oilfield 29\nPacific Intertie 28, 215\nRoad 34\nPlanetable survey of damaged\nPacific Intertie Terminal 132\nNorth Naomi Street 38\nparking lot 183, 187\nPacific Ocean 159\nNorth Normandie Avenue 42\nPleistocene 132, 160, 162, 163, 191,\nPacifico Mountain 234\nNorth Oakgrove Avenue 45\n194, 208\nPacoima 44, 123, 124, 151, 302, 354,\nNorth Oaks 37\nPleistocene fault movement 129\n395\nNorth Olive View fault 192-194,\nPliocene 162, 163\nPacoima Canyon 146, 147, 151\n214, 215\nPlio-Pleistocene 208\nPacoima Dam 16, 27, 28, 32, 34, 81,\nNorthridge 43, 44\nPoint Arguello 9\n148, 151, 152, 208, 230, 330,\nNorthridge Hills 139\nPoint Loma 6\n342, 347, 354, 366, 367, 370,\nNorthridge Hospital 43\nPoint Mugu 240, 295, 302\n375, 376, 381, 383, 386-388,\nNorwalk fault 6\nPolk Street 29\n393-395, 403-405\nNorwich Avenue 36\nPort Hueneme 302\nPacoima Dam accelerogram 370,\nNSF (see National Science\nPorter Ranch 28, 44\n375-391, 395\nFoundation)\nPrecambrian 162\nPacoima Dam accelerogram records\nPreliminary Determination of\nof largest aftershocks 81\nEpicenters (PDE) 18\nPacoima Dam response to\no\nPrivate property damage estimates\naftershocks 403-415\n26\nOak Canyon oilfield 29\nPacoima Formation 132, 162\nPropagation-path attenuation\nOak Hill fault 131, 133, 179, 181\nPacoima Memorial Lutheran\neffects in S-wave spectra 79\nOak Hill Trench 179-181\nHospital 29, 32, 173\nProperty damage estimates 26\nOdessa Avenue 35\nPacoima Reservoir 27\nProperty owner, implications of\nOilfield facilities, damage to 29\nPacoima strong-motion instrument\nland movement to 223\nOjai 7\n123\nPublic property damage estimates\nOld Ridge Route 393, 394\nPacoima Wash 28, 129, 133, 142,\n26\nOld Sierra Highway 27\n166, 220\nPuente Formation 163\nOligocene 163\nPaleocene 163\nPuente Hills 159\nOlive 6\nPalmdale 228, 240, 302\nPurisima 6\nOlive Switching Station 29\nPalos Verdes Hills 159, 162, 163\nP-wave 49, 50, 55, 64, 65, 66, 67\nOlive View 131, 142\nP-wave solutions of focal\nPanorama City 44\nOlive View fault 131, 139, 148,\nmechanism 49-67\nPark View Avenue 45\n192, 194, 200","430\nSan Fernando Earthquake of 1971\nQ\nSan Diego Freeway 27, 131, 132\nSan Francisco Companies, oil wells\nSan Fernando 6-10, 14, 18, 23, 26-\nof 8\nQuail 302\n30, 35, 49, 124, 126-129, 132,\nSan Francisco earthquake of 1906:\nQuaternary 159, 166, 171, 181, 182\n133, 139, 142, 147, 149, 151,\n2\nQuestionnaire card canvass 23, 30\n152, 162, 165, 178, 181, 183,\nSan Gabriel 6\n212, 213, 228, 230, 241, 254,\nSan Gabriel fault 139, 161, 162, 243\n295, 330\nSan Gabriel Mission 6, 7\nR\nSan Fernando Airport 31\nSan Gabriel Mountains 20, 23, 27,\nSan Fernando Dam 354, 360\n49, 50, 131, 137-139, 147, 152,\nRailroad tracks 27, 217\nSan Fernando fault 11, 14, 20,\n153, 155, 159, 161, 162, 191,\nRailroad traffic disrupted 27\n137-140, 142, 153, 189\n208, 235, 241, 330\nRajah Street 27\nLakeview segment 130-131\nSan Gabriel Range 34\nRamona oilfield 29\nMission Wells segment 128-129\nSan Gabriel River 160\nRanger seismometer 70\nSylmar segment 19, 27, 128-129,\nSan Gabriel Valley 6\nRapid Blue Print Company 366\n165, 166-171, 178, 183, 189\nSan Gorgonio Pass 7\nRathburn Avenue 43\nTujunga segment 14, 19, 27, 128,\nSan Jacinto fault 6\nRaymond fault 7\n129-130, 165-166, 171\nSan Jacinto fault zone 141, 347\nRaymond Hill fault zone 159, 160\nSan Fernando fault system 181, 182\nSan Jacinto Valley 220\nRecent 159, 162, 163, 208\nSan Fernando fault zone 128-131,\nSan Jose (street) 35\nReflection of seismic waves 124\n181, 184, 198\nSan Juan Bautista 9\nRepetto Formation 162, 163, 171\nSylmar segment 183, 208\nSan Juan Capistrano 6\nRepetto Hills 159-161\nSan Fernando Industrial Park 129\nSan Luis Obispo County 7\nReseda 43, 44, 45\nSan Fernando Industrial Tract 29\nSan Pedro 295, 297, 302\nRFT-250 accelerograph 350, 366,\nSan Fernando Juvenile Facility 151\nSan Pedro Formation 163\n368, 369\nSan Fernando Juvenile Hall 29\nSan Simeon 6\nRFT-250 accelerograph records\nSan Fernando Pass 128\nSand boils 27, 198\n326\nSan Fernando Range 8\nSand Canyon Fire Station 419\nRhoda Street 47\nSan Fernando Ranger Station 29,\nSanta Ana 7, 9\nRichter magnitude of aftershocks\n30\nSanta Ana River 6\n69\nSan Fernando Reservoir 230\nSanta Barbara 6, 7, 9, 10, 17, 18\nRinaldi 133\nSan Fernando Reservoir complex\nSanta Barbara Channel 6\nRinaldi Street 132, 133\n147, 148\nSanta Clara River 146, 147, 235\nRiverside 6, 17, 18\nSan Fernando Reservoir landslides\nSanta Clara River Valley 142\nRiverside County 226, 240, 295\n147\nSanta Felicia Dam 332\nRockfalls 27\nSan Fernando Reservoirs 141, 142,\nSanta Margarita 295\nRockslides 34\n147, 149\nSanta Monica 9\nRosamond 240, 302\nSan Fernando Rey de España 6\nSanta Monica Bay 10\nRoscoe Boulevard 43, 45\nSan Fernando Road 29, 31, 132,\nSanta Monica fault zone 162\nRossi-Forel Intensity Scale 5, 7, 9\n134, 189, 190, 198, 200-202, 205\nSanta Monica Formation 161\nRoute 5/14 interchange 27\nSan Fernando rupture zone 147\nSanta Monica-Hollywood fault\nRoute 5/210 interchange 27\nSan Fernando segment 142\nzone 159\nRoxford Street 31, 132\nSan Fernando State College 44\nSanta Monica Mountains 155, 159,\nSan Fernando thrust fault,\n161, 162, 233.\ndisplacement on 124\nSanta Susana 9\nS\nSan Fernando Tunnel 28, 213, 214\nSanta Susana fault 128, 134, 138,\nSan Fernando Valley 5, 6, 9-11, 14,\n139, 214\nSan Andreas fault 6, 7, 9, 10, 138,\n20, 27, 28, 30, 128, 137-139,\nSanta Susana fault system 139, 146\n139, 153, 181, 330, 417\n141, 142, 147-149, 151, 152,\nSanta Susaná fault zone 128\nSan Andreas fault system 139, 141,\n155, 160-163, 213, 219, 240,\nSanta Susana Mountains 128, 155,\n417\n346, 376\n159, 161, 162\nSan Andreas fault zone 347\nSan Fernando Valley Juvenile\nSanta Susana thrust 20, 144, 149\nSan Andreas rift 226, 241\nFacility 151\nSanta Susana thrust fault 139, 142\nSan Andreas-type faults 137\nSan Fernando Valley Juvenile Hall\nSanta Ynez 6\nSan Bernardino 7, 9\n27, 131, 134, 189-196, 198, 215\nSantiago Formation 163\nSan Bernardino County 226, 228,\nSan Fernando Veterans Administra-\nSaugus 5-9, 27, 28, 36, 37, 234, 251,\n240, 295\ntion Hospital 29, 151\n254, 297, 302\nSan Buenaventura 6, 7\nSan Fernando Veterans Hospital\nSaugus Formation 128, 129, 131-\nSan Diego 6, 7, 20\n28\n133, 139, 146, 162, 191, 203,\nSan Diego County 226, 240, 295\nSan Francisco 9, 374\n208, 211, 215, 218","Index\n431\nSubcommittee on Geodesy 226, 242\nalong Golden State Freeway 194\nSayre Street 31\nSubcommittee on Sociological\nSoil, settlement and downslope\nSCE (see Southern California\nAspects 223\nmovement 3\nEdison Company)\nSubsidence, areas of 147\nSoledad 36, 37\nSchonstedt HMS-1-magnetometer\nSubsurface investigation of ground\nSoledad Canyon 23, 37\n418\nrupturing 165-172\nSoledad Canyon Road 27, 37\nSchool buildings damaged by\nSugarload Peak 214\nSoledad Canyon School 38\nearthquake 30\nSun Valley 47, 298\nSolemint 20, 38\nSchool buildings, pre-1933: 151\nSunland 27, 46, 128\nSombrero Canyon 191\nSchwartz Canyon 27, 130, 144\nSunland Tunnels 213\nSouth Figueroa Street 393, 394\nSecond Owens River Aqueduct 28\nSunset Place 42\nSouth Pasadena 46\nSeismic history 14\nSunshine Ranch Member of\nSouth Serrano Avenue 42\nSeismic refraction survey 195\nSaugus Formation 128\nSouthern California 6, 10, 11, 14,\nSeismic risk to those occupying\nSurface breaks resulting from\n17, 18, 55, 67, 127, 138, 141,\nbuildings 152\nearthquake 127-135\n226, 295, 325, 326, 348-350,\nSeismic shaking above thrust fault\nSurface-wave magnitude 50\n354, 365, 377\n123-126\nSusana trunkline 28\nSouthern California Cooperative\nSeismic shaking, hazardous areas\nS-wave 49, 50, 55, 64, 65, 66, 67\nLeveling Program 226, 235,\n152\nS-wave solutions of focal\n240, 242\nSeismic-wave energy 124\nmechanism 49-67\nSouthern California crustal model\nSeismogram, low-gain 17\nS-wave spectra for aftershocks 69-\nSeismograms for aftershocks 69-121\n17\n121\nSouthern California Edison\nSeismograms for focal mechanism\nSwimming pool damage 30\nCompany (SCE) 220, 228, 230\nsolutions 49\nSylmar 3, 18, 23, 26-29, 31, 33, 35,\ntransmission tower bases 220\nSeismograph station locations 15\n127-129, 134, 139, 142, 144,\nSouthern Pacific Railroad 9, 132,\nSeismograph stations used for\n147-149, 151, 152, 162, 165,\nepicentral locations 15\n217\n189, 207, 212, 213, 218, 220,\nSpecial Projects Party, NOAA 348,\nSeismological Field Survey, NOAA\n228, 230, 330\n23, 30, 325, 326, 348, 349, 351,\n350, 403\nSylmar Central Office of General\nS-polarization angles 49, 50, 55, 65,\n353, 364-368, 374, 375, 377\nTelephone Company 29\nSeismological Research Group,\n67\nSylmar Converter Station 27, 28,\nSprengnether seismoscope 354\nNOAA 49\n29, 190, 193, 198, 204, 215\nS-residual 50\nSeismometer, Ranger 70\nSylmar fault 214\nSt. Vincent de Paul Camp 128, 134\nSeismoscope results 353-364\nSylmar fault trace 220\nStandard Coast and Geodetic\nSeismoscope, Sprengnether 354\nSylmar fault segment 20, 27, 133\nSurvey trong-motion\nSepulveda 45, 46\nSylmar High School 30, 219\nseismograph 350, 366\nSepulveda Boulevard 190\nSylmar Industrial Park 132\nState College Drive 43\nSespe Formation 163\nSylmar Industrial Tract 29\nState Highway 14: 147\nSheman Oaks 46\nSylmar notch 128\nState Project water distribution\nShaking damage north of Sylmar\nSylmar segment of San Fernando\n213, 214\n151\nfault 19, 27, 128, 129, 165, 166,\nShaking, intensity of 123, 141, 142\nStockton 23\n189\nStrandwood Avenue 28\nShaking, severity of 137\nSylmar segment of San Fernando\nStratigraphy of:\nShell Oil Company 367\nfault zone 128, 183, 208\nLos Angeles Basin 162, 163\nSherman Oaks 46\nSylmar Tap Transmission Lines\nSan Fernando Valley 161, 162\nSierra Estates Drive 36\n230\nStress drops for earthquakes 2\nSierra Madre 152\nSylvia Avenue 44\nStrike-slip aftershocks 19\nSierra Madre fault 138, 139, 152\nStrong-motion accelerogram\nSignal Hill 10\nprocessing 365-374\nSilver Lake 42\nT\nStrong-motion accelerograph\nSilverado Formation 163\nrecords 325-348\nSimi 9\nTarzana 47\nStructural damage in North Sylmar\nSimi Hills 155, 159, 162\nTectonic mechanism of the\nhousing development 207-212\nSimshaw Avenue 31\nearthquake 14\nStructural damage relative to\nSlickensides 130\nTejon Pass 9\nSmall Business Administration 151\ngeology:\nTeledyne-Geotech 326\nnorthern San Fernando Valley\nSMA-1 accelerograph 350, 366,\nTelfair Avenue 44\narea 149 (map)\n368, 369\nTellurometer 230\nSan Fernando Valley-Los Angeles\nSoil profile:\nTerminal Hill 28\nBasin area 150 (map)\nacross Juvenile Hall site 193","432\nSan Fernando Earthquake of 1971\nTerry Street 42\nUpper Van Norman Reservoir 35,\nVertical crustal movements 295-324\nTertiary 129, 332\n190, 191, 195, 197, 215, 217\nVertical earth movements 235-240\nTest borings prior to tunneling\nU.S. Army Corps of Engineers\nVeterans Administration Hospital\n213, 214\n(USCE) 228, 230, 326\n30, 31, 32, 45, 151, 207, 208,\nThe Gables 129\nU.S. Atomic Energy Commission\n218\nThrust fault 19, 20\n173\nVeterans fault 131, 146, 208, 212\ngeometry and movement 124\nU.S. Coast and Geodetic Survey\nVeterans Hospital 27, 33, 34\nseismic shaking above 123-126\n(USC&GS) 226, 234, 325, 326,\nVia Calinda (street) 37\nThrust-fault scarp 129\n353\nVRES (see Velocity response\nThrust-type aftershocks 19\nU.S. Forest Service 36, 230\nenvelope spectrum)\nTilting, regional 147\nU.S. Geological Survey (USGS)\nTime of main shock 13, 23\n16, 17, 20, 30, 71, 72, 120, 128,\nW\nTinemaha 6, 17, 18\n142, 173, 193, 198, 200, 214,\nTonopah, Nev. 23\n228, 230, 232, 234, 241, 246\nWallaby Street 27\nTopanga Canyon 159\nU.S. Highway 5: 27\nWalnut (street) 36\nTopanga Creek 302\nU.S. Highway 14: 33\nWameda Avenue 43\nTopanga Formation 162, 163\nUSGS National Center for\nWater levels in wells 222\nTopanga Plaza 39\nEarthquake Research 20, 230\nWater table 217\nTowsley Formation 129, 133, 162\nUSGS network, explosion\nWaterline damage 29\nTransverse Ranges 138, 141\ncalibration of 17\nWeldon Canyon 191\nTraveltime correction factors 17\nUtah 23\nWest Eighth Street 41\nTrenches:\nUtilities damaged by earthquake:\nWest Trail, Kagel Canyon 34\nacross zone of displacement at\nSan Fernando, Sylmar, and\nWestern United States strong-\nJuvenile Hall 190\nenvirons 28\nmotion accelerograph network\nacross surface breaks 133, 134,\n326, 349\n165-172\nWhitaker 251\nV\nacross surface fault ruptures 173-\nWhite Wolf fault 9, 10, 153\n182\nValencia 36, 37\nWhittier fault 6\nTriassic 163\nVan Gogh School 35, 131, 132, 198\nWhittier fault system 161\nTrilateration surveys by MWD 214\nVan Gogh Street Elementary\nWilbur Avenue 133\nTujunga 47, 302\nSchool 30, 34, 198, 215\nWild T-2 Theodolite 230\nTujunga segment of San Fernando\nVan Norman Dam 23\nWilmington 240\nfault 14, 19, 27, 129, 130, 165,\nVan Norman Lakes 27, 197, 198,\nWilmot seismoscope 354, 376\n166\n205, 302\nWilshire 42\nTujunga segment of San Fernando\nruptures and displacements in vi-\nWilson Canyon Channel 28\nfault zone 128\ncinity 197-206\nWilson-Mansfield Channel 230\nTyler Street 134\nVan Norman Reservoirs 228, 230\nWish Avenue 43\nVan Nuys 47\nWood-Anderson instruments 17\nVan Nuys Airport 47\nU\nWood-Anderson torsion\nVan Nuys Avenue 44\nseismometers 18\nUniform Building Code, 1970: 326\nVan Nuys Boulevard 44, 198\nWoodland Hills 47\nUnion Bank Building 46\nVan Nuys District Office 228\nW. T. Grant Building 37\nUnited Electro-Dynamics 326\nVaqueros Formation 163\nUnited Water Conservation\nVarian-M50 magnetometer 418\nY\nDistrict 332\nVaughn Street 31, 129\nUniversity of California, Berkeley\nVelocity response envelope\nYale Laboratories in Los Angeles\n374, 405\nspectrum (VRES) for selected\n367\nUniversity of California, Los\naccelerograms 393-401\nYarnell Street 200\nAngeles (U.C.L.A.) 367\nVentura 7, 9, 46\nYerba Buena Ridge 131\nUniversity of California, San Diego\nVentura County 6, 226, 240, 295\nYolanda Avenue 44, 133\n20\nVentura Freeway 43\nYosemite National Park 23\nUplift, regional 147\nVerdugo City 47\nUpper San Fernando Reservoir 151\nVerdugo fault 132, 139, 159\nZ\nUpper Van Norman Dam 132\nVerdugo Mountains 155, 159, 161\nUpper Van Norman earthfill dam\nVernon 47\nZones of bending (surface\n27\nVertical acceleration 3\ndeformation) 147\nUpper Van Norman Lake 27, 28,\nVertical cross section of:\nZones of earthquake intensity 23-48\n131, 132\nhypocenters 19\nZones of surface faulting 128-131\n* U.S. GOVERNMENT PRINTING OFFICE: 1974 0-469-530"]}