DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY United States Earthquakes, 1971 By Jerry L. Coffman and Carl A. von Hake Open-File report 84-971 Prepared in cooperation with National Oceanic and Atmospheric Administration, This report has not been reviewed for conformity with U.S. Geological Survey editorial standards. 1984 The Environmental Data Service does not approve, recommend, or endorse any proprietary product or proprietary material mentioned in this publication. No reference shall be made to the Environmental Data Service, or to this publication furnished by the Environmental Data Service, in any advertising or sales promotion which would indicate or imply that the Environmental Data Service approves, recommends, or endorses any proprietary product or proprietary material mentioned herein, or which has as its purpose an intent to cause directly or indirectly the ad­ vertised product to be used or purchased because of this Environmental Data Service publication. Contents LIST OF TABLES Page Table \ Instrumentally determined locations of earthquakes and related phenomena that occurred in the United States during 1971 ........................ 79 2 Principal earthquakes of the world during 1971 ........................ 97 3 Fluctuations in well-water levels during 1971 ........................... 104 4 Earthquakes in 1971 believed to have caused fluctuations in well-water levels. 110 5 Occurrence of 'earthquakes and number of records for 1971 ............ 119 6 Compilation of strong-motion accelerograph data for 1971 .............. 120 7 Compilation of southern California seismoscope stations and data for the San Fernando earthquake of February 9. 1971 ............................. 170 LIST OF ILLUSTRATIONS Page 1 I Xunagiiiu earthquakes in (lie United Stales from earliest history through 1971. 5 2 Locations of earthquakes thai were felt or caused damage in the United States during 1971 ........................................................ 10 3 Area affected by Arkansas earthquake of October 1 .................... 15 4 Area affected by San Fernando, Calif., earthquake of February 9 ........ 23 5 Kpiccntral area of San Fernando. Calif., earthquake of February 9 ....... 26 6 Area affected by southern California earthquake of March 31 ........... 62 7 XOAA strong-motion accelerograph network (as of June 30. 1972) ...... 112 8 Act elerograph slalions in central and southern California during San Fernando earthquake ......................................................... 114 9 At c clerograph slalions in extended Los Angeles area during San Fernando earthquake ......................................................... 115 10 Accelerograph slalions in central Los Angeles during San Fernando earthquake ......................................................... 116 1 1 Seisnmscope location map for southern California network during San Fernando earthquake ................................................ 117 12 Magnitude and direction of maximum seismoscope response of each station during San Fernando earthquake ..................................... 118 Introduction United States Earthquakes, prepared an­ for data activities in the field of seismology. nually since 1928, lists epicenters of all earth­ NGSDC is a focal point for the dissemina­ quakes and associated phenomena recorded tion of historical seismic information for both in the United States and nearby territories technical and general users. Its services in­ during the year. It includes brief descriptions clude preparing local and regional seismic of earthquakes that were felt or caused histories for engineers, actuaries, and other damage in the United States, and summarizes scientists; answering direct inquiries from the all available data on tremors noted by public on all aspects of historical earth­ residents of the Panama Canal Zone, Puerto quakes; publishing annual, quarterly, month­ Rico, and the Virgin Islands. In addition, a ly, and revised historical earthquake reports; list of principal earthquakes of the world and making available at a nominal fee copies during the year is presented with brief ac­ of seismograms, accelerograms, displacement counts of their effects. meter records, digitized strong-motion Sources of noninstrumental information seismograms, and epicenter lists (since used in this compilation include reports January 1900). Information concerning ser­ received from questionnaire canvasses, vices and products of NGSDC may be ob­ newspaper clippings, bulletins of the tained from the National Geophysical and Seismological Society of America, special Solar-Terrestrial Data Center, Environmental reports of other organizations, and data from Data Service, National Oceanic and At­ the National Weather Service of NOAA mospheric Administration, Boulder, Colorado whose observers prepare periodic reports on 80302. Some of the seismological services and local seismic activity. products are described in the following Instrumental data utilized in computing paragraphs. earthquake locations, depths, magnitude, and times of occurrence are obtained from Earthquake Epicenter Data NOAA and cooperating seismological ob­ The earthquake data files contain data on servatories, both domestic and foreign. earthquakes, known or suspected explosions, associated collapse phenomena, coal bumps, rock bursts, quarry blasts, and other earth NATIONAL GEOPHYSICAL disturbances recorded by seismographs. The AND SOLAR-TERRESTRIAL date, origin time, geographic location, focal DATA CENTER depth, magnitude, and Modified Mercalli in­ tensity are listed for each event when The National Geophysical and Solar- available. These data may be obtained on Terrestrial Data Center (NGSDC), previously magnetic tape, punched cards, or microfilm. the National Geophysical Data Center and the Aeronomy and Space Data Center, is one Conventional Seismograms of the five major facilities of NOAA's En­ Copies of seismograms from the World­ vironmental Data Service. NGSDC's Solid wide Network of Standard Seismographs Earth Data Services Division is responsible (WWNSS) and other selected foreign 1 United States Earthquakes, 1971 stations, as well as from the Canadian and Institute of Technology, Pasadena. The 114 NOAA networks of seismic stations, are records in the six series represent the record­ available in 35-mm. or 70-mm. film format or ed data for 22 earthquakes in California, as full-size paper copies. Montana, and Washington. High-Gain, Long-Period Seismograms Publications Seismograms from January 1971 recorded Publications issued by NGSDC include the at Albuquerque, N. Mex., Ogdensburg, N.Y., following: Fairbanks, Alaska, Eilat, Israel, and Charters 1. C&GS Special Publication 282, Earthquake Towers, Australia, are now available. Ad­ Investigation in the United States (Revised 1969 ditional stations have been installed recently Edition). This semitechnical booklet explains in Toledo, Spain, Chieng-Mai, Thailand, important facts about earthquakes and Honolulu, Hawaii, Matsushiro, Japan, and discusses major historical shocks of the Kongsberg, Norway. The records are on stan­ United States and nearby territories. It also dard-size paper, and reproductions can be contains sections on seismographs and the obtained in the same formats and costs as the nature of earthquakes and seismic waves. WWNSS seismograms. Six components are 2. C&GS Publication No. 41-1, Earthquake recorded daily three high- and three in­ History of the United States (Revised Edition termediate-gain values in the vertical, north- Through 1970). This report describes south, and east-west directions. prominent earthquakes (generally Modified Mercalli intensity V and above) in the United Earthquake Strong-Motion Data States from historical times through 1970. It All records from the NOAA strong-motion contains regional tables that list earthquake file, starting from the initial accelerograms epicenters or probable locations, intensity, and displacement meter records recorded in and extent of felt area. 1932, may be obtained in full-size paper The preceding reports were prepared in copies, film chips, or 35-mm. roll film. collaboration with Environmental Research A set of accelerograms from 227 locations Laboratories (ERL) groups, especially the affected by the San Fernando, Calif., earth­ Seismological Field Survey and the National quake in February 1971 is also available. Earthquake Information Center. Records are generally from Los Angeles and surrounding areas and include (among others) recordings from Pacoima Dam, San Onofre, EARTHQUAKE EARLY Vernon, and Santa Ana. REPORTING SYSTEM Additional conventional seismograms from the February 9, 1971, earthquake also can be The ERL National Earthquake Informa­ purchased on 70-mm. film, 35-mm. film, or tion Center (NEIC) maintains an earthquake as full-size paper copies. These include most reporting system that provides accurate and of the WWNSS seismograms, as well as rapid epicenter locations and magnitude records from many nonstandard stations. values to the press and other interested Digitized accelerograms of strong earth­ groups. These results are available within 2 to quake ground motions, as processed from 3 hours for earthquakes of magnitude 6'/z or records of the Environmental Research larger. Locations and magnitudes of smaller Laboratories (previously Coast and Geodetic events are computed on request or on receipt Survey records) accelerograph network, are of a press report. NEIC relies on NOAA and available on magnetic tape or punched cards. cooperating observatories