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Seismicity Remotely Triggered by the Magnitude 7.3 Landers, California, Earthquake Author(S): D

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Seismicity Remotely Triggered by the Magnitude 7.3 Landers, California, Earthquake Author(S): D Seismicity Remotely Triggered by the Magnitude 7.3 Landers, California, Earthquake Author(s): D. P. Hill, P. A. Reasenberg, A. Michael, W. J. Arabaz, G. Beroza, D. Brumbaugh, J. N. Brune, R. Castro, S. Davis, D. dePolo, W. L. Ellsworth, J. Gomberg, S. Harmsen, L. House, S. M. Jackson, M. J. S. Johnston, L. Jones, R. Keller, S. Malone, L. Munguia, S. Nava, J. C. Pechmann, A. Sanford, R. W. Simpson, R. B. Smith, M. Stark, M. Stickney, A. Vidal, S. Walter, V. Wong and J. Zollweg Source: Science, New Series, Vol. 260, No. 5114 (Jun. 11, 1993), pp. 1617-1623 Published by: American Association for the Advancement of Science Stable URL: http://www.jstor.org/stable/2881709 . Accessed: 28/10/2013 21:58 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. American Association for the Advancement of Science is collaborating with JSTOR to digitize, preserve and extend access to Science. http://www.jstor.org This content downloaded from 128.95.104.66 on Mon, 28 Oct 2013 21:58:06 PM All use subject to JSTOR Terms and Conditions ............................................---.----..;- Rv'>'E S5'5.' EA ; a ar"T I_Cl E few tens of kilometersor less of the induc- Seismicity Remotely Triggered by ing source (4). In marked contrast, the widespreadsurge in post-Landersseismic activity extendedover 1250 km (17 source the Magnitude 7.3 Landers, dimensions)from the mainshock. This abrupt,widespread, and unexpected California, Earthquake seismicityincrease challenges a long-stand- ing skepticismregarding the realityof trig- D. P. Hill,P. A. Reasenberg, A. Michael,W. J. Arabaz, geredseismic activity at greatdistances from G. Beroza, D. Brumbaugh,J. N. Brune, R. Castro, S. Davis, an earthquake.This skepticismhas its roots, D. dePolo, W. L. Ellsworth,J. Gomberg, S. Harmsen, L. House, in part, in the uncertainsignificance associ- ated with an increasein earthquakeactivity S. M. Jackson, M. J. S. Johnston, L. Jones, R. Keller,S. Malone, at a solitary,remote site aftera largeearth- L. Munguia,S. Nava, J. C. Pechmann, A. Sanford, quake,and, in part,in the lackof a plausible R. W. Simpson, R. B. Smith, M. Stark, M. Stickney, A. Vidal, physical model for remote triggering.In S. Walter,V. Wong, J. Zollweg particular,Earth models based on linear elasticity, which have been successfulin The magnitude 7.3 Landers earthquake of 28 June 1992 triggered a remarkably sudden explaininga vast rangeof seismologicalphe- and widespread increase in earthquake activity across much of the western United States. nomena, seem incapableof accountingfor The triggered earthquakes, which occurred at distances up to 1250 kilometers (17 source triggeredseismicity beyond a few source dimensions) from the Landers mainshock, were confined to areas of persistent seismicity dimensionsof an earthquakerupture (5). and strike-slip to normal faulting. Many of the triggered areas also are sites of geothermal The simultaneousincrease in seismicactiv- and recent volcanic activity. Static stress changes calculated for elastic models of the ity at many remote sites following the earthquake appear to be too small to have caused the triggering. The most promising Landersearthquake thus forces consider- explanations involve nonlinear interactions between large dynamic strains accompanying ation of an expandedrange of models that seismic waves from the mainshock and crustal fluids (perhaps including crustal magma). includenonlinear interactions. In this article we document the spatial distributionand temporalevolution of the seismic activity that followed the Landers At 1157 UT (04:57 PDT) on 28 June gered by a nearby source is well known. mainshock and the tectonic settings in 1992, southern California was rocked by Aftershocksof large and moderateearth- which the activityoccurred. We arguethat the magnitude (M) 7.3 Landers earth- quakescommonly occur at distancesof one this activity is not explained by random quake, the largest earthquake to strike the or two sourcedimensions from a mainshock coincidence and commenton evidence for region in 40 years (1). The earthquake (3). Seismicityinduced by humanactivities remote triggeringby other major (M 2 7) resulted from a northward propagating rup- (which include the undergrounddetona- earthquakes.We conclude by exploring ture producing up to 6 m of right-lateral, tion of nuclearexplosions, filling or empty- some possiblephysical processes that might strike-slip displacement on a series of faults ing of water reservoirs,injecting and ex- explain remote triggering. extending over 70 km north-northwest into tractingfluids in deep boreholes,and min- Distribution and nature of triggered the Mojave desert from the epicenter 5 km ing) is usuallyconfined to an areawithin a seismicity. Recognition of remotely trig- southwest of the town of Landers (Fig. 1). Within minutes after the Landers main- shock, earthquake activity abruptly in- Fig. 1. Map showing seis- creased at widely scattered sites across the mograph stations in the western United States (2). >. ,7t .< . .* 8t >+' < '. l . _>. _ * Grat western United States and f ~PlainsPlaiDs That earthquake activity can be trig- K.W t: *WAs *Mexico used in this study .- J *. MT (2). The Landers main- D. P. Hill, P. A. Reasenberg, A. Michael, W. L. Ell- shock ruptureis shown by sworth, M. J. S. Johnston, R. W. Simpson, and S. / ; * t vx [*-* ,N heavy solid line. Major Walter are at the U.S. Geological Survey, Menlo Park, CPSP t +w * / ; , physiographic provinces CA 94025. W. J. Arabaz, S. Nava, J. C. Pechmann, *tt --J___ * \*_/* b .2* 0 are outlined by dashed and R. B. Smith are at the University of Utah, Salt Lake /cot; ^ so . So. X * 4 , lines. Abbreviation: CP- City, UT 84112. G. Beroza is at Stanford University, ,L'*_*I ( R \ Columbia-- o .-: Plateau- Stanford, CA 94305. D. Brumbaugh is at Northern !SRP, | ..... ?et Arizona University, Flagstaff, AZ 86011. J. N. Brune | a .CA1 NV WY_ Snake River Plain. and D. dePolo are at the University of Nevada, Reno, NV 89557. R. Castro, L. Munguia, A. Vidal, and V. Wong are at CICESE, Ensenada, Mexico. S. Davis is at 'Great Basin the University of Texas, Austin, TX 78712. J. Gomberg and S. Harmsen are at the U.S. Geological Survey, Golden, CO. L. House is at Los Alamos National Laboratories, Los Alamos, NM 87545. S. M. Jackson is at Idaho National Engineering Laboratory, Idaho Falls, Colorado ID 83401. L. Jones is at the U.S. Geological Survey, Pateau Pasadena, CA. R. Keller is at the University of Texas at El Paso, El Paso, TX 79968. S. Malone is at the University of Washington, Seattle, WA 98195. A. San- ford is at the New Mexico Institute of Mining and Technology, Socorro, NM 87801. M. Stark is at Unocal Corporation, Santa Rosa, CA. M. Stickney is at the * .'.Southern. Basin Montana Bureau of Mines and Geology, Butte, MT 500 km and Range 59701. J. Zollweg is at Boise State University, Boise, - - NM ID 83725. SCIENCE * VOL. 260 * 11 JUNE 1993 1617 This content downloaded from 128.95.104.66 on Mon, 28 Oct 2013 21:58:06 PM All use subject to JSTOR Terms and Conditions gered seismicitydepends critically on the geothermalactivity or youngvolcanism are lion yearold) basalticvents (9). Only a few distributionof seismic networks. Because concentratedjust east of the California- of the many seismicallyactive geothermal the networks operating in the western Nevada borderfrom the easternside of the and young volcanic systemsin the region, United Statesand northernMexico (Fig. 1) White Mountains to near Lake Tahoe. however,responded with triggeredactivity. do not provide spatiallyuniform coverage Triggeredsites in southernNevada (Little The seismogenicBrawley and CerroPrieto and their detection thresholdsvary, recog- Skull Mountain)and westernUtah (Cedar geothermalareas in the ImperialValley- nition of seismicitytriggered by the Landers City) are not near geothermalsystems but Salton Trough south of Landers(distance event is probablyincomplete. For example, are within 20 km of Pleistocene (<1 mil- fromLanders epicenter A\ = 150 to 250 km; a sequenceof M < 2 earthquakestriggered in southeasternOregon or southernArizo- na would not be detected by any of the Fig. 2. Map showing - / operating networks. Furthermore,before earthquake activitydetect- NV the late 1970smany of the presentnetworks ed by the combined seis- 'MSN / , were sparse or nonexistent. Had the mic networkin the 10 days C Landersearthquake occurred before then, immediately after the ? a, j* I, Landers earthquake. Ma- (,L,' i /o I. the chances are poor that triggeredactivity jor physiographic provinc- CM& \ (/a ) would have been recognized. es are outlined by dashed 0 $,u roatBasin The most dramaticincrease in earth- lines. Faultswith quaterna- f{( , quake activity occurredin the Landersaf- ry movement are shown X) tershockzone within 100 km of the rupture by solid lines. Shaded el- (Fig. 2), which we do not considerfurther lipse extending approxi- (6). We also do not considerpossible trig- mately 100 km beyond the \ L gered activity in southern Californiabe- Landers rupture repre -L , tween the Garlock fault and the interna- sents the aftershock zone. M Abbreviations: AZ, Arizo-
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