Seismicity Remotely Triggered by the Magnitude 7.3 Landers, California, Earthquake

Hill, David P.; Reasenberg, Paul A.; Michael, Ashley N.; Arabaz, W.J.; Beroza, G. C.; Brumbaugh, D. S.; Brune, James N.; Castro, Raúl R.; Davis, Scott D.; Depolo, D.; Ellsworth, W. L.; Gomberg, Joan; Harmsen, Stephen C.; House, L.; Jackson, Suzette M.; Johnston, M. J. S.; Jones, Lucile M.; Keller, Rebecca Hylton; Malone, Stephen D.; Munguía, Luis; Nava, Susan J.; Pechmann, James C.; Sanford, Allan R.; Simpson, Robert W.; Smith, Robert B.; Stark, M.; Stickney, Michael C.; Vidal, Antonio; Walter, Stephen R.; Wong, Victor; Zollweg, James E.

doi:10.1126/science.260.5114.1617

Cited by 825 publications

(624 citation statements)

References 28 publications

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“…Although static stress changes resulting from fault rupture decay rapidly with distance, dynamic triggering is often observed at much larger distances than the traditional aftershock zone (e.g., ref. 22). Surface waves generated by large earthquakes have been observed to trigger small (M < 5) earthquakes at global distances (e.g., refs.…”

Section: Discussionmentioning

confidence: 99%

Global risk of big earthquakes has not recently increased

Shearer

Stark

2011

Proc. Natl. Acad. Sci. U.S.A.

100

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The recent elevated rate of large earthquakes has fueled concern that the underlying global rate of earthquake activity has increased, which would have important implications for assessments of seismic hazard and our understanding of how faults interact. We examine the timing of large (magnitude M ≥ 7) earthquakes from 1900 to the present, after removing local clustering related to aftershocks. The global rate of M ≥ 8 earthquakes has been at a record high roughly since 2004, but rates have been almost as high before, and the rate of smaller earthquakes is close to its historical average. Some features of the global catalog are improbable in retrospect, but so are some features of most random sequences-if the features are selected after looking at the data. For a variety of magnitude cutoffs and three statistical tests, the global catalog, with local clusters removed, is not distinguishable from a homogeneous Poisson process. Moreover, no plausible physical mechanism predicts real changes in the underlying global rate of large events. Together these facts suggest that the global risk of large earthquakes is no higher today than it has been in the past.earthquake statistics | seismology T he above-average rate of earthquakes of magnitude 8 and larger in recent years (e.g., ref. 1) has prompted speculation that the underlying rate of earthquake activity has changed (2-5), that is, that the observed apparent rate fluctuation is larger than would be expected for a homogeneous random process. Similarly, the recent 2011 Tohoku, Japan, M 9.0 earthquake, together with the 2004 M 9.0 Sumatra-Andaman earthquake and the 2010 M 8.8 Maule, Chile, earthquake, has fueled concern that these giant quakes may not have been independent events (see the discussion in ref. 6). Temporal earthquake clustering, including aftershock sequences, is well known at local and regional scales. However, whether earthquake catalogs, with aftershocks removed, follow a temporal Poisson process-the canonical "unpredictable" temporal process-is a long-standing area of research in seismology (7-11).True earthquake rate changes at global scales would have important implications for assessments of seismic danger and our understanding of how faults interact. Here we ask whether the recent elevation in large earthquake activity is statistically significant and the larger question of whether the locally declustered global catalog is Poissonian. Using cataloged events from 1900 to 2011, we address this question in three ways: (i) plotting earthquake activity versus time to identify apparent anomalies in present and past rates of large earthquakes; (ii) performing Monte Carlo tests to estimate the probability of specific observed anomalies if seismicity were Poissonian with the observed average occurrence rate; and (iii) testing whether the locally declustered catalog is statistically distinguishable from a realization of a homogenous Poisson process, by using three statistical tests. Our main conclusion is that the observed fluctuations in the rate of large...

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Section: Discussionmentioning

confidence: 99%

Global risk of big earthquakes has not recently increased

Shearer

Stark

2011

Proc. Natl. Acad. Sci. U.S.A.

100

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“…Great earthquakes commonly generate both instantaneous and delayed seismicity at distances of hundreds to thousands of kilometres, where static stress changes are negligible, but these remote aftershocks usually have small magnitudes and often occur in volcanic or geothermal areas with quite different stress and frictional regimes [34][35][36] . A notable exception was a M w 6.9 earthquake in Japan that initiated during the passage of surface waves from a M w 6.6 event in Indonesia, confirming the potential for larger triggered earthquakes in compressive environments 37 .…”

Section: Triggering Mechanismmentioning

confidence: 99%

Limitations of rupture forecasting exposed by instantaneously triggered earthquake doublet

et al. 2016

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Earthquake hazard assessments and rupture forecasts are based on the potential length of seismic rupture and whether or not slip is arrested at fault segment boundaries. Such forecasts do not generally consider that one earthquake can trigger a second large event, near-instantaneously, at distances greater than a few kilometers. Here we present a geodetic and seismological analysis of a magnitude 7.1 intra-continental earthquake that occurred in Pakistan in 1997. We find that the earthquake, rather than a single event as hitherto assumed, was in fact an earthquake doublet: initial rupture on a shallow, blind 2 reverse fault was followed just 19 seconds later by a second rupture on a separate reverse fault 50 km away. Slip on the second fault increased the total seismic moment by half, and doubled both the combined event duration and the area of maximum ground shaking. We infer that static Coulomb stresses at the initiation location of the second earthquake were probably reduced as a result of the first. Instead, we suggest that a dynamic triggering mechanism is likely, although the responsible seismic wave phase is unclear. Our results expose a flaw in earthquake rupture forecasts that disregard cascading, multiple-fault ruptures of this type.Continental earthquakes typically rupture diffuse systems of shallow fault segments, delineated by bends, step-overs, gaps, and terminations. The largest events generally involve slip on multiple segments, and whether or not rupture is arrested by these boundaries can determine the difference between a moderate earthquake and a potentially devastating one.Compilations of historical surface ruptures suggest that boundary offsets of ~5 km are sufficient to halt earthquakes, regardless of the total rupture length 1,2 . This value is incorporated into modern, fault-based earthquake rupture forecasts such as the UCERF3 model for California 3,4 , whose goals include anticipating the maximum possible rupture length and magnitude of future earthquakes within known fault systems.However, if earthquakes could rapidly trigger failure of neighbouring faults or fault segments, at distances larger than ~5 km, then such scenario planning could be missing an important class of cascading, multiple-fault rupture. Here we exploit the combination of spatial 3 information captured by satellite deformation measurements and timing information of successive fault ruptures from seismology, to reveal how near-instantaneous, probably dynamic triggering may lead to sequential rupture of multiple large earthquakes separated by distances of 10s of kilometers.The destructive Harnai earthquake occurred on 27 February 1997 at 21:08 UTC (02:08 on 28February, local time) in the western Sulaiman mountains of Pakistan 5 (Figure 1a). Published source catalogues ascribe it a single, largely (85% 99%) double-couple focal mechanism with gentle ~N-dipping and steep ~S-dipping nodal planes and a moment magnitude M w of 7.0 7.1 (Supplementary Table 1 The south-eastern fringe ellipse is caused by slip on another NE-di...

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“…Fluids affect ground strength and shaking behaviour at near-field distances from earthquake epicentres, and transient stresses of seismic waves have potential to interact with fluids and dynamically trigger seismicity at far-field distances (Hill et al 1993;Brodsky et al 2000;Husen et al 2004;Taira et al 2009). Post-seismic fluid flow can have implications for groundwater supply and quality, contaminant transport, underground repository safety and hydrocarbon production (Wang et al 2013;Wells et al 2013).…”

Section: Introductionmentioning

confidence: 99%