Remotely Triggered Earthquakes Following Moderate Mainshocks (or, Why California Is Not Falling into the Ocean)

Hough, Susan E.

doi:10.1785/gssrl.76.1.58

Cited by 40 publications

(21 citation statements)

References 33 publications

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“…One cannot ascribe any statistical significance to the very weakly positive β values between 10 and 50 km ( Figure 7B). However, previous results considering β-statistics averaged over large numbers of earthquakes suggest the small increase in seismicity over this distance range might reflect an extended aftershock zone (Hough 2005;Felzer and Brodsky 2006).…”

Section: Remotely Triggered Earthquakesmentioning

confidence: 67%

“…Recent studies (e.g., Hough 2005;Felzer and Brodsky 2006) have concluded that aftershock/triggered earthquake sequences following small and moderate mainshocks extend to distances of many fault lengths. To explore the spatial distribution of the aftershock sequence of the Chino Hills earthquake, we use the β-statistic to quantify the seismicity rate change at close and regional distances (e.g., Matthews and Reasenberg 1988).…”

Section: Remotely Triggered Earthquakesmentioning

confidence: 99%

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Preliminary Report on the 29 July 2008 Mw 5.4 Chino Hills, Eastern Los Angeles Basin, California, Earthquake Sequence

Hauksson

Felzer

Given

et al. 2008

Seismological Research Letters

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Section: Remotely Triggered Earthquakesmentioning

confidence: 67%

Section: Remotely Triggered Earthquakesmentioning

confidence: 99%

Preliminary Report on the 29 July 2008 Mw 5.4 Chino Hills, Eastern Los Angeles Basin, California, Earthquake Sequence

Hauksson

Felzer

Given

et al. 2008

Seismological Research Letters

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“…Recent studies have shown that remotely triggered earthquakes occur ubiquitously following even small and moderate mainshocks, suggesting that triggering occurs pervasively and in diverse tectonic settings (e.g., Hough, 2005;Felzer and Brodsky, 2006). It remains open to debate whether there is a physical basis for distinguishing these events from conventional aftershocks.…”

Section: Triggered Earthquakementioning

confidence: 99%

Revisiting the 1872 Owens Valley, California, Earthquake

Hough

Hutton

2008

Bulletin of the Seismological Society of America

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The 26 March 1872 Owens Valley earthquake is among the largest historical earthquakes in California. The felt area and maximum fault displacements have long been regarded as comparable to, if not greater than, those of the great San Andreas fault earthquakes of 1857 and 1906, but mapped surface ruptures of the latter two events were 2-3 times longer than that inferred for the 1872 rupture. The preferred magnitude estimate of the Owens Valley earthquake has thus been 7.4, based largely on the geological evidence. Reinterpreting macroseismic accounts of the Owens Valley earthquake, we infer generally lower intensity values than those estimated in earlier studies. Nonetheless, as recognized in the early twentieth century, the effects of this earthquake were still generally more dramatic at regional distances than the macroseismic effects from the 1906 earthquake, with light damage to masonry buildings at (nearest-fault) distances as large as 400 km. Macroseismic observations thus suggest a magnitude greater than that of the 1906 San Francisco earthquake, which appears to be at odds with geological observations. However, while the mapped rupture length of the Owens Valley earthquake is relatively low, the average slip was high. The surface rupture was also complex and extended over multiple fault segments. It was first mapped in detail over a century after the earthquake occurred, and recent evidence suggests it might have been longer than earlier studies indicated. Our preferred magnitude estimate is M w 7.8-7.9, values that we show are consistent with the geological observations. The results of our study suggest that either the Owens Valley earthquake was larger than the 1906 San Francisco earthquake or that, by virtue of source properties and/or propagation effects, it produced systematically higher ground motions at regional distances. The latter possibility implies that some large earthquakes in California will generate significantly larger ground motions than San Andreas fault events of comparable magnitude.

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“…Since then, a number of other M ≥ 7 earthquakes (Brodsky et al, 2000;Glowacka et al, 2002;Prejean et al, 2004;West et al, 2005) as well as smaller M 2-4 mainshocks (Felzer and Brodsky, 2006) have been shown to trigger earthquakes at distances out to tens of mainshock fault lengths. These new observations have generated substantial controversy regarding whether distant triggered earthquakes are regular aftershocks-that is, generated by the same physical process as near-field events-or represent a separate phenomena (Hough, 2005;Steacy et al, 2005;Main, 2006).…”

Section: Introductionmentioning

confidence: 99%

A Case Study of Two M 5 Mainshocks in Anza, California: Is the Footprint of an Aftershock Sequence Larger Than We Think?

Felzer¹,

Kilb²

2009

Bulletin of the Seismological Society of America

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It has been traditionally held that aftershocks occur within one to two fault lengths of the mainshock. Here we demonstrate that this perception has been shaped by the sensitivity of seismic networks. The 31 October 2001 M w 5.0 and 12 June 2005 M w 5.2 Anza mainshocks in southern California occurred in the middle of the densely instrumented ANZA seismic network and thus were unusually well recorded. For the June 2005 event, aftershocks as small as M 0.0 could be observed stretching for at least 50 km along the San Jacinto fault even though the mainshock fault was only ∼4:5 km long. It was hypothesized that an observed aseismic slipping patch produced a spatially extended aftershock-triggering source, presumably slowing the decay of aftershock density with distance and leading to a broader aftershock zone. We find, however, the decay of aftershock density with distance for both Anza sequences to be similar to that observed elsewhere in California. This indicates there is no need for an additional triggering mechanism and suggests that given widespread dense instrumentation, aftershock sequences would routinely have footprints much larger than currently expected. Despite the large 2005 aftershock zone, we find that the probability that the 2005 Anza mainshock triggered the M 4.9 Yucaipa mainshock, which occurred 4.2 days later and 72 km away, to be only 14% 1%. This probability is a strong function of the time delay; had the earthquakes been separated by only an hour, the probability of triggering would have been 89%.

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Remotely Triggered Earthquakes Following Moderate Mainshocks (or, Why California Is Not Falling into the Ocean)

Cited by 40 publications

References 33 publications

Preliminary Report on the 29 July 2008 Mw 5.4 Chino Hills, Eastern Los Angeles Basin, California, Earthquake Sequence

Preliminary Report on the 29 July 2008 Mw 5.4 Chino Hills, Eastern Los Angeles Basin, California, Earthquake Sequence

Revisiting the 1872 Owens Valley, California, Earthquake

A Case Study of Two M 5 Mainshocks in Anza, California: Is the Footprint of an Aftershock Sequence Larger Than We Think?

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