| Abstract: | Resolving whether static or dynamic stress triggers most aftershocks and subsequent mainshocks is essential to understand earthquake interaction and to forecast seismic hazard. Felzer and Brodsky examined the distance distribution of earthquakes occurring in the first five minutes after 2 ≤ M < 3 and 3 ≤ M < 4 mainshocks and found that their magnitude M ≥ 2 aftershocks showed a uniform power-law decay with slope −1.35 out to 50 km from the mainshocks. From this they argued that the distance decay could be explained only by dynamic triggering. Here we propose an alternative explanation for the decay, and subject their hypothesis to a series of tests, none of which it passes. At distances more than 300 m from the 2 ≤ M< 3 mainshocks, the seismicity decay 5 min before the mainshocks is indistinguishable from the decay five minutes afterwards, indicating that the mainshocks have no effect at distances outside their static triggering range. Omori temporal decay, the fundamental signature of aftershocks, is absent at distances exceeding 10 km from the mainshocks. Finally, the distance decay is found among aftershocks that occur before the arrival of the seismic wave front from the mainshock, which violates causality. We argue that Felzer and Brodsky implicitly assume that the first of two independent aftershocks along a fault rupture triggers the second, and that the first of two shocks in a creep- or intrusion-driven swarm triggers the second, when this need not be the case. |
| Genre: | Article |
| ProdID: | 70037521 |
| Citation Author: | Richards-Dinger, K.; Stein, R. S.; Toda, S. |
| Citation Contributing Office: | Earthquake Science Center |
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| Citation End Page: | 586 |
| Citation Issue: | 7315 |
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| Citation Language: | English |
| Citation Larger Work Title: | Nature |
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| Citation Phsyical Description: | 4 p. |
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| Citation Publisher: | Nature Publishing Group |
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| Citation Search Results Text: | Decay of aftershock density with distance does not indicate triggering by dynamic stress; 2010; Article; Journal; Nature; Richards-Dinger, K.; Stein, R. S.; Toda, S. |
| Citation Start Page: | 583 |
| Citation Volume: | 467 |
| Citation Year: | 2010 |
| Type: | citation/reference |
| Text: | Decay of aftershock density with distance does not indicate triggering by dynamic stress; 2010; Article; Journal; Nature; Richards-Dinger, K.; Stein, R. S.; Toda, S. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| URL (DIGITAL OBJECT IDENTIFIER): | http://dx.doi.org/10.1038/nature09402 |
| Date Other: | Fri, 1 Jan 2010 00:00 -0600 |
| Publisher: | Nature Publishing Group |
