Publication Date:
2009-12-04
Description:
Two of the long-standing relationships of statistical seismology are power laws: the Gutenberg-Richter relation describing the earthquake frequency-magnitude distribution, and the Omori-Utsu law characterizing the temporal decay of aftershock rate following a main shock. Recently, the effect of stress on the slope (the b value) of the earthquake frequency-magnitude distribution was determined by investigations of the faulting-style dependence of the b value. In a similar manner, we study here aftershock sequences according to the faulting style of their main shocks. We show that the time delay before the onset of the power-law aftershock decay rate (the c value) is on average shorter for thrust main shocks than for normal fault earthquakes, taking intermediate values for strike-slip events. These similar dependences on the faulting style indicate that both of the fundamental power laws are governed by the state of stress. Focal mechanisms are known for only 2 per cent of aftershocks. Therefore, c and b values are independent estimates and can be used as new tools to infer the stress field, which remains difficult to measure directly.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Narteau, Clement -- Byrdina, Svetlana -- Shebalin, Peter -- Schorlemmer, Danijel -- England -- Nature. 2009 Dec 3;462(7273):642-5. doi: 10.1038/nature08553.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institut de Physique du Globe de Paris (UMR 7154, CNRS, Univ. P7), 4 Place Jussieu, 75252 Paris Cedex 05, France. narteau@ipgp.jussieu.fr〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19956258" target="_blank"〉PubMed〈/a〉
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
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Chemistry and Pharmacology
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Medicine
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Natural Sciences in General
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Physics
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