Common dependence on stress for the two fundamental laws of statistical seismology | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  Common dependence on stress for the two fundamental laws of statistical seismology

Type de publication:

Journal Article

Source:

Nature, Volume 462, Ticket 7273, p.642-U113 (2009)

ISBN:

0028-0836

Numéro d'accès:

ISI:000272277900039

URL:

http://www.nature.com/nature/journal/v462/n7273/full/nature08553.html

Mots-clés:

UMR 7154 ; Dynamique des fluides géologiques

Résumé:

<p>Two of the long-standing relationships of statistical seismology are power laws: the Gutenberg-Richter relation(1) describing the earthquake frequency-magnitude distribution, and the Omori-Utsu law(2) 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(3) 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.</p>

Notes:

Narteau, Clement Byrdina, Svetlana Shebalin, Peter Schorlemmer, Danijel