Narteau C., Byrdina Svetlana, Shebalin P., Schorlemmer D. (2009). Common dependence on stress for the two fundamental laws of statistical seismology. Nature, 462 (7273), p. 642-U113. ISSN 0028-0836.
Titre du document
Common dependence on stress for the two fundamental laws of statistical seismology
Narteau C., Byrdina Svetlana, Shebalin P., Schorlemmer D.
Source
Nature, 2009,
462 (7273), p. 642-U113 ISSN 0028-0836
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.
