Faulting Style Controls for the Space–Time Aftershock Patterns

Tahir, Mohammad and Grasso, Jean-Robert (2015) Faulting Style Controls for the Space–Time Aftershock Patterns. Bulletin of the Seismological Society of America, 105 (5). pp. 2480-2497. DOI: https://doi.org/10.1785/0120140336

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Abstract

To understand the complexity and thus to predict earthquake occurrence insize, time, and space, seismicity patterns are characterized by two robust empirical laws:the exponential distribution of magnitude and the power law decrease of aftershock rateover time. These laws are known as the Gutenberg–Richter law and the Omori law, re-spectively. Using global earthquake catalogs, we resolve that on average the K(after-shock productivity) and the p-value (exponent of the power law decrease of aftershockrate over time) are dependent on the mainshock faulting style. Strike-slip events have alower aftershock rate (N)andK-values and a larger p-value than thrust and normalevents, respectively. Within the epidemic-type aftershock sequence model, strong K,Nvalues are driven by a high-branching ratio value (n). Within the same framework, arelatively higher nvalue for the thrust events also predicts the lower p-value we observefor thrust events as compared to strike-slip and normal-faulting events, respectively.Furthermore, we observed that earthquake interactions through time and space area function of the faulting style when measured by μt, the exponent of the power lawdecrease of earthquake density over space. The μtvalues of thrust events for differ-ent time windows always remain smaller than those of the strike-slip events. Whenchanges in faulting styles are driven by stress pattern, the Anderson faulting theorypredicts thrust faulting that requires somewhat larger stresses, in absolute magnitude,than do normal and strike-slip faulting. Within the framework of rate-and-state frictionlaw, changes in the stress heterogeneity patterns reproduce the p-value changes weobserve. Our results suggest that only stress perturbations associated with mainshockrupture affect the productivity and decay rate over time of aftershocks

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Item Type:	Article
Application references:	Earthquake interactions-mainshock scale, Earthquake interactions-georesource scale
Subjects:	Methodology > Method and procesing > Collective properties of seismicity
Project:	EPOS-IP