Are Aftershocks of Large Californian Earthquakes Diffusing?

Abstract

We analyze 21 aftershock sequences of California to test for evidence of space-time diffusion. Aftershock diffusion may result from stress diffusion and is also predicted by any mechanism of stress weakening. Here, we test an alternative mechanism to explain aftershock diffusion, based on multiple cascades of triggering. In order to characterize aftershock diffusion, we develop two methods, one based on a suitable time and space windowing, the other using a wavelet transform adapted to the removal of background seismicity. Both methods confirm that diffusion of seismic activity is very weak, much weaker than reported in previous studies. A possible mechanism explaining the weakness of observed diffusion is the effect of geometry, including the localization of aftershocks on a fractal fault network and the impact of extended rupture lengths which control the typical distances of interaction between earthquakes.

latex file of 34 pages, 15 postscript figures, minor revision. In press in J. Geophys. Res

References in corpus (4)

• Foreshocks Explained by Cascades of Triggered Seismicity
• Is Earthquake Triggering Driven by Small Earthquakes?
• Mainshocks are aftershocks of conditional foreshocks: How do foreshock statistical properties emerge from aftershock laws
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• Anomalous Power Law Distribution of Total Lifetimes of Branching Processes Relevant to Earthquakes
• Renormalization of the ETAS branching model of triggered seismicity from total to observable seismicity
• Network of recurrent events for the Olami-Feder-Christensen model
• Search for Direct Stress Correlation Signatures of the Critical Earthquake Model
• Influence length and space-time correlation between earthquakes