Aftershock Statistics Constitute the Strongest Evidence for Elastic Rebound in Large Earthquakes?
Abstract
The forecast models developed by the Working Groups on California Earthquake Probabilities (WGCEPs) have constituted the most official statements of time-dependent earthquake probabilities for California. The recurrence models used in these studies have been based on elastic-rebound theory (and the related seismic-gap hypothesis), while spatiotemporal clustering has been excluded as negligible. However, the recent earthquake sequences in both New Zealand and Japan are only the latest reminders that aftershocks can be large and damaging. The 1999 debate on earthquake prediction in Nature identified consensus that "... earthquake triggering leads to a transient, local increase in probability of future earthquakes...", whereas there remains "...a continuing debate on the applicability of the seismic gap hypothesis..." (Main, week 7, http://www.nature.com/nature/debates/earthquake). In other words, the influence of elastic rebound is still questionable for large events because long recurrence intervals preclude definitive tests. Lack of spatiotemporal clustering was explicitly identified as a limitation in the last WGCEP model (UCERF2), and has since been a priority for inclusion in the next model (UCERF3). Progress thus far in implementing spatiotemporal clustering via ETAS aftershock statistics indicate that elastic rebound must also be included; otherwise large, triggered events will tend to occur close to the main shock, or even re-rupture the same fault surface, much more frequently than is observed in nature. Ironically, this implies that aftershock statistics may represent the strongest evidence for the influence of elastic rebound in large earthquakes.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.S22B..08F
- Keywords:
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- 7223 SEISMOLOGY / Earthquake interaction;
- forecasting;
- and prediction