HR: 16:30h
AN: NG54A-03    [Abstracts]
TI: Accelerating Moment Release Before Large Earthquakes: Stress Triggering Versus Stress Accumulation
AU: Mignan, A
EM: mignan@ipgp.jussieu.fr
AF: Laboratoire Tectonique, Institut de Physique du Globe de Paris, 4, place jussieu, Paris, 75252 France
AU: * Bowman, D D
EM: dbowman@fullerton.edu
AF: Dept. of Geological Sciences, Cal State Fullerton, 800 N. State College Blvd, Fullerton, CA 92834-6850 United States
AU: King, G C
EM: king@ipgp.jussieu.fr
AF: Laboratoire Tectonique, Institut de Physique du Globe de Paris, 4, place jussieu, Paris, 75252 France
AB: Stress triggering has been proposed as an explanation for the widely observed phenomenon of accelerating moment release (AMR) before large earthquakes. This model is based on the idea that large earthquakes are the result of a period of self-organization in the background stress field (i.e. smaller earthquakes). In contrast to this concept is the Stress Accumulation model (SAM), which treats the evolution of seismicity before a large earthquake as the result of loading of the main fault primarily by creep on an extension of the fault at depth. While both of these models predict accelerating seismicity before the mainshock, they make different predictions of the spatial distribution of this activity. We examine the statistical significance of AMR for the spatial distributions for the two models by comparing them to random catalogues. While each of the events had a spatial distribution of pre-event seismicity consistent with the Stress Accumulation model, only for one event - Hector Mine - can stress triggering reasonably be invoked as the origin of the observed AMR. Our study does not suggest that stress transfer is unimportant in understanding earthquake interactions; merely that it is not the main cause of accelerating moment release.
DE: 7223 Seismic hazard assessment and prediction
DE: 7230 Seismicity and seismotectonics
SC: Nonlinear Geophysics [NG]
MN: 2004 AGU Fall Meeting