HR: 13:40h
AN: S32D-01    [PDF]
TI: Is earthquake triggering driven by small earthquakes?
AU: * Helmstetter, A
EM: helmstet@moho.ess.ucla.edu
AF: Institute of Geophysics and Planetary Physics, University of California Los Angeles, 3845 Slichter Hall, Los Angeles, CA 90095-1567 United States
AB: Using a catalog of seismicity for Southern California, we show that the number of triggered earthquakes increases exponentially with the mainshock magnitude. The trade-off between this scaling and the distribution of earthquake magnitudes controls the relative role of small compared to large earthquakes. We show that seismicity triggering is driven by the smallest earthquakes, which trigger fewer aftershocks than larger earthquakes, but which are much more numerous. The magnitude of triggered earthquakes obeys the Gutenberg-Richter distribution, with the same b-value as other earthquakes, independently of the size of the triggering earthquake. We propose that the non-trivial scaling of the number of aftershocks with the mainshock magnitude emerges from the fractal spatial distribution of aftershocks. These observations highlight the importance of taking into account the effect of small earthquakes to model earthquake triggering.
DE: 7209 Earthquake dynamics and mechanics
DE: 7215 Earthquake parameters
DE: 7223 Seismic hazard assessment and prediction
DE: 7230 Seismicity and seismotectonics
DE: 7260 Theory and modeling
SC: Seismology [S]
MN: 2003 Fall Meeting