HR: 16:30h
AN: S32F-03    [PDF]
TI: Using Seismicity Rates to Assess Coulomb Stress Transfer Models
AU: * Mallman, E P
EM: emallman@pangea.stanford.edu
AF: Stanford University Department of Geophysics, 397 Panama Mall, Stanford, CA 94305 United States
AU: Zoback, M D
EM: zoback@pangea.stanford.edu
AF: Stanford University Department of Geophysics, 397 Panama Mall, Stanford, CA 94305 United States
AB: One of the major goals of stress transfer studies has been to calculate changes in earthquake probabilities following a moderate to large event. Previous studies have demonstrated that stress transfer models utilizing the Coulomb failure criterion are often successful in predicting where aftershocks are likely to be triggered or suppressed. However, few studies have attempted to determine if Coulomb stress-changes affect the long-term seismicity rate of the regions surrounding the causative event. In addition, most studies comparing seismicity rate and Coulomb stress have been largely qualitative. In this study the dense seismic networks of Southern California and Southwestern Japan are used to test the correlation of static Coulomb stress changes due to the 1992 Landers and 1995 Kobe earthquakes and the observed changes in seismicity rate in the regions. First, the elastic Coulomb stress change on optimally oriented faults at a specified depth is calculated. Then, seismicity rate-changes over 8-to-10-year periods before and after the main shock are determined using the z-value (Habermann, 1987). The z-value represents significance between two different means. Finally, a quantitative comparison of the changes in static (elastic) Coulomb stress and seismicity rate is made to determine the correlation between the two. In addition, it allows us to examine changes in correlation with depth, for optimal planes versus specified planes and allows us to assess variations in correlation with time to determine if inelastic stress transfer processes become important over time. Specifically, we hope to use this approach to assess the relative impacts of post-seismic relaxation, poroelastic effects, and rate and state friction on seismicity rates, and thus incorporate all of the appropriate physical processes when attempting to compute earthquake probability changes following an initial earthquake.
DE: 7209 Earthquake dynamics and mechanics
DE: 7223 Seismic hazard assessment and prediction
DE: 7230 Seismicity and seismotectonics
SC: Seismology [S]
MN: 2003 Fall Meeting