Simulations of Stress Drops for Evolving Seismicity on a Heterogeneous Fault in an Elastic Halfspace
Abstract
Understanding what limits the size of earthquake stress drops has important implications for estimating ground motion. Seismological derivations of stress drops are typically of order ~110 MPa, yet theoretical estimates based on laboratory friction data and measurements of stress in the crust are two orders of magnitude higher. The discrepancy may stem from the fact that earthquake stress drops are average values over a rupture area that may have highly heterogeneous initial stress, while the theoretical estimates assume an essentially homogeneous stress. We investigate properties of stress drops in simulations of evolving seismicity and stress field on a strongly heterogeneous fault. The model fault (BenZion and Rice, 1993) consists of a set of inherently discrete slip patches surrounded by a 3D elastic halfspace. The discrete slip patches provide a simple representation of heterogeneities associated with segmentation and other geometrical complexities. Previous studies have shown that the model produces many statistical features of seismicity compatible with observations including frequencysize and temporal event statistics, hypocenter distributions, intermittent criticality, and scaling of sourcetime functions. We apply similar analyses to understand how stress drops in an evolving heterogeneous stress field depend on rheological properties of the model (spatial distribution of static/kinetic friction values and coefficients of power law creep), hypocentral depth, earthquake magnitude and temporal position within large earthquake cycles.
 Publication:

AGU Fall Meeting Abstracts
 Pub Date:
 December 2007
 Bibcode:
 2007AGUFM.S21B0573B
 Keywords:

 4430 Complex systems;
 7209 Earthquake dynamics (1242);
 7212 Earthquake ground motions and engineering seismology;
 7215 Earthquake source observations (1240);
 8118 Dynamics and mechanics of faulting (8004)