HR: 0800h
AN: S41A-0942    [Abstracts]
TI: Simulating Spatio-Temporal Slip Evolution of Fault Zones at Different Evolutionary Stages
AU: * Hillers, G
EM: hillers@sed.ethz.ch
AF: Institute of Geophysics, ETH Zurich, ETH Honggerberg, HPP P, Zurich, 8093 Switzerland
AU: Mai, M
EM: mai@sed.ethz.ch
AF: Institute of Geophysics, ETH Zurich, ETH Honggerberg, HPP P, Zurich, 8093 Switzerland
AU: Ben-Zion, Y
EM: benzion@terra.usc.edu
AF: Department of Earth Sciences, University of Southern CA, 3651 University Ave., SCI 117, Los Angeles, CA 90089-0740 United States
AB: Previous studies of spatio-temporal evolution of slip on a fault governed by rate-and-state friction (e.g., Rice, 1993; Ben-Zion and Rice, 1995, 1997; Tullis, 1996; Lapusta et al., 2000) employed frictional properties corresponding to fairly homogeneous faults. In most cases, the only types of heterogeneities were the lab-based depth-variations of the parameters $a$ and $b$ that produce transitions between stable velocity-strengthening and unstable velocity-weakening regimes. In this study we use a constant $a-b$ profile and a depth-dependent distribution of the critical slip distance parameter $L$. In addition, correlated heterogeneities of $L$ along strike are used to model geometrical heterogeneities on faults related to roughness. More specifically, we will perform 3D quasi-static and quasi-dynamic simulations of slip on a strike-slip fault using a family of 2D anisotropic correlated distributions of $L$ having different correlation lengths along strike and downdip. The depth-variation of $L$ over the depth range 3km $< z <$ 12 km, representing the seismogenic zone, accounts for an overall reduction of the gouge thickness (and hence $L$) with depth. Above and below the seismogenic zone, $L$ increases rapidly. The variations of $L$ along strike are chosen to provide approximate representations of faults at different evolutionary stages. Relatively smooth mature faults (like the San Andreas) will be represented with distributions that have large horizontal correlation length, while distributions with small correlation lengths are used to represent rougher immature faults (like the San Jacinto and faults in the eastern CA shear zone). The choices of representative correlation lengths is guided and constrained by maps of fault structures of the type compiled by Wesnousky (1994), and by the compilation of inverted slip histories. The 3D code with various cases of anisotropic correlated distributions of $L$ will be used to study many issues related to observed complex behavior of seismogenic faults including: (1) Nucleation and arrest properties of failure episodes on a heterogeneous fault governed by RSD friction. (2) Comparison between properties of final simulated slip histories and those of the inverted slip histories. (3) Frequency-size and temporal statistics of simulated earthquakes on a heterogeneous fault governed by rate-and-state friction.
UR: http://www.seismo.ethz.ch/srcmod
DE: 7260 Theory and modeling
DE: 8123 Dynamics, seismotectonics
DE: 7209 Earthquake dynamics and mechanics
DE: 3220 Nonlinear dynamics
SC: Seismology [S]
MN: 2004 AGU Fall Meeting