HR: 1340h
AN: S13B-1308    [Abstracts]
TI: Rate-State Modeling of Stress Relaxation in Geometrically Complex Fault Systems
AU: Dieterich, J
EM: dieterichj@ucr.edu
AF: University of California, Riverside, Department of Earth Sciences, Institute of Geophysics and Planetary Physics, University of California, Riverside, Riverside, CA 92521, United States
AU: * Smith, D E
EM: desmith@ucr.edu
AF: University of California, Riverside, Department of Earth Sciences, Institute of Geophysics and Planetary Physics, University of California, Riverside, Riverside, CA 92521, United States
AB: Slip of geometrically complex faults involves interactions and processes that do not occur in standard planar fault models. These include off-fault yielding and stress relaxation, which are required to prevent the development of pathological stress conditions on the fault (or in extreme cases fault lock-up). Nielsen and Knopoff [1988] introduced yielding through a simplified form of viscoelastic stress relaxation. However, the mechanical characteristics of the brittle seismogenic crust indicate that faulting processes will dominate the stress relaxation processes. The fractal-like character of fault systems and fault roughness, together with the finite strength of rocks, insures that slight movements of secondary faults, at all scales, will be necessary to accommodate slip of major through-going faults. To model the integrated effect of these processes, we employ an earthquake rate formulation [Dieterich, 1994], which incorporates laboratory-derived rate- and state-dependent frictional properties, on geometrically complex faults. With the rate-state formulation we find that stress relaxation occurs co-seismically during large earthquakes, as delayed stress relaxation in the form of aftershocks, and as spatially distributed background seismicity. During aftershocks the spatial mean of stresses decay at a rate proportional to 1/t. We find large spatial and temporal differences in models of slip of faults with relaxation compared to faults in purely elastic media. We conclude that that yielding and relaxation are important controlling processes that are the mechanics of slip on geometically complex faults
DE: 4440 Fractals and multifractals
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 7260 Theory
DE: 8010 Fractures and faults
DE: 8164 Stresses: crust and lithosphere
SC: Seismology [S]
MN: 2007 Fall Meeting