HR: 0800h
AN: S21B-0562    [Abstracts]
TI: Spectral element modeling of dynamic rupture and long-term slip on rate and state faults
AU: * Kaneko, Y
EM: ykaneko@gps.caltech.edu
AF: Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Boulevard, Pasadena, CA 91125, United States
AU: Lapusta, N
EM: lapusta@caltech.edu
AF: Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Boulevard, Pasadena, CA 91125, United States
AU: Lapusta, N
EM: lapusta@caltech.edu
AF: Division of Engineering and Applied Science, California Institute of Technology, 1200 E. California Boulevard, Pasadena, CA 91125, United States
AU: Ampuero, J
EM: ampuero@erdw.ethz.ch
AF: Institute of Geophysics, HPP P ETH Honggerberg, Zurich, CH 8093, Swaziland
AB: In this work, the spectral element method (SEM) is used to model earthquake rupture and longer-term slip on a vertical strike-slip fault governed by rate and state friction. Previous studies of long-term slip behavior on rate and state faults mostly used boundary integral methods (BIM) which cannot include, at least in their current implementation, complex crustal structures such as variable bulk properties, fault damage zones, and non-planar fault geometries. SEM approach will allow us to include those factors into models that simulate long histories of seismic and aseismic slip. We have extended SEM to dynamic rupture simulations on rate and state faults and validated it by comparison with BIM solutions for a 2D test problem. We use the 3D dynamic SEM formulation to study several problems, including the effect of a shallow steady-state velocity-strengthening fault region (or layer) on a single simulated earthquake. In the absence of the layer, the rupture speed becomes supershear near the free surface due to a phase conversion, as also observed on linear slip-weakening faults. In contrast, when a velocity-strengthening layer exits, the supershear pulse is suppressed, which could explain the lack of universally observed supershear rupture near the free surface. The addition of the shallow velocity-strengthening layer in the model also suppresses slip on the fault. The slip suppression is larger next to the free surface but there is an appreciable slip reduction over the entire fault. The resulting profile of slip with depth is consistent with observations of shallow co-seismic slip deficit. We are also advancing towards a SEM formulation for modeling long-term slip histories, by combining the dynamic SEM with a quasi-static SEM formulation that we developed for simulations of aseismic slip. We have used the combined formulation to simulate seismic cycles in the form of small repeating earthquakes in a 2D SEM model, and find that the results are in agreement with those of BIM. We will report our current effort to extend the combined SEM formulation to 3D.
DE: 7209 Earthquake dynamics (1242)
DE: 7290 Computational seismology
DE: 8004 Dynamics and mechanics of faulting (8118)
DE: 8163 Rheology and friction of fault zones (8034)
SC: Seismology [S]
MN: 2007 Fall Meeting