HR: 14:55h
AN: S13D-06    [Abstracts]
TI: Effective Friction Resulting from the Presence of Heterogeneous Strength for Rupture Dynamics
AU: * Schmedes, J
EM: jasch@crustal.ucsb.edu
AF: Institute for Crustal Studies, 1140 Girvetz Hall University of California Santa Barbara, Santa Barbara, CA 93106, United States
AU: Campillo, M
EM: campillo@obs.ujf-grenoble.fr
AF: LGIT, Universite Joseph Fourier BP 53, Grenoble, 38041, France
AU: Archuleta, R
EM: ralph@crustal.ucsb.edu
AF: Institute for Crustal Studies, 1140 Girvetz Hall University of California Santa Barbara, Santa Barbara, CA 93106, United States
AU: Lavallee, D
EM: daniel@crustal.ucsb.edu
AF: Institute for Crustal Studies, 1140 Girvetz Hall University of California Santa Barbara, Santa Barbara, CA 93106, United States
AB: Inversions of strong motion records can produce reliable descriptions of the evolution of the slip during an earthquake. However, the resolution of the kinematic parameters for these models is limited by the distribution of stations and by our knowledge of the details of the Earth structure. As a result, the rupture models we deduce are restricted to large length scales, typically larger than one kilometer. These models can be reproduced in dynamic simulations with simple friction laws and heterogeneities in friction parameters and initial stress. These simulations are used to constrain the values of friction parameter such as weakening rate, critical slip or fracture energy on actual faults. Indeed there are numerous arguments for the existence of fault heterogeneity at all scales. We investigate numerically the implication of neglecting small wavelength heterogeneity on faults by computing 3D finite element solutions of heterogeneous faulting under slip weakening friction. We show that the average properties of a spontaneous rupture (evolution of the rupture and amplitude of slip) on a fault with stationary heterogeneity are well reproduced when imposing an effective friction on a homogeneous fault. We deduce the properties of the effective friction from the elastic deformation in the bulk off the fault in a way similar to what was proposed for the 2D antiplane case on the basis of the mathematical analysis of the initiation phase. The effective friction law exhibits a nonlinear slip dependence with an initial weakening rate different from the one imposed on the heterogeneous fault. With strongly heterogeneous faults, the effective critical slip is larger than the actual one. This indicates that neglecting small-scale heterogeneity in the interpretation of kinematic rupture models likely leads to a misconstruction of actual friction properties of faults. We further investigate different types of heterogeneity to assess the validity of the concept of effective friction.
DE: 7200 SEISMOLOGY
DE: 7209 Earthquake dynamics (1242)
DE: 7260 Theory
DE: 7290 Computational seismology
SC: Seismology [S]
MN: 2007 Fall Meeting