HR: 0800h
AN: S21B-0560    [Abstracts]
TI: Numerical Study of Frictional Properties and the Role of Cohesive End-Zones in Large Strike- Slip Earthquakes
AU: * Lovely, P J
EM: plovely@stanford.edu
AF: Department of Geological and Environmental Sciences, Stanford University, Braun Hall, Building 320 450 Serra Mall, Stanford, CA 94305, United States
AU: Mutlu, O
EM: omutlu@stanford.edu
AF: Department of Geological and Environmental Sciences, Stanford University, Braun Hall, Building 320 450 Serra Mall, Stanford, CA 94305, United States
AU: Pollard, D D
EM: dpollard@pangea.stanford.edu
AF: Department of Geological and Environmental Sciences, Stanford University, Braun Hall, Building 320 450 Serra Mall, Stanford, CA 94305, United States
AB: Cohesive end-zones (CEZs) are regions of increased frictional strength and/or cohesion near the peripheries of faults that cause slip distributions to taper toward the fault-tip. Laboratory results, field observations, and theoretical models suggest an important role for CEZs in small-scale fractures and faults; however, their role in crustal-scale faulting and associated large earthquakes is less thoroughly understood. We present a numerical study of the potential role of CEZs on slip distributions in large, multi-segmented, strike-slip earthquake ruptures including the 1992 Landers Earthquake (M_w 7.2) and 1999 Hector Mine Earthquake (M_w 7.1). Displacement discontinuity is calculated using a quasi-static, 2D plane-strain boundary element (BEM) code for a homogeneous, isotropic, linear-elastic material. Friction is implemented by enforcing principles of complementarity. Model results with and without CEZs are compared with slip distributions measured by combined inversion of geodetic, strong ground motion, and teleseismic data. Stepwise and linear distributions of increasing frictional strength within CEZs are considered. The incorporation of CEZs in our model enables an improved match to slip distributions measured by inversion, suggesting that CEZs play a role in governing slip in large, strike-slip earthquakes. Additionally, we present a parametric study highlighting the very great sensitivity of modeled slip magnitude to small variations of the coefficient of friction. This result suggests that, provided a sufficiently well-constrained stress tensor and elastic moduli for the surrounding rock, relatively simple models could provide precise estimates of the magnitude of frictional strength. These results are verified by comparison with geometrically comparable finite element (FEM) models using the commercial code ABAQUS. In FEM models, friction is implemented by use of both Lagrange multipliers and penalty methods.
DE: 0545 Modeling (4255)
DE: 8118 Dynamics and mechanics of faulting (8004)
DE: 8163 Rheology and friction of fault zones (8034)
SC: Seismology [S]
MN: 2007 Fall Meeting