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Published December 2001 | Published
Journal Article Open

Dynamic Earthquake Ruptures in the Presence of Lithostatic Normal Stresses: Implications for Friction Models and Heat Production


We simulate dynamic ruptures on a strike-slip fault in homogeneous and layered half-spaces and on a thrust fault in a layered half-space. With traditional friction models, sliding friction exceeds 50% of the fault normal compressive stress, and unless the pore pressures approach the lithostatic stress, the rupture characteristics depend strongly on the depth, and sliding generates large amounts of heat. Under application of reasonable stress distributions with depth, variation of the effective coefficient of friction with the square root of the shear modulus and the inverse of the depth creates distributions of stress drop and fracture energy that produce realistic rupture behavior. This ad hoc friction model results in (1) low-sliding friction at all depths and (2) fracture energy that is relatively independent of depth. Additionally, friction models with rate-weakening behavior (which form pulselike ruptures) appear to generate heterogeneity in the distributions of final slip and shear stress more effectively than those without such behavior (which form cracklike ruptures). For surface rupture on a thrust fault, the simple slip-weakening friction model, which lacks rate-weakening behavior, accentuates the dynamic interactions between the seismic waves and the rupture and leads to excessively large ground motions on the hanging wall. Waveforms below the center of the fault (which are associated with waves radiated to teleseismic distances) indicate that source inversions of thrust events may slightly underestimate the slip at shallow depths.

Additional Information

© 2001 Seismological Society of America. Manuscript received 12 October 2000. This work was supported by a National Science Foundation fellowship, the Southern California Earthquake Center, and the California Institute of Technology. Access to the Hewlett-Packard X-Class computer, located at the California Institute of Technology, was provided by the Center for Advanced Computing Research. We appreciate the helpful reviews from Steven Day, Ruth Harris, and David Oglesby.

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