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Estimating Future Strong Ground Motions in the Los Angeles and San Francisco Areas: Brad Aagaard

Project Title: Estimating Future Strong Ground Motions in the Los Angeles and San Francisco Areas
Mendenhall Fellow: Brad Aagaard, baagaard@usgs.gov
Duty Station: Pasadena, California
Start Date: October 1, 2001
Education: Ph.D. Civil Engineering (engineering seismology), California Institute of Technology, 2000
Research Advisors: David Wald, wald@usgs.gov
Project Description: The primary goal is to characterize the spatial and temporal characteristics of near-source ground motion for scenario events in the Los Angeles and San Francisco areas. While current kinematic source models provide useful information for modeling and estimating strong ground motions, more accurate source models require significant progress in understanding the underlying fundamental physical processes involved in fault rupture. Numerical finite-element simulations, which include the basic physics of the rupture process through frictional sliding, will be used to model the earthquake ruptures and wave propagation which generate the ground motions. By using a self-consistent stress field that includes the effect of gravity, and geologic models that incorporate the three-dimensional heterogeneity of the material properties and fault geometries, some of the simplifying assumptions will be removed in order to create dynamic ruptures under more realistic conditions. The friction models and crustal stress field will be constrained with many kinds observations, including kinematic source models, stress variations due to topography and density variations, and the lack of substantial melting observed on fault surfaces. Compared to conventional techniques, this approach not only adds important constraints on the simulation parameters, but also yields significantly more information about the dynamics of the rupture process and state of stress in the crust.

Publications:
Aagaard, B.T., Heaton, T.H., and Hall, J.F., 2001,Dynamic earthquake ruptures in the presence of lithostatic normal stresses: Implications for friction models and heat production. Bulletin of the Seismological Society of America, v. 91, no, 6, p. 1765-1796.

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