Studies in Western U.S. Geodynamics

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Intellectual Merit:Three regional studies will address the processes responsible for the tectonicbehavior in each region. The study areas are:1) Southern California. Study will focus on the cause of mountain building in thetransform-fault environment of the San Andreas fault;2) the Sierra Nevada. Study will focus on the tectonic strengths of the boundingSan Andreas fault and eastern California shear zone and on the nature of thegravitationally driven extension of the Basin and Range; and3) the Pacific Northwest. Study will focus on the interplay between the sheartectonics imposed by Pacific-North America interaction and the subduction margin,which varies from weakly to strongly compressive.These regional studies will be modeled in a manner consistent with plate scale stressesand will be used to improve the current plate scale dynamic model.The proposed research will be accomplished in two and three dimensions with a finiteelement computer simulations that incorporate faults, viscous and plastic rock deformationmechanisms, and gravity-driven processes in realistic ways.This project will produce results that will help to understand the relative importanceof plate interaction and internal buoyancy driven continental deformation.Also, improved models of the distribution and rate of deformation will be producedbased on geodetic and geologic faulting data. These results will be used both to evaluatethe quality of the computer simulations and to constrain lithospheric strength.Broader Impacts:Results will help constrain the strength and behavior of faults, which is important tounderstanding earthquake processes.This project will prepare a graduate student for the future through collaborations,participation in a diverse set of disciplines, and integration of the range of findingsinto consistent results. It also will help foster an international collaboration.