The evolution of the San Andreas Fault System is controlled by thermal-mechanical processes associated with development and evolution of a "slabless window" formed beneath the western edge of North America. As a consequence of the slabless window, the plate boundary separating the North American and Pacific plates has a complex 3-D geometry which varies through time, with important consequences for tectonic processes associated with the San Andreas Fault System. In conjunction with a research effort at Lawrence Livermore National Laboratory, modeling and data interpretation activities will be conducted to address the following: 1) Evaluation of the thermal, seismic, and stress/strength evolution of the southern edge of the Gorda Plate as it interacts with the slabless window beneath Northern California; 2) Investigation of the thermal/petrologic evolution of the North American crust in association with perturbations from mantle upwelling, magmatic underplating, and crust-mantle mixing; 3) Detailed analyses of the evolution of the lower crustal - upper mantle shear zones which serve as components of the plate boundary, the development of crustal faults, and the displacement and deformation behavior of crustal blocks associated with the San Andreas Fault System.
