This research involves the study of the crust and upper mantle of the region encompassing southeastern California and western Arizona, which covers the southwest quarter of the Colorado Plateau and much of the southern Basin and Range. An existing data set from a 75-station, 200km by 450km array will be analyzed to complete a seismic tomography study, incorporating modeling of available digital Bouguer gravity data, and to model existing broadband waveforms to characterize the upper mantle structure in the study region. This important data set fills a large gap in high-resolution P-wave tomography coverage for the western U.S. The region's Cenozoic tectonic history of transition from subduction related compression and crustal thickening to orogenic collapse with core complex formation, volcanism, and extension is unusually well documented in the geologic record. This study will constrain the present day composition and physical state of the upper mantle beneath the area to evaluate the ways it has retained, or lost, the imprint of the Cenozoic tectonic events.
