Colorado Plateau/Rio Grande Rift/Great Plains Seismic Transect

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EAR-0207812 Aster The Rio Grande Rift Seismic Transect (RISTRA) project is designed to study the crust and mantle beneath the southwestern U.S. utilizing an exceptional data set consisting of 18 months of broadband teleseismic IRIS PASSCAL data from 57 sites along a 1000-km transect in TX, NM, AZ, and UT recorded during 1999-2001. Under initial NSF funding extensive fieldwork was completed, data were processed and archived at the IRIS data management center, and preliminary analysis was performed and disseminated to the earth science and broader communities. This project continues the analysis of RISTRA to illuminate and interpret structure and processes associated with the Rio Grande Rift (RGR), Colorado Plateau (CP), and Great Plains (GP) at unprecedented resolution. Principal goals are to determine the: (1) nature the support of the present high elevation of the CP; (2) depth extent of mantle processes associated with surface morphology and tectonics; (3) connection between mantle and crustal strain beneath the RGR region; (4) location in the mantle of remnants of the Farallon plate and any possible detached continental lithosphere. Imaging of discontinuities using receiver function methods is being coupled with studies of shear wave splitting, 3-D seismic tomography, xenolith, and other geological/geophysical constraints to reveal the structure of the region to depths of approximately 800 km. Seismic migration processing techniques that take full advantage of the quality, length, and dense (~18 km) station spacing of the RISTRA experiment are being applied. Elastic 2- and 3-D modeling efforts are being incorporated into the DOE/SEG Next Generation Modeling (NGM) Project in association with Los Alamos National Laboratory and the University of Houston.