Multivariate Inversion for the Seismic Structure of the Western United States Public

APPLICATION OF ADVANCED MULTIVARIATE INVERSION TECHNIQUES TO THE WESTERN U.S. MACEIRA, M., Los Alamos National Laboratory, Los Alamos, NM, USA,  mmaceira@lanl.gov; AMMON, C. J., The Pennsylvania State University, State College, PA, USA,  cja12@psu.edu; CHAI, C., The Pennsylvania State University, State College, PA, USA,  cxc754@psu.edu; HERRMANN, R. B., Saint Louis University, Saint Louis, MO, USA,  rbh@eas.slu.edu Western USA is an ideal location to test advanced multivariate imaging techniques due to excellent data density provided by the USArray. We simultaneously invert surface-wave dispersion, receiver functions, and gravity anomalies to determine the structure of the crust and upper mantle of the western US. Specifically, our target region spans latitudes from 27 to 54 degrees North and longitudes from 90 to 130 degrees West. Rayleigh and Love surface-wave dispersion data between 5 and 150 seconds come from multiple filter analysis of regional earthquakes. Receiver functions come from the EarthScope Automated Receiver system, and are stacked to produce an average model for each cell in our parameterized region. The gravity observations are extracted from the global EGM2008 model. Our starting model is comprised of an oceanic PREM model west of the Pacific coast, a western US model between that and the eastern front of the Rocky Mountains, and a continental PREM model east of the Rocky Mountain Front. The addition of receiver functions produces sharper boundaries for the observed crustal anomalies. The addition of gravity produces subtle changes to the final model. Our inversion offers a nice compromise between fitting the three different datasets and simultaneously reducing RMS residuals for all. Our final results are consistent with numerous previous studies in the region. In general, the craton exhibits higher velocities than the tectonically active regions to its west. We see high mid-crustal velocities under the Snake River Plain and the Colorado Plateau. In the lower crust we observe lowest velocities in the western Basin and Range and under the Colorado Mineral Belt. At 80km depth we see broad low velocities fanning out from the Snake River Plain likely associated with the mantle plume feeding Yellowstone Caldera. Additionally we see high and low velocity anomalies along the west coast that reflect ongoing subduction processes beneath the western US.

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