T11C-2911
Upper-Mantle Seismic Structure Beneath the Western Cordillera in Oregon and Idaho: Preliminary Results from EarthScope IDOR Teleseismic Travel Time Tomography
Monday, 14 December 2015
Poster Hall (Moscone South)
Adrian Christian Stanciu1, Ray Russo2, Victor I Mocanu3, John C VanDecar4, Sutatcha Hongsresawat5, Paul M Bremner6, Megan E Torpey6 and Mark P Panning2, (1)Virginia Polytechnic Institute and State University, Department of Geosciences, Blacksburg, VA, United States, (2)University of Florida, Department of Geological Sciences, Gainesville, FL, United States, (3)University of Bucharest, Dept. of Geophysics, Bucharest, Romania, (4)Carnegie Inst Washington, DTM, Washington, DC, United States, (5)Mahidol University, Geoscience Division, Kanchanaburi, Thailand, (6)University of Florida, Department of Geological Sciences, Ft Walton Beach, FL, United States
Abstract:
We present new results of the upper-mantle velocity structure beneath the Western U.S. Cordillera from travel time inversion of teleseismic P and S waves recorded at the 85 broadband seismic stations of the EarthScope IDOR passive experiment, deployed in Eastern Oregon and Idaho between 2011 and 2013. Tectonics that could have affected seismic structure still present in this region include long-term subduction of the Farallon plate beneath North America, processes associated with the Columbia River flood basalts and Yellowstone mantle plume, Basin and Range extension, and the current Juan de Fuca subduction just west of the IDOR deployment. Fragments of the Farallon slab, clearly identified elsewhere beneath North America, might be present in the upper mantle of the study region. One such slab remnant, due to subduction associated with accretion of the Siltezia terrane, has been identified in the upper mantle just NW of our study region (Schmandt and Humphreys, 2011). The Juan de Fuca microplate, another remnant of the Farallon slab, subducts eastward beneath North America and is resolved at upper mantle depths regionally. In addition, the distribution of upper mantle asthenosphere is likely affected by the Yellowstone mantle plume and ongoing Basin and Range extension in our study area. We analyzed 239 teleseismic events recorded at the IDOR network with an epicentral distance between 30 and 95 degrees and magnitudes of 5.5 and higher. We picked P and S arrivals using the Automated and Interactive Measurement of Body-wave Arrival Times (AIMBAT) tool, based on the multi–channel cross-correlation method of VanDecar and Crosson (1990). We determined more than 7600 travel-time measurements. Preliminary results indicate a significant variation from west to east in delay times for event-station pairs across the IDOR network.
