HR: 0800h
AN: T51B-0539    [Abstracts]
TI: Shear wave splitting measurements and interpretation beneath Acapulco-Tampico transect in Mexico
AU: * Stubailo, I
EM: stubailo@ess.ucla.edu
AF: UCLA, Department of Earth and Space Sciences, 3806 Geology Building, Los Angeles, CA 90095, United States
AU: Davis, P
EM: pdavis@ess.ucla.edu
AF: UCLA, Department of Earth and Space Sciences, 3806 Geology Building, Los Angeles, CA 90095, United States
AB: We have examined shear wave splitting in teleseismic shear waves from 100 broadband stations installed from Acapulco to Tampico in Mexico over a period of 1.5 years (2005-2007). The instruments were part of the MASE (Middle America Subduction Experiment) which has the objective to build a geodynamical model of the subduction process beneath the Middle America Trench. The stations had a 5-6 km spacing and provided a unique data set which allows examination of the variation in splitting in high detail. Tomographic and receiver function studies in this area (done by MASE colleagues) show the presence of a flat slab under the western part of the array, and a steeply dipping slab beneath its center. According to geochronological data, the onset of flat slab subduction took place ~15-20 Ma, after the Cocos plate broke off the Farallon plate. We observe large splitting delay times with, on average, a fast direction in the northeast-southwest direction, but with considerable variation along the network. We compare the splitting results with the three dimensional structure inferred from the geochemistry and seismic analyses.
DE: 1213 Earth's interior: dynamics (1507, 7207, 7208, 8115, 8120)
DE: 7203 Body waves
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 7294 Seismic instruments and networks (0935, 3025)
DE: 8180 Tomography (6982, 7270)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting