HR: 1340h
AN: T13E-1630    [Abstracts]
TI: 3D Model of Vp/Vs Ratios in the Crust and Uppermost Mantle Beneath East Asia
AU: * Sun, Y
EM: youshun@mit.edu
AF: Earth Resources Lab, MIT, 77 Mass Ave, Cambridge, 02139, United States
AU: Toksoz, M
EM: toksoz@mit.edu
AF: Earth Resources Lab, MIT, 77 Mass Ave, Cambridge, 02139, United States
AB: We obtain a 3D model of the Vp/Vs ratio of the crust and uppermost mantle beneath East Asia by performing joint P- and S-wave travel-time tomography. Travel-time data from the extensive Annual Bulletin of Chinese Earthquakes (ABCE) and the International Seismological Centre (ISC/EHB) are used. The regional travel-time data from the ABCE is used to obtain the crust/uppermost mantle (0 to 100 km depth) velocity model. A total of 500,000 P-wave and 350,000 S-wave regional travel-times are used for the tomography. Two discontinuities (Conrad and Moho) are allowed in the inversion. The tomographic models provide three-dimensional (3-D) velocities in the crust and uppermost mantle, depth to the Moho, detailed Pn and Sn velocities, and Vp/Vs ratios. High Vp/Vs ratios exist beneath the East and South China Sea, Japan Sea and the Pacific Ocean. Along the east- west profiles crossing the Tibet, high Vp/Vs ratios in the crust beneath part of the Tibetan plateau suggest the presence of high temperatures and/or fluid. This observation is consistent with the results of previous studies in these areas based on seismic soundings and gravity surveys. Prominent high Vp/Vs ratios are observed beneath the active volcanic and geothermal sites in the Tengchong region, in the Changbai region, and in the Hainan region. Our Vp/Vs profiles clearly indicate the presence of high temperatures beneath these well-known volcanic sites. From this study, we conclude that the structure and Vp/Vs ratios we obtained for the crust and uppermost mantle are significant for better understanding of tectonic features in China and the surrounding area.
DE: 7200 SEISMOLOGY
DE: 7208 Mantle (1212, 1213, 8124)
DE: 7218 Lithosphere (1236)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 7270 Tomography (6982, 8180)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting