HR: 13:55h
AN: T53D-02    [Abstracts]
TI: Lithospheric Structure of East Asia from Seismic Tomography
AU: * Sun, Y
EM: youshun@mit.edu
AF: MIT, E34-566 42 Carleton St, Cambridge, MA 02142 United States
AU: Toksoz, N
EM: toksoz@mit.edu
AF: MIT, E34-566 42 Carleton St, Cambridge, MA 02142 United States
AB: P- and S-wave velocity models based on travel-time tomography are presented. Travel-time data from the extensive Annual Bulletin of Chinese Earthquakes (ABCE) and the International Seismological Centre (ISC/EHB) are used. The tomographic inversion is carried out in two steps. First, 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, and detailed Pn and Sn velocities. Tests conducted by relocating large events (explosions and earthquakes) and fitting seismograms validate the 3-D velocity models. The crust and upper mantle velocity structure derived from regional travel-times, as described above, are used to counteract the ``smearing effect" for teleseismic tomography. A 3-D P-wave velocity model extending to 1,700 km depth is obtained using a variable grid method based on ray density. ISC/EHB data for P and pP phases are combined with the ABCE data to extend the P-wave model deeper into the mantle through the upper mantle transition zone. The combined regional-teleseismic tomography provides a high-resolution, 3-D P-wave velocity model for the crust, upper mantle, and transition zone. The crustal models correlate well with geologic and tectonic features. The mantle models show the images of current and past subduction zones. A surprising result is that the ``roots'' of some geologic features, such as the Sichuan Basin and Ordos Plateau, extend deep into the upper mantle.
DE: 7200 SEISMOLOGY
DE: 7203 Body waves
DE: 7218 Lithosphere (1236)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
SC: Tectonophysics [T]
MN: Fall Meeting 2005