HR: 1340h
AN: T13E-1627    [Abstracts]
TI: Joint inversion for crustal and Pn velocities and Moho depth for eastern margin of Tibetan Plateau
AU: * Xu, Z
EM: zhenxu2@uiuc.edu
AF: Department of Geology University of Illinois at Urbana-Champaign, 1301 W. Green St., 245 NHB, Urbana, IL 61801, United States
AU: Song, X
EM: xsong@uiuc.edu
AF: Department of Geology University of Illinois at Urbana-Champaign, 1301 W. Green St., 245 NHB, Urbana, IL 61801, United States
AB: A classical problem in seismic tomography is the trade-off between a discontinuity location and the velocity of the medium. For that reason, crustal tomography and Pn tomography are typically done separately by isolating first arriving Pg and Pn waves. Although this avoids the contamination of secondary arrivals because of the existence of the Moho, lots of good data are discarded and, as a result, the lower crust is particularly poorly constrained. Here we design an iterative scheme to invert jointly for the velocities of the whole crust and the Pn waves as well as the Moho depth. We use a spherical pseudo bending ray tracing method for the heterogeneous crust and include secondary Pg waves at large distances. The advantage of a joint inversion approach is several fold. First, with accurate 2D Moho depth, different types of waves can be better separated, thus preventing the contamination of Pg from Pn waves. Secondly, with the resolution of 3D crustal velocity structure, Moho depth variation can be separated and simultaneously solved in the inversion. Thirdly, Pn waves and secondary Pg waves at large distances can also put constraint on crustal velocity, especially in the lower crust. We are applying the method to the eastern and southeastern margin of the Tibetan Plateau, where this method is particularly useful because of the rapid variation of crustal structure and Moho depth. Resolution of mid-lower crust structure is important for testing contested "channel-flow" model. Our data include arrival times from provincial, national, international bulletins, and our own hand picks as well as relative time measurements from cross-correlation between events. Preliminary results of our inversion will be reported.
DE: 1209 Tectonic deformation (6924)
DE: 7203 Body waves
DE: 7205 Continental crust (1219)
DE: 7270 Tomography (6982, 8180)
DE: 9320 Asia
SC: Tectonophysics [T]
MN: 2007 Fall Meeting