HR: 0800h
AN: S41A-08    [Abstracts]
TI: 3D Shear-Wave Structure Beneath Central Tien Shan
AU: * Lisi, A
EM: arianna.lisi@libero.it
AF: University of Houston, 4800 Calhoun Rd., Houston, TX 77004, United States
AU: Li, A
EM: ali2@mail.uh.edu
AF: University of Houston, 4800 Calhoun Rd., Houston, TX 77004, United States
AB: The Tien Shan is the world's largest and most active intracontinental orogen with the actual shortening rate of 20 mm/year and earthquake magnitude up to 8.0. The tectonic reactivation is usually attributed to the India-Eurasia collision. However the mechanism responsible for the actual tectonic setting of the Tien Shan remains debated. The aim of this study is to construct 3D shear-wave structure beneath the central Tien Shan and to understand the geodynamic mechanism for the intraplate mountain building. We have analyzed Rayleigh waves recorded at the CHENGIS and KNET seismic networks, which consist of 41 broadband seismic stations. We extract fundamental mode Rayleigh wave trains from 100 teleseismic events at central frequencies from 7.5 mHz to 50 mHz with a 10 mHz frequency interval. A two-plane-wave tomography technique is used to solve for 2-D phase velocities by inverting all the Rayleigh wave phases and amplitudes. We have generated phase velocity maps at the periods of 30-150 s. Our preliminary results of phase velocity maps at periods of 40, 50, 67 and 87 s, based on 10 events, show that a low velocity structure is present beneath the Tien Shan range and that the lateral variations of phase velocities increase with depth. 3-D shear-wave structure in the crust and upper mantle will be computed from the 2-D phase velocities. We will present our findings and discuss their implications.
DE: 6982 Tomography and imaging (7270, 8180)
DE: 7270 Tomography (6982, 8180)
DE: 8180 Tomography (6982, 7270)
SC: Seismology [S]
MN: 2007 Joint Assembly