HR: 0800h
AN: T31D-0675    [Abstracts]
TI: S-wave crustal structure in the eastern Tibetan Plateau and its tectonic implications
AU: * Wang, C
EM: wangcy@cea-igp.ac.cn
AF: Institute of Geophysics, China Earthquake Administration, No 5 Minzuxueyuan South Road, Haidian District, Beijing, 100081, China
AU: Zhu, L
EM: lupei@eas.slu.edu
AF: Department of Earth and Atmospheric Sciences, Saint Louis University, 3507 Laclede Ave, St.Louis, MO 63103, United States
AU: Silver, P
EM: silver@dtm.ciw.edu
AF: Carnegie Institute of Washington, 5241 Broad Branch Rd.NW, Washington DC, 20015, United States
AU: Lou, H
EM: louhai@cea-igp.ac.cn
AF: Institute of Geophysics, China Earthquake Administration, No 5 Minzuxueyuan South Road, Haidian District, Beijing, 100081, China
AU: Chang, L
EM: changlijun@eyou.com
AF: Institute of Geophysics, China Earthquake Administration, No 5 Minzuxueyuan South Road, Haidian District, Beijing, 100081, China
AB: A teleseismic profile composed of 26 broadband seismic stations was deployed along 30¡ãN latitude in the Eastern Tibetan plateau in 2004-2006. Based on the receiver functions inferred from the teleseismic records, the crustal thickness and Poisson ratio beneath the stations were determined by the H-k slant stacking method. Along the profile, the crustal thickness and Poisson ratio are averaged to be (62.1 km, 0.248) in the Lhasa block, (72.4 km, 0.269) in the Banggong-Nujiang suture, (65.8 km, 0.275) in the Qiangtang block, ( 57.4 km, 0.293) in the Songpan-Garze block, (42.0 km, 0.268) in the Sichuan basin, respectively. The Sichuan basin has a huge thick sedimentary (~10 km in thickness) with low S velocity, which may cause higher crustal Poisson ratio. The inversion of teleseismic P-wave receiver function was used to obtain S-wave velocity structures at stations along the profile, which are characterized by low velocity layer in mid-lower crust (at depth of 30-60 km) in the Qiangtang and the Songpan-Garze blocks, and in upper crust (at depth of 10-20 km) in the Lhasa block. There is a significant lateral variation of crustal thickness along the profile. The maximum crustal thickness (~73 km) along the profile is located at the Bangong-Nujiang suture, which is considered as the continent-continent collision between the Indian and the Eurasian plates. Low S-wave velocity anomaly in lower crust, weak Moho transition, and high crustal Poisson ratio in the Qiangtang and the Songpan-Garze blocks are generally related to hot and weak state in lower crust. The results in this study indicate that the deep crustal material in the eastern Tibetan Plateau is in a state of the lower crustal flow.
DE: 8011 Kinematics of crustal and mantle deformation
DE: 8108 Continental tectonics: compressional
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8159 Rheology: crust and lithosphere (8031)
DE: 8175 Tectonics and landscape evolution
SC: Tectonophysics [T]
MN: 2007 Fall Meeting