HR: 1340h
AN: T43B-1358    [Abstracts]
TI: Crustal Structure Across the Three Gorges Dam from Wide-Angle Seismic Data
AU: Zhang, Z
EM: zjzhang1@yahoo.com
AF: State Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics Chinese Academy of Science, Beijing, 100029, China
AU: Bai, Z
EM: a37171@hotmail.com
AF: State Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics Chinese Academy of Science, Beijing, 100029, China
AU: Mooney, W D
EM: mooney@usgs.gov
AF: US Geological Survey, 345 Middlefield Rd. MS 977, Menlo Park, CA 94025, United States
AU: * Wang, C
EM: wangcy@cea-igp.ac.cn
AF: Institute of Geophysics, China Earthquake Administration, Beijing, 100080, China
AU: Chen, X
EM: a37171@hotmail.com
AF: Institute of Dynamic Deformation, China Earthquake Administration, Beijing, 100081`, China
AU: Wang, E
EM: erchie-wang@mail.iggcas.ac.cn
AF: State Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics Chinese Academy of Science, Beijing, 100029, China
AU: Teng, J
EM: a37171@hotmail.com
AF: State Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics Chinese Academy of Science, Beijing, 100029, China
AB: The Three Gorges Dam (TGD) is one of the biggest engineering projects in the world. In order to understand the crustal structure across the TGD, a wide-angle seismic profile was acquired from Fengjie, Sichuan Province, to Guanyindang, Hubei Province. The crustal velocity and reflectivity cross-section across the TGD shows lateral velocity variation and a northward-slipping, crustal-scale, strong reflector. The TGD is located at a transition in crustal thickness from about 45 km in the northwest to about 35 km in the southeast. The topography of China is characterized by three terraces. The Qinghai-Tibet Plateau is the first terrace with a surface elevation above sea level of >4500 m; the second terrace lies north and east of the Qinghai-Tibet Plateau at an elevation of 1000-2000 m; the third terrace is in the eastern part of China with an elevation of <500 m. Three cross sections along latitude 30, 31 and 32 from eastern Tibet to the East China Sea illuminate two steep topographic gradients at Longmenshan (97.5E), between eastern Tibet and the Sichuan basin, the TGD area (110E), and the flanking marginal seas (125E). The TGD area, named after the three gorges of Xiling Xia, Wu Xia, and Qutang Xia (Xia means "gorge" in Chinese), is located at the middle segmentations of the Yangtze River, extending from Fengjie, Sichuan Province, to Yichang, Hubei Province, with a total length of about 200 km. Due to the abrupt relief from the second to third topographic terrace of China, the unstopping, huge amounts of river stream provide the best place for the construction of the largest hydro power plant ever in the world. In order to provide a background of the crustal environment for the dam project, a wide-angle seismic profile along the Yangtze River was carried out. Tectonically, the studied area belongs to the Yangtze block and cut several sub-tectonic units: the Wanxian depression fold belt, the Zigui platform fold belt, the southwestern Hubei province complex fold belt, the Huangling Faulted Dome (HLFD), and the Jiangling Depression (JLD). We present the interpretation results of the crustal structure along the Three Gorges extension which shows: there are strong lateral variations both of crustal thickness and P-wave velocity, the Jiangling depression (the southeast of the profile) acts as the strong foreland, and the TGD experienced crustal thickening.
DE: 1219 Gravity anomalies and Earth structure (0920, 7205, 7240)
DE: 7209 Earthquake dynamics (1242)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8110 Continental tectonics: general (0905)
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting