S-wave velocity structure of the crust and upper mantle under southeastern China by surface wave dispersion analysis |
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| Institution: | 1. Research Institute of Earthquake and Volcano Geology, Geological Survey of Japan, AIST, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8567, Japan;2. Hydrographic and Oceanographic Department, Japan Coast Guard, 3-1-1, Kasumigaseki, Chiyoda-ku, Tokyo 100-8932, Japan;1. Department of Civil Engineering, National Central University, 300 Zhongda, Rd., Zhongli Dist., Taoyuan 320, Taiwan;2. Department of Civil Engineering, National Chiao Tung University, 1001 Ta-Hsueh, Rd., Hsinchu 300, Taiwan;3. Department of Marine Environment and Engineering, National Sun Yat-sen University, 70 Lienhai Rd., Kaohsiung 804, Taiwan;1. Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China;2. 44 Rue du Cloître, 29280 Plouzané, France;3. Ifremer Centre de Brest, B.P. 70, 29280 Plouzané Cedex, France;4. University of Chinese Academy of Sciences, Beijing 100049, China;5. University of Houston, Department of Earth and Atmospheric Sciences, Science & Research Building 1, 3507 Cullen Boulevard, Houston, TX 77204, USA;6. Institute of Applied Geophysics, National Taiwan Ocean University, 2 Pei-Ning Road, Keelung 202, Taiwan |
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| Abstract: | Group velocity dispersion data of fundamental-mode Rayleigh and Love waves for 12 wave paths within southeastern China have been measured by applying the multiple-filter technique to the properly rotated three-component digital seismograms from two Seismic Research Observatory stations, TATO and CHTO. The generalized surface wave inversion technique was applied to these group velocity dispersion data to determine the S-wave velocity structures of the crust and upper mantle for various regions of southeastern China. The results clearly demonstrate that the crust and upper mantle under southeastern China are laterally heterogeneous. The southern China region south of 25°N and the eastern China region both have a crustal thickness of 30 km. The eastern Tibet plateau along the 100°E meridian has a crustal thickness of 60 km. Central China, consisting mainly of the Yangtze and Sino-Korean platforms, has a crustal thickness of 40 km. A distinct S-wave low-velocity layer at 10–20 km depth in the middle crust was found under wave paths in southeastern China. On the other hand, no such crustal low-velocity layer is evident under the eastern Tibet plateau. This low-velocity layer in the middle crust appears to reflect the presence of a sialic low-velocity layer perhaps consisting of intruded granitic laccoliths, or possibly the remnant of the source zone of widespread magmatic activities known to have taken place in these regions since the late Carboniferous. |
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