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| Three dimensional shear wave velocity structure of the crust and upper mantle beneath China from ambient noise surface wave tomography |
| Xinlei Sun1, Xiaodong Song1, Sihua Zheng1, 2, Yingjie Yang3, Michael H. Ritzwoller3 |
1 Department of Geology, University of Illinois at Urbana-Champaign, Urbana IL 61801, USA
2 Institute of Earthquake Science, China Earthquake Administration, Beijing 100036, China
3 CIEI, Department of Physics, University of Colorado at Boulder, Boulder CO 80309, USA |
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Abstract We determine the three-dimensional shear wave velocity structure of the crust and upper mantle in China using Green’s functions obtained from seismic ambient noise cross-correlation. The data we use are from the China National Seismic Network, global and regional networks and PASSCAL stations in the region. We first acquire cross-correlation seismograms between all possible station pairs. We then measure the Rayleigh wave group and phase dispersion curves using a frequency-time analysis method from 8 s to 60 s. After that, Rayleigh wave group and phase velocity dispersion maps on 1° by 1° spatial grids are obtained at different periods. Finally, we invert these maps for the 3-D shear wave velocity structure of the crust and upper mantle beneath China at each grid node. The inversion results show large-scale structures that correlate well with surface geology. Near the surface, velocities in major basins are anomalously slow, consistent with the thick sediments. East-west contrasts are striking in Moho depth. There is also a fast mid-to-lower crust and mantle lithosphere beneath the major basins surrounding the Tibetan plateau (TP) and Tianshan (Junggar, Tarim, Ordos, and Sichuan). These strong blocks, therefore, appear to play an important role in confining the deformation of the TP and constraining its geometry to form its current triangular shape. In northwest TP in Qiangtang, slow anomalies extend from the crust to the mantle lithosphere. Meanwhile, widespread, a prominent low-velocity zone is observed in the middle crust beneath most of the central, eastern and southeastern Tibetan plateau, consistent with a weak (and perhaps mobile) middle crust.
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Received: 29 April 2010
Published: 10 October 2010
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| Fund:National Science Foundation of United States (EAR-0838188) and Department of Geology, UIUC. The work at CU-Boulder was supported by NSF-EAR award 0944022 and a sub-award from NSF-OISE 0730154 |
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Corresponding Authors:
Xinlei Sun
E-mail: xsun@seismo.wustl.edu
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