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| Tomographic structure of East Asia: I. No fast (slab) anomalies beneath 660 km discontinuity |
| Shunping Pei1, 2, Yongshun John Chen2 |
1 Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100085, China
2 Computational Geodynamics Laboratory, Department of Geophysics, School of Earth and Space Sciences, Peking University, Beijing 100871, China |
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Abstract This is the first of two papers that describes a regional tomography investigation, which combines P-wave arrival times of both regional and teleseismic earthquakes to obtain 3D mantle structures of East Asia up to 1 000 km depth. The most important findings of this tomography study are reported in this paper as follows. (1) No fast P-wave velocity anomalies can be related to subducted oceanic slabs beneath the 660 km discontinuity; instead the subducted oceanic slabs become flattened and stagnant within the transition zone. (2) The high velocity anomalies in the transition zone extend up to 1 500 km to the westward of the active trenches, which is a unique feature in the worldwide subduction systems. (3) Slow P-wave velocity anomalies are visible up to ~250 km underneath most of the East Asia on the east of 115°E, similar to the area of the stagnant slabs. These observations have important implications for the geodynamic process at depths beneath the East Asia, which might in turn control the widespread Cenozoic volcanism and associated extensional tectonics seen at the Earth’s surface.
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Received: 04 September 2010
Published: 10 December 2010
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| Fund:the Chinese Academy of Sciences (No. KZCX2-EW-QN102) and the National Natural Science Foundation of China (Nos. 41074041, 90814002 and 40125011) |
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Corresponding Authors:
Yongshun John Chen
E-mail: johnyc@pku.edu.cn
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