Tomographic structure of East Asia: II. Stagnant slab above 660 km discontinuity and its geodynamic implications
Yongshun John Chen1, Shunping Pei2, 1
1 Computational Geodynamics Laboratory, Department of Geophysics, School of Earth and Space Sciences, Peking University, Beijing 100871, China 2 Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100085, China
Tomographic structure of East Asia: II. Stagnant slab above 660 km discontinuity and its geodynamic implications
Yongshun John Chen1, Shunping Pei2, 1
1 Computational Geodynamics Laboratory, Department of Geophysics, School of Earth and Space Sciences, Peking University, Beijing 100871, China 2 Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100085, China
摘要P-wave arrival times of both regional and teleseismic earthquakes were inverted to obtain mantle structures of East Asia. No fast (slab) velocity anomalies was not find beneath the 660-km discontinuity through tomography besides a stagnant slab within the transition zone. Slow P-wave velocity anomalies are present at depths of 100-250 km below the active volcanic arc and East Asia. The western end of the flat stagnant slab is about 1 500 km west to active trench and may also be correlated with prominent surface topographic break in eastern China. We suggested that active mantle convection might be operating within this horizontally expanded “mantle wedge” above both the active subducting slabs and the stagnant flat slabs beneath much of the North China plain. Both the widespread Cenozoic volcanism and associated extensional basins in East Asia could be the manifestation of this vigorous upper mantle convection. Cold or thermal anomalies associated with the stagnant slabs above the 660-km discontinuity have not only caused a broad depression of the boundary due to its negative Clapeyron slope but also effectively shielded the asthenosphere and continental lithosphere above from any possible influence of mantle plumes in the lower mantle.
Abstract：P-wave arrival times of both regional and teleseismic earthquakes were inverted to obtain mantle structures of East Asia. No fast (slab) velocity anomalies was not find beneath the 660-km discontinuity through tomography besides a stagnant slab within the transition zone. Slow P-wave velocity anomalies are present at depths of 100-250 km below the active volcanic arc and East Asia. The western end of the flat stagnant slab is about 1 500 km west to active trench and may also be correlated with prominent surface topographic break in eastern China. We suggested that active mantle convection might be operating within this horizontally expanded “mantle wedge” above both the active subducting slabs and the stagnant flat slabs beneath much of the North China plain. Both the widespread Cenozoic volcanism and associated extensional basins in East Asia could be the manifestation of this vigorous upper mantle convection. Cold or thermal anomalies associated with the stagnant slabs above the 660-km discontinuity have not only caused a broad depression of the boundary due to its negative Clapeyron slope but also effectively shielded the asthenosphere and continental lithosphere above from any possible influence of mantle plumes in the lower mantle.
基金资助:the National Natural Science Foundation of China (Nos. 40125011, 90814002 and 41074041) and the Chinese Academy of Sciences (No. KZCX2-EW-QN102)
通讯作者:
Yongshun John Chen
E-mail: johnyc@pku.edu.cn
引用本文:
Yongshun John Chen, Shunping Pei. Tomographic structure of East Asia: II. Stagnant slab above 660 km discontinuity and its geodynamic implications[J]. 《地震学报》英文版, 2010, 23(6): 613-626.
Yongshun John Chen, Shunping Pei. Tomographic structure of East Asia: II. Stagnant slab above 660 km discontinuity and its geodynamic implications. Earthquake Science, 2010, 23(6): 613-626.
