Seismic anisotropy and mantle dynamics beneath China
Seismic anisotropy and mantle dynamics beneath China
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DOI：
10.1016/j.epsl.2011.03.038
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发表时间：
2011-06
影响因子：
5.3
通讯作者：
Zhouchuan Huang;Liangshu Wang;Dapeng Zhao;N. Mi;Mingjie Xu
中科院分区：
文献类型：
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作者：
Zhouchuan Huang;Liangshu Wang;Dapeng Zhao;N. Mi;Mingjie Xu
为了研究中国大陆地区地震各向异性和地幔动力学，我们分析了138个常设地震台站的剪切波分裂。为了获得可靠的结果，我们使用了三种不同的方法来测量剪切波分裂参数，使用核心相位（SKS，SKKS，SKiKS和PKS）以及区域和远震的直接S波。结果表明，中国东部各向异性的快速方向（WNW-ESE）与欧亚板块的绝对板块运动方向（APM）基本一致，表明各向异性主要位于软流圈中，这是由于软流圈中的橄榄石在剪切变形过程中产生的晶格择优取向。中国西部地区的快轴与造山带和活动断裂的走向基本一致，而与最大水平应力方向垂直，表明岩石圈各向异性对剪切波分裂有重要贡献。中国西部地区的快轴也与APM方向一致，表明APM驱动的软流圈各向异性是造成剪切波分裂的另一个原因。这些结果表明，APM驱动的各向异性普遍存在于大陆，类似于在海洋地区，即使大陆岩石圈遭受了广泛的变形。
We analyzed the shear-wave splitting at 138 permanent seismograph stations to study seismic anisotropy and mantle dynamics under Mainland China. To obtain reliable results we used three different methods to measure the shear-wave splitting parameters using core phases (SKS, SKKS, SKiKS and PKS) as well as the direct S waves from regional and distant earthquakes. Our results show that the fast orientations of the anisotropy (WNW–ESE) in eastern China are generally consistent with the absolute plate motion (APM) direction of the Eurasian plate, suggesting that the anisotropy is mainly located in the asthenosphere resulting from the lattice-preferred orientation of olivine due to the shear deformation there. The fast axes in western China generally agree with the strikes of the orogens and active faults, while they are perpendicular to the direction of the maximum horizontal stress, suggesting that the anisotropy in the lithosphere contributes significantly to the observed shear-wave splitting. The fast axes in western China are also consistent with the APM direction, suggesting that the APM-driven anisotropy in the asthenosphere is another source of the shear-wave splitting there. These results suggest that APM-driven anisotropy commonly exists under continents, similar to that under oceanic regions, even though the continental lithosphere has suffered extensive deformation.