Upper mantle anisotropy and crust-mantle deformation pattern beneath the Chinese mainland
Upper mantle anisotropy and crust-mantle deformation pattern beneath the Chinese mainland
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中国大陆上地幔各向异性与壳幔变形模式
DOI：
10.1007/s11430-013-4675-5
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Flesch, Lucy M.
中科院分区：
文献类型：
--
作者：
Ding ZhiFeng;Liu QiongLin;Liao WuLin;Flesch, Lucy M.
10年来，我国宽带地震台站数量大幅增加。宽频带地震记录中含有剪切波分裂信息，对揭示中国大陆上地幔各向异性具有重要作用。根据地震台记录的快波SKS和SKKS震相，采用最小横向能量分析法确定了快波偏振方向和横波分裂延迟时间。我们还从以前发表的论文中收集了中国和周边地区的剪切波分裂结果。从组合的数据集，我们形成了一个剪切波分裂数据集包含1020个参数对。这些分裂参数揭示了上地幔各向异性图像的复杂性。统计分析表明，中国大陆上地幔各向异性较强，剪切波平均延迟时间为0.95 s，西部各向异性（1.01 s）略大于东部（0.92 s）。在更大尺度上，青藏高原和天山地区的SKS分裂和地表形变数据共同支持岩石圈变形模式，即地壳-岩石圈地幔相干变形。在中国东部，平均快波方向近似平行于绝对板块运动方向，因此，上地幔各向异性可以归因于软流层流动。鄂尔多斯地块至四川盆地是中国中部地区变形模式的东、西部过渡带，各向异性图像较为复杂，表现为“化石”各向异性和（或）两层各向异性。印度板块与欧亚板块的碰撞是中国大陆西部地区上地幔各向异性的主要因素，而东部地区上地幔各向异性则与太平洋板块和菲律宾海板块向欧亚板块之下俯冲有关。
Over the past 10 years, the number of broadband seismic stations in China has increased significantly. The broadband seismic records contain information about shear-wave splitting which plays an important role in revealing the upper mantle anisotropy in the Chinese mainland. Based on teleseismic SKS and SKKS phases recorded in the seismic stations, we used the analytical method of minimum transverse energy to determine the fast wave polarization direction and delay time of shear-wave splitting. We also collected results of shear-wave splitting in China and the surrounding regions from previously published papers. From the combined dataset we formed a shear-wave splitting dataset containing 1020 parameter pairs. These splitting parameters reveal the complexity of the upper mantle anisotropy image. Our statistical analysis indicates stronger upper mantle anisotropy in the Chinese mainland, with an average shear-wave time delay of 0.95 s; the anisotropy in the western region is slightly larger (1.01 s) than in the eastern region (0.92 s). On a larger scale, the SKS splitting and surface deformation data in the Tibetan Plateau and the Tianshan region jointly support the lithospheric deformation mode, i.e. the crust-lithospheric mantle coherent deformation. In eastern China, the average fast-wave direction is approximately parallel to the direction of the absolute plate motion; thus, the upper mantle anisotropy can be attributed to the asthenospheric flow. The area from the Ordos block to the Sichuan Basin in central China is the transition zone of deformation modes between the east and the west regions, where the anisotropy images are more complicated, exhibiting “fossil” anisotropy and/or two-layer anisotropy. The collision between the Indian Plate and the Eurasian Plate is the main factor of upper mantle anisotropy in the western region of the Chinese mainland, while the upper mantle anisotropy in the eastern region is related to the subduction of the Pacific Plate and the Philippine Sea Plate beneath the Eurasian Plate.
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