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用Rayleigh波层析成像研究青藏高原地壳上地幔方位各向异性.收集了包括近年来在云南和川西藏东地区布设的流动台网在内的青藏高原及周边地区宽频带地震台站的记录,使得大部分地区有理想的射线覆盖,因此反演结果获得较高的分辨.模型分辨率的测试表明,大于400km范围内的各向异性特征以及大于2%的各向异性强度是可靠的.青藏高原内部的方位各向异性具有与大地构造相似的分区特征.高原东部大部分地区地壳各向异性强度大于2%,且表现为环绕喜马拉雅东构造结的顺时针旋转.在垂直方向上,高原内部的上地壳、下地壳和岩石圈地幔的各向异性方向基本一致,也与GPS所观测到的速度场和SKS快波方向基本一致,揭示高原下方的岩石圈变形是垂直连贯变形.在高原外部的云南地区,地壳和上地幔岩石圈方位各向异性的强度均小于2%,因此SKS波从核幔边界至台站间产生的分裂应主要归因于软流圈.
Rayleigh wave tomography was used to study the azimuthal anisotropy of the crust and upper mantle in the Qinghai-Xizang Plateau, and records of broadband seismic stations in the Qinghai-Xizang Plateau and its surrounding areas, including the mobile stations deployed in Yunnan and western Tibet, So that most of the region has ideal ray coverage, so the inversion result gets a higher resolution.The test of model resolution shows that the anisotropy of more than 400km and the anisotropy of more than 2% are reliable. The azimuthal anisotropy in the interior of the plateau is similar to the tectonic features of the earth’s crust. The crustal anisotropy in most parts of the eastern plateau is greater than 2% and appears clockwise around the east Himalayan tectonic knot. In the vertical direction, The anisotropy direction of the upper crust, the lower crust and the lithospheric mantle is basically the same, which is also consistent with the velocity field observed by GPS and the SKS fast wave direction, revealing that the lithospheric deformation beneath the plateau is vertically coherent deformation. Of the Yunnan region, the azimuthal anisotropy of crust and upper mantle is less than 2%, so the SKS wave is generated from the boundary of the mantle to the station The division should be mainly due to asthenosphere.