Teleseimic Anisotropy and Corresponding Features of the Upper Mantle in Tibet Plateau and Its Neighboring Areas
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摘要: 通过研究在青藏高原及其部分邻区由三分量宽频地震资料获得的剪切波各向异性的特征,得出了上地幔构造的若干认识。在本区200 km以上的上地幔范围内各向异性的方向性变化主要是上地幔物质运移方向的影响,各地体的岩石圈与地壳在相当长时间内是连贯的运移。各向异性的主要方向决定于上地幔承受的主应力剪切作用方向常常与地表的山系和构造方向不一致。最强的各向异性特征出现在高速体地体边缘,与深部热的地幔物质有关。在各地体边缘的走滑断裂附近各向异性与断裂带走向一致。Abstract: Based on an analysis of the characteristics of shear wave anisotropy achieved from three-component broadband teleseismic data collected in Tibet plateau and its neighboring areas, the authors have reached some understanding concerning the upper mantle structure. In these areas, the anisotropic direction of the upper mantle above the depth of 200 km is mainly affected by the movement direction of the upper mantle material. In a long period in geohistory, the crust and lithosphere of different terranes shared continuous movement, and the corresponding main direction of anisotropy was determined by the shear stress exerted on the upper mantle, probabaly inconsistent with the strike direction of mountains and upper crust structures. The strongest anisotropy appears along the margin of high velocity terranes, often relevent to the partial melt material deep in the mantle. Near the strike-slip faults on the edges of these terrans, the anisotropic direction is consistent with the strikes of the fault systems.
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