青藏高原西部叶城-狮泉河地区岩石圈各向异性研究

对青藏高原西部新疆叶城—西藏狮泉河地区宽频地震探测记录到的剪切波进行了各向异性分析,计算结果给出了该地区上地幔各向异性的特征:西昆仑地区各向异性大都沿北东方向分布,总体方向变化不大,各向异性整体走向与青藏高原和塔里木盆地北缘各向异性空间分布一致。由此得出:印度板块向北推进的构造运动是形成本区岩石圈剪切波各向异性的主要原因,青藏高原各地体的各向异性在较大的东西向范围内保持稳定,各地体岩石圈固有的各向异性方向为北东向;作为羌塘地体和拉萨地体的分界线,班公怒江断裂带是主要的地表分界位置,在深部,无论西部剖面还是中部剖面,印度板块岩石圈的各向异性在该断裂带上均没有变化。

Anisotropy of lithosphere in Yecheng-Shiquanhe area, western Tibetan Plateau

The authors made an anisotropic analysis of shear waves obtained from broadband seismic experiments along the Yecheng (Xinjiang)-Ali (Tibet) profile. The result reveals the anisotropic characteristics in the upper mantle of western Tibet. The anisotropy is generally in NE direction and the orientation only varies insignificantly, being identical with the anisotropic direction in Tibetan Plateau and northern Tarim. The northward movement of Indian plate plays a key role in forming the shear wave anisotropy within the lithosphere of this region. The anisotropy in all blocks of Tibetan Plateau remains stable in a large EW-trending area. The original anisotropy in the lithosphere of each block stretches northeastward. Bangong-Nujiang faulted belt, as the boundary between Qiangtang block and Lhasa block, is mainly a boundary at the surface. In depth, the anisotropy in Indian lithosphere remains unchanged over Bangong-Nujiang fault belt, both in the western segment and in the central segment of Tibetan Plateau.