喜马拉雅造山带西构造结是青藏高原地形变化最剧烈、构造最复杂、地震活动剧烈的地区，是研究大陆碰撞及其动力学的天然实验室。前人研究表明喜马拉雅造山带西构造结的岩石圈正经历强烈的大陆内部变形和南北向缩短增厚。而大陆俯冲被认为是造成该区域岩石圈变形与缩短增厚的主要机制。然而，对该区域的大陆俯冲模式仍存不同看法。如，下地壳物质是否发生了俯冲？是单一板片的单向俯冲，还是两个板片的双向俯冲？本项目拟利用德国GFZ Potsdam的TIPAGE地震台网和其他地震台网在喜马拉雅造山带西构造结及邻区观测到的地震波形资料，通过双平面波层析成像研究，获取基阶Rayleigh波和Love波相速度分布，开展三维S波速度和各向异性（方位角和径向各向异性）结构反演，据此确定不同构造块体下方地壳和上地幔深部结构与变形特征，为探索以上关键科学问题进而理解喜马拉雅造山带的动力演化过程及西构造结中源地震的发生机制提供重要的约束。

The western Himalayan Syntaxis, as a part of the Himalaya-Tibet orogenic belt, where is characterized with variable topography, complex tectonic history, and intense seismic activity, has been the prime site to understand the processes and geodynamic of continental collision and mountain building. Previous geological and geophysical studies indicate that the western Himalayan Syntaxis has experienced intense intra-continental deformation and lithosphere shortening and thickening. Intra-continental subduction has been considered as a main mechanism responsible for lithosphere shortening and thickening in this region. However, there are still topics of debate regarding the subduction, for example, has the lower crust subducted into the lithospheric mantle? Is the subduction slab of the Himalayan orogenic belt either a single plate subduction, or two break-off opposing plates? In this project, based on the waveform data recorded by TIPAGE (deployed by GFZ Potsdam) and other permanent seismic networks in this region we propose to carry out two-plane-wave surface wave tomography (fundamental mode Rayleigh wave and Love wave) to obtain three-dimensional velocity and anisotropy (azimuthal and radial anisotropy) models of the crust and upper mantle in the western Himalayan Syntaxis, in an attempt to understand lithosphere structure and deformation in this region. With the completion of this project, we expect to answer above scientific questions and provide important constraints on the dynamic mountain building process of the Himalaya-Tibet and the mechanisms responsible for the intermediate earthquakes frequently occurred in the western Himalayan Syntaxis.