SKS splitting beneath Capital area of China

Based on the polarization analysis of teleseismic SKS waveform data recorded at 49 seismic stations in Capital Area Seismograph Network, the SKS fast-wave direction and the delay time between the fast and slow shear waves at each station were determined by using the grid searching method of minimum transverse energy and the stacking analysis method, and then we acquired the image of upper mantle anisotropy in Capital area. In the study area, the fast-wave polarization direction is basically WNW-ESE, and the delay time falls into the interval from 0.56 s to 1.56 s. The results imply that the upper mantle anisotropy in Capital area is mainly caused by the subduction of the Pacific plate to Eurasian plate. The subduction has resulted in the asthenospheric material deformation in Capital area, and made the alignment of upper mantle peridotite lattice parallel to the deformation direction. And the collision between the Indian and Eurasian plates made the crust of western China thickening and uplifting and material eastwards extruding, and then caused the upper mantle flow eastwards, and made the upper mantle deformation direction parallel to the fast-wave direction. The deformation model of the crust and upper mantle is possibly vertically coherent deformation by comparing the fast-wave polarization direction with the direction of lithospheric extension and the GPS velocity direction.