Crustal structure and deformation beneath the NE margin of the Tibetan plateau constrained by teleseismic receiver function data
We analysed a large amount of teleseismic receiver function data recorded by 172 broadband stations in the NE Tibetan plateau and its surrounding areas to investigate the crustal velocity and anisotropy structure beneath the margin. We first applied the modified H–κ stacking technique to measure the crustal thickness and average Vp/Vs ratio, and then employed a joint inversion scheme to measure azimuthal anisotropy of the crust beneath each station. The observed crustal thickness and Vp/Vs ratio exhibit large variations across the study area, varying from 32 to 75.6 km and from 1.601 to 1.864, respectively. We also found significant azimuthal anisotropy within the crust beneath 12 stations, with a splitting time between 0.36 and 1.06s. The fast polarization directions align well with surface structures, and follow the directions of the maximum horizontal tensile stress. The low Vp/Vs ratio and the strong azimuthal anisotropy observed beneath the margin suggest that whole crustal shortening might be the dominant mechanism for producing the thick crust in NE Tibet. We compared the measured seismic anisotropy with those measured from XKS (SKS, PKS and SKKS), and found that crustal anisotropy appears to play an important role in explaining the amount of XKS splitting times. More importantly, the Moho Ps and the XKS share similar fast polarization directions, suggesting a vertically coherent deformation within the lithosphere beneath the margin.
Seismicity and tectonic; Body waves; Seismic anisotropy; Crustal structure; Asia