Joint inversion of receiver function and surface wave dispersion for crust and upper mantle S-wave velocity structure beneath Tianshan and its adjacent regions

The crust and upper mantle S-wave velocity structure beneath 88 seismic stations were established by joint inversion of surface wave dispersion and teleseismic receiver functions, and the 3D S-wave velocity structure for Tian-shan and its adjacent regions were constructed based on 1D models beneath 88 stations at each depth by linear isotropic variogram Kriging technique. The 3D velocity model was illustrated by images of depth slices and cross section profiles, and relations between the velocity structures and tectonic activities were discussed. The crust of Tianshan and its adjacent regions consists of upper, middle and lower layers. The boundaries of these layers are located at about 20, 40 and 50 km, respectively, and the topography of these boundaries varies with different tectonic terrains. The upper crust of Tianshan and the uplift of Tarim basin are characterized by relative high velocities, whereas the upper crust of most part of basins and depressions in front of mountains show relative low velocities. The approximately NS-trending low velocity zone of lower crust and the high velocity lid of upper mantle vary with depths between east and west parts of Tianshan, implying the differences in tectonic activities and deformations for eastern and western Tianshan. The differences may be caused by the different responses of western and eastern Tianshan to the India-Eurasia collision.