青藏高原东缘及东北缘S波速度结构和径向各向异性

The northeastern and eastern margins of Tibetan Plateau (TP) are the frontiers of growth and expansion of the plateau. It is helpful to explore the growth mechanism of the plateau by studying the subsurface material and deformation characteristics. We collect 7 years of three-component continuous waveform data recorded by 187 seismic stations and 3 years of waveform data recorded by 189 transportable stations. The Rayleigh wave and Love wave dispersion at the periods of 8~40 s are carried out by ambient noise tomography. Based on the group velocities of Rayleigh wave and Love wave, the three-dimensional SH and SV velocity structures in the depth range of 0~50 km are inverted by linear inversion method. We define the radial anisotropy parameter as ψ=2(v_SH-v_SV)/(v_SH+v_SV) in the crust to show whether the subsurface deformation is dominated by horizontally extension (v_SH>v_SV) or vertically (v_SH<v_SV) thickening. The radial anisotropy shows distinct deformation mechanisms in the eastern and northeastern margins of the TP. The eastern margin is dominated by horizontal extension, which agrees with crustal flow model in this area. The northeastern margin shows prominent vertical thickening, which indicates that the crustal flow model is unlikely the main deformation mechanism in this region. Significant difference in radial anisotropy between Qaidam Basin and Sichuan Basin indicates that the stable blocks on the edge of the plateau play different roles in the plateau growth.