The lithospheric S-velocity structure of the western Yangtze craton inferred from surface waves inversion
用面波方法研究上扬子克拉通壳幔速度结构

The fundamental mode surface wave group and phase velocities dispersion measurements have been made for paths traversing the western Yangtze craton. A joint inversion of surface wave phase and group dispersion data provides the regionalized shear wave velocity structure of the lithosphere across the western Yangtze craton. The 1-D SV model shows that the lower crust velocity of the western Yangtze craton is similar to that of typical cratonic regions. The model also shows that the average velocity perturbations in the mantle are 2%~3% faster than the AK135 to at least 170 km depth and thus define the cratonic lithosphere. Horizontal fabric (SH is 2%~4% faster than SV) are observed in the lower crust and upper lithospheric mantle. And a similar radial anisotropy (SH is 3%~5% faster than SV) has also been finding in the asthenosphere. Azimuthal anisotropy is well resolved at short periods (25~45 s) with a dominant fast direction of 147°~174°. Our results suggest the presence of depth-dependent anisotropic structure, where the anisotropy in the lithosphere may correspond to regional crustal and uppermost mantle structure resulting from Yangtze craton formation, and the anisotropy in the asthenosphere may result from present-day asthenospheric flow.