【摘要】 本文研究采用单台法和双台法提取了穿越上扬子的基阶面波相速度和群速度频散;通过对提取的面波群速度和相速度频散进行联合反演,得到的1-D SV速度模型显示上扬子块体下地壳S波速度与典型克拉通区域相当,其上地幔顶部80～170 km深处存在高速的岩石圈盖层,较AK135模型要快2%～3%,其岩石圈厚度约为180 km..在上扬子地区,径向各向异性集中分布在300 km以浅的岩石圈与软流圈部分,其中岩石圈部分SH波比SV波波速要快2%～4%,软流圈部分SH波比SV波波速要快3%～5%;Rayleigh波相速度方位各向异性分析结果显示,上扬子块体周期为25～45 s(大致相当于30～70 km深度范围内)的Rayleigh波相速度存在1.8%～2.7%不等的方位各向异性,其快波方向介于147°～174°.我们认为上扬子块体径向各向异性集中分布在岩石圈、软流圈部分,且各向异性随深度变化,其岩石圈部分各向异性为大陆克拉通化的遗迹,软流圈部分各向异性与现今板块运动相关.更多还原

【Abstract】 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.更多还原