固体地球物理研究生学术报告第四期

A high-resolution 3D Vs model of the crust and upper mantle was obtained by joint inversion of body wave travel times and surface wave dispersion data in South China. For body wave data, we assembled P- and S-wave travel times from 25,922 earthquakes during the period of 2010-2011 recorded at 676 stations in South China. For surface wave dispersion data, we assembled Rayleigh wave phase velocity for the period of 8 ~ 70 s and group velocity for the period of 8 ~ 50 s from ambient noise seismic tomography of Shen et al. (2016). Due to the complementary strengths of the two data types, the resolution of the velocity structure has improved. From the new velocity model, we can see that the velocity beneath the eastern Yangtze craton is different from velocity beneath the western Yangtze craton, but is similar with the velocity beneath the Cathaysia block. It shows thin Moho depth and lithosphere-asthenosphere boundary beneath the eastern Yangtze craton and Cathaysia block, while thick beneath the western Yangtze craton. This may be caused by the flat slab subduction (Li & Li, 2007). Moreover, in the middle crust, there are four high-velocity belts corresponding to four faults well. The high-velocity belt which along Jiangnan orogen corresponds well to the distribution of Neoproterozoic stratigraphy (Zhao Guochun, 2015; Dong et al., 2015), so we speculate that this high-velocity belt maybe an indicator of the suture between Yangtze craton and Cathaysia block.