3D Velocity Structure in Shanxi Graben and Ordos from Two Plane Waves Method

Using the broad-band seismic data of Peking University and CENC,taking the method of two plane waves tomography,we have obtain the phase velocities of Rayleigh wave and the 3D shear velocities in Ordos region.Through analyzing the results,we have found the phase velocities of Rayleigh wave in Shanxi graben and Weihe graben are lower.High velocity anomaly beneath moho has been observed in Ordos block,indicate that Ordos block is a stable craton,and its effect extend to 120km depth at least;in the depth between 70 and 120km of Shanxi graben and Weihe graben,shear velocities were lower than origin model,indicating that the substance there had plasticity and these region are strong activity,which is consistent with the activity of earthquake.