Crustal structure in the Dasanjiang basin and its adjacent areas

We collected continuous waveforms and teleseismic events both from the regional permanent seismic network and several temporary seismic arrays in the Dasanjiang basin and its adjacent areas and obtained the 3D S-wave velocity structure, basement depth, Moho depth and Poisson’s ratio by using the ambient noise tomography and receiver function methods. Our results show that the shallow velocity structure corresponds well to the surface topography and geological features. The Sanjiang basin shows obvious low-velocity and small basins such as Hulin and Boli basins are also imaged as relatively low velocities, while the Xiaoxing’anling and Zhangguangcailing are characterized by high velocities. In the mid-lower crust, all basins show obvious high velocities, which indicates that they are stable at this depth. The low-velocity anomaly beneath the Yilan-Yitong fault extends down to deep, indicating that it is a regional deep fault. The results of the receiver function show that the Moho depth varies gently in the range of 30 km to 36 km. In the Sanjiang basin, the sedimentary thickness beneath Qianjin depression is the thickest, which could reach 5.4 km. While the sedimentary thickness beneath Fujin uplift is the thinnest, which could be 2.7 km. Beneath the western Suibin depression, sedimentary layer becomes thick again. The above features are consistent with the known tectonics of two depressions sandwiching one uplift.