3-D S-wave Lithosphere Structure of South China Block Based on Ambient Noise Tomography
Using continuous records of 704 stations from several mobile arrays,high-resolution S wave velocity structure of South China Block(SCB)was obtained by ambient noise tomography.In 3-D S wave velocity model,the velocities in shallow crust are well consistent with the surface geology and low velocity anomalies concentrate in Sichuan Basin and Jianghan Basin.The boundary between Yangtze Block and Cathaysian Block can be identified by a high-velocity belt in crust,which is Jiangnan Orogeny generated in collision.The low velocity anomaly of Cathaysian Block in middle crust is related to the widespread Mesozoic granite.In upper mantle,there are significant differences between the east and west South China Block:the west South China Block presents a significant high velocity anomaly which reflects a stable craton in Sichuan Basin;the low velocity anomaly in east South China Block reveals that the lithosphere has been thinned(<70 km)by the subduction of paleo-Pacific Plate.Besides,it is speculated that the low velocity anomaly of Qiongzhou Strait in upper mantle may correspond to the Hainan plume.
South China Block(SCB)S wave velocity structureJiangnan Orogenyplate subduction