Three-Dimensional Lithospheric VP/VS Structure Beneath Chinese Continent

Abstract V P and VS models have been obtained for the lithosphere of Chinese continent by tomography of body-wave travel times, surface-wave data, and joint inversion of surface- and body-wave data. However, the VP/VS ratio model derived directly from them shows unphysical values, indicating internal inconsistency of model resolutions and uncertainties. In this study, we use P- and S-wave first arrival times for phases Pg, Pn, P, Sg, Sn, and S from regional earthquakes at 1294 permanent seismic stations in China and directly invert for a new 3D VP/VS model (USTClitho1.0k). Resolution analysis indicates that the obtained VP/VS ratio model has a 2° horizontal spatial resolution down to 100 km in most of Chinese continent. Overall, there is a good agreement between the crustal VP/VS images and the surface geologic features. The Songliao, Sichuan, and North China basins all show high VP/VS values. In contrast, the Tarim basin exhibits low VP/VS values. The Qilian fold belt, Tibetan Plateau, and the Tanlu fault zone in eastern China exhibit lower VP/VS features. High VP/VS values are present in the middle-lower crust and uppermost mantle beneath the Tienshan orogenic belt, the Qiangtang block, the Songpan–Ganzi block, and the eastern part of continental China. There are local high VP/VS anomalies in the middle crust beneath some volcanoes such as Datong, Tengchong, and Changbaishan. In addition, the uppermost mantle is generally associated with high VP/VS values. Our VP/VS model is consistent with many other studies and may be useful for future geoscience studies in the China region.