Crustal structures beneath southern central Tibetan Plateau : new constraints from teleseismic P wave coda autocorrelation

Many active and passive seismic observations have been carried out in the southern Tibetan Plateau and provide substantial seismological evidences of the process and mechanism of the collision between the Indian plate and Eurasian continent. The subduction of the Indian plate produces widespread dipping structures beneath the Tibetan Plateau, which are complex and challenging for geophysical imaging. In this paper, we obtained a clear P-wave reflectivity profile beneath the Hi-CLIMB seismic array based on the improved teleseismic P wave coda autocorrelation (TsPCA) method. The results show a double Moho feature beneath the Lhasa Terrane, which is similar to receiver function results, indicating the eclogitization phenomenon that occurred when the Indian lower crust subducted below the Tibetan Plateau. The feature can be traced northward beyond 31 N, indicating the subduction front of the Indian lower crust. Our results support the hypothesis that the Indian plate subducted to the Tibetan Plateau, then the Indian upper crust was stripped off near the Yarlung Zangbo Suture (YZS), and the Indian lower crust and lithospheric mantle continued to subduct northward and almost horizontally underplating below the Tibetan Plateau. The P-wave reflectivity profile also reveals detailed interior structures of the crust, such as the thinning of Indian lower crust; the reflection features of the YZS and the Banggong-Nujiang Suture (BNS); the crust internal stratification features of the Lhasa Terrane and the Qiangtang Terrane; two low-velocity zones in the middle and upper crust of northern Himalaya and northern Lhasa Terrane.