Eastward Asthenospheric Flow From NE Tibet Inferred by Joint Inversion of Teleseismic Body and Surface Waves: Insight Into Widespread Continental Deformation in Eastern China

During the last 50 Ma, the eastern Eurasian continent has experienced widespread crustal and lithospheric deformation. However, mechanisms in creating such widespread intra-continental deformation are still not well understood. Here, we present a 3-D S-wave velocity model of the northeastern Tibetan Plateau and adjacent regions by jointly inverting teleseismic body and surface waves. The resulting model clearly suggests that lateral extrusion of asthenosphere from northern Tibet is being blocked by the thick cratonic keels of Ordos and Sichuan, and therefore the asthenosphere is channeled into a strong eastward flow beneath the northern Qinglin between these two cratonic keels. Our results also demonstrate that continental deformation in eastern Eurasia is likely influenced by the small-scale convection when the lateral asthenospheric flow from NE Tibet encounters preexisting continental lithospheric steps to the east of Ordos.