Crustal and upper mantle structure beneath the northeastern Tibetan Plateau from joint analysis of receiver functions and Rayleigh wave dispersions

Abstract

The crustal and upper mantle velocity structure in the northeastern Tibetan Plateau is obtained from joint analysis of receiver functions and Rayleigh wave dispersions. The resulting velocity model reveals a close correlation between the thick (>60 km) crust and the presence of an intracrustal low-velocity zone beneath the Qiangtang and Songpan-Ganzi terranes as well as the northwestern Qilian orogen. However, the high V p /V s ratio of the crust is found only beneath the Qiangtang and Songpan-Ganzi terranes. The crustal low velocity zone does not appear in the west Qinling and southeastern Qilian orogens, which have a relatively thin (50 km) crust, indicating that crustal channel flow is not the primary mechanism by which the northeastern Tibetan Plateau grows. A continuous low velocity zone from the mid-to-lower crust down to 160 km beneath the eastern Kunlun fault suggests an induced local mantle upwelling after partial detachment of the lithosphere.