Imaging the Northeastern Crustal Boundary of the Tibetan Plateau With Radial Anisotropy

Abstract

AbstractWe obtained a 3‐D crustal radial anisotropy model beneath northeastern (NE) Tibet by joint inversion of Rayleigh and Love dispersion curves from ambient noise tomography. Positive crustal radial anisotropy and significant low velocity are dominant beneath the Songpan‐Ganzi Terrane (SGT), indicating the presence of crustal channel flow. The Qilian orogen is characterized by negative radial anisotropy, which could be caused by folding and thrusting due to crustal shortening. This difference in radial anisotropy suggests that crustal shortening deformation may have occurred at a relatively early stage of the plateau evolution (the Qilian orogen) and crustal channel flow at the later stage (the SGT). The crustal radial anisotropy clearly defines the NE crustal boundary of the expanding Tibetan Plateau, which is roughly situated along the north Qilian frontal thrust from 97° to 103.5°E in the north and turns north‐south, passing the Zhuanglanghe Fault and terminating at the Kunlun Fault in the south.