Ambient noise tomography reveals complex crustal structure beneath eastern and northeastern Tibet: Insight into regional crustal flow

We present a 3-D crustal S-wave velocity (Vs) model for eastern and northeastern Tibet utilizing ambient noise tomography. Our model reveals that crustal flow channels are absent in northeastern Tibet. In this region, the Kunlun Fault (KLF) significantly impacts mid-lower crust low-Vs anomalies. In addition, isolated low-Vs anomalies beneath the Qilian orogeny are unrelated to the low-Vs materials of the Tibetan Plateau. In the mid-lower crust of the Songpan-Ganzi terrane, its northeastern corner exhibits continuous low-Vs anomalies, limited to areas south of the West Qinglin and west of 104 degrees E. This suggests that a small-scale northward viscous flow of crustal materials exists in the eastern KLF. However, two significant crustal flow channels (Vs <= 3.3 km/s) are observed in eastern Tibet. The east-west tectonic movements and the obstruction of the Sichuan Basin together facilitate the dispersion of crustal materials southward from eastern Tibet.