Less‐Well‐Developed Crustal Channel‐Flow in the Central Tibetan Plateau Revealed by Receiver Function and Surface Wave Joint Inversion

Abstract

AbstractA crustal channel‐flow model has been previously used to explain the formation of crustal extensional structures in the Tibetan Plateau. However, the existence of massive crustal channel‐flow in the central plateau is still controversial. To reveal the crustal S‐wave velocity structure with high vertical resolution, we conducted a joint inversion of receiver functions and surface wave dispersions from the 2‐D broadband seismic array SANDWICH deployed in the central plateau. Our results show a low‐velocity layer (LVL) in the middle‐lower crust beneath all stations. The minimum S‐wave velocity in each LVL is mostly within 3.0–3.4 km/s, which result in the maximum velocity reductions are less than 17.5%. It deduces a melt volume percentage (MVP) less than 7% even attributing all velocity reduction to partial melting of rocks. Our study suggests that there is not a high enough melt volume in central Tibet to develop crustal channel‐flow, which requires a larger MVP to decrease rock strength more than an order of magnitude. The formation of extensional structures in the central plateau may contribute to ductile deformation in the middle‐lower crust but not crustal channel‐flow.