Distribution of the crustal low velocity zones beneath the central and northeastern Tibetan Plateau: Insights from joint analysis of receiver functions and surface wave dispersion observations

摘要

A crustal and uppermost mantle shear-wave velocity model beneath the central and northeastern Tibetan Plateau is obtained from the joint analysis of Rayleigh wave phase dispersions and teleseismic P-wave receiver functions at 188 broadband seismic stations deployed in this region. This newly presented model reveals widespread low velocity zones in the middle crust, and these zones are mainly confined to the region south of the Kunlun Fault. The velocities in the low velocity zones are extremely low ( < similar to 3.3 km/s), suggesting the presence of actively melting or previously melted materials in the crust, and further implying the possibly large contributions of the crustal channel flow model to the deformation in the Tibetan Plateau. Additionally, a continuous low velocity anomaly in the uppermost mantle beneath the eastern Kunlun Fault, the Songpan-Ganzi terrane and part of the Qiangtang terrane is observed, which may suggest an induced local mantle upwelling in this region.