Shear-Wave Velocity Structure Beneath Northeast China From Joint Inversion of Receiver Functions and Rayleigh Wave Phase Velocities: Implications for Intraplate Volcanism

A high-resolution 3D crustal and upper-mantle shear-wave velocity model of Northeast China is established by joint inversion of receiver functions and fundamental-mode Rayleigh wave phase velocities. The teleseismic data used to calculate receiver functions are collected from 107 CEA permanent sites and 118 NECESSArray portable stations. Rayleigh wave dispersion measurements are extracted from an independent tomographic study. Our model exhibits significant detail in S wave velocity structure. Particularly, we observe a nearly constant S wave velocity of 3.4-3.6 km/s from shallow to deep crystalline crust under the study area, which we attribute to a high thermal gradient. Some modestly positive S wave velocity anomalies in the crust beneath the Songliao basin are interpreted as solidified late-Mesozoic mafic intrusions. In the upper mantle, we confirm the local presence of low-velocity zones below the Changbai mountains and Lesser Xing'an mountain range, consistent with asthenospheric mantle upwelling models. Furthermore, moderately low shear velocities imaged beneath the Halaha and Abaga volcanoes indicate possible pathways of magma ascent through the lithospheric mantle from the asthenosphere. At a regional scale, the average lithosphere-asthenosphere boundary depth increases from similar to 70 km under the greater Changbai mountains to similar to 100 km below the Songliao basin, and reaches similar to 110-120 km beneath the Greater Xing'an mountain range in the west. The conjectured dense mantle lid under the Songliao basin, characterized by fast S velocities, may have prevented sublithospheric melts from migrating to the surface.