S-wave velocity structure of northeastern China from joint inversion of Rayleigh wave phase and group velocities

We imaged the crust and uppermost mantle structure beneath northeastern (NE) China with fundamental mode Rayleigh waves recorded by 125 broad-band stations deployed in the region. Rayleigh wave phase and group velocities along more than 700 interstation paths were estimated using the wavelet transformation method and then these data were utilized to construct 2-D phase and group velocity maps in the period range of 1560 s. Owing to the dense ray coverage and short ray path, our results provide better lateral resolution in the NE China region compared with previous phase and group velocity studies. The regularized Rayleigh wave phase and group velocity dispersions at each cell were jointly inverted to determine 1-D shear wave velocity structure using the linear inversion method and then assembled into a 3-D model. Our results show that obvious low velocities exist in the uppermost mantle beneath the Changbaishan volcanic region, which may be due to asthenospheric upwelling. The thin lithosphere with fast S-wave velocity in the lower crust of the Songliao Basin implies that the lithospheric mantle beneath NE China is partly removed.