Shear-wave tomography of the Changbai volcanic area in NE China derived from ambient noise and seismic surface waves

A detailed 3-D shear-wave velocity (Vs) model of the crust and upper mantle beneath the Changbai volcano and adjacent areas in NE China is obtained by conducting a joint inversion of group-velocity dispersion curves at periods of 5-30 s and phase-velocity dispersion curves at periods of 5-100 s from ambient noise and earthquake surface waves. We use 1602 group-velocity dispersion curves and 3125 phase-velocity dispersion curves, which were recorded at 57 permanent stations of the China Earthquake Administration and 27 portable stations of Jilin University during 2010 to 2014. Our results reveal strong heterogeneities in the crust and upper mantle beneath the study area. A remarkable low-Vs zone is revealed in the crust beneath the Changbai volcano, indicating a hot magma chamber. The Longgang volcano is also characterized by a low-Vs anomaly reflecting partial melt in the crust. In contrast, there is no notable low-Vs anomaly in the crust beneath the Jingpohu volcano. Previous geological results and our tomographic images suggest that Changbai is a composite volcano, whereas Jingpohu and Longgang are monogenetic volcanoes. Low-Vs zones are revealed in the upper mantle beneath the three active volcanoes, which are interconnected at different depths. Combining the present results with previous findings, we deem that the three active intraplate volcanoes are caused by hot and wet upwelling flows in the big mantle wedge associated with deep subduction of the western Pacific plate beneath NE Asia.