Crustal structure beneath Northeast China from ambient noise tomography

To investigate the deep origin of Cenozoic intraplate volcanism in Northeast (NE) China, especially the Wudalianchi volcanism, a new 3-D S-wave velocity model of the crust and uppermost mantle is constructed through ambient noise tomography. Rayleigh wave phase velocity dispersion curves of 5-40 s periods are collected from seismograms recorded at our newly deployed WAVESArray portable stations around the Wudalianchi volcano and NECESSArray portable stations and CEA provincial seismic stations in NE China. Compared to images resolved in previous studies, the addition of WAVESArray data provides much higher resolution in NE China. Under the Songliao, Erlian and Hailar basins, obvious low-velocity (low-V) anomalies are imaged above 5 km depth, which are well correlated with the sediments and have good correlations with the outlines of the basins. Under the Changbaishan volcano and Abaga and Halaha volcanic groups, low-V anomalies extend continuously down to the uppermost mantle, suggesting their continuous mantle magma provision. Under the Wudalianchi volcano, low-V anomalies above 20 km depth and in the upper mantle are revealed, but a high-velocity anomaly zone appears in the lower crust, suggesting that the Wudalianchi volcano is a type of mantle origin but parts of magma have been solidified in the lower crust, likely due to intermittent mantle magma provision. All these results indicate that the intraplate volcanism in NE China could be related to complicated mantle dynamics of the big mantle wedge that has been formed due to the stagnancy and dehydration of the subducted Pacific slab in the mantle transition zone.