Detailed Moho variations under Northeast China inferred from receiver function analyses and their tectonic implications

Abstract

In this study we investigate detailed Moho variations beneath Northeast China by applying the arithmetic mean, back-projected and Fresnel-zone migration imaging methods to a total of 169,602 high-quality P-wave receiver functions from seismograms of 2903 teleseismic events recorded at 127 NECESSArray stations and 321 China Earthquake Administration stations. Our results show that the Moho depth variations are correlated with the surface geology in the study region. The Moho is deeper (~34.0–42.0 km) under the Great Xing'an range, the Lesser Xing'an range, the Zhangguangcai range, and the Changbaishan mountain, whereas it is shallower (~26.0–32.0 km) under the Songliao basin. Our results also reveal obvious Moho variations across the North-South Gravity Lineament. The Moho offsets up to ~5.0 km are clearly observed under the Nenjiang-Balihan, Yilan-Yitong, and Dunhua-Mishan faults, indicating that they are lithospheric-scale faults. A deeper Moho is revealed under the volcanoes, such as the Jingpohu, Wudalianchi, and Changbaishan volcanoes and Abaga and Halaha volcanic groups. In particular, the Moho under the Changbaishan volcano reaches ~40.0 km depth and the observation varies with the teleseismic back-azimuths, suggesting a complicated magma system in the crust. In addition, the Moho under the Songliao basin varies significantly from ~26.0 km depth in the east to ~32.0 km depth in the west, which could be related to the lithosphere extension and thinning. All these results suggest that there exists a hot and wet mantle upwelling in the big mantle wedge formed by the deep dehydration of the long stagnant Pacific slab in the mantle transition zone under Northeast China.