Abstract:

 The volcanoes locating in northeast China are very active. Some researchers consider that the origin of volcanoes is closely related to the subducting western Pacific plate and the upwelling asthenosphere. The thickness and the existing range of the subducted plate are not clear as far although the seismic tomography results obviously show that the Pacific plate exists below the volcano region. Therefore, in this study, we adopted the method combining the teleseismic tomography with travel time forward modeling to further study the velocity structure beneath northeast China, especially the precise model of subducted Pacific plate. Our results show that (1） the average thickness and velocity perturbation of slab are 85 km and 1%, respectively, and the slab has not been thickened compared with the previous result of the Japan Sea; (2） the Pacific plate subducted into the mantle transition zone with a shallow dip angle, and changed horizontally when it touched the bottom of mantle transition zone, and extended westward to Longitude 127°E and then stops over there; (3） the horizontal slab locates right below the volcano region. These above features help people understand the origin of intraplate volcanoes and the geodynamical process better.

Key words: northeast China, western Pacific plate, mantle transition zone, teleseismic tomography, travel time forward modeling