Abstract In this paper, using double-difference tomography, we inverse the three-dimensional velocity structure of the Ruoergai region of Sichuan province. We obtain the fine 3D velocity structure and high precision source position parameters of the region. The inversion results show that the whole velocity structure of the study area is in a low-speed state, which reflects the partial melting material characteristics within the Qinghai-Tibet plateau. In the northeast margin of Qinghai-Tibet plateau, the strong structural deformation characteristics and the spreading direction of the low-speed region confirm the scientific speculation that the material overflows to the southeast. The stress accumulation results from the compression of the Qinghai-Tibet plateau plate and relatively hard Ruoergai block, so the Ruoergai series earthquakes occurred in the high and low-speed transition zone.
