Abstract:In this paper, the cut-and-paste (CAP) method was used to calculate and study the focal mechanism solutions of 270 MS>3.0 earthquakes in the range of 26°N -42°N and 90°E-110°E based on the seismic observation data of the regional seismic network. Then combining the global centroid moment tensor (GCMT) catalog and the data of 759 focal mechanism solutions, the stress field in the study region was calculated using the spatial and temporal stress inversion (SATSI) method. The distribution results of 154 stress fields were obtained by meshing the study area into 1°×1°. Compared with the early tectonic stress field, the direction of maximum principal compressive stress had a clockwise rotation. The results showed that in the extrusion process of the Tibetan Plateau block toward NE and NNE, the northern and eastern parts of the block were stopped by two hard blocks: Ordos and Arashan, respectively, resulting in the thickening of the Tibetan block and the lateral flow of material between the blocks. The study of the R value of the stress form factor in the whole study area showed that the relative stress along the boundary of the Tibetan Plateau block such as the Qilian Mountain in Qinghai, southeastern Gansu, and Longmenshan in Sichuan is large; the relative stress is directly proportional to the seismicity of these areas in recent years. The results of this research agree well with the study results of stress field, GPS research, and numerical simulation. The research results can provide a reliable reference for earthquake initiation mechanism, active structure, and seismic trend determination in the Tibetan Plateau.
