Abstract：In order to analyze the shallow tectonic background, earthquake inoculation mechanism and the relationship between the earthquake and the structure, we use high-resolution gravity anomaly data and gravity 3D inversion algorithm based on block growth mode to analyze the shallow 3D inversion density structure in the earthquake area. We verify the validity and stability of the method based on block growth mode inversion, and retrieve the high-resolution gravity Bouguer anomaly data in the study area. The results show that the Sanhe-Pinggu M8.0 earthquake is located in the low-value part of intersection transition of the local high gravity of Daxing and Sanhe-Mafang and the low gravity of Dachang. The inversion results of the shallow 3D density structure of the study area show that the Sanhe-Pinggu M8.0 earthquake is obviously controlled by the NE-trending Xiadian fault. The density difference on both sides of the fault is obvious and extended down about 10 km. It is estimated that the earthquake occurred at a depth of about 10 km.
