Relationship between Geomagnetic Anomaly and the Geologic Structure of Daixian M_S3.0 Earthquake in Shanxi Province

Daixian M_S3.0 earthquake occurred on September 13, 2019 in Shanxi Province. By processing two phases observation data of mobile geomagnetic total intensity in and around the earthquake area, we obtained the variation model of total magnetic field intensity of lithosphere from April to August 2019. It is found that the epicenter is just on the zero line. On the east side of the epicenter, there is a local significant negative anomaly area distributed in NE direction, which is consistent with the strike of the seismogenic fault. The abnormal energy of the measuring points distributed along the fault is strong, and obvious anomalies also appear at the measuring points near the fault in the periphery of the earthquake area, which shows that the peripheral structure also has the phenomenon of stress state change. There may be a background of high stress field in some areas of northern Shanxi. The abnormal amplitude has a good correlation with the distance from the measuring point to the fault.