Characteristics of geomagnetic disturbance anomalies before the Luxian,Sichuan Ms6.0 earthquake on September 16,2021
Based on the observational data from three geomagnetic disturbance stations in the Si-chuan area,the evolution characteristics of geomagnetic disturbance anomalies before the Ms6.0 earthquake in Luxian County,Sichuan Province,on September 16,2021,were analyzed using the geomagnetic vertical intensity polarization method,which is based on the pulse amplitude method.Results show that before the moderate-to-strong earthquake,the vertical intensity polar-ization values at the stations,as well as the frequency of polarization values exceeding the thresh-old,exhibit high-value anomalies.These frequency anomalies followed a pattern of initially increasing,then decreasing,and finally exhibiting an increasing-decreasing trend.Many stations exhibiting abnormal changes are located within 300 km of the epicenter,with the anomalies occurring in a quasi-synchronous manner over time.Most earthquakes tend to occur within one month after the anomalies,and the frequency of outliers often reaches its maximum value during the study period.In terms of the underlying mechanism,the evolution patterns and characteris-tics of these anomalies are influenced by the fracture properties of rocks,which reflect,to some extent,the earthquake preparation process.Furthermore,the geomagnetic disturbance anomaly before the earthquake is unrelated to external magnetic field variations.
万方数据
