Characteristics of the dominant azimuth anomalies of geoelectric field at Dawu station before M_S7.4 Maduo，Qinghai earthquake in 2021

In order to know whether there were seismic electrical signals before M_S7.4 Maduo, Qinghai earthquake on 22 May 2021, this paper analyzed the original data of geoelectric field from Dawu seismic station by using the dominant azimuth method, and the variation characteristics of rockmass fracture structure before the M_S7.4 Maduo earthquake were obtained. Furthermore, the rockmass frasture structure characteristics of eight geoelectric stations within 500 km of the earthquake and previous related earthquake cases are comprehensively analyzed. The results show that the geoelectric field dominant azimuths of the two observation sites at Dawu had a significantly synchronous deflection phenomenon eleven months before the earthquake, and the geoelectric field of one site increased sharply again one month before the earthquake. The abnormal characteristics of the site are mainly manifested as the rapid deflection of the jump range of the dominant azimuth, with the maximum deflection reaching 45°−90°. Additionally, the stations Garze and Maqu in the same secondary block showed quasisynchronous changes with the Dawu station, while the stations in other secondary blocks showed no anomalies, indicating that the abnormal responses are affected by regional tectonic settings. And combined with the previous earthquake case analyses, it is deduced that the dominant azimuth anomaly based on the Dawu electric field has good prediction efficiency for the short and medium term earthquake.