Focal depth determination of earthquakes with <i<M</i<≥2.5 in Jiaokou reservoir area in 2019 by multiple methods

In this paper, the focal depth of earthquakes with magnitude 2.5 or above in Jiaokou reservoir area in 2019 was determined using the CAP method, the sPL depth phase method and the double difference positioning method. The inversion is carried out by CAP method to calculate the optimal focal mechanism solution and focal depth. The clear sPL seismic phase is identified at the near station about 50 km away from the epicenter, the theoretical waveform of various focal depths is drawn using the frequency wave velocity (F-K) method, and the focal depth is determined through fitting with the actual waveform. The seismic event pair is established, and its relative position and depth are determined using the residual between the observed value and the theoretical value of travel time difference. The results of various methods are basically the same. In contrast, the double difference positioning method is more suitable for focal depth determination of earthquakes in Jiaokou reservoir area.