Abstract:On September 4, 2018, an MS5.5 earthquake occurred in Jiashi, Xinjiang. In this paper, the CAP method was applied to calculate the focal mechanism solutions of the MS5.5 mainshock and MS≥3.0 aftershocks, and the result showed that the strike, dip, and rake angles of nodal plane Ⅰ and Ⅱ are 48°, 83°, 3°, and 318°, 87°, 173°, respectively. The azimuth and plunge of the principal compressive stress P axis are 3° and 3°, respectively, and the azimuth and plunge of the principal tensile stress T axis are 273° and 7°, respectively. The moment magnitude of the mainshock is MW5.3. The double-difference location method was used to relocate 129 earthquakes with MS≥1.5, and the focal mechanism solutions and relocation results were comprehensively analyzed. It is found that the earthquake distribution obtained from relocation result is consistent with that from the inversion result of CAP method, and the earthquakes are concentrated in the NEE direction. Therefore, it is considered that nodal plane I is the main rupture plane of this earthquake. After relocation, the average relative errors of NS, EW, and UD directions are 0.25, 0.23, and 0.09 km, respectively. The average travel-time residual is 0.026 s, and the focal depth is concentrated in 5-15 km. It is preliminarily determined that the 2018 Jiashi MS5.5 earthquake may be controlled by the hidden fault near the Keping fault zone.
