Physical mechanism of the 2021 M 5.1 Shuangbai earthquake and its aftershock sequence in Yunnan Province, China

On June 10, 2021, a M 5.1 earthquake occurred in the region between two large parallel strike-slip faults in Shuangbai County, Yunnan Province. To investigate the earthquake's mechanism, the spatial and temporal distribution characteristics of the mainshock and its aftershock sequence were analyzed using template matching detection and relocation methods. Additionally, the regional stress field and fault slip tendency were examined. Other factors, such as tidal stress and the triggering effects of previous seismic events, were also considered. The results reveal that the 2021 M 5.1 Shuangbai earthquake sequence exhibited fluid-driven outward migration from the initial hypocenters. The study area is characterized by a strike-slip stress regime, with a nearly horizontal σ₁ oriented in the NNW-SSE direction and a horizontal σ₃. It was found that the seismogenic fault of the Shuangbai earthquake sequence was not optimally aligned with the regional stress conditions. The findings suggest that fluid overpressure played a primary role, while tidal stress had a secondary influence, in the occurrence of the mainshock and its aftershocks.