Stress Inversion and Fault Instability in the Source Region of the 2021 (MS 5.0) Yingjiang Earthquake

On 12 June 2021, an earthquake with MS 5.0 occurred in Yingjiang, adjacent to eastern Myanmar, where seismic activity is frequent due to plate collision. To explore the mechanism of this earthquake, the regional stress field of the Yingjiang zone was inverted using the focal mechanisms of 187 historical earthquakes in this area. Furthermore, based on the obtained orientation of the principal stress axes and the stress shape ratio, the fault slip tendency (Ts) was also estimated to evaluate fault instability in the study area. The stress variation results show that the diffusion and migration of the aftershocks suggested strike–slip-type stress accumulation in Yingjiang with a principal compressive stress axis direction-oriented NNE–SSW. Fault slip tendency results show that the seismogenic faults feature strikes within the ranges of 40~80° and 110~150° and dips of 60~90° and exhibit enhanced stress coupling. The distribution of the aftershock sequence is conjectured to have a high correlation with local fluid migration and was likely controlled by the hydrated rock-induced ruptures of the stressed fault systems near the source region. This study provides insights into potential earthquake risks in this region.