Focal Mechanisms and Stress Field Characteristics of Microearthquakes in Baihetan Reservoir in the Downstream Area of Jinsha River

The Baihetan Reservoir was impounded on 6 April 2021, after which the water level rose significantly. Notably, one week of impoundment, microseismic activities were prominent around reservoir area, highly associated with change. From 2021 to 31 December over 7000 microearthquakes recorded by seismic stations in vicinity reservoir, including 12 ML > 3 events. maximum 21 ML3.9 earthquake Qiluogou town, Sichuan. post-impoundment events clustered Hulukou town Qiaojia Basin, an overall “Y-shaped” pattern. In this study, taking advantage high-frequency waveform matching approach, pre- and focal mechanism solutions totaling 207 2 earthquakes are successfully obtained. impoundment-induced stress change is analyzed, iterative joint inversion method used invert field. Major results conclusions include following: (1) After number normal fault remarkably increased area; (2) Impoundment has led a vertical compressive field horizontal tensile area where occurred. It necessary pay close attention possible moderate-to-strong future.