## 1 Introduction  
Southwest China is located in the first and second steps of China's three-step \"staircase\" topography, with complex terrain, numerous rivers, and abundant hydropower resources, accounting for 69% of China's total hydropower resources. With the rapid development of China's economy, the demand for energy is growing, and there is an urgent need for the exploitation and utilization of hydropower resources. A large number of hydropower stations are under construction or in the preparatory stage in Southwest China. Due to the rolling hills and deep valleys in this region, a large number of underground caverns need to be constructed for these hydropower stations. Against the background of complex geological conditions in the engineering area, various underground engineering problems arise, such as surrounding rock deformation during excavation, local collapse and rock bursts in a high-stress environment. These problems not only cause a lot of economic losses, but also seriously threaten the safety and life of on-site workers. Therefore, the evaluation and research of surrounding rock deformation and stability in underground engineering is an urgent need for hydropower engineering construction in Southwest China. The conventional monitoring of stress, strain, displacement and deformation is widely used in the safety assessment of underground caverns. It can give quantitative monitoring results after the occurrence of large deformation in the surrounding rock but can hardly capture the microfractures formed during the stress adjustment of the deep rock mass in real time. However, the expansion and development of these microfractures are usually considered precursors to macroscopic instability and failure of the rock mass, so conventional monitoring has a certain time lag and space limitations. As a real-time 3D monitoring technology [1], microseismic monitoring allows determining the source information, such as the occurrence time, location, and intensity when surrounding rock fractures occur based on acoustic analysis, studying the expansion and evolution of surrounding rock microfractures, and analyzing the stability of the surrounding rock so as to give a warning or forecast for site construction. At present, microseismic monitoring is widely used in mines [2; 3; 4], tunnels [5; 6; 7], slope instability [8; 9; 10; 11; 12], the exploitation of oil, gas and geothermal energy [13; 14; 15], and underground storage [16] in Western countries as an effective means to study and prevent dynamic disasters in the rock mass. [PERSON] et al. [8] installed a microseismic monitoring system on a steep rock slope in northern Italy, and microseismic events caused by crack propagation and collapse were located and classified. The final results show that source location is a promising method to improve the final classification of microseismic events. [PERSON] et al. [14] produced a high-resolution microseismic image of a hydraulic fracture stimulation in the Carthage Cotton Valley gas field of East Texas. The final results show that shear activation of these fractures indicates a stronger correlation of induced seismicity with low-impedance flow paths than is normally found or assumed during injection stimulation. The research and application of microseismic monitoring in China is relatively late. Specifically, microseismic monitoring was first used in the Mentougo Mine to monitor rock bursts in 1959 [17]. With the development of the mining industry, mining areas are facing various safety risks, and microseismic monitoring is widely promoted and applied to monitor the stability of mine-surrounding rock [18; 19; 20; 21]. For example, [PERSON] et al. [18] introduced microseismic monitoring into the Dongguashan Mine and applied the moment tensor theory to study the failure mechanism of the surrounding rock; [PERSON] et al.