Moment Tensor and Stress Field Inversions of Mining-Induced Seismicity in A Thick-Hard Roof Zone

Coal mining in thick-hard roof areas leads to frequent high-energy seismicity and may even induce coal–rock dynamic disasters such as rockburst. It is important to explore the focal mechanism of mining-induced seismicity to understand the failure behaviour of the coal–rock mass and the characteristics of the stress field. It is helpful to propose a seismic absorption method. Taking the 6306 working face of the Dongtan coal mine as the study area, the rupture type, focal mechanism, characteristics of the local stress field, and main controlling factors of the mining-induced 22 high-energy seismic events were investigated using the probabilistic full-waveform optimization inversion and the stress field inversion. The main conclusions were as follows: (1) the rupture types of 22 seismic events were shear, tensile, compression, and mixed failure, and the corresponding number of events was 11, 4, 1, and 6, respectively; (2) the focal mechanism of the above events was eight strike-slips, twelve reverse fault slips, and two normal fault slips; and (3) the stress field using the inversion of focal mechanisms was discovered. There was no significant variation of the maximum compressive stress σ1 and minimum compressive stress σ3 directions in the seismicity concentration area, fold 1, and fold 2. The principal stresses σ1 and σ3 were the main controlling factors inducing seismicity. This study is helpful in revealing the mechanism of the mining-induced high-energy seismicity and proposing corresponding prevention measures in the future.