Objective Frequent mine earthquakes that cause surface seismaesthesia, induced by the fracturing of significantly thick overburden in deep coal mining, are identified as the most severe challenge to the efficient production of mining areas. There is an urgent need to overcome the current difficulty caused by mine earthquakes induced by significantly thick overburden, which feature high frequency and challenging prevention and control.

Methods Using such mine earthquakes occurring in a certain fully mechanized mining face adjacent to goaves in the Khujirt mining area in Ordos, Inner Mongolia Autonomous Region, as an example, this study (1) analyzed the evolutionary patterns of structural fracturing of the significantly thick overburden based on the thick plate theory; (2) extracted the principal components of mine earthquake waveforms and quantitatively explored the fracturing mechanisms of seismic sources using the moment tensor inversion method; (3) corrected the stress inversion model and algorithm based on the acting mechanisms of principal stresses acting on seismic sources subjected to tensile, compressive, or mixed-type fracturing; and (4) analyzed the fracturing characteristics of the sources of mine earthquakes and the evolutionary patterns of stress fields and quantitatively analyzed the stress-triggering mechanisms of the mine earthquakes.

Results and Conclusions  The results indicate that the fracturing and migration of the significantly thick overburden provide impetus and energy for the formation and triggering of mine earthquakes. The principal component analysis method can quickly extract the principal components of the waveforms disturbed by mining environments, thus providing high-quality inversion data for solving the moment tensor. The corrected stress inversion algorithm satisfied the requirements for the stress inversion of seismic sources subjected to mining-induced non-shear fracturing, thus allowing for the inversion of stress fields of typical seismic sources subjected to tensile/compressive fracturing. The mining along the mining face adjacent to goaves caused the roofs, along with lateral goaves, to fracture upwards layer by layer. Under the influence of goaves, the roof activity intensified during the formation of mine earthquakes. The fracturing characteristics of the significantly thick overburden generally manifested a significant tensile state. During the formation of mine earthquakes, principal stresses exhibited roughly consistent orientations, with stress shape factors of 0.66, 0.71, and 0.30. The stress distribution of the overburden transitioned from uniaxial compression to a compressive-tensile state. The uniaxial compression of the maximum principal stress led to the transient fracturing of the significantly thick overburden. This was accompanied by the release of significant elastic energy, which served as the primary cause of the February 6 and October 30, 2021 Hujierte mining area earthquakes. In the case of the mining face adjacent to large goaves, the synergistic effects of compression and tension under the maximum and minimum principal stresses may induce mine earthquakes with higher magnitudes. For mines whose efficient production is restricted by mine earthquakes, the conclusions of this study will provide theoretical support for adjusting loads and reducing mine earthquakes from sources.