Vertical-force-dominated mechanisms and failure processes in mining-induced seismicity via calibrated moment tensor inversion

Uncertainties in moment tensor inversion for mining-induced seismicity can produce systematic biases in focal mechanism solutions. These biases can systematically cause tensile failures from mining-induced stress release to be misclassified as shear failures, obscuring the true mechanisms governing overburden instability. This misinterpretation fundamentally hinders the transition of mining-induced seismicity research from phenomenological description to mechanistic understanding. To address this limitation, we develop a physically constrained full moment tensor inversion method (PCW-MT) incorporating a priori source constraints and geophone calibration, which stabilizes inversion results and improves mechanism interpretability. The PCW-MT method is applied to systematically resolve the source mechanisms and failure processes of 60 mining-induced seismic events at Laohutai Coal Mine. The results demonstrate that mining-induced seismic events are dominated by pronounced non–double-couple source characteristics and a persistent dominance of the vertical force component ( M 33 ) , indicating rupture processes distinct from shear-controlled tectonic earthquakes. Seismic energy release is not governed by fault slip. Instead, it is primarily associated with vertical deformation of the overburden, manifested as tensile opening and compressive closure of bed-separation spaces. By integrating high-fidelity moment tensor evidence with overburden structural evolution, this study proposes a vertically dominated, key-stratum–controlled seismogenic framework. In this framework, mining-induced seismicity arises from the dynamic evolution, mechanical shielding, and eventual rupture of the overburden primary key stratum. This framework provides a unified physical explanation for source mechanisms and seismic energy release in mining-induced seismicity, advancing its interpretation from fault-slip–centered models to structurally controlled overburden instability.