Source Parameters and Scaling Relationships for Mining-induced Seismicity in the Datong Coal

To determine the source characteristics of mining-induced earthquakes, the corner frequency f_c, rupture radius r, seismic moment M₀, radiated seismic energy E_s, and stress drop Δσ of 80 micro-earthquakes with 1.0≤M_L≤3.3 in the Datong coal mine were calculated based on waveform records from the regional digital seismic network. The Scaling relationships between these parameters and M₀ were studied, and the reasons for the lower levels of corner frequency and stress drop in mining-induced seismicity were analyzed. The results show that the displacement spectrum of the source of mining-induced earthquakes in the Datong coal mining is consistent with the Brune model ω^-2 attenuation pattern. Using this ω^-2 model, the source parameters of micro-earthquakes in the Datong coal mine were estimated. The f_c ranges mainly from 0.82 to 4.64 Hz, the r ranges from 67.89 to 382.65 m, and the Δσ from 0.03 to 0.85 MPa. The M₀ estimated from the zero frequency limit ranges from 5.85e+10 to 7.66e+13 Nm, and the E_s ranges from 7.34e+4 to 7.07e+8 J. With the increase of M₀, the source parameters of r, Δσ, and E_s show an increasing trend, while the fc decreases gradually, exhibiting characteristics similar to tectonic earthquakes. Mining-induced earthquakes in the Datong coal mining area have lower corner frequencies and stress drop levels than tectonic earthquakes. This is mainly due to the artificial alteration of the initially stable geological structure and stress state during mining. This leads to deformation and micro-fracturing of the coal and rock mass in the roof and floor, approaching or reaching a critical, unstable state. With the continuous mining operation, mining-induced earthquakes occur in a lower-stress environment under the multiple coupling effects of the self-weight stress of the coal and rock mass and mining-induced stress disturbance.