Propagation and surface-underground disturbance of high-position mine earthquakes based on frequency-domain simulation

Frequent occurrences of strong mining-induced earthquakes in the Ordos mining area, although not causing visible underground damage, have generated noticeable surface vibrations with significant social impacts, severely disrupting normal mining operations. To assess the hazard potential of seismic waves from mining-induced earthquakes, the wavefield characteristics of seismic events induced by Cretaceous strata rupture and surface blasting in overlying formations are investigated. Using frequency-domain finite difference simulations, we systematically analyze the propagation attenuation patterns and determine the surface-underground disturbance effects. The results indicate significantly different disturbance characteristics on underground coal seams and the ground surface for different types of mine earthquakes. For high-position mine earthquakes and ground blasting sources located relatively far from the coal seam, the PPV, SED_v, and A₀ recorded by ground surface stations are significantly greater than those recorded by underground stations. Furthermore, the central frequency and corner frequency of the waveforms monitored by ground surface stations are slightly higher than those of underground stations, indicating that the amplitude and high-frequency components of the high-position sources decay more rapidly due to the influence of underground coal seam excavation and sedimentary environment. In contrast, for underground blasting and underground microseismic events occurring in close proximity to the coal seam, the observed waveform characteristics exhibit an inverse pattern. When the seismic waves cross layers, the PPV demonstrates obvious enhancement and weakening. At the surface, the collapse zone, and the fracture zone boundaries, the reflection, transmission, and transformation of seismic waves has a relatively obvious amplification effect. For example, at the boundary position of the caving zone and the fracture zone, the maximum amplification coefficient is approximately 1.5. The disturbance effect of mine earthquake waves on coal seams decreases monotonically with the increase of the distance between the source and the station, the height of the caving zone, and the source frequency. The disturbance effect on the ground is generally greater than that on the coal seam and is greatly affected by the layer where the source is located and the source frequency. When the source is within the fracture zone, the PPV at the source increases by approximately 1.6 times. Both numerical analysis and field observation results show that the distance between the source and the station is directly related to PPV, SED_v, and A₀. Each parameter shows a significant exponential attenuation with the increase of the distance between the source and the station. Under the same distance conditions, the disturbance effect of the ground station is significantly stronger than that of the coal seam, and the attenuation coefficients for all parameters are greater for underground stations than those of the ground station. Among them, SED_v attenuates the fastest, and the disturbance range on the surface is 3.07 times that of underground. A₀ shows the smallest difference in disturbance between the surface and the underground, with the disturbance range on the surface is only 1.47 times that of underground. The research results can provide reference and guidance for the prevention and control of strong mine earthquakes and associated disasters.