Focal Mechanism and Source Parameters Analysis of Mining-Induced Earthquakes Based on Relative Moment Tensor Inversion

Abstract

Mining-induced earthquakes (MIEs) in underground coal mines have been a common phenomenon that easily triggers rock bursts, but the mechanism is not understood clearly. This research investigates the laws of focal mechanism and source parameters based on focal mechanism and source parameters analysis of MIEs in three frequent rock burst areas. The relative moment tensor inversion (MTI) method was introduced, and the way to construct the inversion matrix was modified. The minimum ray and source number conditions were calculated, and an optimized identification criterion for source rupture type was proposed. Results show that the geological structure, stress environment, and source horizon influence the focal mechanism. The tensile type sources can distribute in the roof and coal seam, while the shear types are primarily located in the coal seam. In the typical fold structure area, the difference in source rupture strength and stress adjustment between tensile and shear types is negligible, while the disturbance scale of tensile types is distinct. The shear types have higher apparent volume and seismic moment in the deep buried fault area but lower source energy. The apparent stress of the tensile types is higher than that of the shear types, representing that the stress concentration still exists in the roof after the MIEs, but the stress near the faults could be effectively released. In the high-stress roadway pillar area, the primary fracture of the coal pillar easily produces a continuous shear rupture along the dominant stress direction under the extrusion of the roof and floor. The source parameters (except apparent stress) of shear types are higher than tensile types and have higher dynamic risk. The results contribute to expanding the understanding of rock burst mechanisms and guide MIEs’ prevention.

Characteristics of Earthquake Mechanisms Along the Andaman - Nicobar Region derived from Bayesian Moment Tensor Inversion

“…In geothermal fields or volcanic areas, ISO and CLVD values tend to be positive due to the combination of shear movements from opening faults being filled by fluid or magma [9]. Conversely, a negative sign on the non-DC component suggests the presence of a compression component in the source mechanism, such as the collapse of a mine cavity [10].…”

Study on the Mechanism and Prevention of Frequent Mine Seismic Events in Goaf Mining under a Multi-Layer Thick Hard Roof: A Case Study

“…Dou et al [18,19] comprehensively analyzed the characteristics of massive mine seismic information, such as mine seismic wave characteristics, wave velocity and underground ore pressure appearance, where mine seismic events were divided into three types (namely, mining fracture, ultra-thick overburden and high-energy mine seismicity) and conducted studies on the attenuation law of mine seismic in goaf. Cao et al [14,20,21] explored the focal mechanism of large-energy mine seismic events induced by mining in a solid coal and a goaf section under a super-thick overburden rock by quantitatively analyzing the evolution characteristics of roof rupture and how the orientation was affected by vibration wave radiation. Orlecka et al [22] studied the influence of static load stress transfer caused by two strong mine seismic events occurring in the same mining area on subsequent mine seismic activities.…”

Investigation into Occurrence Mechanism of Rock Burst Induced by Water Drainage in Deep Mines

“…Zhao et al [23] studied the loading characteristics and instability mechanism of gob-side roadway in deep mining and revealed the "three-load" superimposition rock-burst-inducing mechanism of gob-side roadway under the influence of lateral static load, advanced static load and disturbance dynamic load in goaf. Cao et al [24][25][26] conducted an investigation into the stress distribution law and multi-dimensional information of microseismic events near the residual coal pillar, holding that the residual coal pillar was the main influencing factor of rock burst.…”