Discrimination of Microseismic Events in Coal Mine Using Multifractal Method and Moment Tensor Inversion

Discrimination of various microseismic (MS) events induced by blasting and mining in coal mines is significant for the evaluation and forecasting of rock bursts. In this paper, multifractal and moment tensor inversion methods were used to investigate the waveform characteristics and focal mechanisms of different MS events in a more quantitative way. The multifractal spectrum calculation results indicate that the three types of MS waveform have different distribution ranges in the multifractal parameters of increment alpha and Delta f(alpha). The results show that the blasting schemes also have a great influence on MS waveform characteristics. Consequently, the multifractal parameters of increment alpha and Delta f(alpha) can be used to discriminate different MS events. Further, the focal mechanisms of MS events were calculated by seismic moment tensor inversion. The results show that an explosion is not the dominant mechanism of deep-hole blasting MS events, and the CLVD and DC components account for an important proportion, indicating that some additional processes occur during blasting. Moreover, the coal-rock fracture MS events are characterized by compression implosion or compression/shear implosion mixed focal mechanisms, while the overburden movement MS events are tensile explosion or tensile/shear explosion mixed focal mechanisms. The focal mechanisms and nodal plane parameters have close relationships with the inducing factors and occurrence processes of MS events.

Automated summary

This paper investigates the waveform characteristics and focal mechanisms of different microseismic events induced by blasting and mining in coal mines using multifractal and moment tensor inversion methods. The results show that the multifractal parameters can be used to discriminate different microseismic events, and the blasting schemes have a significant influence on the waveform characteristics. Furthermore, the focal mechanisms of microseismic events were calculated, revealing the dominant mechanisms and their relationships with inducing factors and occurrence processes.