Signal characteristics of coal and rock dynamics with micro-seismic monitoring technique

Abstract In this study, differences of signal characteristics between mine shocks and coal and gas outbursts in coal mines were examined with the micro-seismic monitoring technique and time–frequency analysis. The duration of the mine shock is short while the coal and gas outburst lasts longer. The outburst consists of three stages: the pre-shock, secondary shock and main shock stage, respectively. The velocity amplitude of the mine shock is between 10 −5 and 10 −3  m/s, which is higher than that of the outburst with the same energy level. In addition, in both cases, the correlation between the velocity amplitude and energy is positive while the correlation between the signal frequency band distribution and energy is negative. The signal frequency band of the high energy mine shock is distributed between 0 and 50 Hz, and the low energy mine shock is between 50 and 100 Hz. The fractal characteristics of mine shocks were studied based on a fractal theory. The box dimensions of high energy mine shocks are lower than the low energy ones, however, the box dimensions of outbursts are higher than that of mine shocks with the same energy level. The higher box dimensions indicate more dangerous dynamic events.