Microseismic frequency-spectrum evolutionary rule of rockburst triggered by roof fall

●Microseismic precursor shows the increasing energy and event and lower frequency.●Predominant frequency will move to low-frequency band prior to rockburst.●Mainshock characterizes the maximum energy, wider spectrum, and higher frequency.●Frequency-spectrum of aftershock will move to high-frequency band after rockburst.

Strong rockburst disaster in deep coal mines is easily triggered by the higher static stress of mining coal seam and the dynamic stress wave disturbance generated by hard and thick roof fall. Revealing the frequency-spectrum evolutionary rule of microseismic (MS) signals before and after roof fall is a very important issue for evaluating and forecasting rockburst danger. By experimental tests for combined coal and rock samples rockburst failure and in-situ measurements in a strong rockburst coal mine, the frequency-spectrum evolutionary rule and precursory characters were analyzed in detail. The following conclusions were drawn: (1) Precursory MS signals show the elevated energy and events, lower frequency and trend of spectrum moving to low-frequency band; (2) mainshock signals of rockburst are characterized by maximum amplitude (vibration velocity), wider spectrum, and higher predominant frequency; and (3) aftershock signals are characterized by the sudden decreasing amplitude, highest predominant frequency, and trend of spectrum moving to high-frequency band.