Effect of fault-slip source mechanism on seismic source parameters

Fault-slip bursts in underground mines could cause devastating damage to mine openings. In the present study, three types of underlying mechanisms that could trigger fault slip are examined, namely asperity shear, stope extraction, and a combination thereof, with numerical analysis. First, a numerical model is constructed, in which a fault running parallel to a steeply dipping, tabular orebody is modeled. Static analysis is then performed, whereby stopes in the orebody are extracted. Based on the stress state obtained from the analysis, dynamic analyses are carried out to simulate fault-slip, using different simulation techniques representing the mechanisms of fault-slip. The results show that when fault-slip is induced by asperity shear, slips could spread over an extensive area of the fault. In contrast, the fault-slip area is limited to the vicinity of an extracted stope when fault-slip is caused by stope extraction. The results further indicate that asperity shear could induce strike-slip faulting. It is revealed that when fault-slip is caused by the combination, the magnitude of fault-slip significantly increases. Investigation of the slip rate shows that fault-slip induced by stope extraction induces slightly higher slip rates than that caused by asperity shear. It is also found that fault-slip induced by stope extraction ruptures faster along the fault than that induced by asperity shear. Lastly, the effect of the mining rate on the magnitude of fault-slip is examined. The result indicates that stope extraction with a low mining rate can considerably decrease the cumulative seismic moment of fault-slip that takes place during the mining sequence.