Induced stress and microseismicity in the 3000 Orebody, Mount Isa

Summary The 3000 Orebody is one of two orebodies in the Deep Copper Mine at Mount Isa, Australia. Owing to concerns about potential shaft pillar instabilities, an integrated seismic system was introduced to monitor seismic activity associated with pillar and country rock deformation. Coupled with numerical modelling of the stress regime, the system may assist in the characterization of rock mass damage resulting from mining, and perhaps the identification of near- and far-field geological structures that affect stope performance. A study was undertaken to quantify the seismicity and to determine potential applications of the seismic technology. The relation between geological structure and seismicity is strong, suggesting good prospects for the use of the system in the ground-control activities noted above. The induction of seismicity, which involves small magnitude events, is associated with reduction of normal stress on planes of weakness, suggesting that stress path may be an important factor in the level of seismicity observed in hard rock mines.