Seismicity is a form of vibration or movement of ground. Typically it is due to movement of major rock structures deep underground along fault lines. The Kalgoorlie-Boulder region has a long history of seismic vibrations with anecdotal experiences of some large seismic events, which can feel like earth-tremor vibrations.
Seismic vibrations often feel similar to blast vibrations to people at the ground surface. The two have significant differences however, as they usually come from different areas, are of different frequencies, and generally do not occur at the same time. Vibration monitors are designed to detect the differences, and identify the source locations of both kinds of vibrations.
Although seismic events occur naturally in our region, some of these events may also be related to mining activity. Mining causes changes in the pressure on underground rock structures. Mining is designed with due consideration of how rock extraction will affect pressures, so that readjustments from mining are less likely to cause seismic vibrations.
In 1994 KCGM installed an underground-seismic-monitoring system at Mt Charlotte to help understand and manage the vibration impacts from mining. At that time it was the first mine seismic monitoring system to be installed in Australia. There are currently ten permanent seismic monitoring sites at Mt Charlotte. Data from these sites are automatically recorded, then analysed and reported to management.
In 1998, and again in 2000, KCGM in consultation with experts reviewed the Mt Charlotte mine plan and the geology of the area. The mine plan was assessed and the seismic potential of future mining zones was estimated. Only ore with a classification of "low seismic risk" is now being mined. Mt Charlotte co-sponsored a MERIWA Research and Development project "Mine Seismicity and Rockburst Risk Management" which has resulted in further reduction of seismic risk.