Analysis of High Frequency Microseismicity Recorded at an Underground Hardrock Mine

This research involved monitoring for high frequency (HF) microseismic activity, in the effective frequency range of 100 to 400 kHz, at an underground hardrock mine. An HF monitor was installed to record activity in and near a pillar at a depth of 2100 m near active mining stopes. Analysis of the recorded events was done in light of production blasting records, the mine-wide microseismic data set for events below a depth of 1800 m and laboratory studies conducted to assist with a general HF data analysis. Data analysis indicated that there were two types of periods of increased activity the first associated with the passage of the direct seismic waves from the blast through the local area, and the second associated with the arrival of the transient stress change induced by the blast in the local area. Indications of locally increased stress levels towards the end of the monitoring period agreed with the occurrence of two nearby strong seismic events.