John McGaughey, President, Mira Geoscience Ltd
-five to thirty years ago a number of seismic tomography experiments were undertaken in underground mines for the purpose of assessing the value of the method in mapping and monitoring rock mass condition. In this presentation I review some of these experiments conducted for imaging the effects of de-stress blasting in a burst-prone sill pillar in a before-and-after experiment at BMS#12 Mine, characterizing rock mass condition in crown pillars from mines in Ontario and Quebec, and documenting rock mass changes over a period of several months in the footwall rocks adjacent to an active blasthole stope at Strathcona Mine in Sudbury. The purpose of presenting observations and key conclusions from a couple of decades ago is to help provide context for interpretation of modern experiments, as interest in the subject has been renewed. The discussion will include lessons learned regarding spatial resolution limits, realistic strategies for seismic monitoring of rock mass changes versus time, the importance of recognizing seismic anisotropy in fractured rock masses, and thoughts on useful ways forward.