Estimating changes in seismic wave velocity from a pneumatic source in an operational mine

Rock mass characteristics such as applied stress, pore pressure, and fracture density are coupled to the seismic wave propagation velocity. Therefore, measuring small relative changes of seismic wave velocities in operational mines has the potential for tracking changes in these important rock mass properties. To this end, we have conducted an experiment with the aim of measuring seismic body wave velocities in situ at Williams mine, Hemlo, Canada, using a pneumatic source and multiple receivers. We determine that the signal-to-noise ratio is improved by deconvolving the source signal from the signal recorded at the remotely grouted geophones. We evaluate the estimated relative changes in traveltimes and assume that these are due to changes in the body wave velocity caused by mining-related activities. We are able to successfully detect the source response at remote receivers in an operational mine at a distance of more than 430 m.