Seismic P wave velocity imaging in underground mines: Observations on the relationship between velocity structure and mining-induced seismicity

The objective of this study was to evaluate the relationship between mining-induced seismicity and the P-wave velocity structure in underground mines. Three case studies were performed to evaluate different methods of imaging velocity structure, and to examine the seismicity-velocity relationship in different environments.;The first case study examined the seismicity-velocity relationship within a horizontal sill pillar in Falconbridge's Lockerby Mine, Sudbury. The tremors were observed to be predominantly located in a region of high seismic velocity, whereas a low-velocity zone was aseismic. The low-velocity zone was known to have been the site of an earlier m;The second case study used data from a 3D controlled-source velocity survey at Falconbridge's Strathcona Mine in the Sudbury Basin, to compare a controlled-source travel-time image with results from different passive-source arrival-time imaging methods. All the methods of passive source imaging produced results which agreed with the controlled-source image within error estimates. The best agreement was found for the simultaneous inversion for velocity structure and hypocentre relocations.;The final case study was a 3D sequential controlled source imaging experiment at the Strathcona Mine, to examine temporal changes in the velocity structure. A review of techniques used to image velocity changes, found that images produced by inverting travel-time changes were more accurate than those produced by the difference between two images. In particular, travel-time changes measured with cross-correlation techniques proved to be the most accurate. Two case-studies were implemented, where 3D controlled-source images of temporal velocity changes were compared to induced seismicity. Both cases indicated an association between zones of concentrated seismicity and zones of high static velocity, although the activity appeared to be centred in zones of high seismic gradient.;The practical outcome of this study is the development of a powerful and unique tool, seismic velocity imaging, capable of assessing the spatial variation of the rockburst potential throughout a mine. The resulting rockburst potential map may then be incorporated into the design of stope extraction sequencing, which may result in the design of safer and more productive mines through a trade-off between rockburst risk and operational considerations.