Controlled sources for shear‐wave surveys in mines

Abstract

The ability to analyse shear‐wave anisotropy in a mine environment is greatly aided by using multiple source orientations of a reproducible, impulsive shear‐wave source. The analysis of what is probably the first controlled source shear‐wave experiment in a mine environment demonstrates clearly that shear‐wave polarizations and time delays between split shear‐wave arrivals are reliably measured because of the use of multiple source orientations rather than a single shear‐wave source. Reliability is further aided by modelling the shear‐wave source radiation pattern, which allows for the unequivocal discrimination between seismic raypaths where shear‐wave splitting did and did not occur. The analysis also demonstrates the great importance of high reproducibility of the seismic source for the use of shear waves in time‐lapse surveys to monitor changes in a rockmass.

Geophysical Properties of the Near Surface Earth: Seismic Properties

“…Stress-induced anisotropy is important in many geophysical problems from complicated stress conditions near a wellbore (Schmitt et al, 1989;Winkler, 1996), in mines (Holmes et al, 2000a;Holmes et al, 2000b), over petroleum reservoirs (Wuestefeld et al, 2011), and in stress changes related to seismicity. (Crampin, 1994;Crampin and Peacock, 2008) in particular had championed the interpretation of shear wave splitting to infer stress states for reservoir monitoring and earthquake forecasting.…”