: The inversion of the seismic moment tensor allows for a characterization of failure components. An original technique is proposed, using time domain equivalent low-frequency spectral displacements with first arrival polarities attached. The identification of each particular wave-type is based on wave energy functions and polarization criteria. The technique is applied to microseisemic events recorded at the Kidd mine, Ontario, with their underground microseismic array. This array includes 20 uniaxial and 8 triaxial accelerometers and monitors a volume of about 300 x 300 x 400 m. Inversions are carried out for pure shear, complex shear, and a general mechanism, including both shear and tensile components. The results show that distinct mechanisms are responsible for the stress transfer effects observed in different regions of the mine. Events that occur within a pillar on the 4,700 Level have positive tensile components, whereas events that occur outside the orebody are characterized as pure-shear failures, similar to those induced in a fractured rockmass on the 5,600 Level.
The seismic moment tensor representation of the seismic source allows for a relatively simple characterization of the failure mechanism, accounting for both volumetric and deviatoric failure components. The employment of this methodology in case of earthquakes has outlined their pure-shear mechanism. This is in agreement with earthquakes being generally associated with slip on pre-existent faults. In case of mines, the presence of faults, dykes, and joint sets will likely result in similar mechanisms. However, the existence of stops, drifts, and other underground excavations creates the potential for the occurrence of volumetric components. As such, the above technique appears particularly attractive at a mine site, where the identification of failure components can provide additional information for an objective assessment of the rockmass condition as a result of mining operations.
