A seismic source model for dynamic stress fracturing around mining excavations

The fracturing/yielding of rock around an excavation can be approximated as an expansion of the excavation. If this process occurs dynamically, then it radiates seismic waves, which can be used to determine a seismic source mechanism. In the context of dynamic stress fracturing around tunnels, a model has been proposed in the literature that approximates the source process as an elliptical-cavity expansion. This source model permits inferred source mechanisms to be related back to geomechanical properties of the source (elastic parameters, loading, and geometry). In this paper, a more generic source model (i.e., an expression for the seismic potency/moment tensor) is developed based on an ellipsoidal-cavity expansion. This allows application to dynamic stress fracturing around excavations of different geometries (e.g., caves, stopes, chambers, etc.). The utility of the developed source model is demonstrated through application to a synthetic case of stress fracturing in the back of an isolated stope.