title of the thesis - Department of Geology - Queen's University

mechanism shows that over 57% of the events have predominant strike-slip mechanisms (Fig.
3.16) while the remaining mechanisms represent either primarily reverse, dip-slip or strike-slip
failures. Though fault mechanism types have little meaning in the underground environment, mechanism
types show consistency. Strike-slip mechanisms share similar P- and T-axis orientations and have
similar axis clusters as those plotted in Figure 3.15, suggesting slip along favourably oriented
fractures. For such events, P-axes plunge shallowly to the west; T-axes trend plunge shallowly to
the north; while B-axes are near vertical.
The similarity in axis orientation suggests that while some slip occurs on randomly oriented
fractures, lateral slip preferentially occurs on steeply dipping NNW or ENE striking
discontinuities. No absolute discrimination between the fault plane and auxiliary plane can be
made. The strike of the ENE-oriented fault plane solution is similar to the strike of the 118 Fault
System, though the dip direction is opposite. If movement should occur along this ideal fault
plane, the solution suggests that motion would be dextral. If strike-slip movement were to occur
along the NNW-trending plane, motion would be sinistral. The representative mechanism, plotted
using average P-, B- and T-axis orientations, is shown in Figure 3.17.
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