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

double couple events. As a result, a large number of events within the mine environment cannot
be characterized with this method but are better represented as a moment tensor. A poor fit of
fault planes to plotted first arrivals may also arise as a result of the event being detected by a low
number of sensors, poor first polarity picks, source location error or the homogeneous velocity
model used by the mine. To relate microseismicity to structure, fault plane solutions for
macroseismic and microseismic events corresponding to the 7400 Level were generated and
analyzed for common faulting mechanisms.
3.3.1.1 Fault plane solutions for macroseismic events
Although macroseismic events saturate the underground network, first arrivals are well recorded
and their polarities preserved, allowing for fault plane analysis. P-axes, T-axes and nodal planes
were estimated for 93 events with adequate statistical and visual double-couple solutions. Fault
plane solutions and calculated fits were generated using the grid search algorithm in the program
VFps by the Engineering Seismology Group. This method returns the best fit (between 0 and
100%) which has the least error. Events are located between the 7400 Level and 7810 Level but
are mostly confined to the south of the main excavation on the 7400 and 7530 Levels. These
occurred during the 2006-2007 time span. Plotted P- and T-axes and nodal planes for these events
do not show consistent axes or mechanism types (Fig. 3.12); poles to nodal planes do not form
distinct clusters and no common axes are revealed (Fig. 3.13). A sample of fault plane solutions
for macroseismic events corresponding to the 7400 Level is shown in Figure 3.14.
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