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

located events were removed from clustering analyses by filtering events by error using a cut-off
of 30 feet. The distribution of macroseismic events is shown in Fig. 3.6B for comparison.
Seismicity that is not directly related to blasting and extraction tends to occur south of and remote
to the excavation. Microseismic events are mostly restricted to a distinct zone extending from the
southeastern corner of the excavation to approximately 300 feet south of the excavation. Very
little seismic activity occurs directly south, southwest and north of the excavation. These trends in
seismicity pertaining to the 7200 Level, 7400 Level and 7530 Level are shown in Figure 3.7.
Events do not tend to align with mapped geological structures but rather occur in proximity to
both shears and openings. Events on the 7200 Level appear to align with the 402 Shear Zone but
also occur in close proximity to excavations. Macroseismic events are often attributed to fault
movement by mine staff. Macroseismic events within the study area appear randomly distributed
and do not cluster or conform to geological structure (Fig. 3.6B). Areas of dense microseismic
activity are generally related to these events; spatial and temporal clustering of microseismic
events tends to occur following a macroseismic event. Macroseismic events tend to have little to
no precursory seismicity followed by high rates of seismicity that decay to background levels over
a matter of hours or days, sometimes including additional macroseismic events. A review of
rockbursting in Creighton mine by Blake and Hedley (2003) agrees that macroseismic events in
Creighton that are expressed as rockbursts are almost always unexpected; events do not occur at
regular intervals and do not have seismic precursors.
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