The role of geologic structure and stress in triggering remote seismicity in Creighton Mine, Sudbury, Canada

A study was undertaken at the Creighton Mine, near Sudbury, Canada, to investigate the relationships between geologic structure, stress, and seismicity. Creighton Mine hosts numerous families of shear zones and experiences frequent microseismic and often macroseismic events. Underground structural mapping as well as microstructural and kinematic analysis are used to characterize faults. Fault geometries are then compared to those derived from seismic event focal mechanisms. Focal mechanism information is next used for stress inversion to obtain estimates of in-situ principal stresses for three spatial clusters of events on the 7400-foot (2256m) level. Fault characteristics are then integrated into a numerical discontinuum model of the 7400-foot level of the mine to examine the distribution of stresses in the study volume. The synthesis of these elements is used to determine the sources of seismicity within the deepest levels of the mine. The major shear zones within the mine have not been found to contribute to seismicity via fault-slip but do influence the flow of stress around the main excavation. An anomalous cluster of microseismic events is postulated to be a result of induced stresses from mine development on deeper levels. ► The relationship between stress, geologic structure and seismicity was studied. ► Modelling results show agreement between high maximum stress and dense seismicity. ► No distinct relationship between mapped structure and seismicity was revealed. ► Footwall shear zones realign the stress field with the strike of major structures. ► Seismicity in the Creighton Deep is likely a result of diffusive rock degradation.