Over the past decade, parts of western Canada have seen a rise in
clustered seismic activity coinciding with the growing use of a
hydrocarbon reservoir stimulation technique known as hydraulic
fracturing. This recent upsurge has the potential to increase the local
seismic hazard, particularly in affected areas characterized by a
sparser tectonic environment. It is therefore critically important to
assess and characterize the space, time and magnitude distributions of
induced earthquakes from a statistical standpoint, in order to develop a
better understanding of triggering processes and improve forecasting
models. In this study, the nearest-neighbour distance method was used to
analyze the distribution of space-time inter-event distances across the
Western Canada Sedimentary Basin from a regional perspective.
Additionally, the epidemic type aftershock sequence model and the
Gutenberg-Richter relation were used to compare the structuring and
magnitude scaling of several seismic clusters induced by different human
operations. The results demonstrate that a transformation in the
regional distribution of inter-earthquake distances occurred after 2009,
where an emergent subpopulation of abnormally tightly clustered events
became distinguishable from both natural and prior-induced seismicity.
Several distinctions were also revealed between earthquake clusters
occurring near different anthropogenic operations, including a higher
proportion of tightly clustered events near hydraulic fracturing
treatments which were largely swarm-like in nature.