Statistical Modeling and Characterization of Induced Seismicity Within the Western Canada Sedimentary Basin

摘要

In western Canada, there has been an increase in seismic activity linked to anthropogenic energy-related operations including conventional hydrocarbon production, wastewater fluid injection, and, more recently, hydraulic fracturing (HF). Statistical modeling and characterization of the space, time, and magnitude distributions of the seismicity are vital for a better understanding of induced earthquake processes and development of forecasting models. In this work, a statistical analysis of the seismicity in the Western Canada Sedimentary Basin was performed across past and present time periods by utilizing a compiled earthquake catalog for Alberta and eastern British Columbia. Specifically, the interevent space-time distance distributions of earthquakes were studied using the nearest-neighbor distance (NND) method. Additionally, the frequency-magnitude statistics and aftershock parameters of several clusters were analyzed using the Gutenberg-Richter relation and the epidemic-type aftershock sequence model. The results suggest that recent regional changes in the NND distributions, namely, a disproportionate increase in loosely and tightly clustered seismic activity over time, are unnatural and likely due to the rise in HF operations for the development of unconventional resources. It is concluded that both these loosely and tightly clustered earthquake subpopulations differ measurably from what may be the region's tectonic seismic activity. Additionally, HF treatments have a greater probability of triggering swarm-like sequences that sharply spike the seismicity rate and are characterized by larger Gutenberg-Richter b values. In contrast, conventional production and wastewater disposal operations largely trigger loosely clustered activity with more typical magnitude occurrence distributions.