Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Geophysics

Supervisor

Shcherbakov, Robert

Abstract

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 clusters is vital for a better understanding of induced earthquake processes and development of predictive 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 catalogue for Alberta and eastern British Columbia. Specifically, the frequency-magnitude statistics were analyzed using the Gutenberg-Richter (GR) relation. The clustering of seismicity was studied using the Nearest-Neighbour Distance (NND) method and the Epidemic Type Aftershock Sequence (ETAS) model. The obtained 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 steeper frequency-magnitude distributions. Conventional production and wastewater disposal operations largely trigger loosely clustered activity with more typical magnitude-occurrence rates.

Summary for Lay Audience

In western Canada, there has been an increase in earthquake activity linked to industrial activities including fossil fuel extraction, wastewater disposal and more recently hydraulic fracturing (HF). Statistical modeling of earthquake phenomena is important for the understanding of the specific mechanisms involved in triggering earthquakes. In this work, a statistical analysis of the recorded earthquakes in the Western Canada Sedimentary Basin was performed. The results of this study suggest that there are discrete statistical differences between natural, tectonic earthquakes and those triggered artificially by human activity. Additionally, HF operations appear capable of triggering swarm-like sequences that temporarily increase the earthquake rate and tend to occur at small-to-moderate magnitudes. Conventional fuel production and wastewater disposal operations largely trigger earthquakes that are loosely clustered together in space and time across a broader magnitude range.

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