An integrated study of induced earthquakes and crust-mantle seismic structure

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Earthquakes can be categorized into two main groups: ones that occur as a result of tectonic forces, often referred to as natural earthquakes, and ones that are triggered by human activities such as mining, hydrocarbon production or fluid injection/withdrawal. Natural earthquakes come in all sizes, depths and magnitudes, and the seismic waves associated with them have been widely utilized to infer the structure of the Earth’s interior. On the other hand, anthropogenic sources, also known as induced earthquakes, are less well understood but are being reported at increasing frequencies and sizes. Recent earthquakes in central and western Alberta are compelling case studies in connection with wastewater disposal and hydraulic fracturing (for short, ‘fracking’) operations. The proposed research program in the upcoming years will target both seismic risks in the Western Canada Sedimentary Basin (WCSB) and structures at different spatial scales. The regional component of the proposed program will combine passive-source deployments with laboratory-based analyses of seismic risk and structure. It will take advantage of increased station density and coverage by analyzing the source characteristics and origins of induced earthquakes. It also aims to provide an updated, more accurate map of three-dimensional seismic velocity beneath western Canada. Expected research outcomes pertaining to induced earthquakes may directly impact the environmental policies and decisions vital for the sustained economic growth in the province of Alberta. The extensive database from this regional seismic array also presents a rare opportunity to address scientific issues regarding the crust and mantle seismic structure and the tectonic history of the North American continent. This regional research component will be complemented by a laboratory-based, global analysis of earthquake data. Seismological observations pertaining to the depths and strengths of crust/mantle interfaces provide a crucial link between mineral physics, seismology and thermal/compositional conditions. The availability of broadband data and array-based imaging methods will enable high-resolution snapshots of the crust and mantle beneath various tectonic regimes. The proposed research will utilize high frequency methods (e.g., P'P' precursors), in combination with full waveform inversion and spectral decompositional approaches, to achieve the type of resolution typical of active-source experiments. The two components of the proposed research program are complementary in scale and scope. Together, they form a solid foundation for long-term studies of seismic risks in western Canada and the history/dynamics of both ancient landmasses and more recently formed plate boundary zones. The proposed program will be an integral part of the training of existing graduate students and other highly qualified personnel.