Use GNSS to investigate the Present-day Tectonic Deformation in Western Canada

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Contrary to the well-studied Cascadia Subduction Zone, crustal deformation in the Canadian Cordillera and its relation to the earthquake is not well understood. For example, GPS observations show that Puget Sound is a zone of northward-directed crustal compression (shortening) and seismicity. However, the existing crustal motion model does not show in detail how the pattern of deformation extends north into the Fraser Lowland and Vancouver, a region of high development and population density. The current lack of understanding of the deformation adds considerable uncertainty to the hazard model in Western Canada. An improved understanding of the present-day tectonics contributes to a better seismic hazard model, which is incorporated into residential building codes and the building codes of critical infrastructure (dams, power facilities, LNG plants), which will reduce risk and increase societal resilience. We will measure and model large-scale tectonic motions in Western Canada, focusing mainly on the Southern Canadian Cordillera, covering most of British Columbia and the nearby population centers in Alberta, such as Calgary and Edmonton. This model divides the elastic lithosphere into small blocks, assuming that the blocks are bounded by block boundary faults. The observed crustal deformation rate is assumed to be the sum of the rigid block rotation rate and elastic deformation rate due to the coupling of the block boundary faults. The block motion model has been successfully applied in the Western US and Alaska to explain the observed deformation field and seismicity, considering the elastic deformation caused by slip deficit at the subducting plate, rigid rotation, and coupling on the inland faults. However, a block model covering the entire Western Canada currently does not exist due to a sparse GNSS network coverage in the past. An increased number of newly installed continuous Global Navigation Satellite System (GNSS) stations improves the data coverage in the southern Cordillera. In addition, episodic GNSS sites will be occupied to improve the density further. We will collect and process GNSS data using up-to-date hardware and software. Advanced time series processing techniques will be used to derive GNSS secular rate and the noise model for accurate velocity determination. We will combine the GNSS velocity field with geological and seismological data to define crustal blocks in Western Canada and calculate the bounding fault slip rates. The outputs will provide a unified velocity model and present-day crustal fault slip rates in Western Canada. Comparing the present-day fault slip rate with the geologically determined fault slip rate will provide insights into the tectonic history of the Cordillera. Such a GNSS-based kinematic block motion model provides critical constraints on the first-order deformation pattern and the possibility of future earthquakes on faults and improves our understanding of the crustal dynamics in the cordillera.