A comparative analysis of approaches to expanding Canada’s Earthquake Scenario Catalogue

Canada’s earthquake scenario catalogue is a nation-wide collection of possible earthquake rupture scenarios that allows us to understand which populations and assets will be impacted by the rupture of particular faults (or their segments). In the past, scenarios were often generated on an ad hoc basis, when they were needed by practitioners. As new information from geologic, geomorphic, geophysical, and geodetic studies become available, it is possible to model additional earthquake rupture scenarios for inclusion in Canada’s earthquake scenario catalogue, which will be crucial to providing relevant seismic hazard and risk estimates to end users such as community planners and emergency managers. This is especially valuable in the seismically active intraplate regions of eastern Canada, where the seismic risk awareness, perception and, consequently, preparedness, is relatively low. In updating this catalogue, we employed different approaches to modelling earthquake hazard and risk scenarios using the Global Earthquake Model Foundation’s (GEM) OpenQuake Engine. We conducted a ‘known events’ approach, which involved modelling representative events for historical earthquakes and potentially active faults. We also implemented a ‘systematic risk-based’ approach, which involved disaggregating the seismic risk at certain locations into the relative contributions from different seismic source zones, and ranking the seismic risk for each census subdivision (approximately aligned with municipalities) across Canada. The goal of the ‘systematic risk-based’ approach was to mitigate the irregular coverage of the existing catalogue. We compare the nature of the two catalogues for one community, taking into account the ways these kinds of catalogues are used in Canada and elsewhere. Finally, we described the overall spatial variations in seismic risk, focusing on regions where seismic zones are close to densely-populated areas, such as the offshore BC region and Cascadia subduction zone in western Canada; and the Western Quebec, Charlevoix, lower St. Lawrence, and southern Great Lakes seismic zones in eastern Canada.