A Disaster Risk Management Approach to Seismic Risk on Vancouver Island, British Columbia.

摘要

Communities on Vancouver Island, British Columbia face significant exposure to damaging earthquakes. This seismic risk arises not only from the Island's proximity to crustal, sub-crustal and subduction earthquake sources in the Cascadia Subduction Zone and from their associated aftershock sequences, but also from environmental (natural and human-made) and social vulnerabilities in Vancouver Island communities and their current capacities to respond and recover from a large seismic event. Seeking to 1) assist community officials and the general public to better understand the scope of the earthquake risk on Vancouver Island; 2) raise awareness of the gaps in Vancouver Island's risk assessment; 3) encourage and facilitate comprehensive seismic risk discussions at all levels of governance; and 4) offer quantitative data on which to base sound funding and policy decisions, this dissertation offers three new studies, presented in paper format, toward the comprehensive management of seismic risk on Vancouver Island.;The first paper reviews the components of risk and, building on international risk management standards and best practices, develops a new, comprehensive Disaster Risk Management (DRM) Framework for practitioners. This DRM Framework is then used to review existing knowledge of Vancouver Island's seismic risk. A number of information gaps are identified, and two in particular, mainshock and aftershock hazard assessment, are targeted for further analysis.;Vancouver Island's mainshock seismic hazard is investigated in the second paper, and it includes source contributions from a full-rupture Cascadia subduction earthquake as well as from crustal and sub-crustal sources. Rather than using engineering parameters to describe seismic hazard, this dissertation research focuses on the development of simplified, readily-understandable earthquake shaking probability estimates. These probabilities, based on the latest available Geological Survey of Canada seismic hazard models are presented as the chance of exceeding one of three shaking intensity levels (Widely-Felt Shaking; the threshold for Non-Structurally-Damaging Shaking; and, the threshold for Structurally-Damaging Shaking) over one of four timeframes (10, 25, 50 and 100 years). In addition to individual source calculations, for the first time aggregate shaking probabilities are calculated to provide the combined shaking hazard from all three seismic sources. Results are calculated for over 50 Vancouver Island locations. Seismic hazard is greatest in the sparsely populated northwest quadrant of Vancouver Island, and on the southern tip of the Island where most of the Island's population is concentrated. Uncertainties associated with these calculations are identified and discussed.;The third paper provides the first estimates of aftershock shaking hazard for communities along the west coast of North America following a full-rupture Cascadia subduction event. Owing to uncertainties associated with the size of the rupture zone, two possible rupture zone scenarios are modeled and presented. Results provide the probabilities of exceeding each of three shaking intensity thresholds identified above. Coastal communities on southern Vancouver Island and along the Washington coast are subject to the greatest Cascadia subduction aftershock hazard.;Research presented in this dissertation contributes to the growing body of disaster risk management literature generally, and the seismic risk literature for Vancouver Island specifically.