Long-term Earthquake-Tsunami Risk Assessment Considering Time-dependent Hazards and Nonstationary Sea Level Rise: Tofino, British Columbia, Canada
Abstract
A nonstationary multi-hazard risk model for earthquakes and tsunamis is developed to facilitate long-term risk management strategies for coastal communities. The model incorporates the time-dependency of earthquake occurrence, non-tsunamigenic earthquakes, uncertainty of tidal levels, and future projections of sea level rise and considers numerous scenarios via a stochastic source modeling approach. The model focuses on Tofino, British Columbia, Canada, which is directly exposed to the Cascadia subduction earthquakes. High-resolution topography and high-quality exposure data are incorporated to evaluate multi-hazard economic loss to buildings in Tofino. The results are expressed as earthquake-tsunami risk curves for different elapsed times since the last major event and different seal level conditions. The evolutionary aspects of Tofino's time-dependent multi-hazard risk profiles show that the current earthquake-tsunami risk is lower than that based on the conventional time-independent Poisson occurrence model. In contrast, the future risk in 2100 will exceed the time-independent risk estimate. Moreover, variable tidal levels have noticeable effects on the tsunami risk curves, while the influence of relative sea level rise becomes increasingly more significant with the progress of time. The results obtained in this study are useful for emergency managers and city planners.
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