Earthquake and Tsunami Resiliency Assessment for a Coastal Community in the Pacific Northwest, USA

In this paper we examine and compare the vulnerabilities of building and highway bridge to the combined effect of earthquake and tsunami loading. Earthquake-induced ground shaking, ground failure (e.g., landslides and liquefaction), and tsunami inundation fragility functions are combined with regional hazard data to estimate the damage and direct economic loss of building and bridge. We use the city of Seaside, Oregon, as a case study site, because it is one of the most vulnerable coastal cities in the Pacific North United States given the threat of an extreme nearfield Cascadia Subduction Zone earthquake and resulting tsunami. We test sensitivity of damage levels using various fragility curves. For the fragility curve analysis, we consider flow depth, velocity and momentum flux ad the intensity measure to estimate the probability of a certain damage level based on the known structure type and characteristic tsunami and earthquake intensity. We also evaluate the disaster resilience. The results indicate that when ground failure and tsunami inundation are considered, there is an overwhelming increase in the loss estimates when compared to the estimates obtained when ground shaking alone is considered.