Application of fragility curves to estimate building damage and economic loss at a community scale: a case study of Seaside, Oregon

Community-scale estimates of building damage and economic loss are modeled for Seaside, Oregon, for Cascadia subduction zone events ranging from 8.7 to 9.3 M W with corresponding slip distances of 3–25 m considering only the effects of the tsunami. Numerical simulations are obtained from the National Oceanic and Atmospheric Administration’s method of splitting tsunami model which includes a source model, subsidence, and calculations of the propagation and inundation flow characteristics. The damage estimates are based on fragility curves from the literature which relate flow depth with probability of damage for two different structural materials of buildings. Calculations are performed at the parcel level for the inundation hazard without including damage caused by the earthquake itself. Calculations show that the severity of building damage in Seaside is sensitive to the magnitude of the event or degree of slip because the majority of the city is located on low-lying coastal land within the estimated inundation zone. For the events modeled, the percentage of building within the inundation zone ranges from 9 to 88 %, with average direct economic losses ranging from $2 million to $1.2 billion.