Assessing direct and indirect long-term economic impacts from earthquakes to the U.S. National Bridge Inventory

Using the 2018 National Seismic Hazard Model and the 2018 National Bridge Inventory, an annualized earthquake loss (AEL) study was conducted for approximately 610,000 bridges in the conterminous United States, quantifying both direct and indirect economic losses. The typical AEL framework has been augmented with new replacement unit cost data and bridge-specific parameters for modifying default fragility curves. Earthquake hazard is defined using spectral acceleration hazard curves that account for location-specific soil conditions. Hazard is integrated with bridge-specific fragility curves to compute annual probabilities of exceeding various damage states. Further, economic loss for each bridge was estimated using the repair costs associated with specific damage states and indirect costs incurred from downtimes. Quantitative assessments of seismic risk, especially those that account for downtime-related impacts, enable us to illustrate the distribution of risk with respect to geographic region, era of construction, or type of bridge.