Earthquake Damage Estimations: ShakeCast Case Study on Nevada Bridges

Abstract

This case study evaluates the vulnerability of Nevada bridges relative to earthquake hazard using two different methods. First, a distributed set of 112 realistic earthquake scenarios were processed with USGS program ShakeMap, and site-specific ground motion levels extracted for 1831 bridges in Nevada using ShakeCast. Second, using hazard curves underlying the 2014 USGS National Seismic Hazard Map (NSHM), return periods for earthquakes causing extensive damage to bridges were extracted and compared to the 1000-year design level adopted by the AASHTO. Lower capacities than those used in ShakeCast were proposed for five continuous bridge types based on a literature review. Scenarios provide points in a deterministic seismic hazard approach, with large earthquakes on known faults. NSHM hazard curves are based on a probabilistic approach. A graphical method is presented to unite the two approaches. A list of potentially vulnerable bridges was developed for Nevada Department of Transportation (NDOT) use in bridge retrofit planning. As a continuing benefit, ShakeCast now operates in Nevada to provide near-real-time inspection priorities in the event of a serious earthquake.