Probabilistic SMF tsunami hazard assessment for the upper east coast of the United States

The level of tsunami hazard to the east coast of the United States is not well understood. This information is critical for the population, emergency services, and industry of the region. Assessing this hazard is particularly difficult because of the lack of tsunamis in the historical record and the uncertainty regarding the return periods of large-scale events that have been proposed, such as a large transoceanic tsunami possibly caused by a collapse of the Cumbre Vieja volcano in the Canary Islands, or a large co-seismic tsunami initiated in the Puerto Rican subduction zone. The most significant tsunami hazard in this region, however, may be due to local submarine mass failures (SMF), which could cause concentrated damage in coastal communities located near the failures. This paper presents results of a probabilistic analysis that estimates the hazard, expressed in terms of runup (at a given probability of occurrence), of SMF tsunamis triggered by earthquakes, on the upper northeast coast of the United States. A Monte Carlo approach is employed, in which distributions of relevant parameters (seismicity, sediment properties, type and location of slide, volume of slide, water depth, etc.) are used to perform large numbers of stochastic stability analyses of underwater slopes, based on standard geotechnical methods. When slope failure occurs, initial tsunami characteristic height and runup are estimated, based on earlier numerical work, for specified return periods of seismic events. The overall hazard associated with SMF tsunamis along the coast is found to be quite low at most locations as compared, e.g., to the typical 100 year hurricane storm surge in the region (5 m). Two sites, however, located off of Long Island, New York and Atlantic City, New Jersey, show an elevated risk of higher tsunami runup (5.0-7.5 m). These two sites should be the focus of more detailed studies.