Potential for tsunami generation by submarine slope failures along the western Great Bahama Bank

Multibeam and seismic data reveal repeated slope failures at various scales along the western slope of Great Bahama Bank. In addition, creeping and incipient slump scars indicate slope instabilities that will lead to large-scale slope failures in the near future. To assess the potential of tsunami generation by these slope failures several tsunami scenarios have been constructed and simulated numerically for the Straits of Florida. They are based on the estimated volume and nature of a potential landslide, and failure scenarios of the known scars and mass transport complexes (MTC). During the 2010 Carambar cruise four connected scars with widths of 2.0, 2.2, 3.7 and 1.6 km and lengths of 3.0, 1.4, 3.2 and 3.0 km, respectively, were identified. In the Scenario A, the mass 1.18 km3 of the largest of the four failures was calculated. In Scenario B it is assumed that all scars were generated in one event producing a large MTC with an initial failure mass 3.42 km3. Three different terminal velocities for the failure masses were used; i.e. 20 m/s, 50 m/s and 100 m/s. The numerical model is based on the non-hydrostatic wave model NHWAVE developed at the Center for Applied Coastal Research at the University of Delaware. Initial wave heights generated are discussed in terms of terminal landslide velocity, failure volume, and outrun distance. The results show that for scenario A within one minute after the failure event a wave height up to 1 m is generated. For scenario B initial wave heights from 1 up to 2 m can be expected. The waves propagate across the entire Straits of Florida impacting the coastline for about 150 km. An 80 km long scar with abundant creeping features in the downslope area is a potential massive slope failure. If released in one event the mass would be 24 km3. A catastrophic release would generate an initial tsunami wave height of 2.5 up to 4 m with a possible major impact on both sides of the Straits. The modeling demonstrates that the generation of tsunamis by slope failure in a tectonically inactive area can cause a potential hazard in the densely populated urban areas of south Florida and the Keys.