Modeling the potential genesis of tsunamis from below an accretionary prism and their potential impact: a case study along the eastern boundary of the Caribbean Plate

The Lesser Antilles subduction zone marks the convergence between the Caribbean Plate and the oceanic Atlantic part of the America Plate. A specificity of this subduction is the development of a huge accretionary prism, the Barbados complex. As other subduction zones, the Lesser Antilles one has the potential to produce megathrust-associated earthquakes and related tsunamis. This study evaluates the potential hazard of tsunami scenarios along this eastern boundary of the Caribbean Plate, taking into account its specificities. We define six scenarios along the Lesser Antilles subduction zone including three Mw7.5 , 8.0 and 8.5 earthquake models, in both northern and southern parts of the arc. We incorporate in tsunami simulations the effect of sediment amplification in tsunami generation. In the southern half, the thick sediments pile, related to tectonic accretion, appears much more effective than the much thinner accumulation characterizing the northern half. The bed shear stress is also computed in this study as it is an important factor in sediment transport which can show the potential locations for sediment movement by tsunamis. Our results indicate the ability of scenario earthquakes to produce powerful tsunamis. The impacts of northern scenarios on Guadeloupe could be severe (maximum tsunami wave height of >5m), whereas the impacts from southern scenarios are relatively less strong (maximum wave amplitude of <5m). The tsunami waves produced by Mw8.0 and 8.5 appear able to inundate the coast of Sainte-Anne, Guadeloupe, up to 2km . The distributions of bed shear stress from northern scenarios suggest that the offshore Leeward Islands could be potentially prone to sediment transport as possible tsunami deposits have been found in the region in former geological studies.