A New Seismic Source Zone Model for Lesser Antilles Seismic Hazard Assessment

Seismic hazard levels used as reference for the French Lesser Antilles are derived from probabilistic seismic hazard assessment studies performed in 2002. However, our scientific knowledge has greatly increased over the past 20 years in this area. As part of a project linking the French Ministry of Ecological Transition and Solidarity, and the Seismicity Transverse Action of RéSiF (French seismological and geodetic network), we are developing a new seismotectonic model of the Lesser Antilles Subduction Zone (LASZ). The LASZ results from the subduction of the North and South American plates beneath the Caribbean plate since the Eocene. The boundary extends along 850 km in an ENE-WSW convergence direction at 18-20 mm/yr. Significant N-S variations in tectonic, seismic and volcanic activities raise questions on the undergoing geodynamic processes. Fractures and ridges entering into the subduction deform the trench, adding seismotectonic complexities. Several controversial hypothesis remain, such as the origins of the 1839 (Mw 7.5-8) and 1843 (Mw 8-8.5) earthquakes and the long term interseismic coupling, which is currently interpreted as being low. New seismic imageries and more complete seismic catalogs help to better constrain the slab and Moho shapes, as well as the hydrological behavior of the plate interface. In this study, we propose a compilation of existing data and hypothesis, completed by an analysis of focal mechanisms rupture types averaged on grid and strain tensor derived from GPS. For the first time, we add a particular attention in the role and influence of the mantle wedge seismicity, observed in only few subduction zones.