Lesser Antilles seismotectonic zoning model for seismic hazard assessment

Abstract

Subduction zones pose a considerable challenge within the realm of seismotectonics, owing to their fault and structure interactions. The Lesser Antilles arc is a good example of how these complexities impact seismic hazard studies with strong along-strike variations in tectonic, seismic, and volcanic activities. While these activities have generated significant damage, the 1839 and 1843 event characteristics (locations, depths, mechanisms, magnitudes) along with their potential implications for megathrust seismicity remain a subject of debate, in particular in the frame of low interseismic coupling. This study is grounded in the compilation of instrumental and historical seismicity and fault catalogs, complemented by analyses of focal mechanisms and rupture types as well as geodetic velocities and strain rates. The resulting seismotectonic zoning model of the Lesser Antilles encompasses the upper plate, subducting oceanic plate, subduction interface, mantle wedge, and volcanoes. We propose a better depth resolution, resulting from recent studies on slab top and upper-plate bottom geometries; a specific area source for the Marie-Galante graben; new propositions for mantle wedge and volcanic zoning; and fully revised area sources for the subduction interface. Our study highlights specific needs for a better seismic hazard assessment in this region.