ISTerre seminar

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Mapping Mantle Wedge Seismicity for Ground Motion Assessment: The Lesser Antilles Subduction Zone Case (Guadeloupe, Martinique)

Friday 9 October 2026 - 14h00

Océane Foix - ISTerre
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Estimating seismic hazard in a given area requires defining the ground response to seismic waves during an earthquake. This ground response depends on the source, the path, and site effects. Regarding source-to-site characteristic variations, each seismogenic source is defined by specific ground motion laws. At subduction zones, seismogenic sources come in a wide range, from crustal to interface and intraslab sources. Thanks to advances in seismic instrumentation, more and more seismicity has been observed and recorded in the forearc mantle wedge (MW), as in New Zealand, Peru, the Lesser Antilles, Greece, and the Alps. Nowadays, this seismicity is not properly accounted for in the seismic hazard calculation chain, and it is not considered as a specific seismic source. Its seismicity is instead distributed among other sources, such as the crust of the upper or lower plate, or along the megathrust of the plate interface. This means that the distances between the MW hypocenters and the hazard calculation sites are not properly resolved. The Lesser Antilles subduction zone, home to French territories, has the highest seismic hazard level in France. In previous seismic hazard estimations, MW seismicity was not considered. To assess its significance for the islands of Guadeloupe and Martinique, we mapped the MW seismicity to build and refine a specific seismic catalog, and evaluated, from onshore accelerometric stations, the peak ground acceleration and velocity. In this presentation, I invite you to explore and discuss our results and their implications for seismic hazard at subduction zones worldwide.

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Organizing team : Géophysique des risques sismiques et gravitaires

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères