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Rapport Année : 2023

SUBSAINTES’17 Cruise Report: Coseismic ruptures & tecto-volcanic interactions at the French Antilles Arc between Les Saintes and Dominica

Résumé

The SUBSAINTES’17 cruise took place between the 2nd and 24th of April in an area be- tween the islands of Les Saintes and Dominica. This area has been mapped with ship- board multibeam surveys (Bathysaintes’10 onboard N/O Pourquoi Pas? PI: N. Feuillet & C. Deplus). Les Saintes and Dominica are linked by a network of normal faults that inter- act with various seamounts in the area, unsampled to date and whose nature is un- known. This area also witnessed in 2004 a Mw6.4 seismic event along the Roseau Fault, one of the major fault structures that runs NW-SE and bounds the fault network system to the SW. This earthquake, in addition to causing damage in the nearby Les Saintes (including one casualty), also triggered a minor tsunami. During the ODEMAR’13 cruise onboard N/O Pourquoi Pas? A preliminary, 3-day long survey, was conducted using deep-sea vehicles as a second leg of the ODEMAR cruise; F. Leclerc, who was conducting PhD research on the links between faulting and volcanism, joined this second cruise leg. During ODEMAR’13 a section of the Roseau Fault was mapped using the Remus 6000 AUV (Geomar, Germany) and the ROV Victor 6000, equipped with a multibeam system, conducted near-bottom multibeam mapping, still electronic image surveys, and 3D video surveys. These preliminary observations re- vealed the Roseau Fault plane, and evidence of recent fault ruptures that are most likely associated with the 2004 Les Saintes seismic event; these include fractures in the hang- ingwall at the base of the fault scarp, and a recently exposed fault slip plane. 3D video models were also used to estimate a vertical fault displacement of ~0.9 m associated with this seismic event. The SUBSAINTES cruise thus builds on data gathered in 2013 during the ODEMAR cruise in the area, as the fault rupture was only partially mapped and characterized over a length of ~3 km. The main goals of the SUBSAINTES’17 cruise are A) toinvestigatetheextentandnatureofthecoseismicfaultruptureassociatedwith the Mw 6.4 Les Saintes Earthquake, and quantify the displacement associated with it along the Roseau Normal fault, B) Investigate the volcanic and tectonic features in the area, sample them and ob- serve their interactions, C) Evaluate and constrain erosion and sedimentation processes in the area and the links to active tectonics and volcanism, D) Develop video-derived 3D mapping techniques to obtain quantitative infor- mation on fault and volcanic structures (e.g., fault displacement, fine-scale geom- etry of lava flows, etc.)
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hal-04116330 , version 1 (10-08-2023)

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J. Escartin, Nathalie Feuillet, Anne Lefriant. SUBSAINTES’17 Cruise Report: Coseismic ruptures & tecto-volcanic interactions at the French Antilles Arc between Les Saintes and Dominica. Laboratoire de Géologie, ENS; Institut de Physique du Globe de Paris (IPGP). 2023. ⟨hal-04116330⟩
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