Seafloor earthquake ruptures and mass wasting from the 2004 Mw 6.3 Les Saintes submarine earthquake

The seismic hazard posed by submarine faults and the capacity of submarine earthquakes to trigger mass wasting are poorly understood because we lack detailed characterizations of coseismic ruptures at the seafloor. Here, we present comprehensive mapping of a seafloor rupture caused by the 2004 Mw 6.3 Les Saintes earthquake on the Roseau normal fault in the Lesser Antilles. We report the visual characteristics, displacement profile, and note pronounced asymmetry of the rupture that bears similarities with well-studied subaerial normal fault ruptures. We also identify footwall-derived mass wasted debris that locally cover the coseismic rupture, and show that ground accelerations of 0.1–0.2 g can trigger submarine mass wasting events in well consolidated bedrock along unstable, over-steepened, scarps. Our study demonstrates the potential of underwater vehicles for detailed mapping of seafloor ruptures and hints at a key role for earthquakes in shaping submarine bedrock landscapes by triggering mass wasting events.

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Hughes Alex, Escartín Javier, Billant Jeremy, Leclerc Frédérique, Andreani Muriel, Olive Jean-Arthur, Arnaubec Aurelien, Dano Alexandre, Delorme Arthur, Deplus Christine, Feuillet Nathalie, Gini Caroline, Gracias Nuno, Hamelin Cédric, Istenič Klemen, Komorowski Jean-Christophe, Le Friant Anne, Marchand Claire, Mével Catherine, Onstad Solveig Lie, Quidelleur Xavier (2023). Seafloor earthquake ruptures and mass wasting from the 2004 Mw 6.3 Les Saintes submarine earthquake. Communications Earth & Environment. 4 (1). 270 (13p.).,

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