First direct observation of coseismic slip and seafloor rupture along a submarine normal fault and implications for fault slip history

• Main Authors: Tominaga, Masako, Triebe, Lars, Godard, Marguerite, Haaga, Kristian A., Hamelin, Cédric, Ildefonse, Benoit, Jamieson, John W., John, Barbara E., Leleu, Thomas, MacLeod, Christopher J., Massot-Campos, Miquel, Nomikou, Paraskevi, Paquet, Marine, Rommevaux-Jestin, Céline, Rothenbeck, Marcel, Steinführer, Anja, Campos, Ricard, Gracias, Nuno, Garcia, Rafael, Andreani, Muriel, Vilaseca, Géraud, Escartín, Javier, Leclerc, Frédérique, Olive, Jean-Arthur, Mevel, Catherine, Cannat, Mathilde, Petersen, Sven, Augustin, Nico, Feuillet, Nathalie, Deplus, Christine, Bezos, Antoine, Bonnemains, Diane, Chavagnac, Valérie, Choi, Yujin
• Other Authors: Earth Observatory of Singapore
• Format: Article
• Language: English
• Published: 2019
• Subjects: Science::Geology::Volcanoes and earthquakes; Submarine Fault; Earthquake
• Online Access: https://hdl.handle.net/10356/83972; http://hdl.handle.net/10220/50418
• Institution: Nanyang Technological University

Properly assessing the extent and magnitude of fault ruptures associated with large earthquakes is critical for understanding fault behavior and associated hazard. Submarine faults can trigger tsunamis, whose characteristics are defined by the geometry of seafloor displacement, studied primarily through indirect observations (e.g., seismic event parameters, seismic profiles, shipboard bathymetry, coring) rather than direct ones. Using deep-sea vehicles, we identify for the first time a marker of coseismic slip on a submarine fault plane along the Roseau Fault (Lesser Antilles), and measure its vertical displacement of ∼0.9min situ. We also map recent fissuring and faulting of sediments on the hangingwall, along ∼3km of rupture in close proximity to the fault’s base, and document the reactivation of erosion and sedimentation within and downslope of the scarp. These deformation structures were caused by the 2004Mw6.3 Les Saintes earthquake, which triggered a subsequent tsunami. Their characterization informs estimates of earthquake recurrence on this fault and provides new constraints on the geometry of fault rupture, which is both shorter and displayslocally larger coseismic displacements than available model predictions that lack field constraints. This methodology of detailed field observations coupled with near-bottom geophysical surveying can be readily applied to numerous submarine fault systems, and should prove useful in evaluating seismic and tsunamigenic hazard in all geodynamic contexts.