Quantifying Coseismic normal fault rupture at the seafloor: the 2004 Les Saintes Earthquake (Mw 6.3) along the Roseau Fault (French Antilles)

Escartín, Javier, Leclerc, Frédérique, Olive, Jean Arthur, Romero-Garcia, Rafael, Gracias, Nuno and Massot Campos, Miguel (2016) Quantifying Coseismic normal fault rupture at the seafloor: the 2004 Les Saintes Earthquake (Mw 6.3) along the Roseau Fault (French Antilles). In American Geophysical Union Fall Meeting. American Geophysical Union..

Abstract

While >70% of Earth’s seismicity is submarine, almost all observations of earthquake-related ruptures and surface deformation are restricted to subaerial environments. Such observations are critical for understanding fault behavior and associated hazards (including tsunamis), but are not routinely conducted at the seafloor due to obvious constraints. During the 2013 ODEMAR cruise we used autonomous and remotely operated vehicles to map the Roseau normal Fault (Lesser Antilles), source of the 2004 Mw6.3 earthquake and associated tsunami (<3.5m run-up). These vehicles acquired acoustic (multibeam bathymetry) and optical data (video and electronic images) spanning from regional (>1 km) to outcrop (<1 m) scales. These high-resolution submarine observations, analogous to those routinely conducted subaerially, rely on advanced image and video processing techniques, such as mosaicking and structure-from-motion (SFM).
We identify sub-vertical fault slip planes along the Roseau scarp, displaying coseismic deformation structures undoubtedly due to the 2004 event. First, video mosaicking allows us to identify the freshly exposed fault plane at the base of one of these scarps. A maximum vertical coseismic displacement of ~0.9 m can be measured from the video-derived terrain models and the texture-mapped imagery, which have better resolution than any available acoustic systems (<10 cm). Second, seafloor photomosaics allow us to identify and map both additional sub-vertical fault scarps, and cracks and fissures at their base, recording hangingwall damage from the same event. These observations provide critical parameters to understand the seismic cycle and long-term seismic behavior of this submarine fault.
Our work demonstrates the feasibility of extensive, high-resolution underwater surveys using underwater vehicles and novel imaging techniques, thereby opening new possibilities to study recent seafloor changes associated with tectonic, volcanic, or hydrothermal activity.

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Contributors

Author: Miguel Massot Campos

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