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

Javier Escartin (1) , Frédérique E Leclerc (2) , Jean-Arthur J Olive (3) , Catherine Mevel (1) , Mathilde Cannat (1) , Sven E Petersen (4) , Nico E Augustin (4) , Nathalie Feuillet (1) , Christine Deplus (1) , Antoine A Bezos (5) , Diane Bonnemains (1) , Valérie E Chavagnac (6) , Yujin Choi (1) , Marguerite Godard (7) , Kristian A Haaga (8) , Cédric Hamelin (8) , Benoit Ildefonse (7) , John W Jamieson (4) , Barbara J John (9) , Thomas E Leleu (6) , Christopher J Macleod (10) , Miquel Campos (11) , Paraskevi A Nomikou (12) , Marine Paquet (1) , Céline J Rommevaux-Jestin (1) , Marcel E Rothenbeck (4) , Anja E Steinführer (4) , Masako A Tominaga (13) , Lars E Triebe (2) , Ricard Campos (14) , Nuno Gracias (14) , Rafael Garcia (14) , Muriel A Andreani (15) , Géraud Vilaseca (1)

1 IPGP - Institut de Physique du Globe de Paris
2 EOS - Earth Observatory of Singapore
3 LDEO - Lamont-Doherty Earth Observatory
4 GEOMAR - Helmholtz Centre for Ocean Research [Kiel]
5 LPG - Laboratoire de Planétologie et Géodynamique [UMR 6112]
6 GET - Géosciences Environnement Toulouse
7 Géosciences Montpellier
8 UiB - Department of Earth Science [Bergen]
9 UW - University of Wyoming
10 Cardiff University
11 Universitat des Illes Balears
12 NKUA - National and Kapodistrian University of Athens
13 Texas A&M University [College Station]
14 UdG - Universitat de Girona
15 LGL-TPE - Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement

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 ∼0.9 m in situ. We also map recent fissuring and faulting of sediments on the hangingwall, along ∼3 km 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 2004 M w 6.3 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 displays locally 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.

Domains: Tectonics

Javier Escartin, Frédérique E Leclerc, Jean-Arthur J Olive, Catherine Mevel, Mathilde Cannat, et al.. First direct observation of coseismic slip and seafloor rupture along a submarine normal fault and implications for fault slip history. Earth and Planetary Science Letters, 2016, 450, pp.96-107. ⟨10.1016/j.epsl.2016.06.024⟩. ⟨insu-01557932⟩