Seismic Rupture of Submarine Normal Faults – SerSurF

The SerSurF project is focused on the acquisition and analysis of submarine observations of length, displacement and nature of co-seismic seafloor ruptures. These observations are required to evaluate seismic and tsunami hazard in the short term, and characterize the long term dynamic response of the fault to earthquakes. Detailed fault morphology is also necessary to understand fault evolution, constrain the links between deformation, erosion and sedimentation, and determine other processes interacting with faults (e.g., volcanism). While this type of study is routinely carried out on land, direct submarine observations so far have not provided systematic and complete information on submarine fault ruptures due to the technological difficulties of working underwater. SerSurf is designed to use and develop state-of-the-art techniques to conduct fieldwork at the seafloor at high resolution, at scales similar to those applied for land studies.

During the scheduled oceanographic cruise (SubSaintes, April 2017, R/V Atalante), we will deploy remotely operated (ROV VICTOR) and autonomous (AUV Aster X) deep-sea vehicles to explore, map, sample, and fully characterize a submarine co-seismic rupture for the first time, and to determine its tectonic/volcanic environment. The target area is the active Roseau normal fault in the Lesser Antilles, which ruptured during the 2004 Mw 6.3 Les Saintes earthquake. It is part of a network of faults interacting with submarine volcanoes along an extensional graben accommodating intra-arc deformation between Guadeloupe and Dominica islands. The feasibility of this approach has been demonstrated by a pilot study in 2013 during which co-seismic displacement related to the 2004 earthquake was unequivocally documented on a portion of the fault

The project will address three main objectives: (1) characterizing comprehensively co-seismic deformation structures associated with a submarine fault rupture, and measuring co-seismic seafloor displacement; (2) Determining whether, sedimentation, and fault damage development are co-seismic, inter-seismic, or post-seismic; (3) Constraining the long term fault history, including rates of uplift, erosion, sedimentation, and seismic recurrence interval; and (4) assessing whether numerical models developed for sub-aerial fault morphology are applicable to submarine faults, and contrasting observations with model results. We expect that the protocol developed for this project will be generally applicable to faults in other submarine environments

This project will be carried out by a multidisciplinary team from 5 national and 4 international partners, who are leaders in seafloor imaging and mapping, fault dynamics, seismo-tectonics and earthquake geology, volcanology, geochemistry and geochronology, and have as well extensive cruise experience with deep-sea exploration. They also have a strong knowledge of the area acquired through land and offshore field work in and around the French Antilles.

The French Antilles are located in an area subjected to geohazards that are monitored by IPGP Volcanological and Seismological Observatories. The outcome of the project will help provide better risk assessment and prevention strategies in the area, and thus have a significant societal impact.