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Portal > Offres > Offre UMR7329-FRELEC-001 - H/F jeune chercheur(se) : réaliser une étude paléo-sismologique de carottes sédimentaires marines dans l'archipel de Guadeloupe

Man/Woman scientist : Perform a paleo-seismologic study based on the analyses of sediment core from

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Français - Anglais

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General information

Reference : UMR7329-FRELEC-001
Workplace : VALBONNE
Date of publication : Tuesday, December 03, 2019
Type of Contract : FTC Scientist
Contract Period : 6 months
Expected date of employment : 2 March 2020
Proportion of work : Full time
Remuneration : The ANR Sersurf provide the salary that is comprised between 2600 and 2700€ before taxes.
Desired level of education : PhD
Experience required : 1 to 4 years

Missions

Perform a paleo-seismologic study based on the analyses of sediment cores from the Saintes basin (graben) in the Guadeloupe Archipelago, in order to reconstruct the seismic rupture history of the nearby submarine faults. Study sedimentary transfers between the Saintes carbonate platform and the deep basin.

Activities

-Acquisition and interpretation of different datasets on four short sediment cores sampled by an ROV, and one long Küllenberg core :
radioscopy RX (SCOPIX), spectrometry by X fluorescence (Core Scanner), physical analyses (spectrocolorimetry, magnetic susceptibility, gamma density), granulometry (with the microgranulometer MALVERN Mastersizer 2000), 14C and 210Pb datings, carbonates mineralogy (X ray diffractometer)

- Age model determination (OxCal and Calib)
- Perform a morpho-sedimentary study of the basin
- Present the findings of this project during a congress and in at least one scientific publication

Skills

- Interpret geophysical data (bathymetry, chirp) acquired in the Saintes basin.
- Use a GIS software
- Lead the sampling of the sediment cores following the appropriate rules
- Perform the physical analyses on the samples (spectro-colorimetry, magnetic susceptibility, gamma density) using a Multi Sensor Core Logger.

The candidate must be autonomous, used to work in a team and communicate, and is intended to behave as the leader of this project.

Work Context

This project is part of the ANR Sersurf (PI : J. Escartin, https://anr.fr/fr/projets-finances-et-impact/projets-finances/projet/funded/project/anr-17-ce31-0020/?tx_anrprojects_funded%5Bcontroller%5D=Funded&cHash=b1c5acddc69f620d48e763bec235c40e).

It is based on the data acquired during the SUBSAINTES cruise(http://subsaintes2017.weebly.com/), and is closely related to a first paleo-seismological study performed at Geoazur between 2018 and 2019, based on the morphology of the submarine fault.

The candidate will be supervised by F. Leclerc in Géoazur, Associate professor at the university Côte d'Azur (250 rue Albert Einstein, 06250 Valbonne). Geoazur laboratory is attached to the CNRS, Université Côte d'Azur, Institut de Recherche pour le Développement (IRD) and Observatoire de la Côte d'Azur (OCA).

The candidate will however be based in Paris, at the Institut de Physique du Globe de Paris (1 rue Jussieu, 75005 Paris), where he/she will be supervised by N. Feuillet and J. Escartin (Research directors). The sedimentary cores are indeed stored in Paris where most of the analyses will be performed. Additional analyses will be performed in other french laboratories (Géoazur, Université de Bordeaux, Université de Bretagne Occidentale).

Constraints and risks

The candidate will travel between different laboratories to acquire the different datasets, therefore he/she must be mobile.

Additional Information

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.

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