Long-term autonomous hydrophones for large-scale hydroacoustic monitoring of the oceans

International audienceWe have developed a set of long-term autonomous hydrophones dedicated to long-term monitoring of low-frequency sounds in the ocean (<120Hz). Deploying arrays of such hydrophones (at least 4 instruments) proves a very efficient approach to monitor acoustic events of geological origin (earthquakes, icequakes), sea state or large baleen whales, over large and remote areas of the world ocean (up to 1000 km between instruments or more). Such approach takes advantage of the high sensitivity of hydrophones and of the long-range acoustic properties of the water column. Our instrument have been designed to be deployed for more than one year, continuously recording the ocean sounds at 240Hz with high dynamic 24-bit resolution

Sondeur électromagnétique innovant pour l'imagerie du sous-sol et la détection en milieu marin

Jean-François a reçu le prix lauréat toutes catégories confondues lors des NIDAYS le 12 Février 2013Article rédigé à la demande de National Instruments. Le système MAPPEM devrait permettre de mener à bien des campagnes de mesure sur des navires côtiersObjectif : développer un instrument basé sur l'imagerie électromagnétique pour pallier les limites des techniques classiques de prospection géophysique Solution : S'appuyer sur un système NI CompactRIO et NI LabVIEW pour faire l'acquisition rapide et simultanée de toutes les mesures, enregistrer et visualiser les données en temps réel à bord du navir

An electromagnetic-based streamer for near-shore investigations

International audienceWe developed an underwater electromagnetic-based streamer to image the near-shore marine substratum. The system was tested to assess its feasibility to map the electrical resistivity of the near-surface geological seabed. The results are very encouraging to describe the main lithology or to recover the position of buried large objects. We present results in various contexts (geology, pipeline detection, free gas hazard) and suggest a way forward for higher resolution and deeper investigation depth with respect to the actual system

Mapping the geometry of volcanic systems with magnetotelluric soundings: results from a land and marine magnetotelluric survey performed during the 2018-2019 Mayotte seismovolcanic crisis

International audienceA major seismovolcanic crisis has afflicted the islands of Mayotte, Comoros Archipelago, since May 2018, although the origin is debated. Magnetotellurics (MT), which is sensitive to hydrothermal and/or magmatic fluids and can map the subsurface electrical resistivity structure, can provide insight by revealing the internal structure of the volcanic system. In this paper, we report the results of a preliminary land and shallow marine MT survey performed on and offshore the island nearest the crisis. The 3D inversion-derived electrical resistivity model suggests that the island is underlain by a shallow ~500-m-thick conductive layer atop a deeper, more resistive layer, possibly associated with a high-temperature geothermal system. At depths of ~15 km, the resistivity drops by almost two orders of magnitude, possibly due to partial melting. Further petrophysical and geophysical studies are underway for confirmation and to map the geometry and evolution of the volcanic system

Test d'un prototype de gravimètre sous-marin pour AUV

International audienceRecherche fondamentale :- Etudes géophysiques- Amélioration des modèles de champ de pesanteur- Détermination et amélioration du géoïde terrestre(Densification des mesures gravimétriques, développement gravimètre mobile