Geodesea-2019: une expérience de géodésie fond de mer en rade de Brest

Du 22 au 26 juillet 2019, dans le cadre du projet ERC FOCUS, le laboratoire Géosciences Océan (LGO) a organisé une expérience de géodésie fond de mer en rade de Brest, intitulée Geodesea-2019. Il s’agissait de tester les balises acoustiques acquises pour le projet FOCUS et de tester des protocoles expérimentaux de positionnement fond de mer. L’expérience a été réalisée à partir du navire de station Albert Lucas. Outre le LGO, ont participé à cette expérience la société IXblue et le Laboratoire Environnement et Sociétés de la Rochelle.

Pour plus d’informations sur les protocoles testés, le déroulement et les premiers résultats de cette expérience, consultez Geodesea-2019_FR (en français) ou Geodesea-2019_EN (in English).

Contact : J.-Y. Royer  (LGO)

 

Soutenances Master 1 Physique Marine

9h00 Chamorro Garrido Eva

Analysis of the influence of the marine traffic noise in whales trajectories

9h35 Gauvrit Edouard

Characterizing sub-mesoscale variability in the South-West Indian Ocean using in-situ and satellite data

10h10 Humblet Maelle

Caractérisation de signature en SSS des tourbillons des Aiguilles avec les données de satellites de SSS

10h45 L’Her Alexandre

Lagrangian study of Kamchatka eddies

11h20 Reinert Markus

Numerical Study of the Kamchatka Eddy

13h30 Gaillard Cécile

Projet d’étude des conditions de la dispersion océanique et de l’effet d’île aux Marquises

14h05 Laval Marine

Analyse de la distribution spatio-temporelle de franc-bord et volume des icebergs inférieur à 10 km autour du Groenland et de l’Antarctique de 2010 à 2018

14h40 Schweizer Ellen

Surface waves signature of small scale equatorial currents with application to SKIM satellite mission

15h30 Colin Line

Modélisation numérique des anomalies magnétiques au niveau de la zone de fracture de Saint Paul

16h05 de Lamotte Jean

Modélisation d’un système sous-marin soumis à l’action de la houle. Estimation de la part d’énergie récupérable (statique, dynamique, puissance capturée)

Séminaire de Nadine Tisnerat-Laborde (LSCE)

Visit to Nexans factory in Norway

On 21 June PI of ERC project FOCUS (Marc-André Gutscher) and ERC partner Lionel Quetel (IDIL) visited the Nexans cable factory in arctic Norway (Rognan). Here the 7.9 kilometer cable core can be seen, the armoring and cable jacket were completed in mid July. 1 kilometer of the completed cable will be shipped to IDIL in Lannion (France) in August and used to perform initial tests.

Séminaire de Eiichi Asakawa (J-MARES/JGI, Tokyo, Japan)

“Cross-ministerial Strategic Innovation Promotion Program (SIP)” was launched by the Council for Science, Technology and Innovation (CSTI) in 2014. It has addressed eleven issues selected considering the critical social needs. “Next-generation technology for ocean resources exploration (Zipangu in the Ocean) “is one of the SIP issues. In this project, we aim to establish the survey protocol for seafloor mineral resources and have been developing technologies for ocean resources exploration at efficient and low cost.

The primary target is seafloor massive sulphide (SMS). Many hydrothermal activities have been found in submarine volcanic areas distributed along the Izu-Bonin Arc and the Okinawa Trough in Japan. SMS ore deposits exist in deep water (>1500m) and the target depth is less than 50m below the sea bottom. Therefore the survey platforms that can reach close to the sea bottom, such as AUV and ROV, are important. For example, the technology of multiple AUVs operation using ASV enables us the efficient and minute bathymetry measurement that is the first step of SMS exploration in the deep-sea floor. Figure 1 shows the fleet of AUVs and the specifications developed by National Maritime Research Institute (NMRI) in SIP. Development of ROVs equipped with multipoint coring system and sonar imaging system enables efficient, low cost sampling.

In my presentation, I particularly focus on seismic surveys. High resolution seismic technologies are essential to investigate the concealed SMS ore deposit. Our patented technology, developed for high resolution seismic survey systems are shown in the Figure below. ACS is a survey system using a deep-towed streamer with surface and/or deep- towed seismic sources. We carry out ACS at the first stage of the exploration to extract possible hydrothermally active areas ranging from tens square kilometers. ZVCS consists of a deep-towed vertical receiver cable with surface and/or deep-towed seismic sources. There are two kinds of ZVCS, using deep-tow(ZVCS-DT) or ROV(ZVCS-R). Compared to ZVCS-DT, ZVCS-R enables high lateral density shooting and very flexible operation. As a second stage survey, ZVCS-DT and ZVCS-R are planned to narrow down the prospective areas which has been extracted by ACS. In 3DVCS, multiple vertical cables are moored on the seafloor. A circular shooting at the sea surface can clearly visualize detailed 3D sub-seafloor images. To obtain a precise depth image, a 3D pre-stack depth migration (3D-PSDM) is applied to the 3DVCS data. The velocity model for 3D-PSDM can be built by the velocity analysis of common scattering point gathers obtained by the equivalent offset migration and the result of refraction tomography.

 

21 juin 2019