Summary of Marsitecruise

The scientific cruise MARSITECRUISE of R/V Pourquoi pas? Took place from 28 October to 17 November 2014. Part of the operations were carried out within the frame of the MARSITE programme supported by the European Union, which aims at better understanding the behaviour of the North Anatolian fault in the Marmara sea in view of improving the assessment of the seismic hazard weighing on the Istanbul region. Coordinated by the Observatory of the University of Kandilli (KOERI, based in Istanbul), MARSITE groups 23 partners and includes different components: land, spatial and marine. The marine operations of the programme were coordinated by Ifremer and conducted using Italian (R/V Urania) and French (R/V Pourquoi pas?) naval means.

During the first part of the cruise (28/10 to 1/11, 2014), 10 geodetic acoustic stations were deployed on the seafloor to measure directly the relative plate motion along the submerged part of the North Anatolian Fault. Four stations were implemented by the "LDO : Laboratoire Domaines Océaniques” from Brest ; the six others by Geomar. The stations have been designed to remain 3 years on the seafloor. Visits are programmed every six months, using Turkish naval means, to check their functioning and to collect data.

During the second part of the cruise (2/11 to 13/11), the ROV VICTOR 6000 was deployed in order to collect in situ samples and measurements (interstitial waters, gas, brines, oil) to understand the migration of fluids along the faults. During Leg 2, 5 ROV dives were conducted (for a total of 148.4 hours) resulting in 18 gas samples, 28 Raman measurements and 41 measurements of gas flow, 35 interface corers and 2 blade corers for geomicrobiology, 7 Titanium seringues to study rare gases. A total of 12 long Calypso sediment cores were made to analyse deep interstitial fluids and 8 CTD associated with the evaluation of 2 methane captors for the geochemical evaluation of plumes observed during acoustic surveys of the water column. The success of in situ Raman spectroscopic measurements is novel at Ifremer ; this is the second only success of such an experiment on a world scale and opens doors to a new in situ gas sampling strategy. Finally, a unique experiment, initially programmed for Leg1, was accomplished. An acoustic bubble detector (BOB) and two seabed seismographs were deployed by ROV/VICTOR to study the phenomena of natural degassing of methane on the seafloor.

The third part of the cruise (13-16 November) had a double objective: i) acquire sediment cores in key sites for paleoseismic studies aiming to specify the recurrence rate of earthquakes in the Marmara sea; ii) recover INGV and Ifremer instruments deployed during previous operations within MARSITE.

The MARSITECRUISE is the result of collaboration between 16 partners: Ifremer; 7 CNRS laboratories (IUEM-Brest, CEREGE-Aix-en-Provence, ITER-Grenoble, LOCEAN-Paris, CRPG-Nancy, MNHN Paris,LIENSs); INGV (Italy); Geomar (Kiel); ITU (Istanbul); KOERI (Istanbul); MTA (Ankara); DEU (Izmir); Beijin University (China) and the University of Munster (Germany).

Organization of the present report.  The MARSITE Cruise report includes 3 volumes:

- Volume 1 describes the different deployments and recovery operations that were completed during legs 1, 2 and 3 of the MarsiteCruise. The final coordinates presented in this report have been checked. These coordinates are thus to be considered as final and definitive.

-Volume 2 provides updated details on the geochemical sampling completed during Leg 2.

- Volume 3 provides updated details on the sediment sampling completed during Legs1 and 3 for seismo-stratigraphy purposes. The updated, final coordinates of the sediment profiler lines are also provided.

Note : This the final report that was officially transferred to the Turkish authorities (SHOD) 6 months after the completion of the cruise. It is thus named « six-months report ».