HR: 1340h
AN: B43E-1659    [Abstracts]
TI: Acoustic detection of gas emissions within the submerged section of the North Anatolian Fault Zone in the Sea of Marmara
AU: Géli, L
EM: geli@ifremer.fr
AF: Ifremer, BP 70, Plouzané, 29280, France
AU: Henry, P
EM: henry@cdf.u-3mrs.fr
AF: CEREGE-Collège de France, Europôle de l'Arbois - BP 80, Aix en Provence, 13545, France
AU: Dupré, S
EM: stephanie.dupre@ifremer.fr
AF: Ifremer, BP 70, Plouzané, 29280, France
AU: Voelker, D
EM: dvoelker@ifm-geomar.de
AF: IFM-GEOMAR, Wischhofstrasse. 1-3, Kiel, 24148, Germany
AU: * Zitter, T
EM: zitter@cdf.u-3mrs.fr
AF: CEREGE-Collège de France, Europôle de l'Arbois - BP 80, Aix en Provence, 13545, France
AU: Le Pichon, X
EM: lepichon@cdf.u-3mrs.fr
AF: CEREGE-Collège de France, Europôle de l'Arbois - BP 80, Aix en Provence, 13545, France
AU: Tryon, M
EM: mtryon@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Drive, 0244, La Jolla, CA 92093-0244, United States
AU: Cagatay, N
EM: cagatay@itu.edu.tr
AF: Istanbul Technical University, Faculty of Mines, Geology Dpt, Maslak, Istanbul, 34469, Turkey
AU: Shipboard Science Party, M
EM: zitter@cdf.u-3mrs.fr
AF: CEREGE-Collège de France, Europôle de l'Arbois - BP 80, Aix en Provence, 13545, France
AB: The 38 kHz, single beam, echo-sounder SIMRAD EK-60 was operated during the Marnaut cruise (May-June 2007) onboard the RV L'Atalante to detect acoustic anomalies related to the presence of gas bubbles in the water column. In the south Cinarcik Basin, strong acoustic anomalies have been found along N140 normal faults within a 3 km wide swath oriented N100. The swath trend corresponds to the orientation of a buried fault system identified in MCS data (Carton and Singh, 2007). Ground-truthing of these anomalies with Nautile submersible enables the founding of gas seeps and bubbles emissions at seafloor. Acoustic anomalies are apparently weaker on the main fault scarp on the northern side of the Cinarcik Basin. In the Central High and Kumburgaz Basin, no acoustic anomalies were detected along the main fault trace. Instead, a cluster with very strong amplitude anomalies was identified at about 1 km away from the fault, on top of a broad anticline. On the Western High, a cluster of acoustic anomalies characterizes the top of an anticline located near 40°49'N, 28°46.8'E, where shallow gas hydrates have been sampled at unexpected water depth of 660 m, well outside the methane hydrate stability field. In the Tekirdag and Central basins, EK-60 lines were implemented along the fault scarps and the acoustic records indicate the presence of gas seeps at fault escarpments. This new set of data confirms previous results obtained with RV Le Suroit in September 2000 with a 112 kHz side-scan sonar towed 200 m above seafloor. Most active sites identified in 2000 were still active in 2007. We note that the only place where no acoustic anomaly was found on the main fault trace corresponds to the Central High and Kumburgaz Basin area. This segment did not rupture during the last century.
DE: 0416 Biogeophysics
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8106 Continental margins: transform
DE: 8135 Hydrothermal systems (0450, 1034, 3017, 3616, 4832, 8424)
DE: 8163 Rheology and friction of fault zones (8034)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting