ALBERT

Description: Between 07.10.2007 and 28.10.2007, bathymetric data was acquired in the Makran region during the R/V METEOR cruise M74/2. The subduction of the Eurasian plate beneath the Arab plate in the Makran Region is associated with continuous sediment input, active mud volcanism and fluid venting. The expedition was dedicated to the investigation of known seeps and the location of new venting sites. Furthermore, the scientists focused on the influence of extreme sediment thickness on the nature of vents and the relationship between local tectonics and spatial distribution of seeps. The multibeam echosounders (MBES) KONGSBERG SIMRAD EM120 and EM710 were utilized for large-scale mapping of vent-related structures on the seafloor. In order to visualize vent-related structures in the shallow subsurface, a deep-tow sidescan sonar, sediment echosounder and high resolution multichannel equipment were utilized. These acoustic methods were supplemented by video observations, gravity corer and multicorer samples, which yielded detailed information at many locations. CI Citation: Paul Wintersteller (seafloor-imaging@marum.de) as responsible party for bathymetry raw data ingest and approval. Description of the data source: During the M74/2 cruise, the hull-mounted KONGSBERG SIMRAD EM120 multibeam ecosounder (MBES) was utilized to perform bathymetric mapping. The system covers full ocean depth and transmits a nominal sounding frequency of 12 kHz. It generates 191 beams with a 1°(Tx)/2°(Rx) footprint and a maximum opening angle of 140°. For further information consult: https://epic.awi.de/26725/1/Kon2007a.pdf The acquisition mode was set to obtain equally spaced soundings on the sea floor. Yaw movements of the ship were compensated automatically by transmitting the swath perpendicular to the track rather than to the ship's axis. The opening angle was limited by either the maximum angle possible, a maximum angle set or a maximum coverage on the sea floor. Those values were adjusted to the requirements of the special surveys. For TOBI lines, which were 5.5 km apart, coverage was limited to obtain overlap at the edges of profiles. During transits in areas, which were covered before by the SIMRAD, swath widths were usually 6 km wide, on surveys over areas covered by data from previous cruises 7 km. Where no data were available at all, the full opening angle of 140° was set. Ship speed varied between 2.5 kn during TOBI profiles, 5 kn during seismic profiling, 8 kn for bathymetric surveys, and up to 12 kn during transits. A sound velocity profile for the cruise was delivered during the first CTD station. The depth of the water column is estimated through the two-way-travel time, beam angle and ray bending due to refraction in the water column by sound speed variations. Responsible person during this cruise / PI: Markus Brüning Chief Scientist: Volkhard Spiess (vspiess@uni-bremen.de) CR: https://www.tib.eu/en/search/id/awi%3Adoi~10.2312%252Fcr_m74/ CSR: https://www2.bsh.de/aktdat/dod/fahrtergebnis/2007/20080085.htm