The Sea of Marmara lies between the Aegean Sea and the Black Sea (Fig. 1). It forms an active system of pull-apart basins developed along the NAF system, that extends east-west for over 1600 km across Turkey and is one of the world's major continental transforms. Earthquake epicenters and focal mechanism solutions in western Anatolia show a clustering on or near the major faults. A sequence of eight M > 7 earthquakes has ruptured this boundary progressively from east to west during the last century. The most recent and westernmost events in this sequence, the M7.4 Izmit and M7.1 Duzce mainshocks in 1999, were particularly destructive [5]. Together they ruptured about 160 km of this fault system including the submarine portion of the fault in the Gulf of Izmit, eastern Marmara Sea. Relatively little strain, however, is thought to have been released by earthquakes along 150km of the transform through the Marmara Sea since the mid 1700's. This portion of the transform is, therefore, identified as a seismic gap where accumulated elastic strain is about as much as it was released by slip in the 1999 sequence.
After the 1999 disastrous Izmit and Durce earthquakes east of the Gulf of Izmit, the international community is facing the attempt to produce maps of the fault distribution in the Sea of Marmara. None of the conducted surveys attempted to study the seismogenic behaviour of the fault system in the Marmara Sea. We believe that an integrated approach involving the acquisition and analysis of geophysical (multibeam, side-scan sonar, chirp), geological (cores) and seismological data would represent an innovative strategy in the emerging field of "submarine earthquake geology" to assess the seismic hazard in the Marmara region. The project involves geological/geophysical surveys combining Multibeam, side-scan sonar maps and chirp sub-bottom profiles with carefully positioned core samples to resolve the shallow geometry and kinematics of portions of the fault system in the northeastern Marmara Sea.
We expect to resolve fault geometry and kinematics and to date their most recent ruptures at the same scale as typical paleoseismic studies on land. We will be guided by previous and ongoing projects studying larger scale and deeper characteristics of the fault system in the Sea of Marmara.
The principal objectives are:
To tackle these objectives an international collaboration between LDEO,TUBITAK, and IGM-CNR was set and resulted with an integrated research project in the area. Being widely recognized the importance of accurate morphobathymetric and SBP investigations, we decided to invest into a preliminary survey, to be done with R/V Odin Finder, operated by GAS, a very well equipped geophysical vessel. This survey was scheduled for high resolution MultiBeam bathymetry, SBP and SSS and some cores. At the same time, we applied for a one month ship time at italian CNR, who operates R/V Urania. This cruise would have further completed SBP and SSS imaging, other than better targeted corings and ROV investigations.
This paper reports the shipboard activities during the cruise MARM2000, which took place during late October-early November 2000 with R/V Odin Finder.
figure
During this 7-days cruise in the area we focused on multibeam bathymetry, SBP and SSS, to study four areas of the Continental shelf and slope in the Eastern Sea of Marmara (Fig. 1:
figure
The accurate bathymetric DTMs, DGPS and HPR positioning and ship's DP capabilities were used also to recover some cores strategically positioned along the SBP profiles that crossed the faults. A particular focus was put on area D, which lies directly on the NAF.
The cruise started in Siracusa 26-oct-2000 and ended in Messina 7-nov-2000. Weather conditions were good and no stand-by meteo occured.
Hereafter, a description of the equipment and of their usage is given, along with details of the general setting, performances and results (Chapter 4).
