The Sea of Marmara forms an active pull-apart basin developed along the North Anatolian Fault 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 M7+ 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. 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 150 km 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. The western end of the Marmara gap is constituted by the Ganos Fault, that ruptured in 1912. The study of this segment of the NAF system is the objective of MARM11 expedition.