STRUCTURAL RELATIONSHIP BETWEEN THE SEA OF MARMARA BASIN AND THE NORTH ANATOLIAN FAULT ZONE

The North Anatolian Fault (NAF) zone is 1500 km long, extending almost up to the Greek mainland in the west. It is a seismically active righ t-lateral strike-slip fault that accommodates the relative motion betw een the Turkish block and Black Sea plate. The Sea of Marmara Lies alo ng the western part of the NAF and shows evidence of subsidence. In th is area pure strike-slip motion of the fault zone changes into extensi onal strike-slip movement that is responsible for the creation of the Sea of Marmara and the North Aegean basins. The northern half of the S ea of Marmara is interpreted as a large pull-apart basin. This basin i s subdivided into three smaller basins separated by strike-slip fault segments of uplifted blocks NE-SW. Basinal areas are covered by horizo ntally layered sedimentary sequences. Uplifted blocks have undergone c ompressional stress. All the blocks are subsiding and are undergoing v ertical motions and rotations relative to one another. The uplifted bl ocks exhibit positive Bouguer gravity anomalies. According to gravity interpretation, there is relative crustal thinning under the Sea of Ma rmara. The northern side of the Sea of Marmara is marked by a distinct ive deep-rooted magnetic anomaly, which is dissected and shifted south ward by strike-slip faulting. The southern shelf areas of the Sea of M armara are dominated by short-wavelength magnetic anomalies of shallow origin.