The active Main Marmara Fault

This paper presents selections from and a synthesis of a high resolution ba thymetric, sparker and deep-towed seismic reflection data set recently acqu ired by the French Ifremer R. V Le Suroit in an E-W deep trough that forms the northern half of the Sea of Marmara in NW Turkey. It includes the first high resolution complete bathymetric map of this area. A single, throughgo ing dextral strike-slip fault system, which is the western continuation of the northern branch of the North Anatolian Fault, cuts this trough lengthwi se and joins the 1999.8.17 Kocaeli earthquake fault with the 1912.8.09 Sark oy-Murefte earthquake fault, both of which display strike-slip offset. In i ts eastern one fourth, the structure follows closely the northern margin of the deep trough, whereas in the west it hugs its southern margin. The east ern one fourth of the structure has a minor component of its displacement d istributed across the deep trough owing to a possible original bend in the course of the dextral structure. The present course of the North Anatolian Fault in the Sea of Marmara originated some 2 x 10(5) a ago, by cutting acr oss the older basin fabric generated by a dominant NNE-SSW extension before it began taking up major motion in the Pliocene. (C) 2001 Published by Els evier Science B.V.