Extension of the North Anatolian Fault into the North Aegean Trough: Evidence for transtension, strain partitioning, and analogues for Sea of Marmara basin models

The North Aegean Trough is tectonically controlled by the projection of the North Anatolian Fault from western Turkey and the Sea of Marmara into the Aegean, where deformation is distributed in contrast to the simple strike-slip fault model for central eastern Turkey. This region accommodates extensional and dextral displacement. New side-scan sonar data coupled with new subbottom profiler and published seismic data reveal evidence for dextral displacement within the eastern trough and Gulf of Saros in the form of oblique en echelon and Riedel (R, R', and P) fractures and displaced geomorphic features. Strain partitioning in the shallow crust allows the following two styles of faulting to coexist, supported by earthquake focal mechanisms: (1) transtensional basin-bounding faults controlling the significant vertical topography of the basin and (2) dextral faulting within the central basin. These styles of faulting merge at greater depths into a single fault. A possible sinistral NW striking fault separates two subbasins and may indicate crustal block rotation with deformation focused in block corners. Such evidence and models from the north Aegean are similar to models of transtension and pull-apart basins within the Sea of Marmara.