Morphologic features of the Marmara Sea from multi-beam data

The bathymetrical image of the Marmara Sea (NW of Turkey) was prepared, using data from mainly multi-beam surveys and from various other sources. The Marmara Sea presents a unique and complicated morphological system, which is mainly controlled by the active tectonic regime of the North Anatolian Fault Zone (NAFZ). The sub-bottom morphology of the Marmara Sea consists of a wide shelf area (55% of the total area) and the Marmara Trough, which includes the slopes, ridges and deep basins. The four basins separated by ridges constitute the E-W trending Marmara Trough in an elliptical form. Submarine canyons and landslides constitute the secondary morphological units of the Marmara Sea. The angle and the shape of the slopes are variable in different parts of the Marmara Sea. The linear-shaped slopes bounding the Cinarcik Basin (eastern extremity of the Marmara Sea) and off the Ganos Mountain System (west of Marmara Sea) are characteristic with their high gradient, and resulted from strike-slip fault. The curve-shaped slopes with low angles are considered to be associated with normal fault. E-W-aligned lineaments are morphological expressions of strike-slip faults and can be traced from the Ganos Mountain System through Qmarcik Basin, cutting through the basins and ridges in the western Marmara Trough, and bounding the Cinarcik Basin at the slope-basin transitions. These lineaments reflect a new rupture of NAFZ and must have occurred after the formation of the Marmara Trough. (C) 2002 Elsevier Science B.V. All rights reserved

Active tectonics of the Izmit Gulf (NE Marmara Sea): from high resolution seismic and multi-beam bathymetry data

Several active faults were determined in the Gulf of Izmit, using high-resolution shallow seismic and multi-beam bathymetry data. One of them is a buried fault (Fault 2), following central axis of the gulf which forms the current morphology within its releasing and restraining bends. Releasing bends control the current morphology of the sub-basins. Also restraining bends form folds in the central basin and a thrust in the western basin. A left step over between two strike-slip faults (Faults 2 and II) creates a transpressional area. Therefore, Hersek and Catal deltas are uplifted

Evidence of NW extension of the North Anatolian Fault Zone in the Marmara Sea: a new interpretation of the Marmara Sea (Izmit) earthquake on 17 August 1999

Active faults aligning in NW-SE direction and forming flower structures of strike-slip faults were observed in shallow seismic data from the shelf offshore of Avcilar in the northern Marmara Sea. By following the parallel drainage pattern and scarps, these faults were traced as NW-SE-directed lineaments in the morphology of the northern onshore sector of the Marmara Sea (eastern Thrace Peninsula). Right-lateral displacements in two watersheds of drainage and on the coast of the Marmara Sea and Black Sea are associated with these lineaments. This right-lateral displacement along the course of these faults suggests a new, active strike-slip fault zone located at the NW extension of the northern boundary fault of the Cinarcik Basin in the Marmara Sea. This new fault zone is interpreted as the NW extension of the northern branch of the North Anatolian Fault Zone (NAFZ), extending from the Cinarcik Basin of the Marmara Sea to the Black Sea coast of the Thrace Peninsula, and passing through Buyukcekmece and Kucukcekmece lagoons. These data suggest that the rupture of the 17 August 1999 earth-quake in the NAFZ may have extended through Avcilar. Indeed, Avcilar and Izmit, both located on the Marmara Sea coast along the rupture route, were strongly struck by the earthquake whereas the settlements between Avcilar and Izmit were much less affected. Therefore, this interpretation can explain the extraordinary damage in Avcilar, based on the newly discovered rupture of the NAFZ in the Marmara Sea. However, this suggestion needs to be confirmed by further seismological studies