The İznik Basin is an active depression created by a series of faults developed in relation to th... more The İznik Basin is an active depression created by a series of faults developed in relation to the Middle Strand of the North Anatolian Fault (NAFMS). The most important of these faults is the oblique Sölöz fault, which runs parallel to the NAFMS. It is interpreted as a releasing bend, and plays a crucial role in the evolution of the 75-m-deep ellipsoid-shaped depression in the southern part of the lake. The faults that limit the coastal alluvial plain on land, some of which developed during the early evolution of the NAFMS, are equally important in the development of the İznik Basin, and correspond to P-shear or secondary synthetic shear faults. These faults are cut by the main fault zone and are right-laterally displaced by approximately 7-8 km. Considering an annual slip rate of 2 mm on the fault, such a displacement is only possible in a time span of 3.5 to 4 million years. An earthquake periodicity of 2000-2500 years is estimated on the basis of recent GPS data, and a limited number of historical earthquakes. Linear terraces observed on the northern and western parts of the Lake İznik, which have been affected by tectonic activity, show occasional rises of the lake level. The seismic data show that the lake level was approximately 40 m below its present level during the last glacial period.
Erdek Bay is located at the SW corner of the Sea of Marmara, separated from the Bandırma and Geml... more Erdek Bay is located at the SW corner of the Sea of Marmara, separated from the Bandırma and Gemlik depressions by a triangular and dome-like shape peninsula which is connected to the mainland by two coastal spits. The bay also divides two main dextral strike-slip strands of the North Anatolian fault system. The moment tensor solutions of the earthquakes to the north of the Marmara Islands, which are scattered at the northern margin of the Erdek Bay, indicate normal faulting with oblique components, contrary to those of the main strike-slip faults. The relative rise in sea-level at the Erdek permanent tide gauge station, located at the southern margin of the Kapidag Peninsula, is high. This may indicate a land subsidence which may be local or regional. The findings on recent crustal deformation (thinning) and strain accumulation in the Sea of Marmara region, however, are not sufficient to represent the vertical movements in detail. The suspended valleys and marine terraces of the Kapidag Peninsula imply that a tectonic uplift is evident at least along the northern coasts. Considering that the subsidence at the sea-level station is not a local event then the Kapidag Peninsula should be tilting southward. In 2010 summer, the signatures of these tectonic evolutions were sought in the Erdek Bay using new Chirp seismic data. Some deformed structures and unknown faults severely affecting the seismic stratigraphic units were detected and considered in the explanation of vertical tectonic movements in the region.
The İznik Basin is an active depression created by a series of faults developed in relation to th... more The İznik Basin is an active depression created by a series of faults developed in relation to the Middle Strand of the North Anatolian Fault (NAFMS). The most important of these faults is the oblique Sölöz fault, which runs parallel to the NAFMS. It is interpreted as a releasing bend, and plays a crucial role in the evolution of the 75-m-deep ellipsoid-shaped depression in the southern part of the lake. The faults that limit the coastal alluvial plain on land, some of which developed during the early evolution of the NAFMS, are equally important in the development of the İznik Basin, and correspond to P-shear or secondary synthetic shear faults. These faults are cut by the main fault zone and are right-laterally displaced by approximately 7-8 km. Considering an annual slip rate of 2 mm on the fault, such a displacement is only possible in a time span of 3.5 to 4 million years. An earthquake periodicity of 2000-2500 years is estimated on the basis of recent GPS data, and a limited number of historical earthquakes. Linear terraces observed on the northern and western parts of the Lake İznik, which have been affected by tectonic activity, show occasional rises of the lake level. The seismic data show that the lake level was approximately 40 m below its present level during the last glacial period.
Erdek Bay is located at the SW corner of the Sea of Marmara, separated from the Bandırma and Geml... more Erdek Bay is located at the SW corner of the Sea of Marmara, separated from the Bandırma and Gemlik depressions by a triangular and dome-like shape peninsula which is connected to the mainland by two coastal spits. The bay also divides two main dextral strike-slip strands of the North Anatolian fault system. The moment tensor solutions of the earthquakes to the north of the Marmara Islands, which are scattered at the northern margin of the Erdek Bay, indicate normal faulting with oblique components, contrary to those of the main strike-slip faults. The relative rise in sea-level at the Erdek permanent tide gauge station, located at the southern margin of the Kapidag Peninsula, is high. This may indicate a land subsidence which may be local or regional. The findings on recent crustal deformation (thinning) and strain accumulation in the Sea of Marmara region, however, are not sufficient to represent the vertical movements in detail. The suspended valleys and marine terraces of the Kapidag Peninsula imply that a tectonic uplift is evident at least along the northern coasts. Considering that the subsidence at the sea-level station is not a local event then the Kapidag Peninsula should be tilting southward. In 2010 summer, the signatures of these tectonic evolutions were sought in the Erdek Bay using new Chirp seismic data. Some deformed structures and unknown faults severely affecting the seismic stratigraphic units were detected and considered in the explanation of vertical tectonic movements in the region.
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