The Northwest Central Anatolian Contractional Area: A neotectonic deformation zone bounded by major strike-slip fault zones in the Anatolian Plate

Abstract

Turkey is a part of the Tethyan orogenic belt, which is one of the most tectonically active regions on Earth where the African, Eurasian, and Arabian plates interact with each other. The Anatolian plate is bounded by the right-lateral North Anatolian Fault Zone to the north, the left-lateral East Anatolian Fault Zone to the east and southeast, and the Aegean-Cyprus subduction zone to the south and southwest. In addition to these boundary fault zones, the Anatolian plate is affected by many intracontinental fault zones including the right-lateral Eskişehir and Kırıkkale-Erbaa strike-slip fault zones in northwest central Anatolia. In this study, a triangle-shaped area between the North Anatolian, Eskişehir, and Kırıkkale-Erbaa fault zones has been defined as the ‘Northwest Central Anatolian Contractional Area’. This area includes the contractional Beypazarı Blind Thrust Zone, Abdüsselam Pinched Crustal Wedge, and Eldivan-Elmadağ Pinched Crustal Wedge from west to east, respectively. Our geological and geophysical observations, focal mechanism solutions of the earthquakes, and the National Geodetic Network (TUTGA)-based GPS strain analysis demonstrate that the whole triangle-shaped area between the major strike-slip fault zones is under the effect of the active northwest-southeast contractional tectonic regime. This conclusion is different than the previous studies which suggest an active extensional regime for the region. The reason of the contraction of the area between the major strike-slip fault zones could be a complex interaction between the nearly north-south contraction in eastern Anatolia and north-south extension in western Anatolia, and the westward movement and counterclockwise rotation of the Anatolian plate.