Quaternary stress regime change along the eastern North Anatolian fault zone, Turkey

Abstract

The North Anatolian fault zone (NAFZ) is a major dextral strike-slip fault extending about 1400 km from Karliova in the east to Saros Gulf in the northern Aegean domain. Fault kinematic inversion results from the easternmost segment show two distinct strike-slip stress regimes with consistent NNW-trending (sigma(1)) and ENE-trending (sigma(3)) axes: the mean arithmetic R-m ratios are 0.68 and 0.17 for the older transpressional and the younger transtensional stress regimes, respectively. This change in strike-slip regime is confirmed by different R values and the chronologies of cross-cutting striations. Both strike-slip stress regimes reflect dextral movement along the major trace of the NAFZ. Together with the sinistral East Anatolian fault zone, this motion contributes to the westward extrusion of Anatolia as a consequence of northward motion of the Arabian plate. A change in stress regime from transpressional to transtensional was related to the combined effects of continental collision in the east, the westward motion of the Anatolian block, and subduction along the Aegean zone in Southwestern Anatolia.