Plio-Quaternary stress states along the Kutahya Fault and surroundings, NW Turkey

Abstract

The Kutahya Fault, which is one of the major neotectonic structures in western Anatolia, Turkey, is an active fault constraining the southern margin of the approximately E-W trending Kutahya Basin between the Eskisehir Fault to the north and the Simav Fault to the south. In the present study, inversion of both fault kinematic analysis of fault-slip data and focal mechanism solutions from the Kutahya Fault and surroundings is used to understand the Late Cenozoic stress states. The fault kinematic analysis result yielded three different stress regimes from Mio-Pliocene to Quaternary. Firstly, strike-slip faulting developed under a NE-SW trending local compressional regime with 51 degrees +/- 24 degrees (sigma(1)) and 140 degrees +/- 7 degrees (sigma(3)) trends and R-m ratio was calculated as 0.61, consistent with this faulting. NW-SE trending consistent extensional direction produced local normal faulting with 144 degrees +/- 3 degrees (sigma(3)) trend. Secondly, strike-slip faulting developed under a NW-SE trending local compressional regime showing 143 degrees +/- 17 degrees (sigma(1)) and 51 degrees +/- 10 degrees (sigma(3)) trends and R-m ratio was calculated as 0.51. Finally actual normal faulting developed under a NNE-SSW trend with a regional extensional direction showing 42 degrees +/- 14 degrees (sigma(3)) and R-m ratio of 0.56 at the present time. Inversion of the earthquakes gives a NNE-SSW extension direction with 21 degrees +/- 19 degrees (sigma(3)) trend and R. ratio calculated as 0.68 at the triaxial. The Kutahya Fault and surroundings are under an extensional regime at the present time. The reason for the regionally effective NNE-SSW trending extensional regime in western and southwestern Anatolian is complex subduction processes (roll-back, retreat, delamination, slab-tear, slab-break-off and/or slab-pull) of the African Plate and the Anatolian Platelet in the Mediterranean region.