Interactions between Eurasian/African and Arabian plates: Eskişehir Fault, NW Turkey

The Eskişehir Fault is an active right-lateral widespread intra-continental deformation zone which separates central western Anatolia from the Aegean domain. The inversion of fault slip vectors along the Eskişehir Fault yields a strike-slip stress state with NW-trending σ_Hmax (σ₁) and NE-trending σ_Hmin (σ₃) axes since the Early Pliocene. A change in strike-slip faulting under a compressional stress regime: from old transpression to young transtension, probably occurred in the Quaternary. The inversion of the earthquake source mechanism indicates that the transtensional stress regime continues up to the present. The İnönü and Eskişehir Basins developed under the transtensional stress regime producing consistent and local normal faulting with a continuing NE-trending σ_Hmin (σ₃). The stress regime change resulted in a decrease in σ_Hmax (σ₁) and/or an increase in σ_Hmin (σ₃) stress magnitudes due to coeval influence of the superimposed plate forces and the interaction of three plates (Eurasian/African/Arabian): (1) continental collision of Eurasian/Arabian plates with Anatolian block in the east, (2) westward escape of the Anatolian block by anticlockwise rotation at the west-southwest border of the Eurasian and Arabian/African plates and (3) a complex subduction process between African and Eurasian plates along the Aegean (Hellenic) and the Cyprus arcs which favors western extrusion of the Anatolian block in the eastern Mediterranean region.