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

• Late Cenozoic to present day stress states by inversion and kinematic analysis of the fault-slip vectors and earthquakes.
• A temporal and spatial tectonic regime change in strike slip faulting from transpressional to transtensional due to increase and/or decrease of stress magnitudes (Sigma 1, 2 and 3).
• Lateral extrusion and anticlockwise block rotation of Anatolian block to westward from Eurasian/Arabian continental collision in eastern Anatolia.
• A complex interaction (roll-back, slab-pull and/or slab break-off) to Eurasian/African plate convergence in eastern Mediterranean.
• The active Eskişehir Fault is a right-lateral strike-slip fault presented in a transtensional tectonic regime in present day.

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 σHmax (σ1) and NE-trending σHmin (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 σHmin (σ3). The stress regime change resulted in a decrease in σHmax (σ1) and/or an increase in σHmin (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.