The mechanical interaction between the propagating North Anatolian Fault and the back-arc extension in the Aegean

We use fracture mechanics concepts to analyse the large-scale deformation of Anatolia and the Aegean. Our purpose is to characterize the process of propagation of the North Anatolian Fault (NAF). Our approach incorporates long-term geological constraints in dislocation modelling of present-day GPS velocities that allows for internal deformation in regions between major structures. Unravelling the superposition of two deformation fields now interacting in the Aegean (propagating NAF and back-arc extension) permits us to characterise the large-scale damage zone at the western end of the NAF and to determine slip rates for the main structures. The contemporary slip-rate profile of the NAF shows that it apparently behaves like a transform fault for 75% of its length. The process zone corresponds to a rapid southwestward tapering of the NAF slip rate. Modelling slip-rate distributions for the NAF under stress-free conditions shows that the development of the process zone depends on the boundary conditions imposed at the Hellenic arc. Our stress-free modelling suggests a scenario for the evolution of the NAF: (1) At an earlier stage before the NAF had reached the Aegean, it was not under the influence of Hellenic arc-pull. Its slip-rate profile is modelled to have a half-elliptical shape corresponding to a crack in elastic solid and an elastically strained Anatolian lithosphere. (2) The present-day NAF penetrates the Aegean and a large process zone has developed due to interaction with the Aegean extension and the Hellenic arc-pull. Elastic strains in the Anatolian lithosphere are relaxed and the NAF resembles a transform fault. The models that we present suggest that changes in subduction zone behaviour should influence all of the boundaries associated with Anatolian extrusion.