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. (C) 2004 Elsevier B.V. All rights reserved.