3d Mechanical Modeling of The Seismic Cycle Along The North Anatolian Fault

The North Anatolian fault (NAF) is part of a complex tectonic setting that extends over 2000 km, and is one of the most seismically active continental regions of the world with a long and well documented history of earthquakes. It thus constitutes an ideal natural laboratory for the study of earthquake cycles along a major fault system. Using the 3D finite element code ADELI (Hassani et al. 1997) we model the seismic cycle along the NAF and we investigate the influence of the rheology of the lithosphere on postseimic deformation. Fault motion is controlled by a Coulomb type friction, and the rheology of the lithosphere is composed of a frictional upper crust and a viscoelas- tic lower crust and mantle. The lithosphere is supported by a hydrostatic pressure at its base (representing the underlying asthenosphere). In a first step we developed a model of the long term deformation of the surroundings of the fault system by adjusting fric- tional and viscous parameters that control the resulting velocity and stress fields in the deforming Anatolian model. We compare the results thus obtained with geodetic measurements (i.e. McClusky et al., 2000) and tectonic observations to define a real- istic long term model. A second step consist of modeling the seismic cycle in itself. We simulate successive earthquakes on the NAF by varying friction over time. Doing so we introduce a finite dislocation on the surface of the fault at a certain period of the deformation process, representing the occurrence of the earthquake. We chose to illustrate the postseismic response to the solicitation imposed on the fault system by the 1939 event, for different types of rheology obtained in the first step.