Numerical modelling of stresses and deformation in Zagros-Iranian plateau region

Abstract. Zagros orogeny System resulted due to the collision of the Arabian plate with the Eurasian plate. The region has ocean-continent subduction and continent-continent collision, and subsequently, the convergence velocity varies from east to west. Therefore, this region shows the complex regime of tectonic stresses and a wide range of diffused or localized deformations. The in-situ stress and GPS data are very limited and sparsely distributed in this region; hence, we performed a numerical simulation of the stresses causing deformation in the Zagros-Iran region. The deviatoric stresses resulting from the variations in lithospheric density and thickness; and those from shear tractions at the base of the lithosphere due to mantle convection were computed using thin-sheet approximation. Stresses associated with both sources can explain various surface observations of strain rates, SH_max, and plate velocities; thus, suggesting a good coupling between lithosphere and mantle in most parts of Zagros and Iran. As the magnitude of stresses due to shear tractions from density-driven mantle convection is higher than those from lithospheric density and topography variations in the Zagros-Iranian plateau region, mantle convection appears to be the dominant driver of deformation in this area. However, the deformation in the east of Iran is caused primarily by lithospheric stresses. The plate velocity of the Arabian plate is found to vary along the Zagros belt from north-northeast in the southeast of Zagros to the northwest in northwestern Zagros, similar to observed GPS velocity vectors. The output of this study can be used in seismic hazard estimations.