New geodynamic model for the South Caspian surroundings based on numerical modeling constrained by GPS and geological data

Over the last decade, GPS measurements in Iran, Azerbaijan, and adjacent regions have provided a direct quantification of the displacements of the earth surface in that region of the Arabia-Eurasia collision zone. We present an up to date velocity field in the southern Caspian region of the collision zone. A striking feature of the velocity field is the change in the azimuth of the velocity vectors across the Tabriz fault. Roughly northward motion south of the Tabriz fault changes to NNE motion north of the fault, with respect to Eurasia. We interpret the velocity field using an elastic block model to obtain an accurate kinematic model of this region of the collision zone. We use this kinematic model to constrain the boundary conditions for dynamic modelling. Our modelling studies indicate that indenter models can not account for the change in orientation of the velocity field of the NW Iran, the Lesser Caucasus and the Kura Basin, and that additional forcing is needed. We suggest that subducted oceanic crust beneath the Caucasus and the onset of subduction beneath the Apsheron-Balkan region could be contributing to the dynamics of this part of the collision zone.