Geomorphic and structural variations along the Doruneh Fault System (central Iran)

This paper focuses on the analysis of geomorphic, structural, and behavioral characteristics along the Doruneh Fault System (DFS), east of longitude 56 degrees 45'E. Detailed geomorphic and structural analyses of different scale satellite images and digital topographic data, accompanied with field surveys allowed us to establish a fault segmentation model in which three discrete fault zones have been recognized: (1) the western fault zone (WFZ) characterized by reverse left-lateral mechanism with left-handed step-over geometry, (2) the central fault zone (CFZ) which is pure left-lateral strike-slip and comprises nearly parallel faults, and (3) the eastern fault zone (EFZ) that is a trailing imbricate fan fault-termination characterized by reverse faulting and fault-related folding. Each fault zone shows discrete geometry and kinematics implying that deformation is not uniformly accommodated along the DFS. We propose a new kinematic model to explain how the DFS accommodate the Arabia-Eurasia convergence normal to the overall fault orientation. According to this model, the DFS takes up the northward motion between central Iran-Lut block relative to Eurasia by a complex kinematics varying from pure reverse to pure left-lateral strike-slip faulting. The kinematics of the WFZ and EFZ corresponds to the direction of the NE-trending regional compression. While, the partitioning of slip into strike-slip and reverse component of faulting on parallel faults (strain partitioning) allows the CFZ to remain pure left-lateral strike-slip. Such a model propose a way to explain how large strike-slip faults such as the DFS accommodate tectonic block motions perpendicular to strike of the faults.