Architecture of normal faults in the rift zone of central north Iceland

This work examines the architecture and propagation of normal faults that accommodate extension in the rift zone of central north Iceland. It is based on a structural study of portions of three grabens, their normal faults and dilational fractures in basaltic lavas of the Fremri-Namur and Dyngjufjِl volcanic systems. We analyzed the shape, throw and dilation along faults in order to infer their possible evolution. The shape of throw profiles departs from elliptical varying along each fault with throw being lower at the fault and segment tips. Propagation of fault segments is accommodated by dilational fractures nucleating at their respective tips. Segments link by lateral propagation of one or both tips or by the development of intervening linking segments. Two orders of fault segmentation indicate that the present throw accumulated by many increments as the fault scarps changed their geometries. Faults have large dilational components weakly correlated with fault throw and length.