Variable coupling across weak oceanic transform fault: Flateyjarskagi, Iceland

Tectonic studies near major fault zones often reveal multiple tectonic regimes. Do these regimes indicate multiphase tectonism with distinct episodes, or do they reflect single-phase tectonism with time-space perturbations along lithospheric weakness zones? Based on tectonic analyses in Flateyjarskagi, North Iceland, we reconstruct the late Cenozoic tectonic regimes related to right-lateral transform motion along the Tjornes Fracture Zone, which connects the Kolbeinsey Ridge and the North Iceland Rift. Rifting and transform motion have induced eight normal and strike-slip regimes, four of which are inconsistent with the overall kinematics las a probable result of stress drop, elastic rebound and dyke injection). For the consistent regimes, contrasting angles between extension and transform trends reflect repeated changes from moderate (25 degrees) to very low mechanical coupling (85 degrees) across the transform zone. Thus, the tectonic regimes need not be interpreted in terms of numerous tectonic episodes but rather as a consequence of variable coupling across the transform zone.