Migration of activity within normal fault systems: examples from the Quaternary of mainland Greece

We examine five areas of mainland Greece where active extension occurs on s ub-parallel systems of normal faults, and where geomorphological and strati graphic evidence indicates that the faulting has migrated basinwards into t he original hanging walls. in several cases within the late Quaternary. By comparing fault slip rates estimated from geomorphological data with curren t extension rates known from geodetic measurements, it appears that the new est faults can account for effectively all the present-day motions. Fault m igration of this sort is easy to recognize in young systems close to sea le vel, because vertical movements of footwalls and hanging walls are obvious and reveal which faults are currently most active, but is less easy to conf irm away from reliable reference levels or in older terrains with poorer ti me resolution. It ii probably more common than is appreciated, and has a pr ofound effect on syn-rift sedimentation and erosion patterns. Fault migrati on is probably an inevitable consequence of the interplay between stresses generated by the fault-related topography and the ultimate strength of majo r faults. It is likely to be further encouraged in places where lower crust al flow or rotations about a vertical axis are important. However, it is no t clear why migration should preferentially occur into the hanging walls, a s observed in central Greece. (C) 2001 Elsevier Science Ltd. All rights res erved.