Active normal faulting in central Greece: an overview

Abstract Rapid extension in central Greece is accommodated by large active normal faults that largely control the geomorphology. The faults bound graben whose asymmetry is evident in the topography, bathymetry, vertical movements of the coastline and tilting of Neogene sediments adjacent to them. Graben up to 20 km in width appear to be simple half-graben, whereas the hangingwalls in wider graben are generally broken by faults antithetic to the major bounding faults. The graben form basins up to 100 km long, but the faults bounding these basins are segmented, with individual segments no longer than about 20 km. The fault segments step en echelon or change polarity along strike of the large basins, but are not linked by simple strike-slip (‘transfer’) faults: the regions between the main fault segments appear to be pervasively deformed by numerous small faults. Drainage in central Greece is controlled by fault segmentation and footwall lithology. Where footwalls consist of Mesozoic limestone the drainage is often axial, breaking through the fault system into the main basin by flowing round the ends of fault segments or through gaps where the fault segments step. In such places, drainage directly off the fault scarps is relatively minor, and the fault segmentation controls the spacing of major fans along the basin margin. Where footwalls consist of Neogene sediments, drainage may flow directly across the fault scarp, though in such cases the catchment areas are relatively small and linear. The origin of the fault segmentation is unclear, but may be related to rotations of the fault-bounded blocks about horizontal and vertical axes.