Variation in fault-slip directions along active and segmented normal fault systems

Local fault-slip directions show a systematic variation over distances of 20–35 km along the active and segmented Gulf of Corinth normal fault system, central Greece. Where fault throws are large (several km) close to the centres of fault segment map traces, local fault-slip directions parallel the regional N-S (±20°) slip-vector azimuth interpreted from earthquake focal mechanisms. However, where fault throws are small (tens of metres) close to fault segment boundaries, local fault-slip directions are oriented ∼NE-SW when measured close to the western ends of fault segments, and ∼NW-SE close to the eastern ends of fault segments. Local fault-slip directions change by ∼90° across fault segment boundaries. It is suggested that fault-slip directions close to fault segment boundaries record local strain patterns at fault tips so that care should be taken when using this information during attempts to infer regional stress trajectories.