Surface ruptures of historical earthquakes are partly visible along the northern side of the graben but most evidence for faulting no longer exists, either as a result of geological processes (erosion and sedimentation) or of man-made activity. The GPR method provided useful results, and we were able to identify the precise location of the most recent buried normal fault zone at two sites – Argavli (Fig. 2a) and Atc¸ a (Fig. 4a). In addition, the vertical displacement on each fault branch was estimated from disturbed reflectors on GPR profiles before trenching.