Identification of a historical morphogenic earthquake through trenching at ancient Sagalassos (SW Turkey)

The Sagalassos Fault is one of the candidate faults for the devastating earthquakes that struck the ancient Pisidian town of Sagalassos, situated some 10 km SSW of Isparta (SW Turkey), early in the 6th century a.d . and in the middle or during the second half of the 7th century a.d . The Sagalassos Fault is an at least 150-m wide and ∼10 km long active normal fault zone, passing through and behind the ancient town. The southern base of the limestone cliff at the northwestern extremity of Sagalassos is believed to represent the strongly degraded master fault. The Sagalassos Fault Necropolis -trench, exposing this limestone face and its hanging wall deposits, reveals a fresh normal fault slip plane. Fault breccia, dip-slip frictional-wear striae, tool tracks, spall marks, dilational fractures and a flowstone are present on the excavated limestone face. Moreover, in the excavated part of the hanging wall, evidence of historical reactivation of the main fault has been inferred within anthropogenic deposits. The main argument is a 20-cm thick shear zone against the limestone face. This shear zone affects a man-made dump of the Early Imperial Period (ca. 25 b.c .–100 a.d .). The shear zone has an indurated and compact aspect, a parallel alignment of ceramic and limestone fragments, dip-slip striae and a vertical displacement of layers within the dump. The new findings of this study suggest that the surface-rupturing event identified may very well correspond to the 6th or 7th century earthquake, thus identifying a to date unknown seismically active and potentially hazardous fault in the Burdur–Isparta area.