Morphotectonic analysis of the East Anatolian Fault, Turkey

Abstract

The East Anatolian Fault (EAF) is a morphologically distinct and seismically active left-lateral strike-slip fault that extends for ~400 km and forms the Arabian/Anatolian plate boundary in southeastern Turkey. The EAF together with its conjugate fault, the North Anatolian Fault, help accommodate the westward escape of the Anatolian plate from the Arabian/Eurasian collision zone. Morphotectonic features along the EAF provide insights into the nature of landscape development and aid in understanding variations in tectonic activity and fault evolution. Several geomorphic indices, namely stream length-gradient index, mountain-front sinuosity, valley width to valley height ratio, basin asymmetry factor, and drainage density, and hypsometric analysis were examined using digital elevation models. The EAF can be divided into five segments based on its tectonic geomorphology. The stream length-gradient index values are between 50 and 350 along the five segments. Mountain-front sinuosity varies from 1.01 to 1.46 on the five segments. The mean ratio of valley floor width to valley height along the studied segments ranges from 0.11 to 1.32, which is well correlated with the mountain-front sinuosity values. Basin asymmetry factors for 18 catchments range from 1.88 to 26.25 along the study fault zone. Drainage density values for the studied catchments range from 3.5 to 5.6. Finally, the hypsometric analysis index of the 18 catchments indicates high, intermediate, and low relative tectonic activity. The results show that all geomorphic indices are remarkably uniform along the entire length of the fault, thus indicating that fault development was essentially coeval along its length, which supports the view that the present-day Arabian/Anatolian plate boundary (delimited by the EAF) jumped eastwards from the Malatya-Ovacık Fault at ~3 Ma. This is in good agreement with the nearly uniform geological offsets and the GPS-determined present-day slip rate of ~10 mm/year along the entire fault.