The North Anatolian Fault in the Region of Iznik (Turkey) : Geomorphological Evolution and Archeoseismicity

Abstract:

This work based on a pluridisciplinary approach coupling earth sciences and archaeology aims to study the recent tectonics along Iznik Lake, which follows the North Anatolian fault middle strand (NAFMS), south of the Marmara Sea in Turkey. Today this strand records a low seismicity and presents a lower slip rate (<5 mm/yr) than the northern strand . However, historical texts suggest a significant earthquake hazard over the last two millennia in this area. Data are needed to attest for the tectonic origin of the lake and the precise location of the faults. Long-term slip rates and stress accumulation on these faults zone are also unknown, which makes it difficult to estimate seismic hazard. The main goal of this work is to collect new data on the past activity of the NAFMS and to estimate slip rates at different time scales. For this, we observe geomorphic and archeological markers of past deformation.

The main fault zones were identified using a high resolution DEM (<2m) derived from Pleiades images, and confirmed on the field. These faults intersect and deform geomorphic features, such as terraces, paleoshorelines, alluvial fans.... Terraces deposited by Iznik Lake during high stands, which were tilted and crossed by several faults, were sampled for dating in order to constrain the normal and strike-slip Quaternary slip rate of the faults and their influence on the lake formation. The valley of Kirandere river east of Iznik presents many deflected and offset rivers and ridges, that will be used to constrain a Holocene strike-slip rate. To document the historical activity of the NAFMS around Iznik, we have identified ancient buildings that underwent successive damages and repairs and characterized them through an archeoseismological approach. We particularly studied the roman aqueduct of Iznik which is cut and deformed by a small fault.