ANR BASILIZNIK-SECRETS

The famous city of Nicaea (now Iznik) was established on the shore of the Lake Iznik (Turkey), 5 km north of the active Middle segment of the North Anatolian Fault (MNAF). In May 325 AD, the city has hosted the first Council of Christians, the founding event of Christian religions. The location of this council remained unknown until Prof. M. Şahin discovered a basilica in the Lake Iznik in 2014 (under 1.5 m of water and 50 m from shore). The basilica was destroyed and submerged after an unknown catastrophic event, probably an earthquake, as suggested by the damage observed on the city’s archaeological remains. Six large earthquakes (Mw>7) were documented in the past 2500 years according to the texts and archaeo-sismotectonic studies carried out in the Iznik region. Seismic hazard remains poorly assessed on the MNAF, as no earthquake was documented over the last 150 years. The horizontal slip rate on the MNAF (5 mm/yr) is four time lower than the one on the northern segment NNAF, which explain its lower seismicity level, and a long recurrence time (>500 yr) between earthquakes. Two super-shear earthquakes (with a break propagation faster than the speed of sound) were described along the NNAF during the Izmit and Düzce earthquakes, 1999. This type of earthquake is very destructive, often associated with soil liquefaction. It is important to know if such earthquake could have destroyed in Nicea basilica and to better characterize the MNAF seismic behaviour on a long-time scale.

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