A 2,500 YEAR-LONG PALEOSEISMIC RECORD OF LARGE EARTHQUAKES ON THE NORTH ANATOLIAN FAULT AT YAYLABELI, TURKEY

As part of our ongoing analysis of the paleo-earthquake history of the North Anatolian fault (NAF) in Turkey, we excavated four fault-perpendicular trenches at Yaylabeli (aka Lorut) along the eastern part of the fault. The Yaylabeli site is a small, semi-enclosed, marshy basin into which a small alluvial fan has been deposited. The trenches reveal well-preserved, thin-bedded couplets of sand/silt and peat and clear event horizons, allowing us to place precise age constraints on the ages of ancient NAF earthquakes through the site. We document evidence for at least five, and possibly six, surface ruptures during the last 2,500 years. We interpret these events as: (1) the historic 1939 M_w 7.9 Ercinzan earthquake; (2) the historic 1254 A.D. event; (3) the historic 1045 earthquake; (4) an earthquake between 650 A.D. and 950 A.D.; (5) an earthquake that occurred between 250 A.D. and 800 A.D., possibly the historic 499 A.D. event. One or more earlier events occurred before 120 A.D. These results corroborate the earlier results from the nearby Çukurçimen trench site, located 2 km to the east of Yaylabeli, with the exception of the additional 7^th-10^th century event observed at Yaylabeli. These data suggest relatively regular earthquake recurrence for the eastern section of the NAF, with inter-event times that range from ~200 to <700 years, and which vary by a factor of ≤3.5. We attribute this relatively simple behavior to overall structural simplicity of the NAF and consequent lack of nearby faults capable of generating frequent, large-magnitude earthquakes.