Turkish Journal of Earth Sciences (Turkish J. Earth Sci.), Vol.C. ZABCI20, 2011, ET pp. AL. 411–427. Copyright ©TÜBİTAK doi:10.3906/yer-0910-48 First published online 14 June 2010 Palaeoearthquakes on the Kelkit Valley Segment of the North Anatolian Fault, Turkey: Implications for the Surface Rupture of the Historical 17 August 1668 Anatolian Earthquake CENGİZ ZABCI1,*, HÜSNÜ SERDAR AKYÜZ1, VOLKAN KARABACAK2, TAYLAN SANÇAR3,4, ERHAN ALTUNEL2, HALİL GÜRSOY5 & ORHAN TATAR5 1 İstanbul Teknik Üniversitesi, Ayazağa Yerleşkesi, Jeoloji Mühendisliği Bölümü, Maslak, TR−34469 İstanbul, Turkey (E-mail:
[email protected]) 2 Eskişehir Osmangazi Üniversitesi, Jeoloji Mühendisliği Bölümü, TR−26040 Eskişehir, Turkey 3 İstanbul Teknik Üniversitesi, Ayazağa Yerleşkesi, Avrasya Yerbilimleri Enstitüsü, Maslak, TR−34469 İstanbul, Turkey 4 Tunceli Üniversitesi, Mühendislik Fakültesi, Jeoloji Mühendisliği Bölümü, TR−62000 Tunceli, Turkey 5 Cumhuriyet Üniversitesi, Jeoloji Mühendisliği Bölümü, TR−58140 Sivas, Turkey Received 02 November 2009; revised typescript receipts 20 May 2010; accepted 14 June 2010 Abstract: Th e 26 December 1939 Erzincan (Ms= 7.8) and 20 December 1942 Erbaa-Niksar (Ms= 7.1) earthquakes created a total surface rupture more than 400 km between Erzincan and Erbaa on the middle to eastern sections of the North Anatolian Fault. Th ese two faulting events are separated by a 10-km-wide releasing stepover, which acted like a seismic barrier in the 20th century. To understand the rupture behaviour in this structurally complex section of the North Anatolian Fault, we undertook palaeoseismological trench investigations on the Kelkit Valley segment where there is little or no palaeoseismic information. We found evidence for three surface faulting earthquakes predating the 1939 event during the past millennium in trenches excavated in Reşadiye and Umurca.