Palaeoseismological investigations on the Karadere segment, North Anatolian Fault zone, Turkey

The Karadere segment of the North Anatolian Fault (NAF) is the easternmost part that ruptured during the 17 August 1999 İzmit earthquake (Mw 7.4). It has a diff erent orientation, at N65°E to other segments which have a nearly E-W trend, and lesser dextral displacement, with maximum 2.3 m in contrast with 5.2 m in the ruptured neighbouring western segment. Two palaeoseismological trenches, at Kazimiye and Karadere sites, were excavated on the central part of the Karadere segment to determine the timing of past earthquakes. Excavation of the Kazimiye site revealed the occurrence of five past events since the 4^th century A.D., including the 1999 İzmit earthquake. Th e oldest event occurred aft er A.D. 231-407 and before A.D. 420-584 based on ¹⁴C dating results. This event may correspond to either the A.D. 358 earthquake or the A.D. 554 historical earthquake. The younger three events predate 1999 and postdate A.D. 420-584. At the Karadere trench site, three past events, including the 1999 İzmit earthquake, were identifi ed. Th e penultimate event was observed on the trench wall and dated to be after A.D. 1298-1370. Th e older event is dated as before A.D. 1150-1261, which may correspond to one of the determined events in the Kazimiye trench. In summary, palaeoseismological data provide evidence for at least five large earthquakes on the Karadere segment since A.D. 231-407, including the 1999 İzmit earthquake.