The Surface Rupture and Slip Distribution of the 17 August 1999 I˙zmit Earthquake (M 7.4), North Anatolian Fault

of the North Anatolian fault zone. The earthquake is associated with a 145-km-long surface rupture that extends from southwest of Düzce in the east to west of Hersek delta in the west. Detailed mapping of the surface rupture shows that it consists of five segments separated by releasing step-overs; herein named the Hersek, Kara-mürsel–Gölcük, I˙zmit–Sapanca Lake, Sapanca–Akyazi, and Karadere segments from west to east, respectively. The Hersek segment, which cuts the tip of a large delta plain in the western end of the rupture zone, has an orientation of N80. The N70– 80E–trending Karamürsel–Gölcük segment extends along the linear southern coasts of the I˙zmit Gulf between Karamürsel and Gölcük and produced the 470-cm maxi-mum displacement in Gölcük. The northwest–southeast-striking Gölcük normal fault between the Karamürsel–Gölcük and I˙zmit–Sapanca segments has 2.3-m maximum vertical displacement. The maximum dextral offset along the I˙zmit–Sapanca Lake segment was measured to be about 3.5 m, and its trend varies between N80E and east–west. The Sapanca–Akyazi segment trends N75–85W and expresses a maxi-mum displacement of 5.2 m. The Karadere segment trends N65E and produced up to 1.5-m maximum displacement. The Karadere and Sapanca–Akyazi segments form fan-shape or splaying ruptures near their eastern ends where the displacement also diminished