Preliminary report: Kocaeli (Izmit) earthquake of 17 August 1999

The M w 7.4 Kocaeli (Izmit) earthquake occurred at 3:01 am local time 17 August 1999 on the east–west trending north strand of the North Anatolian Fault Zone (NAFZ), about 100 km SE of Istanbul, Turkey. The approximately 125 km long fault rupture and high damage area follows or is close to the south shore of Izmit Bay, and the extension of that line to the east, and has predominantly 2.2 m right lateral displacement, from Adapazari in the east to Yalova in the west. Significant vertical fault scarps of as much as 2 m occur at several locations. Peak ground accelerations of approximately 0.4 g were recorded near the fault, and liquefaction and subsidence were observed on the shores of Izmit Bay and Lake Sapança. Several million persons live in the Izmit region, which has experienced rapid growth and heavy industrialization in the last two decades. The predominant building type is mid-rise non-ductile RC frames with hollow clay tile infill, thousands of which collapsed in a ‘pancake’ mode. Confirmed dead are approximately 17,000. Estimates of population requiring short to long-term shelter range from 400,000 to 600,000. Lifelines generally performed well, with the exception of underground piping in the heavily affected areas, where major damage is reported. Electric power, highways, rail and telephone were generally functional within several days following the earthquake, and the modern Izmit Water Project (the regional water supply and transmission system) was only lightly damaged and fully functional. The modern Izmit gas distribution system similarly sustained relatively little damage. Fires occurred in a number of collapsed buildings but were generally confined to building of origin. Two fires broke out at the Tupras oil refinery, one of which burned for several days.