Which fault caused the 1999 İzmit earthquake in Turkey?

The 1999 İzmit earthquake in Turkey occurred on the North Anatolian Fault.

The earthquake struck on 17 August 1999 near İzmit in northwestern Turkey. It had a moment magnitude of 7.6 and produced a long rupture along the western part of the North Anatolian Fault, a major right-lateral strike-slip fault.

The North Anatolian Fault marks the boundary between the Anatolian Plate and the Eurasian Plate. Because the two sides move mainly horizontally, the fault belongs to the transform-fault family rather than being a subduction zone. The earthquake caused extensive building collapse and killed more than 17,000 people according to commonly cited official figures.

The event is sometimes confused with the 1999 Düzce earthquake, which struck farther east later that year on the same broader fault system. İzmit is also commonly called the Kocaeli or Gölcük earthquake, reflecting affected locations and regional naming conventions.