Earthquake Hazard Assessment in Turkey: The Mw = 7.4, Gölcük (August 17, 1999) and the Mw=7.1, Düzce (November 12, 1999) Earthquakes

During the 1999, the northwestern part of Turkey experienced two major earthquakes (Gölcük and Düzce) along the North Anatolian Fault Zone. The Gölcük Earthquake occurred on August 17, and caused damage in a zone extending from Duzce to Istanbul. The Düzce Earthquake struck on November 12, 1999 and caused damage in Düzce, Kaynaşlı and Bolu. These two earthquakes caused significant changes in natural environment such as; surface rupture, cracks, landslides, offsets in the riverbeds, discharge of subsurface water from underground, liquefaction and coastal collapse. The surface rupture, which is 168 km long, extending from Kaynaşlı to Gölcük, is the most significant. The changes after the earthquakes were identified from field measurements and assembling the existing maps at 1:25,000 and 1:100,000 scales.