The moment magnitude 7.4 Kocaeli, Turkey, earthquake struck the Kocaeli province of North-Western Turkey on Tuesday, August 17, 1999, at 3:02 a.m. local time. The cause of the earthquake was the sudden breakage, or rupture, of the Earth’s crust along a western branch of the 1,500-km-long North Anatolian fault system. The total length of the fault rupture was about 110 km. The region hit by the earthquake is the industrial heartland and the most densely populated section of Turkey. According to official Turkish government estimates, the earthquake caused 17,127 deaths and 43,953 injuries, and displaced more than 250,000 people.
Most of the collapsed and damaged buildings were of reinforced concrete construction. Their poor performance was due primarily to the poor quality of construction and failure to enforce the local building code. The earthquake’s strong velocity pulse and long duration, however, were important factors in the collapse of and damage to residences. Immediately following the earthquake, the USGS was invited by the Kandilli Observatory and Earthquake Research Institute of Bogazici University in Istanbul, Turkey, to assist in its post-earthquake investigations. Teaming up with representatives from the National Institute of Standards and Technology and the U.S. Army Corps of Engineers, the reconnaissance teams created this report to document a series of implications for earthquake risk reduction in the United States.