Factors affecting the greater damage in the Avcilar area of Istanbul during the 17 August 1999 Izmit earthquake

The 17 August 1999 earthquake at Izmit, Turkey was triggered by the North Anatolian Fault Zone. It resulted in widespread damage, particularly in Avcilar, in the European part of Istanbul and some 100 km from the epicentre. This paper reviews the geomorphology, geology, foundations and structures in the Avcilar area, in order to assess the main reasons for the extensive collapse of buildings. It is considered that the basinal structure of the area, the varying thicknesses of bedrock and the presence of secondary tear faults were important contributory factors. In addition, the poor quality of the construction meant the buildings were unable to accommodate ground motions. © Springer-Verlag 2004.