A fault zone cause of large amplification and damage in Avcılar (west of Istanbul) during 1999 Izmit earthquake

Twenty seven buildings collapsed and 2076 buildings were heavily damaged during 17 August 1999 Izmit Earthquake in Avcılar (west of Istanbul), which is nearly 100 km from the epicenter of the earthquake. The geology of Avcılar consists of Upper Miocene poorly bounded conglomerate and sandstone (Çukurçeşme formation), claystone with sandstone and limestone interbedding (Güngören member) and limestone with sandstone and claystone interbedding (Bakırköy formation). Lithological and geotechnical parameters of these formations in Avcılar are not different from non damaged parts of the western Istanbul such as Zeytinburnu, Bakırköy and Beylikdüzü, but these formations were cut by several faults in the damaged area. Collapsed and damaged buildings are located on this fault zone. Thus, cause of large amplification and damage in Avcılar might be related with this fault zone because the fault zone behaves as a waveguide trapping seismic energy. Copyright Springer Science+Business Media, Inc. 2007