The use of geostatistical methods to identify severe earthquake damage in an urban area

Izmit earthquake (Mw 7.4) occurred on the north Anatolian Fault Zone (NAFZ) in the northwest of Turkey on 17 August 1999 and resulted in severe damage to the urban areas of Izmit, Adapazari (Sakarya), Golcuk and Yalova. A semi-variogram approach was used to quantify earthquake-induced spatial variation and as a result, identify severely damaged regions in Adapazari inner city. The inner city of Adapazari was divided into twelve 1 km times 1 km blocks. Omnidirectional semi-variograms of these blocks were calculated using SPOT HRVIR Panchromatic images obtained before and after the earthquake. The differences between the pre and post earthquake semi-variograms were correlated with the location of severely damaged areas. These differences were determined for the range, nugget and sill of the semi-variograms and an independently produced damage map was related to the results of this semi-variogram analysis.