Assessment of Seismic Risk in Istanbul Based on the Integration of Historical Seismology and Structural Engineering

Abstract:

Most seismic disasters in northern Turkey have been caused by large earthquakes generated along the huge active fault called the North Anatolian Fault. We can also see that these large earthquakes occurred sequentially from east to west. Since the latest large earthquake, 1999 Kocaeli earthquake occurred close to Izumit, which is neighboring Istanbul, a next large earthquake can occur in the westernmost segment only several tens km away from Istanbul. Therefore, the seismic risk assessment of Istanbul must be an urgent issue and this study has been carried out for the purpose of an accurate assessment.

To increase the accuracy of seismic risk assessment, we introduced two approaches into this study. The first approach is based on historical seismology. We compiled data of actual seismic damage by investigating past seismic disasters in Istanbul. The experts in Turkish history and seismology examined historical documents and collecting data of actual seismic damage written in them. In particular, there exist photos of seismic damage in the 19th century and later. For example, the figure shows the damage of buildings caused by the 1894 earthquake. We performed a preliminary analysis on these data.

The second approach is based on structural engineering. For useful risk assessments for the people and society of Istanbul, not only the past damage data but also data on currently existing buildings are necessary. For this purpose, we performed cyclic lateral-loading tests on a RC building in the redevelopment area. The experts on structural engineering and earthquake engineering analyzed the data obtained from this full-scale experiment. Finally, we concluded this study by integrating the results of the two approaches.