A FRAMEWORK ON REDUCING THE SEISMIC RISK ON A REGIONAL SCALE: A CASE STUDY FOR ISTANBUL

Past earthquakes and their catastrophic consequences have demonstrated that the seismic risk of sub-standard building stocks must be reduced to limit post-earthquake losses after a future earthquake. In Türkiye, more than 100,000 people died, and more than 1 million buildings became uninhabitable since the beginning of the 20th century. Once more, the heavy losses induced by the recent Kahramanmaraş earthquakes showed that seismically deficient buildings must be identified and intervened in before another future destructive earthquake. However, for large building stocks, intervening in all the buildings is not a realistic approach and cannot respond to the urgency of this task. Starting from the evaluation phase, the process must be efficient in terms of time and economy. In this study, a framework for reducing the seismic risk of a building stock in a reasonable way is outlined. The framework consists of pre-earthquake evaluation and intervention strategies. After that, a case study is conducted for sub-standard buildings in Istanbul. Finally, the change in total intervention cost and post-earthquake losses is compared to discuss the efficiency of the proposed framework. The outputs revealed that the case of no intervention is the most expensive action as a result of excessive post-earthquake losses, and widespread retrofitting of existing structures based on prioritization is the most efficient way to intervene.