Seismic loss assessment of residential buildings in Karaj, Iran, by considering near-source effects using stochastic finite-fault approach

This paper presents the results of a study carried out to assess the probable seismic loss, in terms of damage to residential buildings, in the case of the west segment of the North Tehran Fault (NTF) seismic scenario in Karaj, Iran. Accordingly, it is crucial to first properly estimate the ground motion intensities. However, most of empirical ground motion prediction equations are poorly constrained at short ranges, and the data may only partially account for the rupture process. Hence, the stochastic finite-fault method with dynamic corner frequency was applied. This is an appropriate tool for addressing source, path, and near-source effects. It is noted that this method is dependent on many parameters which should be properly tuned. Thus, a set of sensitivity analyzes for the hypocenter locations and the quality factors were performed. The results from the simulations were used to develop a curve for estimating the ground motion values. Then, a high-quality building exposure model composed of 26 building classes based on the most recent census data was compiled. Finally, by applying appropriate fragility curves, damages to buildings from potential earthquakes were assessed. The outcomes showed that the mean damage ratio for the whole of the city is about 18.2% ± 5.3. In addition, a disaggregation analysis is done to identify the most vulnerable building types. The results showed that adobe and low-quality masonry buildings contribute the most to loss. The findings from this study can be used to provide risk reduction plans in Karaj.