Improvement of Iranian Seismic Design Code Considering the Near-Fault Effects

Characteristics of ground motions close to the earthquake source can be considerably different from those of far-field motions which should be considered in design process of structures. The current study aimed to present new design response spectra for Iranian seismic design code taking into account the near-fault effects. For this purpose, a new attenuation relation based on the ground motion records obtained from fault-normal orientation of near-fault earthquakes at different parts of the world including Iran, has been derived. Subsequently, near-fault modification factors for short and long periods were extracted to present the modified design response spectra for the Iranian design code. The proposed factors are relatively comparable with those of UBC97, Chinese and Taiwanese seismic design codes. Analyses also showed that the distance criterion that defines near-fault region consistence with design spectra of Iranian seismic code can be taken as 18 km.