EFFECTS OF FLING STEP AND FORWARD DIRECTIVITY ON SEISMIC RESPONSES OF SOIL SITES

It is observed that ground motions in the near source zone of large earthquakes are significantly affected by tectonic fling (in this paper called fling step effect) and rupture directivity. In this paper effect of different types of ground motion on response spectra of soil site was evaluated. For this purpose, according to geotechnical and geophysical studies across the Iran, two models for two common soil types in Iran (B and C based on ASCE-07 code classification) were extracted. Equivalent-linear earthquake site response analysis was implemented with simplified assumptions of soil condition like horizontal soil layer in infinite extent. Furthermore record processing effects were considered in this study especially in near field records (fling step records) where conventional record processing canʹt fully recover near field effects like residual displacement in displacement time series. It is observed that applying different types of ground motion can change the shape of design spectra especially in short and long periods, so they can have significant impact on engineered structures. Computed site spectral responses show a peak in short periods and long periods for far fault and near fault records, respectively.