Effect of soil modeling on Site Response Analysis (SRA)

ABSTRACT: In the work the effects of the soil on the seismic input have been studied on a real site, i.e. a Tuscan (Italian) seismic area, whose profile has been defined through different geological investigations. The Site Response Analysis (SRA) has been performed by assuming two different models to describe the filtering effect of the soil. The upward wave-propagation analysis has been performed by assuming for the bedrock an ensemble of real ground motions, spectrum-compatible to the one provided by the Italian Code for the area. Six different seismic intensities have been considered, each of them represented by a proper ensemble of ground motions. The soil propagation has been represented by assuming two alternative models, differing for the soil modeling. The comparison among the obtained surface free-field motions has shown the role of the modeling on the soil filtering. The obtained free-field motions have been compared also to the seismic input as provided by the Code according to the conventional soil classification, in order to point out the importance of considering the effective geological stratigraphy for the seismic input quantification.