Assessment of 2D site effects for seismic microzonation studies: application to Eastern Sicily (Italy)

Using three Levels of detail with increasing complexity in terms of approaches and information required, Seismic Microzonation studies aim to map and assess the seismic ground response and the susceptibility to ground instability phenomena. In this paper, attention is focused on the assessment of 2D site effects for Seismic Microzonation studies of Level 3 performed for several municipalities located in Eastern Sicily (Italy) characterized by high seismic risk. The Seismic Microzonation studies of Level 3 required the collection of all existing geological, geotechnical and geophysical data performed in the investigated areas to define coherent subsoil models and the reference geological cross-sections for each municipality. The software REXELite was employed to select datasets of accelerometric waveforms from the Engineering Strong Motion database to be used for the ground response analyses. 2D Finite Elements Method analyses were performed using PLAXIS2D software. The Hardening Soil model with small-strain stiffness, that includes an increased soil stiffness for small strains, was adopted to model the soil non-linearity. In the framework of Seismic Microzonation studies, Amplification Factors were computed for three different period intervals and then compared with the simplified approach provided by the Italian seismic code for the evaluation of site effects, which is based on the definition of soil and topographic classes. Finally, the Topographic Aggravation Factor was assessed for each reference geological cross-section, demonstrating the importance of considering topographic effects in Seismic Microzonation studies. The outcome of this study provides a valuable base for engineers and planners in developing mitigation policies for the seismic risk reduction.