Seismic site effect in a coastal area: 1D and 2D modelling of a tuff cliff in Sorrento Peninsula, Italy

This paper evaluates the amplification factors at different locations of a tuff cliff subjected to seismic loading. We present a 1D and 2D modelling of a cliff located in the Sorrento Peninsula, a major Quaternary morpho-structural unit of the western flank of Southern Apennines. The geometry of our model is represented by a tuff cliff of 30 m height, with sand deposits at its base, covered by a 7-m-thick volcanoclastic layer. The geotechnical and geophysical parameters used for the analysis have been estimated via field measurements and laboratory tests. We selected seven scaled seismic events as input motions for the analysis, and the linear equivalent assumption was used in both 1D and 2D modelling. The general trend showed that in the cliff edge area, the amplification factor reaches a maximum value of 10 with a period of 0.11 s, while in other areas, its value decreases down to 2.90 seaside and 4.0 landside. The comparison of the 1D and 2D modelling highlights the importance of the topographic effects connected with a cliff. The average amplification factors (AF) for the 1D and the 2D models, have been computed within different time ranges, consistent with the ones adopted in the Italian microzonation studies (0.1–0.5 s, 0.4–0.8 s, 0.7–1.1 s).