NON-LINEAR SITE EFFECTS IN AREAS CHARACTERISED BY A COMPLEX TOPOGRAPHY: AN ITALIAN CASE STUDY

The paper presents the application of a three-dimensional (3D) finite element (FE) non-linear approach to assess the site effects in areas characterised by complex topography. In particular, the seismic response of the Costa del Canneto area, located in the southern Apennines of Italy, is investigated. This region is known for its high base seismic hazard. The presence of soft soils reaching depths up to 200 meters could considerably affect the earthquake amplification at ground surface. To capture the local topographic conditions with reliable accuracy, a 3D FE model is generated from the Digital Terrain Model. In the presented preliminary analyses, the soil deposit is considered homogeneous with depth, characterised by a constant shear wave velocity of 400 m/s and overlying a deep horizontal seismic bedrock. To highlight the effects of soil non-linearity on the ground surface motion, the soil behaviour is described through linear visco-elastic and visco-elastic perfectly plastic schemes, but also implementing the Hardening Soil model with small strain stiffness. The horizontal components of the same reference earthquake, selected according to the base seismic hazard of the site, are simultaneously applied at the base of the FE model. The results of the simulations provide a detailed understanding of the seismic behaviour of the Costa del Canneto area, considering the interaction between the soft soil layers and the topographic irregularities. The case study represents a significant step forward in the analysis of site effects in complex geo-mechanical contexts, such as those occurring in the Italian southern Apennines. Indeed, it can promote the use of advanced seismic hazard assessments for an effective seismic risk mitigation in similar geo-mechanical settings.