Site effects and intervention criteria for seismic risk mitigation in the ancient city of Pompeii: The case of the Insula dei Casti Amanti

This paper deals with site amplification effects and possible strategies for seismic risk mitigations in the ancient Roman city of Pompeii, the well–known archaeological site near Naples, Italy, buried under 4–6 m of volcanic ashes and pumices during the eruption of Mount Vesuvius in 79 AD. The attention is focused on the restoration works of the Insula dei Casti Amanti, a block of masonry buildings in the city centre partly excavated in recent years, which included the stabilization of the excavation fronts, the preservation of the archaeological ruins and the replacement of the actual roofing system realised some decades ago. Two dimensional site amplification analyses carried out to quantify the seismic demand in the excavation fronts allowed to recognize the occurrence of remarkable aggravation phenomena at the crest of the slopes owing to the strong interference between morphology and topography. It is shown that a Newmark–type approach is adequate in this case to define the profile of the artificial slopes in a sustainable way. The focus is then set on the foundations of the new covering system of the Insula, a single span steel truss. A proper consideration of the load path followed until failure and the concept of interaction diagrams are fundamental ingredients to reduce as much as possible the impact of the new foundation system. As a final remark, the attention is placed on the likelihood occurrence of a double resonant mechanism between the subsoil and the archaeological ruins and on actions that have to be taken for the protection of the ancient city from future earthquakes.