Damage survey of a historic town and comparison with past events after the 2016 central Italy earthquake

Central Italy is an active seismic area and many earthquakes struck the historic centre of Campi Alto di Norcia (Perugia) since its foundation in the 13th Cent. Nevertheless, every time, Campi has been restored without losing its identity, until the shocks occurred in 2016 caused the definitive collapse of a large part of it. Residential buildings have been restored introducing modern techniques and materials, as injections, jacketing and substitution of structural parts, which showed, already in the 1997 Umbria-Marche earthquake, their inefficiency and incompatibility with historic masonry. Therefore, today we can observe again the effects of the recent interventions and evaluate them on large scale. A first damage evolution is here reported, by mapping the damage levels to evaluate the causes of such a severe scenario. Surveys and studies after the 1997 earthquake provided the first correlation between structural interventions and damage, but major efforts were put in the definition of collapse mechanisms and in tools which could apply the new approach. Other earthquakes (L’Aquila 2009, Emilia 2012) confirmed the aetiology of certain seismic damages to specific interventions, but only qualitative relations were established. In addition, a description of seismic effects interpreted also as a result of specific interventions is still missing, especially on quantitative basis. The paper presents a systematic damage survey supported by a GIS system and a specific form, both aimed at defining, if possible, a relation between the damage on each intervention and the damage of a building as a whole.