Regional fragility functions for bell towers damaged in the 2016 Central Italy earthquake sequence

This study investigates the seismic vulnerability of bell towers damaged during the Central Italy seismic sequence, which was selected due to its notably prolonged activity, including the occurrence of several moderate to severe shocks between 2016 and 2017. Focusing on territorial-scale vulnerability models, a statistical analysis of observed damage levels is conducted, and fragility functions are calibrated for assets located in specific geographical areas (i.e., Umbria and Marche regions - Perugia and Macerata provinces, respectively), highlighting disparities in their seismic response. To explain these variations, the towers are categorised according to key factors, including the level of maintenance and the presence of strengthening interventions prior to the seismic events, as well as the characteristics of the seismic scenario preceding inspection – specifically, whether the towers were surveyed after a single major shock or following multiple events. The results highlight the importance of a careful analysis of the available asset descriptors and the need to include additional parameters that complement or expand existing survey forms. This is essential to ensure that vulnerability models are both unbiased and truly representative of the asset class to which they are applied.