Empirical seismic vulnerability of Italian URM churches hit by the 2016-17 Central Italy earthquake sequence

Abstract

This study provides some insights on the empirical seismic vulnerability of unreinforced masonry (URM) churches, by statistically processing post-earthquake damage data gathered in the aftermath of the Central Italy (2016-2017) damage and usability assessment campaign. The available damage database, collecting 3356 post-earthquake survey forms, is first critically examined. The peak ground acceleration (PGA), estimated from updated INGV ShakeMaps and suitably accounting for the several main shocks of the earthquake sequence, is adopted for locally characterizing the ground motion severity. A global level of damage is associated with each inspected church, starting from damage information on individual collapse mechanisms available from the post-earthquake survey form. Empirical damage probability matrices (DPMs) are derived by statistically processing the entire dataset of masonry churches, then refined based on further attributes (i.e. plan area and construction age) consistent with exposure data. Parametric representation of the resulting observational damage frequencies is also provided by taking advantage of the binomial distribution, which allows for fully describing the entire damage repartition in the different levels by a single parameter.