Site effects and damage scenarios: The case study of two historic centers following the 2016 Central Italy earthquake

The great influence of site effects on damage patterns produced by seismic events of the past, stresses out the need to find proper relationships between the site local conditions and the potential damage that existing buildings may experience under earthquakes of different intensity. This issue proved to be relevant, especially for those masonry buildings in small historic centers, such as the ones belonging to the Apennine areas of Italy that suffered serious damage after the 2009 L'Aquila and the 2016-2017 Central Italy seismic sequences. Some of these centers showed a not regular damage distribution, suggesting that site effects influenced the seismic response of their buildings. In this perspective, this paper provides an attempt to correlate earthquake damage to site effects, focusing the attention on two historic centers of the Abruzzi region, Campotosto and Cortino, which were damaged by the 2016-2017 Central Italy seismic sequences and for which the amplification factors of the subsoil were carefully identified, resulting more influencing were higher damage was observed. First, the damage patterns observed after the 18 January 2017 seismic shock are represented in terms of Damage Probability Matrices and maps developed in GIS environment. Moreover, the data collected in terms of stats are interpreted through the application of the binomial probability distribution, in order to check its reliability in reproducing the gathered frequencies. Finally, in order to justify the damage of some specific buildings, the results of site response analyses are compared with the damage observed punctually on three damaged masonry buildings.