PSI - Issue 78

Francesco Testa et al. / Procedia Structural Integrity 78 (2026) 905–912

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Accumoli, in the Lazio region. The last severe event, with Mw 5.7, occurred on 17 January 2017, with an epicentre near Capitignano, in the Abruzzo region. The strongest shock of the sequence occurred on 30 October 2016, registering a Mw 6.6 and with an epicentre located in Norcia, Umbria region (Rovida et al., 2020; Sisti et al., 2023). Damage surveys were conducted in three main phases. The first began shortly after August 2016 but was interrupted by the severe earthquakes of late October. Survey activities resumed in November, marking the second phase. The third and final phase of data collection was initiated following the strong event in January 2017 (Carbonari et al., 2019). Data on historic masonry bell towers were obtained from the Italian Da.D.O. web-GIS database, which compiles the digitised post-earthquake inspection forms conceived by the Italian Civil Protection Department (Dolce et al., 2019). These forms capture a range of information, including location, architectural and structural features, observed damage, and seismic input characteristics, among other details. Information on historic masonry bell towers is included as part of the broader survey forms completed for the associated churches. In this study, the analysis focused specifically on mechanisms related to the shaft and belfry (mechanisms 27 and 28 in the Civil Protection form), hereafter named as mechanism A and mechanism B, respectively, with damage levels classified according to the European Macroseismic Scale (EMS-98). From an initial set of 3,356 churches affected by the Central Italy seismic sequence, filters were applied to ensure data reliability, excluding incomplete records, bell gable typologies, and towers in areas with low or missing seismic intensity information. The filtering process resulted in a dataset of 794 historic masonry towers with records indicating potential activation of both damage mechanisms. Following data cleansing, a global damage level for the tower macroelement was calculated as a function of the global damage index according to the method described by Lagomarsino & Podestà (2004a, 2004b), and adapted to towers by Testa et al. (2024a, 2024b). A classification based on geographical location was undertaken, considering potential variations in construction traditions, historical seismic activity, local seismic response and mitigation policies. Figure 1 illustrates the distribution of all inspected towers across the four regions and ten provinces affected by the Central Italy seismic sequence. Most of the towers are located in the Marche and Umbria regions, comprising 61% and 26% of the dataset, respectively. A similar pattern is seen at the provincial level, with most towers situated in the Macerata province (Marche) and Perugia province (Umbria), accounting for 37% and 23% of the dataset, respectively. Consequently, the dataset was divided into these four subsets. Other regions and provinces were excluded due to their limited sample sizes.

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Fig. 1. Towers geographical distribution: (a) regional-based; (b) province-based.