PSI - Issue 78

Cristina Cantagallo et al. / Procedia Structural Integrity 78 (2026) 1482–1489

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before- and after-event socio-economic indicators, enabling the characterization of the typical amplitude of economic and tourism disruption associated with a seismic event of medium – high intensity in a territory with structural and demographic similarities to the case study. Specifically, the following variables were modelled: • Gross Domestic Product (GDP): estimated reduction of overall local value added, capturing contraction in economic activity and consumption. • Employment : projected decline in the number of active employees, with particular attention to tourism-related sectors such as accommodation and food services. • Tourism Demand : reduction in arrivals and overnight stays, reflecting decreased attractiveness and operational capacity of the destination. 5. Results 5.1. Tourism Dependency Index The TDI computed for Popoli Terme is 12.27, a value slightly below the national reference mean of 13.33, which was calculated as the arithmetic mean of the TDI across a dataset of all main Italian municipalities. This dataset covers a representative sample of historic centers with varying degrees of tourism specialization and was not limited to municipalities affected by the 2016 – 2017 earthquake sequence. This result indicates that, although tourism does not constitute the predominant economic sector in the municipality, it plays a strategically relevant role in sustaining local services, seasonal employment, and the vitality of the historic center. Notably, Popoli Terme benefits from a distinctive thermal tourism tradition, which represents an important element of the town’s identity and economic diversification. 5.2. Projected Impacts on GDP, Employment, and Tourism The estimation of the effects of a major earthquake on tourism indicators in Popoli Terme was based on the observed impacts in ten municipalities affected by the 2016 – 2017 Central Italy earthquake sequence. The benchmark group included Cascia, Monteleone di Spoleto, Norcia, and Preci in the Umbria region; Acquasanta Terme, Arquata del Tronto, Montegallo, Montemonaco, and Montefortino in the Marche region; and Capitignano in the Abruzzo region. For these municipalities, detailed data were collected on the evolution of tourism demand and supply from the year before the earthquake through the event year and up to three years after the disaster. This information included the number of hotels and extra-hotel accommodation, the number of available beds, and the volume of tourist arrivals and overnight stays. To define a reference scenario describing how tourism and economic activity evolved nationally in the same period, unaffected by the seismic event, a dataset including the same data was compiled for the entire Italian territory. To make the comparison clearer, all the indicators were rescaled to a base value of 100 in the year preceding the earthquake. This normalization allowed for a direct comparison with the national trend over the same period, which served as a control scenario unaffected by the disaster. Fig. 3(a) shows this comparison. The solid blue line represents the national trend in overnight stays, which increased by approximately 12% over the three years following the earthquake, reflecting a general growth in tourism flows in Italy. In contrast, the orange line shows the aggregated trend for the ten municipalities most affected by the seismic sequence. These areas experienced a marked decline already in the year of the event (2016) and a further contraction exceeding 40% in the first year after the earthquake. The decline persisted in the second and third years, although the losses were progressively less severe. The projection of a gradual return to pre-event levels assumes that, in the absence of additional shocks or extraordinary events ( ceteris paribus ), tourism demand would progressively recover over time. Specifically, the model estimates that the volume of tourist arrivals and overnight stays would return to the same level recorded before the earthquake by the sixth year after the event. The estimated timeline for this gradual return to normality is represented by the dotted orange curve in the graph, which illustrates the expected trajectory of recovery over the years following the disaster. Subsequently, the effects observed in the benchmark municipalities after the 2016 Central Italy earthquake are applied to the three main parameters under consideration — local Gross Domestic Product (GDP), employment, and tourist overnight stays. In this way, a projection of the potential annual impact of a seismic event in Popoli Terme was