Use of Empirical Fragility Curves for Assessing Seismic Risk in Italy

Territorial seismic risk assessment is fundamental for the definition and implementation of strategies aimed at reducing potential damage and losses due to future seismic events. In this context, an invaluable tool is represented by national seismic risk maps, which can be helpful for prioritizing territories within a country where risk reduction measures should be introduced. Quantification of the expected economic losses is also essential for the optimization and allocation of funds in the post-earthquake reconstruction phase. However, consequences due to future seismic events can be effectively mitigated only if accurate risk estimates are available. In this case, the main difficulty is related to the same definition of risk, which results from the convolution of hazard, vulnerability and exposure, thus requiring contributions from different scientific disciplines. In this paper, vulnerability models for Italian residential masonry and reinforced concrete (r.c.) buildings are used for assessing seismic risk at the national scale. The adopted vulnerability models are defined by statistical processing of Italian post-earthquake damage data and include empirical fragility curves for five vulnerability classes, further refined based on the building height. Seismic risk evaluations are carried out by implementing the proposed vulnerability models in the Italian national seismic risk platform (IRMA), using the official Italian seismic hazard model and exposure from national census data. Seismic risk is quantified in terms of physical damage and consequences on building stock and population, such as direct economic losses, unusable and collapsed dwellings, deaths, injured and homeless people. The results obtained in this study, represented in the form of national seismic risk maps, demonstrate the suitability of the employed vulnerability models to be used for large scale seismic risk applications.