GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 2.2 GNGTS 2023 will take a value less than or equal to a given value x . In terms of the hazard indicator, for example, X is the value of PGA for the selected return period at the municipal centroid of all Italian municipalities. Finally, the RI is computed by aggregating the ECDFs of each indicator as follows: = [ ℎ ℎ ( ) • ( )] • ( ) • ( ) (1) where F h s ( h j ), F Pv s ( v j ), F sv ( sv j ) and F p ( p j ) are the ECDF values of the seismic hazard, physical vulnerability, social vulnerability and residential population indicators, respectively, evaluated at municipality j . (Note that physical exposure is accounted for in the definition of the physical vulnerability indicator, in line with the Risk-UE approach). w s , w sv , and w p are the weights adopted for each indicator, representing the relative importance of individual indicators to relevant stakeholders. These weights can be defined using various techniques. For example, the Budget Allocation Process (BAP) quantifies weights by providing users with a “budget” of N points to distribute over a number of individual indicators; the user “pays” more for those indicators whose importance they want to place more emphasis on. The weights take values between 0 and 1 and sum to 1. The aggregation is geometric, where, compared to a linear aggregation, a high value of the ECDF for one indicator does not compensate as much as for a low value of the ECDF for another type of indicator (OECD 2008). (Note that adopting a linear aggregation does not significantly change the results.). For this application, RI calculations are carried out for the case of equal weights ( w s = w sv = w p = 0.333), and the values obtained for each municipality in the Campania region are shown in Figure 1. Figure 1 – Map of the Risk Index values in the Campania region. Figure 1 shows several municipalities with significantly higher RI values than the rest, and Portici produces the highest RI score in Campania.