GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 2.2 GNGTS 2023 assessment of buried pipelines systems located in areas prone to seismic hazard is briefly described. Simulation of earthquake scenarios Earthquake actions can be represented via the simulation of ground shaking scenarios, derived from the selection of potential epicenters and assigning relevant magnitudes in relation to the seismicity of the area under analysis. Once defined a set of potential earthquake scenarios, ground motion is modeled with Ground Motion Prediction Equations (GMPEs), that provide a probabilistic distribution of a given intensity measure conditional to earthquake intensity, point-to-source distance and other parameters related to specific geological features. GMPEs are usually calibrated through regression analyses on data recorded in past events. The general expression of a GMPE relationship is: (1) = , , θ ( ) + σ ν + σ ε where IMij is the intensity measure of interest for a site j far Rij from the source i during an event of magnitude Mi, θ ij encloses geological conditions, σ B ν i represents the residual inter-event variability whereas σ W ε ij is the intra-event residual. The ν i and ε ij terms are random variables normally distributed with mean value μ = 0 and standard deviation σ = 1, whereas σ B and σ W are respectively the inter- and intra-event standard deviation values. Spatial correlation models of intra-event residuals available in literature have been mostly estimated using single non-European earthquakes, for which many records were available from dense seismic networks (see Boore et al. 2003; Goda and Hong 2008). It has been observed how the coefficient of correlation ρ jk between intra-event residuals calculated in j and k sites separated by a distance hjk decreases with increasing mutual distance values. The correlation coefficient is therefore usually a function of the inter-site distance hjk, as follows: (2) ρ ℎ ( ) = −3ℎ / where b represents the inter-site distance at which the spatial correlation is practically lost. In the European strong motion datasets, no dense observations of single earthquakes are available from which reliable estimates of spatial correlation of intensity measures can be obtained. Therefore, strong motion records from multiple events and regions collected in the European Strong-motion Database and the Italian Accelerometric Archive were merged aiming to derive a unique correlation model (Esposito and Iervolino 2011). The use of a correlation function rjk(hjk)