GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 2.2 449 distribution function for displacement values x , where the mean value is provided by Eq. (1) and the standard deviation is σ ln . The second term is derived from differentiation of the PGA hazard curve obtained through a probabilistic seismic hazard analysis (PSHA). In detail is: (3) where λ is the mean rate of occurrence associated with the adjacent PGA values in the hazard curve. Then, the probabilistic approach predicts the annual rate of exceedance λ d of different levels of permanent displacements, similarly to λ for different levels of PGA obtained by a PSHA. The displacement hazard curves depend on the seismic yield coefficient through the standard deviation and the regression parameters of Eq. (1) and take into account for the specific site via the annual probability P [ PGA i ]. In this study the site effects on the displacement hazard curves are investigated while keeping fixed the value of the yield seismic coefficient. To this purpose, the PGA hazard curves for different Italian sites have been extracted from the INGV interactive seismic hazard maps (http://esse1.mi.ingv.it/d2.html) for the distribution of the 84 th percentile. Particularly, twenty sites in the Central Italy and in Emilia, afflicted by the 2016 seismic sequence and the 2012 earthquake, are analysed and the resulting displacement hazard curves for the two investigated areas are shown in Fig. 1 and Fig. 2, respectively. Fig. 1 - Displacement hazard curves – Central Italy. Fig. 2 - Displacement hazard curves – Emilia.