GNGTS 2014 - Atti del 33° Convegno Nazionale

GNGTS 2014 S essione 2.1 11 estimates and, particularly, in the logic trees, which are increasingly leafy. Are GMPE branches really healthy or do they act as knots making the wood timber to sound worse? The previous question is intentionally provocative, although it reflects a common feeling. The purpose of this work is to compare dated and recent GMPEs (see Tab. 1) in order to examine their impact (and that of the relevant aleatory sigma) on the hazard and to quantify their predictive power with reference to real case studies via a statistical scoring test. Tab. 1 - List of GMPEs: Hm is for maximum horizontal, GM is for geometric mean, GMRotI50 indicates that the geometric mean is determined from the 50th percentile of the geometric means computed for all non-redundant rota- tion angles, RotD50 is the median single-component horizontal ground-motion calculated over all non-redundant azimuths. Fig. 1 – a) Number of data used to calibrate the GMPEs considered in this study and b) values of the aleatory sigma for each GMPE. GMPEs are plotted on the X axis following a temporal order.