Spatial variability of non-ergodic GMM residuals related to source and path effects in Italy

Abstract

In this study, we exploit the advantages of non-ergodic modelling of the ground motion to map the regional characteristics of source and propagation effects in Italy. In particular, we focused on the study of source and propagation effects obtained from the decomposition of the total residuals, i.e. the logarithmic difference of ITACAext observations and the model predictions, for active crustal earthquakes in Italy. The spatial trends, obtained from interpolating the residuals, clearly showed areas where the motion was significantly different from that predicted by the reference model, and in particular was underestimated. This is the case, for example, for many events with epicentres in northern Italy and the southern Ionian Sea. In addition, the study shows that paths across the Po Valley and the Adriatic coast are characterised by slower attenuation compared to that observed in the central Apennines. In addition, a marked difference between attenuation in the volcanic domain of Etna and the Hyblaean Mountains is clearly observed.