Probability Map of the Next M>=5.5 Earthquakes in Italy

We provide a probability map of the next M>=5.5 earthquakes in Italy. For this purpose, we use a nonparametric multivariate hazard model to characterize the spatio-temporal distribution of earthquakes. The method is able to account for seismological/geological parameters that can potentially influence the spatio-temporal variability, and tests their relative importance. Moreover, it allows straightforward testing of a variety of hypotheses, such as Seismic Gap, Cluster, and Poisson. The method has been applied to the Italian seismicity (M>=5.5) of the last four centuries. We developed a regionalization of Italy in order to account for heterogeneities both in the tectonic domains and in the spatial distribution of earthquakes. Italy has been divided in 61 irregular zones that are homogeneous with regard to seismic behavior and to kinematics and orientation of the stress field resulting from active stress data (borehole breakouts data, earthquake fault plane solutions, seismogenic fault data). The results indicate a time clustering of the M>=5.5 earthquakes for a few years after an event, then the distribution becomes similar to a memoryless Poisson process, leading to a time dependent probability map. We have found that the most likely regions where the next moderate to large earthquakes may occur in the next 10 years are the Friuli in northeastern Italy, the Umbria-Marche in central Italy, and part of the Southern Apennines and the Calabrian Arc.