A non-parametric hazard model to characterize the spatio-temporal occurrence of large earthquakes; an application to the Italian catalogue

A new non-parametric multivariate model is provided to characterize the spatio-temporal distribution of large earthquakes. The method presents several advantages compared to other more traditional approaches. In particular, it allows straightforward testing of a variety of hypotheses, such as any kind of time dependence (i.e. seismic gap, cluster, and Poisson hypotheses). Moreover, it may account for tectonics/physics parameters that can potentially influence the spatio-temporal variability, and tests their relative importance. The method has been applied to the Italian seismicity of the last four centuries. The results show that large earthquakes in Italy tend to cluster; the instantaneous probability of occurrence in each area is higher immediately after an event and decreases until it reaches, in few years, a constant value representing the average rate of occurrence for that zone. The results also indicate that the clustering is independent of the magnitude of the earthquakes. Finally, a map of the probability of occurrence for the next large earthquakes in Italy is provided.