Some insights into the time clustering of large earthquakes in Italy

The aim of this work is to investigate the clustering properties of the large earthquakes which occurred in Italy in the last four centuries. In particular, we compare the results of a new multivariate nonparametric model applied to the catalog of large earthquakes in Italy, and to a synthetic catalog generated through a specific ETAS model, successfully applied to describe aftershock sequences. The results disclose a longer clustering time for real large earthquakes, suggesting that the physical process that governs aftershock sequences and the occurrence of large earthquakes may be different. Alternatively, the results can be explained by suggesting that the ETAS model, used to describe aftershock sequences, is not a suitable tool to model seismicity as a whole.