Double Branching model to forecast the next M ≥ 5.5 earthquakes in Italy

Abstract

The purpose of this work is to set up a new forecasting model, named Double Branching, for large earthquakes in Italy. The model is time-dependent, since it assumes that each earthquake can generate, or is correlated to, other earthquakes through different physical mechanisms. In a recent paper [Marzocchi, W., Lombardi, A.M., 2008. A Double Branching model for earthquake occurrence, J. Geophys. Res., 113, B08317. doi:10.1029/2007JB005472] we have shown that the model, applied to two worldwide catalogs in different time–magnitude windows, shows a good fit to the data and its earthquake forecasting performances are superior to what is obtained by the ETAS (single branching model) and by the Poisson models. Remarkably, the model can be tested in a forward perspective, which is the most straightforward way to evaluate the reliability of any forecasting model. Here, we apply this model to the Italian historical seismicity of the last four centuries, with magnitude Mw ≥ 5.5. This application shows that the time-dependent features are comparable to what observed in other applications for different time–space–magnitude window. Moreover, the comparison of the forecasting capability of the Double Branching model and of a spatially-variable stationary Poisson process (used in Italy for seismic hazard assessment) shows that the former has significantly better performances. Finally we provide some probability maps for different temporal windows.