Earthquake hazard in Italy, 2001-2030

The study computes time-dependant earthquake probabilities on the basis of seismicity data mainly deriving from historic records. It provides a methodological approach useful for those countries where the scarcity of instrumental data and/or paleoseismological evidences requires that historical information shall be stressed. Thus, the conditional probability that damaging earthquakes (M ‡ 6) may occur in Italy in the next 30 years is shown, and the potential for the main worldwide known Italian cities with a cultural heritage is outlined. Earthquake probabilities are computed referring to the application of renewal processes, where the periodicity is analytically modelled by means of the Brownian Passage Time function; an estimate of the dispersion (i.e., uncertainty) introduced on probabilities is provided making use of Monte Carlo simulations. The computed probabilities refer to seismic source zones deriving from the spatial clustering of the historically documented seismicity. The computation of probabilities based on the interaction of earthquakes occurring in nearby zones, has been also attempted for a test area to explore the influence exerted by the stress transfer effect. The main findings of this study are that (1) seismic source zones in Southern Italy are the most prone to experience damaging earthquakes in the next 30-years, with conditional probabilities a large as 10%; and (2) the influence exerted by the earthquake interaction in increasing such probabilities, doesn’t seem to be relevant, because the mean recurrence times of large earthquakes (above the threshold magnitude of six chosen in this study) are in general much longer than the time shortening produced by the stress transfer.