SEISMIC HAZARD IN TUSCANY: WHICH BEST DEFENCE STRATEGY?

The hypothesis that the probability of major earthquakes in a given zone is strongly influenced by the space-time distribution of previous seismic events in the surrounding area is supported by numerous and significant pieces of evidence. This work describes a particularly clear example of this phenomenon that occurred in the central-northern Apennines during the period 1915-1920. The fact that the strong 1915 Fucino earthquake in the central Apennines was followed by an exceptional seismic reaction of the northern Apennines (6 events of magnitude greater than 5.5 in the 1916-1920 time interval) is consistent with the active tectonic setting of these zones. Furthermore, it can be demonstrated that the time occurrence of each event in the northern Apennines is compatible with the arrival of the highest values of the perturbation induced by the previous shocks, as computed by numerical modelling of postseismic relaxation.