Processo sismico locale in situazione non stazionaria

In many cases the earthquake generation process can be modelled by a renewal process with mixture distributed failure time, often, with a bimodal behaviour of the probability density function. For the attenuation effect, the source stochastic process becomes a more complex site process but with the renewal process characteristics yet. It is interesting to detect if the interoccurrence time density bi-modal behaviour at the source is carried on at the site as well. 2 From the theoretical point of view the transformation of the source process in the site process is based on a attenuation law and on the Laplace Transform (L.T.) and Inverse Laplace Transform (I.L.T.) tools used. This paper presents the I.L.T. approach application at some Italian zones with particular attention at the site location in the seismogenetic zone. The results obtained by the I.L.T. approach and by the direct approach, consisted in the historical data reduction at the site using an attenuation law typical for the zone in object and their direct statistical interpretation, are compared. With the building of a seismic synthetic catalogue with 5,000 events, some uncertainties, which are present the statistical interpretations of the historical data, are analysed and the results obtained from the different three methods are compared. Remarks on the computational efficiency of the three methods are discussed and the seismic local damage valuation problem is introduced.