Scenarios based earthquake hazard assessment

For historical and strategic buildings the applicability of standard probabilistic estimates of seismic hazard (PSHA) is really questionable: when considering time intervals of about a million year (we do not want to lose cultural heritage), PSHA results by far not applicable. A viable alternative capable of mini- mizing the drawbacks of PSHA is represented by the use of the scenario earthquakes, also named neo- deterministic approach (NDSHA), characterized at least in terms of magnitude, distance and faulting style, and by the treatment of complex source processes. The NDSHA naturally supplies realistic time series of ground motion, which represent also reliable estimates of ground displacement readily applicable to seismic isolation techniques, useful to preserve historical monuments and relevant man made structures. An integrated neo-deterministic approach to seismic hazard assessment has been developed that combines different pattern recognition techniques, designed for the space-time identification of strong earthquakes, with the procedure for the NDSHA. The integrated approach allows for a time dependent definition of the seismic input (realistic synthetic seismograms), through the routine updating of earthquake predictions. The time information given by the intermediate-term medium-range earthquake prediction is very useful to plan preparedness and rescue actions and to define priority criteria for the investigations required by the seismic microzonation. Even if strong motion records in near-fault, soft soil, or basin conditions have been recently obtained, their number is still very limited to be statistically significant for seismic engineering applications: the realistic computation of the seismic input, taking in account the source and site effects, combined with the evaluation of the seismic response of buildings provides an effective approach to the assessment of seismic risk.