Neo-deterministic definition of seismic input and its application to seismic isolation of residential building

The neo-deterministic, physically sound, method for the definition of seismic input is based on the computation of synthetic seismograms at different level of detail, depending on the degree of geological, geophysical, seismological and seismotectonical knowledge. Both 1D and 2D structural models are considered, at national and local scale, respectively. The seismic waves due to an extended source are obtained by approximating it with a rectangular plane surface, corresponding to the fault plane on which the main rupture process is assumed to occur, discretized with a grid of point-sources whose seismic moment rate functions are generated considering each of them as realizations (sample functions) of a non-stationary random process. Effects of directivity and of the energy release on the fault are modeled. To calculate the ground motion at a site, Green functions are computed with the highly efficient and accurate modal summation technique, for each point-source site pair, and then convolved with the point-source time functions and at last summed over all point-sources. The practical case of Nimis (UD), is illustrated; the town, located in a seismically active area along the Alps-Dinarides junction, was hardly hit by the 1976 Friuli earthquake. Modelling has demonstrated that the high level of seismicity of the zone makes the construction of a residential building by traditional antiseismic techniques very difficult, while the use of advanced techniques, like seismic isolation, is particularly advantageous.