To use recorded data means a dense set of recording instruments to be triggered when a strong earthquake occurs.
Strong earthquakes are very rare phenomena.
Due to this reason the preparation of a sufficiently large database of recorded strong motion signals that could be analyzed in order to define generally valid ground parameters, to be used in seismic hazard estimations, is difficult, even practically impossible in the near future. While waiting for the increment of the strong ground motion data set, a very useful approach to perform immediate microzonation is the development and use of modeling tools based, on one hand, on the theoretical knowledge of the physics of the seismic source and of wave propagation and, on the other hand, exploiting the rich database about the geotechnical, geological, tectonic, seismotectonic, historical information already available. The initial stage of this work requires the collection of all available data concerning the shallow geology, and the construction of cross-sections along which to model the ground motion. It is multidisciplinary activity by nature, since the requested information is obtained from different disciplines, as seismology, history, archaeology, geology and geophysics. The outcoming result is mapping of the expected ground motions, which is the basement to develop reliable codes for earthquake resistant construction.