Dipartimento di Ingegneria Strutturale – Politecnico di Milano

The European project SERGISAI developed a computational tool where a methodology for seismic risk assessment at different geographical scales has been implemented. Experts of various disciplines, including seismologists, engineers, planners, geologists, and computer scientists, co-operated in an actual multidisciplinary process to develop this tool. Standard procedural codes, Geographical Information Systems (GIS), and Artificial Intelligence (AI) techniques compose the whole system, that will enable the end user to carry out a complete seismic risk assessment at three geographical scales: regional, sub-regional and local. At present, single codes or models that have been incorporated are not new in general, but the modularity of the prototype, based on a user-friendly front end, offers potential users the possibility of updating or replacing any code or model if desired. The proposed procedure is a first attempt to integrate tools, codes and methods for assessing expected earthquake damage, and it was mainly designed to become a useful support for civil defense and land use planning agencies. Risk factors have been treated in the most suitable way for each one, in terms of level of detail, kind of parameters and units of measure. Identifying various geographical scales is not a mere question of dimension; since entities to be studied correspond to areas defined by administrative and geographical borders. The procedure was applied in the following areas: Toscana in Italy, for the regional scale, the Garfagnana area in Toscana, for the sub-regional scale, and a part of Barcelona city, Spain, for the local scale.

After the Umbria Marche seismic sequence of September–October 1997, an extensive microzoning study was conducted, from October 1997 to May 1998, to detect the zones where the ground motion was amplified because of local geological and geomorphological settings. The goal of the investigation was to return amplification coefficients to local authorities for the post-seismic reconstruction and repairing of pre-existing buildings, by examining the seismic behaviour of the most damaged 60 villages. The analysis consisted in the application of well known computer codes and the results were arranged as reference table, used to assign the amplification coefficients to the rest of damaged localities. The present study has the aim of evaluating the accuracy of that methodology, following a completely different approach. The actual damages, detected by an aerial photo interpretation, are compared to the theoretical damages estimated through empirical curves, obtained from the analysis of recent Italian earthquakes. This approach was reliable enough to calibrate the results of the microzoning study and appropriate when an immediate assessment of the damage is required, to assign funds and estimate the amplification zones, that need to be investigated in finer detail.