Extensive Microzonation as a Tool for Seismic Risk Reduction: Methodological and Political Issues

Budget limitations require an optimal allocation of resources devoted to seismic risk reduction. In order to allow local Authorities to operate public interventions to strengthen more exposed structures, increase population preparedness and improve emergency planning, a detailed knowledge of seismic hazard at the scale of a municipality (or of the minimal administrative structure in charge for prevention activities) is mandatory. To this purpose, a gap must be filled between seismic hazard assessment at regional scale and seismic response study at the scale of a single building, which is typical anti seismic engineering practice. Seismic Microzonation operates at this intermediate scale, focusing on heterogeneities in the seismic ground motion expected at the scale of a settlement (village or town) as an effect of local subsoil and morphological conditions. Being extensive in nature, its sustainability requires the development of specific methodologies, characterized by cost-effectiveness and, at the same time, able to provide reliable and useful outcomes. In this paper, the seismic microzonation strategy developed in Italy and applied in the last 10 years is briefly outlined. Sharing this experience with other countries prone to damaging earthquakes like Italy, may be of main importance to develop a common strategy to cope with future earthquakes.