A definition of seismic vulnerability on regional scale: the structural typology as a significant parameter

In this work a criterion is presented to evaluate the seismic vulnerability on a regional scale based on an a posteriori method. This goal has been reached through the analysis of data collected after the 1976 Friuli seismic event on the base of a Regional Law (17/76) that performed a census of the damage for every building of the area struck by the earthquake. It was possible to derive the typological parameters able to define a degree of vulnerability. To this purpose the original database has been reorganized and processed, in particular to assess the quality of the information. This was done by comparing the earthquake intensity as computed on the base of the judgements given in the forms with the published isoseismal maps. After having characterized the building typologies and the associated vulnerability classes, we statistically evaluated the differences in their behaviour under seismic action. The parameters used are present both in the rich damage assessment forms filled in after the 1976 earthquake, and in the poorer census carried out by ISTAT every 10 years. Six significantly different typological classes were selected; these, once mapped to vulnerability classes, highlight the most vulnerable typologies. The following step is a vulnerability map for the Friuli-Venezia Giulia region at different detail degrees. At the most detailed level, vulnerability evaluation is based on the availability of information for each building or structural aggregate. At the other end, a coarse, less detailed vulnerability map only requires statistical data that identify the structural behaviour for different building typologies. The application of GIS techniques allows the integration of these data with other geographical and geophysical information. © 2001 OGS.