Forecasting seismic damage scenarios of residential buildings from rough inventories: a case-study in the Abruzzo Region (Italy)

A model is presented for forecasting the seismic vulnerability and probability of damage of ordinary building types, as a function of the local macroseismic intensity or correlated parameters of the ground motion. The conventional definitions of damage degrees and vulnerability classes of the building types have been assumed according to the EMS98 macroseismic scale. The model allows damage scenarios to be evaluated in selected areas where an inventory of the buildings, containing at least some qualitative information is available, in order to recognize, for the different types, the corresponding vulnerability class or at least the probability of membership to the vulnerability classes. The epistemic uncertainty of the qualitative definitions suggested by the scale for frequencies of damage is taken into account through the formalizing of the imprecise probabilities, i.e. through convex sets of possible probability distributions on the discrete space of the damage degrees, with particular reference to their description by means of random sets, both non-consonant and consonant (fuzzy sets). It is thus possible to obtain upper/lower bounds of the expectation of interesting functions of the damage degrees (e.g. number of victims, unusable buildings, and collapsed buildings). The model has been applied to the entire area of the Abruzzo Region (Central Italy), using the inventory of buildings recorded by the National Statistics Agency. Some comparisons are given between the expected damage and that observed after the strong earthquake that in April 2009 struck a more restricted zone of the region (the town of L'Aquila and surrounding countryside)