Vulnerability instrumental check on strategic structures at regional scale

In order to increase the seismic safety of people, it is necessary to study and assess the risk they may be exposed; obviously it depends mainly on the damageability of buildings and infrastructures affected by a dangerous event. The damageability of the constructions can be evaluated with different widening levels, depending on the amount and the quality of the data available. A low level analysis is usually carried out applying statistical methods, basing on poor data (often documental ones, i.e. ISTAT forms) collected for a wide territory. Otherwise a high level analysis requires a more detailed and complete data set. This typology of analysis produce accurate results, but it is very expensive and time consuming; therefore, it is generally applicable only for assessing a limited number of structures. Intermediate levels of analysis exist too; most of them use data collected using specific forms for each building (i.e. GNDT II level forms). In all methods the results of the analyses depend on the evaluations of the surveyor, on the quality of the data and on the algorithm used. In fact each parameter has its own uncertainty and the result is both a combination of parameter values and of uncertainties; this implies that the results are defined with an uncertainty higher than the one of each parameter. Furthermore the evaluation is subjective, and often it is not possible to recognize or identify all the parameters and the surveyor has to “recognize and assess” them indirectly. In this paper the authors propose a direct way to evaluate some vulnerability parameters, i.e. a vulnerability check based on geophysical surveys, in particular on tremor measurements. Geophysical measures on different structures (buildings or bridges, in this article) allow to derive some objective results that can be used for the evaluation of some vulnerability parameters, in particular to obtain an instrumental check that can address and guide the subsequent analyses, starting from the structures with highest risk.