Analisi dei parametri locali per la riduzione delle incertezze nelle valutazioni di vulnerabilità dei centri storici: il caso di Vezzano (Arquata del Tronto, Marche)

This article develops an overall vulnerability index to seismic hazard based on a spatial approach applied to the historic center of Vezzano in Arquata del Tronto (Marche Region) that is taken as a case study. The identification of the case study is the result of a series of researches that focused on the outcomes of the seismic crisis that hit the inland areas of the Marche region, between 2016 and 2017. Vezzano is a small historic center; it has medieval origins with modifications over the following centuries, especially in the XV-XVI century. In more recent centuries, it has been the subject of a reorganization that has transformed the typological and structural layout of its buildings. This center, despite being composed of advanced degradation buildings, particularly vulnerable due to original construction deficiencies, has reacted better than other neighboring centers, such as Pescara del Tronto or Capodacqua which has been completely destroyed by seismic events. To refine the knowledge of the center, a series of analyzes have been made studying the geometric and architectural relief as well as the definition of the construction systems, in particular the masonry, in addition to the observations of some historical devices (chains, spurs, sleepers), used during past seismic events. The material and structural degradation has been analyzed to better describe the behavior of the buildings. A third level seismic microzonation was set up in order to highlight a series of specific site conditions. These data were compared with the results of the surveys verifying a correspondence between the most damaged or collapsed buildings and the local parameters. This allowed to elaborate a series of thematic maps to illustrate the condition of the center after the seismic crisis. Moreover, accurate evaluations are carried out to compare the observed damages to the local amplification parameters. A methodology is presented here that studies the nature of the vulnerability of such structures, it in the context of risk assessment, accounting to the local parameters. The vulnerability is therefore linked to different local factors that must be carefully analyzed, in order to achieve an effective reduction. Therefore, a specific methodology is identified that allows a vulnerability assessment of the aggregate buildings, in relation to local characteristics.