Test of a building vulnerability model for L'Aquila earthquake

During 2002, as part of a collaboration between the National Civil Protection Department and the University of L'Aquila, a methodology for assessing the vulnerability of an urban center was developed. The methodology considered the urban territory as well as the complex of physical and functional relationships of the urbanized territory and not a simple summation of elements, in order to analyze simultaneously the multiple factors necessary to determine the vulnerability of the whole center. This methodology was applied to the city of L'Aquila and two other smaller towns, and in previous studies, some maps representing the possible vulnerability of buildings were prepared for the centre of the city of l'Aquila. These maps graduate the possible vulnerability in four different classes and have a maximum resolution of 25 m. After the earthquake in April 2009, it is possible to assess the accuracy of the model comparing predicted vulnerability with the map of fitness for human habitation realized after the earthquake. The vulnerability map considered the buildings situated on the emergency routes, therefore, the comparison was carried out only for these areas. After the seismic event, the map of fitness for human habitation and the actual post-earthquake damage were available: these results were archived in an Access database and also mapped on a 1: 2,000 city map. To assure the consistency of these data, Access databases were geocoded and so cross checked with the results reported in the map files. The maps so obtained and verified were compared with the maps of the predicted vulnerability, rasterizing the information reported on the two maps at the same resolution. Thus, it has obtained a raster file containing differences between the vulnerability predicted and observed damages, evidencing that the biggest differences are limited to some small areas. Observing the localization of these areas, it seems that there may exist a correlation between biggest mismatch and some geophysical characteristics of the terrain that can cause local attenuation or amplification of the seismic waves. However, further investigations have to be carried on to confirm these initial results. The main elaborations were performed in open-source packages: GRASS, Q-GIS, and gvSIG.