A GIS system as a tool for the integrated analysis of geological data and seismic effects: historic centre of Palermo

An integrated analysis of data coming from completely different scientific sectors and concerning the area of Palermo's historic centre is introduced, implemented by using a GIS application developed on a data model oriented to issues of urban geology. GIS technology has been an effective tool in constructing a reliable lithostratigraphic database, the starting line for any evaluation of the local seismic response. Palermo's historic centre has been divided using an applied grid characterized by square module geometry, each of which has a spread of 100 m per side. The analysis of the litostratigraphic data, facilitated by the GIS, has allowed us to establish the trend of the most important factors controlling the seismic hazard in the area. For many grid elements we have defined the characterising lithotechnical succession model, the average thickness of soils characterized by poor geomechanical characteristics and the average well depth. The seismic response map constructed by Guidoboni and Mariotti (1999) on the grounds of the cumulative effects caused of the three most damaging earthquakes felt in the Palermo area over the last three centuries has been compared with the map reporting the trend of the evaluated hazard factors. The agreement has been quite remarkable. The grid elements exhibiting higher level damage are characterized by the worst conditions of the seismic hazard factors examined. Only a very small number of grid elements is characterized by damage that appears to be anomalous on the grounds of local geology. This anomalous damage may be result of many other factors, first and. foremost a higher vulnerability of the buildings. The presented case study shows that research and applications based on data crossing can be simplified and thus enhanced using GIS technology.