Building vulnerability and seismic risk analysis in the urban area of Mt. Etna volcano (Italy)

The tectonic system of the eastern flank of Mt. Etna volcano (Sicily, Italy) is
the source of most of the strongest earthquakes occurring in the area over the last
205 years. A total of 12 events with epicentre intensities CVIII EMS have occurred at Mt.
Etna, 10 of which were located on the eastern flank. This indicates a mean recurrence time
of about 20 years. This area is highly urbanised, with many villages around the volcano at
altitudes up to 700 m a.s.l. The southern and eastern flanks are particularly highly populated
areas, with numerous villages very close to each other. The probabilistic seismic
hazard due to local faults for Mt. Etna was calculated by adopting a site approach to
seismic hazard assessment. Only the site histories of local volcano-tectonic earthquakes
were considered, leaving out the effects due to strong regional earthquakes that occurred in
north-eastern and south-eastern Sicily. The inventory used in this application refers to
residential buildings. These data were extracted from the 1991 census of the Italian
National Institute of Statistics, and are grouped according to the census sections. The
seismic vulnerability of the elements at risk belonging to a given building typology is
described by a vulnerability index, in accordance with a damage model based on macroseismic
intensities. For the estimation of economic losses due to physical damage to
buildings, an integrated impact indicator was used, which is equivalent to the lost building
volume. The expected annualised economic earthquake losses were evaluated both in
absolute and in relative terms, and were compared with the geographical distribution of
seismic hazard and with similar evaluations of losses for other regions.