Volcano-tectonic seismicity and related hazard: a component of the multi-hazard assessment in the highly exposed region of Mt. Etna (Italy)

In this study, seismic hazard, a component of the multi-hazard assessment studied in the framework of the PANACEA project, was performed following the probabilistic approach (PSHA) based on historical macroseismic data. This approach uses intensity site observations to compute the seismic history for each investigated locality. Site seismic histories completeness are improved the integrating observed intensities with "virtual" values calculated according to attenuation laws, starting from the earthquake parameters (epicentre and epicentral intensity). The probability distribution of the expected intensities at a given site is calculated for exposure times of 10, 30 and 50 years. Results are given as reference intensity and peak ground acceleration for a chosen exceeding probability. In order to obtain hazard also in terms of expected peak ground acceleration (PGA) a relation between macroseismic intensity and ground acceleration calibrated for Mt. Etna was also developed. A PGA value was predicted for each intensity site observation using a specific ground motion model for Mt. Etna shallow events, assuming a soil class A. We tested the performance of the obtained relationship through synthetic and observed PGAs associated with the most energetic seismic event instrumentally recorded at Etna. Finally, the probability distribution for PGA at the site for a given exposure time results from the combination of the corresponding seismic hazard curve for the macroseismic intensity and the specific local intensity-PGA relationship.