When probabilistic seismic hazard climbs volcanoes: the Mt. Etna case, Italy – Part 2: Computational implementation and first results

Abstract

Abstract. This paper describes the model implementation and presents results of a probabilistic seismic hazard assessment (PSHA) for the Mt. Etna volcanic region in Sicily, Italy, considering local volcano-tectonic earthquakes. Working in a volcanic region presents new challenges not typically faced in standard PSHA, which are broadly due to the nature of the local volcano-tectonic earthquakes, the cone shape of the volcano and the attenuation properties of seismic waves in the volcanic region. These have been accounted for through the development of a seismic source model that integrates data from different disciplines (historical and instrumental earthquake datasets, tectonic data, etc.; presented in Part 1, by Azzaro et al., 2017) and through the development and software implementation of original tools for the computation, such as a new ground-motion prediction equation and magnitude-scaling relationship specifically derived for this volcanic area, and the capability to account for the surficial topography in the hazard calculation, which influences source-to-site distances. Hazard calculations have been carried out after updating the most recent releases of two widely used PSHA software packages (CRISIS, as in Ordaz et al., 2013; the OpenQuake engine, as in Pagani et al., 2014). Results are computed for short-to mid-term exposure times (10% probability of exceedance in 5 and 30 years, Poisson and time dependent) and spectral amplitudes of engineering interest. A preliminary exploration of the impact of sitespecific response is also presented for the densely inhabited Etna's eastern flank, and the change in expected ground motion is finally commented on. These results do not account for M > 6 regional seismogenic sources which control the hazard at long return periods. However, by focusing on the impact of M < 6 local volcano-tectonic earthquakes, which dominate the hazard at the short-to mid-term exposure times considered in this study, we present a different viewpoint that, in our opinion, is relevant for retrofitting the existing buildings and for driving impending interventions of risk reduction.

Preface: Linking faults to seismic hazard assessment in Europe

“…This special issue includes 11 papers focused on data gathering (García-Mayordomo et al, 2017;Hintersberger et al, 2018;Jomard et al, 2017) as well as seismic and surface rupture hazard modelling (Avital et al, 2018;Valentini et al, 2017;Chartier et al, 2017a, b;Gülerce et al, 2017;Azzaro et al, 2017;Peruzza et al, 2017;Boncio et al, 2018).…”

“…Azzaro et al (2017) and Peruzza et al (2017) are two companion papers concerning the seismic hazard assessment of Mt Etna (Italy); the first paper tackles the problem of characterizing low-magnitude and shallow seismic sources in a volcanic area, while the second one presents specific implementations and first seismic hazard results obtained for Mt Etna.…”