Articles | Volume 17, issue 11
Nat. Hazards Earth Syst. Sci., 17, 1999–2015, 2017

Special issue: Linking faults to seismic hazard assessment in Europe

Nat. Hazards Earth Syst. Sci., 17, 1999–2015, 2017

Research article 22 Nov 2017

Research article | 22 Nov 2017

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

Laura Peruzza1, Raffaele Azzaro2, Robin Gee1,5, Salvatore D'Amico2, Horst Langer2, Giuseppe Lombardo3, Bruno Pace4, Marco Pagani5, Francesco Panzera3, Mario Ordaz6, Miguel Leonardo Suarez6, and Giuseppina Tusa2 Laura Peruzza et al.
  • 1Istituto Nazionale di Oceanografia e di Geofisica Sperimentale – OGS, 34010 Sgonico (TS), Italy
  • 2Istituto Nazionale di Geofisica e Vulcanologia (INGV), 95123 Sezione di Catania – Osservatorio Etneo, Italy
  • 3Dept. of Biological, Geological and Environmental Science, University of Catania, 95129 Catania, Italy
  • 4DiSPUTer, University “G. d'Annunzio” Chieti-Pescara, 66013 Chieti, Italy
  • 5GEM Foundation, 27100 Pavia, Italy
  • 6UNAM, 04510 Coyoacan, CDMX, Mexico

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 site-specific 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.

Short summary
It is well known that volcanoes and earthquakes are associated, and some active volcanoes cause damaging earthquakes. Nonetheless, volcanoes usually are not pinpointed on a hazard map, as the effects of shallow, volcanic earthquakes can be overshadowed by stronger tectonic earthquakes in the region, particularly when long exposure periods are considered. In this study we faced some challenges with software implementations and original concept scheme for an original PSHA at Mt. Etna, Italy.
Final-revised paper