Tephra hazard assessment at Mt. Etna (Italy)

Abstract. In this paper we present a probabilistic hazard assessment for tephra fallout at Mt. Etna (Italy) associated with both short- and long-lived eruptions. We analyzed wind data from the atmospheric soundings of the Italian Air Force at Trapani Birgi (western Sicily), and use the TEPHRA advection-diffusion-sedimentation model to capture the variation of wind speed and direction with time. Two different typologies of eruptions were considered in our analysis: eruptions forming strong short-lived plumes (SSL eruptions) and eruptions forming weak long-lived plumes (WLL eruptions). One Eruption Scenario (OES) for both typologies and the Eruption Range Scenario (ERS) for WLL eruptions were identified based on well documented past activity of Etna since the '90. First, model calibration was carried out for two well-known Etna explosive eruptions: the 22 July 1998 and July 2001 Etna eruptions. Second, probabilistic maps were compiled. Results clearly show that the eastern flanks are significantly affected by tephra deposition and that the WLL eruptions and the Plinian eruption of 122 BC represent the largest threat for both infrastructures and agriculture.