GNGTS 2017 - 36° Convegno Nazionale

196 GNGTS 2017 S essione 1.3 ASSESSING THE IMPACTS OF EFFUSIVE ERUPTIONS AND QUANTIFYING ASSOCIATED RISKS AT ETNA VOLCANO C. Del Negro 1 , G. Bilotta 1 , A. Cappello 1 , G. Ganci 1 , A. Herault 1,2 , V. Zago 1,3 1 Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo, Catania, Italy 2 Conservatoire National des Arts et Métiers, Département Ingénierie Mathématique, Paris, France 3 Università di Catania, Dipartimento di Ingegneria Elettrica Elettronica e dei Sistemi, Catania, Italy Despite our knowledge of volcanic hazards and our ability to monitor volcanic activity, the opportunities that effusive eruptions of Etna volcano could harm people, property and services are greater today than ever before. Growing populations, which has almost tripled in the area around Mt. Etna during the last 150 years, and the fertility of volcanic soils encourage people to settle over the volcano’s slopes. Because lavas flows at Mt Etna are usually slow moving (from a few meters to several tens of km/h) and localized hazards, fatalities are rare, but under certain circumstances they can occur. The chance of dying in an eruption is small enough that most people ignore the hazard. However, the dangers are real. A 2013 analysis of lava flow hazards and their distribution around the Etna volcano showed them to be far more dangerous than previously expected (Del Negro et al. , 2013). Effusive eruptions at Mt. Etna have been frequent in historical times both from summit and flank vents, with lava flowing for long distances over the volcano’s slopes (Cappello et al. , 2012). Etnean flank eruptions can bury buildings, infrastructure and vegetation under several meters of hardened rock causing complete destruction. Indeed people are rarely able to use homes and agricultural land buried by lava flows or sell them for a long time. During the past century, major flank eruptions causing significant damage to crops and infrastructures have occurred in 1923, 1971 or in 1983. Additionally lava flows from flank eruptions have also caused damage to towns and villages. Indeed, Mascali was almost completely destroyed in 1928 and Fornazzo was threatened in 1979, as well as Randazzo in 1981 and Zafferana Etnea in 1992. More recently, during the 2001 and the 2002-2003 crisis, tourist facilities in the summit area have been devastated leading to serious consequences for the local economy (Del Negro et al., 2013). The growing number of these abrupt and violent events since 1971 (Vicari et al. , 2011) and the expending use of areas near the volcano increases the potential impact of future eruptions. The increasing exposure of a larger population is often derived from a poor assessment of the volcanic hazard, allowing inappropriate land use in vulnerable areas. Therefore, a correct assessment is an essential component in reducing the losses due to volcanic disasters. To mitigate the potential consequences resulting from the occurrence of an effusive eruption, it is crucial to reliably assess both hazard and risk to forecast the areas likely to be inundated by future lava flows and the associated damage. Risk assessment quantifies the potential economic and social impacts (loss of property, life, etc.) resulting from volcano hazards. Hazard assessment, which is a necessary precursor to risk assessment, deals with evaluating the likelihood of occurrence of events, such as lava flows, that may have serious economic and social impacts. (Del Negro et al., 2013). In order to estimate the amount of damage that can be caused by a lava flow, it is useful to be able to predict the size and extent of such flows. Numerical simulation is a good tool to examine such events (Bilotta et al. , 2012). With such simulations, one can explore various eruptive scenarios and these can specifically be used to estimate the extent of the inundation area, the time required for the flow to reach a particular point and resulting morphological changes (Del Negro et al. , 2016). During the past few decades there has been an ever growing interest in understanding, quantifying and modelling lava flow hazards. This has produced some high quality physics-based models, such as the MAGFLOW lava flow emplacement model, which evaluate occurrence probabilities and spatial extents of lava flow hazards (Del Negro et al. , 2008). These models have allowed a quantitative assessment of lava flow hazards and have greatly contributed to disaster risk reduction and management (Cappello et al ., 2016).