WIT Press

Volcanic Risk Zoning In The Island Of Ischia (Italy)


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M. Mattera, J. F. Martín-Duque, J. Pedraza, M. A. Sanz, R. M. Carrasco & J. M. Bodoque


Ischia constitutes the largest and more populated island of the Neapolitan archipelago. As other active volcanic areas along the middle-west Italian coast (Soma-Vesuvius and Phlegrean Fields), the volcanic activity of Ischia sterns from deep fractures associated with the Tyrrhenian sea-floor spreading over the last 10 million years. The record of historic eruptions along with signs of thermal activity show that there is a potential for hazardous volcanic events. The paper constitutes a first approach to the zoning of the volcanic risk of the island, by considering the three main factors involved -the elements at risk, or value (population), the hazard posed by the volcanic phenomena, and the degree of damage resulting from the hazard (vulnerability). The analysis of the hazard was carried out by using Geographic Information System (GIS) techniques and eruptive models. The analysis was based not only on the evaluation of the probability of occurrence of a future new eruption within the island, but also on the evaluation of the probability of occurrence of different intensities and typologies. As those typologies have different energy and potential for destruction, they also condition the vulnerability of the value, which is different for each volcanic phenomenon. The results show lower volcanic risk levels than for similar volcanic areas. However, if two characteristics of the analysed territory are taken into account -the high tourist affluence and the insularity-, then the risk shouldn't be underestimated. 1 Geological and vulcanological setting of Ischia The island of Ischia is located northwest of the gulf of Naples (figure 1). The volcanic activity of the Neapolitan archipelago is related with the recent geological evolution of the Tyrrhenian Sea. About 10 million years ago, the