Risk assessment of residential buildings for an eruption of Furnas Volcano, São Miguel, the Azores

This paper presents the results of a study of the risks to human settlements of a future eruption of the Furnas Volcano in the Azores. It makes use of previous geological studies to estimate the likely impact of the volcanic hazards on the surrounding settlements, given an eruption comparable with the last major eruption in the island in 1630; it presents the results of a comprehensive building-by-building survey of the settlements at risk to determine the exposure of the residential building stock to these hazards; and it uses data from recent experience of volcanic eruptions elsewhere to estimate the vulnerability of the buildings to each hazard and the likely scale of human casualties and building damage. The paper concludes with some recommendations for preparedness and protective measures which could be taken before an eruption to reduce the risk of human casualties from roof and building collapses. Principal among these are recommendations for strengthening the lateral load resistance of buildings built with the traditional vernacular techniques to better resist groundshaking during eruptions and earthquakes; upgrading local building code requirements with view to increasing the live load resistance of roofs, to levels similar to those applied in areas of heavy snowfalls, to prevent roof collapse from tephra loading. Other preparedness measures are also discussed with respect to volcanic earthquakes, volcanic bomb impact, pyroclastic flows and tephra falls. Many aspects of this paper are relevant to other volcanic areas around the world.