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Title

Long-term multi-hazard assessment for El Misti volcano (Peru)

Authors
Sandri, Laura
Thouret, Jean-Claude
Constantinescu, Robert
Tonini, Roberto
Published in Bulletin of Volcanology. 2014, vol. 76, no. 2, p. 771
Abstract We propose a long-term probabilistic multi-hazard assessment for El Misti Volcano, a composite cone located <20 km from Arequipa. The second largest Peruvian city is a rapidly expanding economic centre and is classified by UNESCO as World Heritage. Weapply theBayesianEvent Tree code for Volcanic Hazard (BET_VH) to produce probabi- listic hazard maps for the predominant volcanic phenomena that may affect c.900,000 people living around the volcano. Themethodology accounts for the natural variability displayed by volcanoes in their eruptive behaviour, such as different types/sizes of eruptions and possible vent locations. For this purpose, we treat probabilistically several model runs for some of the main hazardous phenomena (lahars, pyroclastic density currents (PDCs), tephra fall and ballistic ejecta) and data from past eruptions at El Misti (tephra fall, PDCs and lahars) and at other volcanoes (PDCs). The hazard maps, although neglecting possible interactions among phenomena or cascade effects, have been produced with a homogeneous method and refer to a common timewindow of 1 year. The probabilitymaps reveal that only the north and east suburbs of Arequipa are exposed to all volcanic threats except for ballistic ejecta, which are limited to the uninhabited but touristic summit cone. The probability for pyroclastic density currents reaching recently expanding urban areas and the city along ravines is around 0.05 %/year, similar to the probability obtained for roof-critical tephra load- ing during the rainy season. Lahars represent by far the most probable threat (around 10 %/year) because at least four radial drainage channels can convey themapproximately 20 kmaway from the volcano across the entire city area in heavy rain episodes, even without eruption. The Río Chili Valley repre- sents the major concern to city safety owing to the probable cascading effect of combined threats: PDCs and rockslides, dammed lake break-outs and subsequent lahars or floods. Although this study does not intend to replace the current El Misti hazard map, the quantitative results of this probabilistic multi-hazard assessment can be incorporated into a multi-risk analysis, to support decision makers in any future improvement of the current hazard evaluation, such as further land-use plan- ning and possible emergency management.
Keywords BET_VHTITAN2DTEPHRA2Probabilistic volcanic hazardMulti-hazard assessmentEl MistiArequipa
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Other version: http://link.springer.com/10.1007/s00445-013-0771-9
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Research group Physical Volcanology and Geological Risk
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SANDRI, Laura et al. Long-term multi-hazard assessment for El Misti volcano (Peru). In: Bulletin of Volcanology, 2014, vol. 76, n° 2, p. 771. https://archive-ouverte.unige.ch/unige:42003

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Deposited on : 2014-11-19

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