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4 - Populations around Holocene volcanoes and development of a Population Exposure Index
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- By Sarah K. Brown, University of Bristol, UK, M.R. Auker, University of Bristol, UK, R.S.J. Sparks, University of Bristol, UK
- Edited by Susan C. Loughlin, Steve Sparks, University of Bristol, Sarah K. Brown, University of Bristol, Susanna F. Jenkins, University of Bristol, Charlotte Vye-Brown
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- Book:
- Global Volcanic Hazards and Risk
- Published online:
- 05 August 2015
- Print publication:
- 24 July 2015, pp 223-232
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Summary
A way of ranking the risk to life from volcanoes is to establish how many people live in their vicinity. In addition to being an indicator of lives under threat, population exposure is a proxy for threat to livelihoods, infrastructure, economic assets and social capital. This report uses two indicators of population density around volcanoes to assess the current global exposure and as a risk indicator for individual volcanoes, and discusses this in combination with the Human Development Index (HDI) as a proxy for vulnerability.
Background
Ewert & Harpel (2004) introduced the Volcano Population Index (VPI), which estimates the number of people living within 5 and 10 km radii of volcanoes (VPI5 and VPI10). These population statistics, and VPI30 and VPI100 (population within 30 and 100 km of Holocene volcanoes) are reported in the VOTW4.0 (2013) database (www.volcano.si.edu; Siebert et al. (2010)). The Population Exposure Index, (PEI), was developed by Aspinall et al. (2011) for a study of volcanic risk in the World Bank's Global Facility for Disaster Reduction and Recovery (GFDRR) priority countries. Here, populations within 10 and 30 km radii were estimated and combined using weightings that reflect how historic fatalities vary with distance from volcanoes.
The VPI was developed on the basis that most eruptions are small to moderate in size (VEI ≤3), with footprints of less than 10 km. The VPI therefore represents the population exposures for most eruptions. Indeed, eruptions of VEI2 occur at a rate of approximately one every few weeks, and VEI3 several times a year (Siebert et al., 2010). Eruptions of larger magnitudes (VEI≥4) are less frequent, but often cause fatalities at distances well beyond 10 km (Auker et al., 2013). Hazard footprints from such eruptions commonly extend to tens of kilometres. The PEI thus complements the VPI, accounting for the high threat from large eruptions and potentially distal hazard types. An advantage of PEI is that only a single indicator parameter captures the exposure of populations around each volcano with the various VPI populations all contributing to the index and weighted according to historical evidence on the distribution of fatalities with distance. Here we develop and apply an amended version of the PEI, which correlates quite well with VPI10.
22 - Development of a new global Volcanic Hazard Index (VHI)
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- By M.R. Auker, University of Bristol, UK, R.S.J. Sparks, University of Bristol, UK, S.F. Jenkins, University of Bristol, UK, W. Aspinall, University of Bristol, UK, Sarah K. Brown, University of Bristol, UK, N.I. Deligne, GNS Science, New Zealand, G. Jolly, GNS Science, New Zealand, Susan C. Loughlin, British Geological Survey, UK, W. Marzocchi, Istituto Nazionale di Geofisica e Vulcanologia, Italy, C.G. Newhall, Earth Observatory of Singapore, Singapore, J.L. Palma, University of Concepcion, Chile
- Edited by Susan C. Loughlin, Steve Sparks, University of Bristol, Sarah K. Brown, University of Bristol, Susanna F. Jenkins, University of Bristol, Charlotte Vye-Brown
-
- Book:
- Global Volcanic Hazards and Risk
- Published online:
- 05 August 2015
- Print publication:
- 24 July 2015, pp 349-358
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- You have access Access
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Summary
Background
Globally, more than 800 million people live in areas that have the potential to be affected by volcanic hazards, and this number is growing [Chapter 4]. The need for informed judgements regarding the global extent of potential volcanic hazards and the relative threats is therefore more pressing than ever. There is also an imperative to identify areas of relatively high hazard where studies and risk reduction measures may be best focussed. Various authors have tackled this task at a range of spatial scales, using a variety of techniques. At some well-studied volcanoes, the geological record has been used in combination with numerical modelling to create probabilistic hazard maps of volcanic flows and tephra fall [Chapter 6 and 20]. Such sources of information can be hugely beneficial in land use planning during times of quiescence and in emergency planning during times of unrest. Unfortunately, creating high-resolution probabilistic hazard maps for all volcanoes is not yet feasible. There is therefore a need for a methodology for volcanic hazard assessment that can be applied universally and consistently, which is less data-and computing-intensive. The aim of such an approach is to identify, on some objective overall basis, those volcanoes that pose the greatest danger, in order that more indepth investigations and disaster risk reduction efforts can then be focused on them.
Previous methods
An index-based approach to volcanic hazard assessment involves assigning scores to a series of indicators, which are then combined to give an overall hazard score. Indicators typically include measures of the frequency of eruptions, the relative occurrence of different kinds of eruptions and their related hazards, the footprints of these hazards, and eruption size. Indices are well suited to the problem of volcanic hazard assessment, as they allow the decomposition of the complex system into a suite of volcanic system controls and simple quantitative variables and factors that jointly characterise threat potential.
Ewert (2007) presented an index-based methodology for assessing volcanic threat (the combination of hazard and exposure) in the USA, to permit prioritisation of research, monitoring and mitigation.