IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

4A1_4D-O7

Room A6

Date/Time: July 24 10:15-10:30

TOPAZ: Long-term volcanic risk forecasting for deep geological repositories forradioactive waste
Ellie Scourse1 , Chuck Connor2 , Olivier Jaquet3 , Steve Sparks4 , Willy Aspinall4 , Neil Chapman1 , Mick
Apted5 , Junichi Goto6 , Hideki Kawamura7
1

MCM Consulting, Switzerland, 2 University of South Florida, USA, 3 In2Earth, Switzerland, 4 Universityof Bristol, UK, 5 Intera, USA, 6 NUMO, Japan, 7 Obayashi Corporation, Japan
E-mail: ellie.scourse@mcm-international.chThe TOPAZ Project is an unusual application of volcanic event forecasting as it endeavours to look forward
thousands of years into the future. The 2011 Tohoku earthquake highlighted the susceptibility of Japan to major
disruptive tectonic events, but also the need to adopt risk-based approaches to quantifying specific hazards, inparticular the location-specific likelihood of events exceeding given hazard levels. Japan intends to manage
its higher activity radioactive wastes from nuclear power generation in deep geological repositories. Geologicalrepositories might be susceptible to disruption by direct hit or closely adjacent events such as volcanic intrusion
or major fault shear, as well as by slower processes, such as exhumation by uplift and erosion. The likelihood ofspecific impacts needs to be quantified for different timeframes, so that any consequent radiological risks can beestimated. For tectonic events, a risk-based approach combining specific event likelihood with consequences canbe used to help decide on site suitability, the treatment of hazards from future volcanic events is more challenging.
Since 2002, the Nuclear Waste Management Organisation of Japan has been developing methodologies forquantifying a range of tectonic hazards at potential sites. The avoidance of disruption over the first few thousandsof years is of paramount importance in a safety case for waste disposal, as the intrinsic hazard potential ofthese wastes is high during this period. Although hazard potential decreases considerably after a few thousandyears, regulatory requirements might entail estimating impact scenarios out to 1 Ma. One development of theproject extends the 100 ka methodology for forecasting over longer periods by using expert elicitation to captureexpert judgments on alternative modes of evolution of the tectonic system and associated volcanic events, andto characterize the related process uncertainties. This technique rationalizes the full range of expert knowledge
and converts it into relative scenario weights to support probabilistic assessment for both tectonic and volcanicfutures. For the latter, the approach developed by NUMO produces quantified hazard maps of impacts for use
in site selection. These have been developed to show the probability of any event within 25 km2 blocks and theprobability of explosive volcanic events of a specified magnitude (M5) or greater on the VOGRIPA scale. The maps
provide information for quantitative radiological risk assessments and quantify project risk by identifying locations
where uncertainties/risks are either acceptable or a credible safety case would be difficult to sustain. This paper
briefly outlines the approach, provides examples of the hazard maps produced for different regions of Japan anddiscusses the uncertainties involved in this novel application of volcanic risk evaluation. Additional current work isextending the scope to include caldera-scale event likelihood.

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