Lessons learnt from 2014 Mt Ontake and 2000 Mt Usu eruptions: findings from a post-eruption ballistic impact assessment trip to Japan Rebecca Fitzgerald, Ben Kennedy, Thomas Wilson, Graham Leonard, Kae Tsunematsu, George Williams rebecca.fitzgerald@pg.canterbury.ac.nz
VOLCANIC UNREST Forecasting large eruptions Major Eruption (Mount St. Helens, 1980;Pinatubo 1991) Decision Window when civil officials face critical decisions about public safety before the volcanic outcome is known. Time C.D. Miller, USGS
VOLCANIC UNREST Other possible outcomes of heightened unrest. Sudden onset, no decision window Decision Chaiten, Window 2008 MAJOR ERUPTION: MSH 1980, EVENTUAL ERUPTION: Soufriere Hills 1995 Variable unrest &/or small eruptions RETURN TO QUIET: Cotopaxi 2002 RETURN TO QUIET: Guadeloupe 1976-77 Time C.D. Miller, USGS
What are ballistics? Pieces of lava or rock ejected in an eruption on a ballistic trajectory Can travel hundreds of m/s and up to ~10 km from the vent Range from a few cm to tens of metres in diameter
Why do we care? Ballistics can kill, injure and severely damage buildings and infrastructure Ballistics are a potential hazard at many of New Zealand s volcanoes including Ruapehu, Tongariro and within the Auckland Volcanic Field Tricky risk management We need to better understand their potential impacts and how best to mitigate them
Trip Overview Ballistic impact assessment trip to Japan in July 2015 Mt Usu Life Safety Impacts to buildings Mt Ontake Collaborative project with: University of Canterbury, GNS Science, EQC, Mount Fuji Research Institute, Nagoya University and Geological Survey of Japan
Te Maari 2012 vs. Mt Ontake 2014 Very similar eruptions with very different consequences. Both the same eruption: style, size and types of hazards Both have popular hiking trails Te Maari eruption occurred at night in low season. Ontake occurred around midday in peak season when hundreds of people were on the mountain No injuries or fatalities at Te Maari, 58 fatalities and over 70 injuries at Ontake
Risk context Te Maari ~ 100,000 visitors/yr Three permanent unreinforced huts along TAC Well monitored Had 6 minutes of increasing precursory seismicity Mt Ontake ~ 1,000,000 visitors/yr 15 permanent unreinforced huts and lodges Well monitored Had 7 mins of increasing precursory seismicity and inflation
Ballistic size Ballistics generally thought of as bomb/block size (> 6.4cm) However both Te Maari and Ontake ballistics show that they can be much smaller
Revising protection actions All hikers that hid in buildings survived Many of those sheltering around buildings unable to get inside, died. As did those in the open. Reports of survivors using hiking packs as shields successfully Both successful and unsuccessful attempts at sheltering behind large boulders.
Hazard maps and signage
While in Japan, Grahem Leonard (GNS Science) had meetings with the JMA and GSJ to help improve their alert level system and posed in front of bakeries
NZ JAPAN Ballistic risk cooperation NZ alert levels focused on current volcano status and hazard distance forecasting given in alert bulletins. Japanese alert levels include forecasting and evacuation so reluctant to raise Volcanic research, the production of hazard maps and research around disaster impacts are not connected to JMA Working with JMA and GSJ to improve community linkage and risk management approaches NZ and JMA recently announced rapid warning via mobile phones. NZ = Auckland app, Red Cross, ERS, Google. Still won t help with unheralded eruptions.
Alert levels and restriction zones Level 3 (4km) Level 3 (3km) Level 3 (2km) Level 2 (1km)
Overview Ballistic impact assessment trip to Japan in July 2015 Mt Usu Building Damage Mt Ontake Collaborative project with University of Canterbury, GNS Science, EQC, Mount Fuji Research Institute, Nagoya University and Geological Survey of Japan
Mt. Usu 2000 eruption During the eruption > 60 new craters were formed Produced a wide range of hazards: Ballistics, mudflows, severe ground deformation Surrounded by populated towns Precursory earthquakes 4 days before eruption Residents evacuated the day before eruption
Severe building and infrastructure damage by ballistics
Severe building and infrastructure damage by ballistics
Take away messages Visited Mt Usu and Mt Ontake to learn more about ballistic impacts and Japanese risk management Ballistic risk management presents an immense challenge in populated areas NZ
Questions?? Thanks to: EQC, GNS and DeVoRA for funding this trip Ngai Tahu Research Centre for PhD scholarship Professors Yamaoka and Okada for sharing their data, photos and time.
Recurring ballistic hazard The same buildings were damaged in the 1979 eruption but only repaired NIED report recommended building ballistic shelters but nothing was done
Ballistic mapping and casualty modelling
Post-eruption recovery Land use planning: Land in the worst impacted areas was bought by the Ministry of the Environment Turned into a Geopark educational/tourist attraction Becker et al. 2010 Toya-usu-geopark.org
Hazard management Sabo dams Becker et al. 2010
Early warning systems? Both well monitored volcanoes with unheralded eruptions Had ~6-7 mins precursory activity before eruptions might be enough time to move people off summit or into shelters.