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How do we prepare for infrequent huge volcanic eruptions?
Setsuya Nakada The University of Tokyo
2014/11/28 1
Preface and contents
Experiencing the 2011 Tohoku Large Earthquake, less-frequent huge volcanic eruption also became paid attention by the society. Especially, the impact from huge volcanic eruptions became the final key issue to re-run the Nuclear Power Plants in Japan. In this talk, I would like to share the research background and present situation for forecasting them. 1. Recent volcanic eruptions 2. Regularity: volcanic explosivity index vs. eruption frequency 3. Diverse volcanic hazards 4. Monitoring and forecasting volcanic eruptions 5. Caldera eruptions and precursory phenomena 6. Nuclear Power Plant issue 7. Conclusions and suggestions
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Volcanology
• Volcanology is the study of volcanoes, lava, magma and related geological, geophysical and geochemical phenomena. (--geology, physics, chemistry, astronomical science, philology, archaeology, environmental science, social science, etc.)
• International Association of Volcanology and the Chemistry of Earth’s Interior (IAVCEI): The primary international focus for: (1) research in volcanology, (2) efforts to mitigate volcanic disasters, and (3) research into closely related disciplines, such as igneous geochemistry and petrology, geochronology, volcanogenic mineral deposits, and the physics of the generation and ascent of magmas in the upper mantle and crust.
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Mount Ontake eruption in September 2014; small eruption (VEI=1) but many casualties
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Asahi Shimbun
No precursory!
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Courtesy by Asahi Shimbun
JMA
JMA
BL type
BH type
A type
Dai
ly n
umbe
rs
Tilt change
Seismic signal (up-down)
Sep 1
Oct 1
Oct 1
Sep 1 Oct 1
11:52 11:45
•Seismic swam 17 days before. •LF event continued. •Crater inflation 4 min before.
•Small signals, different modes among eruptions. •Difficult forecasting of small eruptions.
Nishinoshima (2013-14) An continuous moderate eruption but limited access
Taken from Asahi Shimbun aircraft on
Nov. 13, 2014
1,000 km South of Tokyo
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Nov. 24, 2013
Chaitén, Chile: May 2008 VEI=4-5
• No eruption record since 9,400 years ago, not monitored.
• Seismicity activated just one day before eruption at a “remote” station (300 km).
Buenos Aires
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www.dailymail.co.uk
NASA (Image of the day)
Recent large (not huge) eruptions
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AFP/Getty Images Puyehue-Cordón Caulle, erupted in June 2011 VEI=4
NASA Image of the day
Tasmania
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Sinabung (N Sumatra) Dec. 2013~ Magma volume ~0.1 km3
Sinabung, Sumatra Kelud, Java
Kelud (Java) Feb. 13, 2014 (VEI=4) Magma volume ~0.12 km3
Eruption diversity in term of discharge rate
When discharge rate is high, the eruption is explosive.
Explosive eruptions
Lava flow and dome eruptions
Disc
harg
e ra
te (
m3 /
s)
Eruption volume (DRE 106 m3)
106
104
102
100
10-2
10-3 10-1 101 103 105
Kelud 2014
Shinmoe-dake 2011
Shinmoe-dake 2011
Unzen 1991-95
Sinabung 2014
Nishinoshima 2013-14
Original diagram by Kozono et al. (2013)
High discharge rate (roughly, high rate of magma ascent) Magma’s degassing illness introduces explosive eruption.
Ash of explosive eruption
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Regularity: volcanic explosivity index vs. eruption frequency
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Magnitude of volcanic eruptions
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Huge
Moderate
Small
Large
Regularity of volcanic eruptions
1. Eruptions have not occurred randomly in the statistic point of view.
2. Regularity between the magnitude (VEI) and frequency can be seen in different regional scales.
3. Among Indonesia, Japan and Chile, Indonesia is most active.
Lengths of volcanic belts Chile: 4000 km Indonesia: 3000 km Japan: 2500 km
Small Moderate Large Huge Huge eruption: Caldera-forming eruption
Abnormally quiet in recent Japan
Very quiet in Japan during these centuries! Large eruptions are very possible near future in Japan. Annual probability for VEI=6 to 7 eruptions in Japan is =10-4. The latest VEI=7 eruption in Japan is 7,300 years ago.
The largest eruption for these 100 thousand years Toba caldera eruption, 74,000 years ago
(~ 5 cm isopach of fallen ash)
Ash falling area of Toba eruption
In 1991
In 1815
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Impact of the Kikai caldera eruption 7,300 years ago
Erupted magma: >85 km3
All eruptives: >170 km3
Volcanic ash falling area
Tsunami area? Pyroclastic flow area
Courtesy by F. Maeno
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VEI=7
Diverse volcanic hazards
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• Ash fall • Pyroclastic flow/surge • Lava flow • Lahar (mud flow) • Debris
avalanche/landslide/flank failure
• Volcanic tsunami
Varieties of volcanic eruptions/hazards
Tephra: fragmental material produced by a volcanic eruption
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Volcanic Ash Fall and pyroclastic flow
Pompei--AD79 tragedy
Pyroclastic surge
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[Story] Roman People could survived during ash falling. However, they were killed by pyroclastic flow (surge). [Lesson] First priority is for: the area of pyroclastic flows. People can survive in area the ash falling, if prepared. However, the effect to the infrastructure and environment are different.
Volcanic ash problems
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Flashover on glass insulator coated with 3 mm-thick wet volcanic ash, by 40 kV. Watson et al. (2011)
In April 2010, volcanic eruption (Eyjafjallajokull, VEI=4) in Iceland under the glacier produced very fine volcanic ash, which drifted over the northern Europe, resulting in airports closures.
Sulfur dioxide gas combines with water from the atmosphere and the volcanic cloud to produce tiny droplets of sulfuric acid - sulphate aerosols • Stratospheric aerosols have residence times of 2-3 years • Tropospheric aerosols have very short residence times •Ash has very short residence times, but effects are relatively unexplored
Atmospheric effects of volcanic ash
From McCormick et al., 1995
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The Atmospheric transparency after Pinatubo eruption (VEI=6) in 1991
• The aerosols absorbed incoming sunlight, the global temperature dropped by ~0.6 °C
• The effect continued at least four years.
http://earthobservatory.nasa.gov/IOTD/view.php?id=1510
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Monitoring and forecasting volcanic eruptions
The present level of volcanic eruption forecasting: Abnormal phenomena can be detected on the volcanoes equipped with the sufficient monitoring instrument. Based on them together with our empirical knowledge, we can say that an eruption is approaching . The scenario (magnitude, duration, mode, etc.) is difficult to say strictly.
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Seismicity
• Data from Kyushu University, guided in Nakada et al. (1999).
Usu volcano, Hokkaido
Erup
tion
Erup
tion
Felt earthquakes in 1910
Large earthquakes in 2000
Unzen volcano, Kyushu
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Deformation (GPS)
Mauna Loa, Hawaii
Shinmoe-dake (Kirishima), Kyushu VEI=3 Nakada et al. (2013)
Shinmoe-dake
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GPS baseline
Seismicity
Example of ground deformation observed in caldera areas with In-SAR
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Swelling observed at Uturuncu, Southern Central Andes during 1996-2000. Hickey et al. (2013)
Swelling observed at Yellowstone Caldera during 1996-2000
Pinatubo 1991
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1991 eruption (VEI=6) at Pinatubo, Philippines
Plume height
Volcanic gas (SO2)
PF event (column-collapse)
end PF event (dome-collapse)
end
Explosive
Magmatic
Magmatic
end end
Phreatic No collapse
Magma ascent
Yes/No EQ-type change, num. incr. w/ accelerate deformation
Yes/No Local deform. + EQ increase
Modified from 2011 ver.
es/No eform. + EQ
ncrease
Yes/No Juvenile in ash
Since Dec. 30, ‘13 Late Dec. ‘13
Mid-Nov. ‘13
-Dec. ‘13
Aug-Sep. ’10 Sep-Oct. ‘13
Edifice collapse, followed by the above scenarios
Sinabung volcano, Indonesia
Lava flow/dome
Eruption Scenarios • Event trees are beng introduced for forecasting the scenarios
of approaching or on-going eruptions recently. • This probabilistic consideration became important to avoid
misinterpretation.
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Caldera eruptions and precursory phenomena
When is the magma stored under the volcano, and how can we detect the abnormality (forecast the caldera eruption)?
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VEI 9 8 7 6 5 4 3
Caldera eruption
Repose time and magma accumulation rate
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F. Costa (2008)
Magma accumulation in the caldera volcanoes is faster than that in normal volcanoes.
Modeling of elemental diffusion and annealing in crystals Druitt et al (2012), Gualda et al. (2012) and so on.
Recent researches show that magma filled the chamber a hundred to thousands year before the climactic eruptions.
Magma accumulation time Examples in Santorini, Greece and Long Valley, USA
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Residence time deduced by crystal Chanbai-shan (9th Century, VEI=6)
Zou et al (2010) Lithos 119, 289-296.
U-Th disequiliburium age: ~ 9,000 years. As the crystal , zircon, may be recycled. the age determined is the maximum time. Accumulation rate = 107 to 6 m3/year
Pinatubo 1991
5 km3
2.5 km
10 km3 Krakatau 1883
8 km
~100 km3
鬼界 7300年前
20 km
~300 km3
Aso 90,000 years ago
20 km
1000 km3
Yellowstone 640,000 years ago 2800 km3
Toba 74,000 years ago
Thickness of magma stored in the crust before caldera eruptions (d)
d=0.8 km d=0.4 km
d=0.4 km
d=0.2 km
d=1 km d=1 km
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60 km 70 km
d
Caldera size Erupted magma represents the upper <1 km.
Could those amounts of magma be stored geologically suddenly? If so, we can monitor this!
Geological model
Ground deformation at Aira Caldera Magma accumulated under here already?
∆V/dt = ~107 m3/y Takes ~104 yrs to get ~100 km3 of magma in this rate.
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Nakao et al. (2013)
Volume change during 2003 to 2012
Apr. 2003 to Apr. 2009
Sakurajima
Precursory of Super eruptions in Indonesia and Philippines
No catastrophic deformation has not been noticed, but clear precursory phenomena had been observed several months before the climactic eruption. 2014/11/28 35
Mar Apr
Tambora 1815 (VEI=7)
Krakatau 1883 (VEI=6)
Collapse
Collapse
EQs started
EQs started
Plume height (km)
Lava dome
Extensive hydrothermal activity
Extensive hydrothermal
Explosion
EQs started
May Jun Jul
Aug Sep
Mar Apr
May Jun Jul
Pinatubo 1991 (VEI=6)
Day before the climax
days
Takada and Furukawa (2014) Iwanami Kagaku, 84, (1), 64-68
Plume height (km)
• Surface manifestation (small explosion, high seismicity and thermal activity) occurs a few months before the climax.
• Becomes more clear weeks before—maybe long enough for mass evacuation.
1yr 10 yr 100 yr 1 kyr 10 kyr
Precursory and repose times
1 month before
1 year before
1 day before
1 hour before
Prec
urso
ry p
erio
d
Passarelli and Brodsky (2012)
Usu Miyakejima
Unzen Shinmoe
Repose time 2014/11/28 36
Ontake Pinatubo
Tambora
Krakatau
Fuji
Power Plant siting issue
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Map of Nuclear Power Plants in Japan
32 units 1 unit 2 units
Kashiwazaki-Kariwa
Higashidori (Tohoku)
Onagawa
Fukushima-2
Fukushima-1
Tokai
Hamaoka
Ikata
Sendai Genkai
Shimane
Takahama
Ohi
Mihama
Tsuruga
Shiga
Tomari
*
A A
A
A
A
A: ABWR/APWR
A
Higashidori (TEPCO) A *
A Ohma
A
In operation 23 units Under construction 1 unit License applied 2 units
PWR BWR Total 55 units 2 unit 4 units
Tokyo
Before 2011
Aso Volcano
Caldera eruptions in Japan for about
100 kyears
Towada 10 kys
Aira ash
Toya ash
Toya caldera 100 kyrs
Shikotsu caldera 32 kyrs
Kutcharo caldera 110 kyrs
Aso ash
Aira ash Kikai ash
Kikai caldera 7 kyrs
Ata caldera 85 kyrs
Aira caldera 29 kyrs
Yellow: pyroclastic flow field
Aso caldera 90 ka
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Target volcanoes in Sendai NPP
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Aira caldera
Sendai NPP
Genkai NPP
Aso caldera
Ata caldera
Kikai caldera
Kakuto-Kobayashi caldera
Volcanoes requested in monitoring
Wikipedia
The Aira caldera was left as the most capable volcano after screening and evaluation.
Pyroclastic-flow deposits from the Aira Caldera (29 k years ago)
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Geology Simulation by Kyushu Electric Power Company
Sendai
Distribution of the Ito pyroclastic flow deposits Yokoyama (2000)
Issues related to re-running of the Sendai NPP
[background] • It seems that the site evaluation was not strict under the government
decision (rerunning). As a result, the final safety was brought to over-dependence on the volcanic monitoring ability.
• The present volcanology cannot forecast a caldera eruption with the leading time as long as a few years, necessary for transporting spent fuel.
[Solutions] • Setting severe thresholds, the operating company should shut down the
reactor when the thresholds are reached, and transport the spent fuel soon. • Since the spent fuel has already been stored in the NPP sites, however, the
volcanological monitoring and preparation for their transportation should be begun without the judgment of re-running.
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Natural disasters and researchers
• A natural disaster will happen, as long as the earth continues business and man lives. Preventing disasters is not the direct task of researchers.
• We have to recognize threats from nature from which we have received the blessing. There is no other way to minimize natural disasters than preparing for them upon understanding the society’s vulnerability.
• Natural Hazard Research is for understanding the processes, the structures, and results. It provides the wisdom to the society for preparing for the hazards.
• The knowledge should not be over-depended by the society but be utilized effectively. If not, nature’s retaliation is waiting for us in future.
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Conclusions and suggestions • The leading time to the climactic eruption, when forecasted, may be
weeks to months, which is long enough for people’s evacuation, if prepared sufficiently, but too short to start the preparation since then.
• Forecasting caldera eruption is the international issue. • Monitoring technique and modeling of caldera eruptions should be
improved not only by volcanologists but also scientists with various fields, including young scientists.
• Though the probability of huge volcanic eruptions is “VERY” low, it is not late to begin discussion on the situations which we would face.
• It is not too early to start discussion on forecasting and mass evacuation among scientists, economists, politicians and so on in the international level.
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