Unrest that led to eruption: Unzen and Kirishima , Japan
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Transcript of Unrest that led to eruption: Unzen and Kirishima , Japan
Unrest that led to eruption: Unzen and Kirishima, Japan
Setsuya Nakada1 and Hiroshi Shimizu2
1. Volcano Research Center, Earthquake Research Institute, The University of
Tokyo2. Institute of Seismology and Volcanology. Kyushu University
Volcano Observatory Best Practice Workshop - Near Term Eruption Forecasting
Erice, Sicily (IT), 11 - 15 September 2011
1663 - 1664: More than 30 people were killed by earthquakes and debris flows.
1792: Failure of Mt. Mayuyama (old lava dome) generated tsunami. About 15,000 people were killed.
1990 - 1995: Lava effusion continued for almost 4 years.(2x108 m3 of dacite lava was extruded)
44 people were killed by pyroclastic flows. About 2,500 houses were destroyed.
Mt. Fugen-dake(Main Peak of Unzen Volcano)
Mt. Mayuyama
Shimabara City
Eruption history at Mount Unzen
Nov. ‘89 Dec. ‘89
July ‘90 Oct. ‘90
Nov. 19, 1990
Precursor of eruption (seismicity)
Micro-pumice in phreatic eruption products in February 1991
May 3, 1991
Earthquake Volcanic Tremor
Precursors of first eruptions
EDM
Ground tilt
Magnetic total Force
Precursors of lava dome emergence
These were reported to the Coordinating Committee for Predictionof Volcanic Eruptions (CCVEP)
May 20, 1991
GPS at Unzen
Nishi et al, (1999) JVGR v.89
Japan Meteorological Agency (JMA)
Coordinating Committee for Prediction of Volcanic Eruptions (CCPVE)
JMA
Observatoriesof universities
NationalInstitutes
Local government
Massmedia
The public / concerned inhabitants
Transmission of volcanic information in Japan
Observation data/results are reported toCCPVE which assesses the unrest.
JMA only can issue official statements on volcanic activity.
Volcanic information is transmitted toThe public through local government/mass media.
Monitoringdata
Volcanic Information
Volc. Inform.
Pyroclastic flow event• Dome collapse started on May 24,
1991• Pyroclastic surges attacked mass
media and fire station staffs. June 3, 1991
The Yomiuri
June 24, 1993June 3, 1991
The prefectural governor asked the Self Defense Force (SDF) for rescuing casualties.The operation in a limited area needed real-time information on volcanic activity.
Other civil protection agencies also needed real-time information for quickly respond to coming disaster.
The official information flow was too slow during pyroclastic flow events.
Japan Meteorological Agency
Coordinating Committee for Prediction of Volcanic Eruptions (CCPVE)
Local governments
Massmedia
Inhabitants
Transmission of volcanic information at Unzen Volcano
Official information
Massmedia
SelfDefense
Force
Police
Local government
Cable TV
ShimabaraObservatory
Unofficial information (real-time)
Unofficial information (real-time)
Advices
Comments
Cooperation between organizations concerned made it possible to transmit unofficial but useful volcanic information: more quickly, accurately and understandably.
SDFPolice
Volcanologist
Members of SDF and police stationed at the observatory (SEVO), watching seismograms and video monitors all day.They transmitted the monitoring data directly to their headquarters.The information was shared with the local government and cable-TV.
SDF, police, local governments and inhabitants were able to be informed immediately what was monitored.
In addition, volcanologists shared the observation data to SDF, police, local government and mass media soon after helicopter flights every day.
Mass media
Prof. OhtaLocal government official
SDF
Daily observation flight by SDF-helicopter
Mass media braodcasted volcanologists’ comments soon after the daily inspection flight.
SDF supported volcanologists in helicopter flights, Doppler radar observation, and maintaining the observation system within the limited areas.
Doppler radar was used to know the travel distance of pyrolastic flows
(Courtesy by Kazuo Shimousuki)
Jan.26 pm
Eruption at Shinmoedake (Kirishima) in 2011
IUGG (Melbourne) on July 4, 2011
Location of KirishimaVolcano Group
Kirishima
Shinmoedake
Ohachi
Pumice eruption in Shinmoedake crater after about 300 yrs silence.
In 1715-16, plinian explosions with pyrolcastic flows continued for two years
Three sub-plinian explosions in Jan. 26 and 27, 2011
Courtesy by Kazuo Shimousuki
Jan 27, 15:41 explosion
Jan 26 evening
Lava accumulation in crater for Jan. 28-31, 2011
Explosion crater was sealed with new lava.
Taken by Tetsuo Kobayashi on Jan 31, 2011
Explosion crater was covered completely
with new lava|
Insufficient degassing|
Highly possible strong explosions
|This observation data were not reflected to
evacuation plan.
SAR images with a few days interval were very
effective
Courtesy by PASCO Co., Ltd.
Entered into vulcanian stage TerraSAR-X
Data of extensometer (Isa Observation Station of DPRI, Kyoto Univ.)
Vulcanian St.Subplinianexplosions
Lava accum.
stage
MethodsTephraDRE, x104 m3
Lava accum.DRE, x104 m3
Total DRE, x104 m3
Deposit 730~1100 1400 2100
~2500
Strain 1300 1400* 2600
Normal direction toward the source
Direction toward the source
Strain change & magma volume
Typical subplinian
Shinmoedake 2011
Intensity ~106 kg/s ~106 kg/s
Magnitude ~1011 kg 0.3-1.5x1010 kg
Column height <20 km 7-9 km
Eruption rates change
Typical subplinian explosion data from Cioni et al. (2000)
Vulcanian St.Lava accum. St
Plinian St.
2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 20110
1000
2000
3000
Cum
ulat
ive
num
ber
2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 20110
1
2
3
4
Num
ber /
Day
Temporal change in seismicity in Kirishima VolcanoYakiwara and others (2011)
The rate increased with time
3,401
2001/01/01 to 2011/06/30
Earthquakes
The rate increase in mid-2006 and the end of 2009.
Inflation slowly during 2006 to 2007,
accelerated after the end of 2009
Geogr. Surv. Inst. (Data for 119th CCVEP)
Temporal changes of GPS baselinesGraphs after reducing the effects of vapor in air and regional tectonic movement.
Pumice found in tephra of Jan 19 (0.5 mm across)Juvenile in tephra
Phreatic explosions began in 2008, and repeated in 2010.
10% of pumice were observed in the Jan 19, 2011 product, a week before sub-plinian explosions.
Unzen (1)1. What kind of eruption forecasting assessment?Start of eruption (Nov 1990)
1) Elevated seismicity and its migration2) Clear attenuation of seismic waves passing under the summit3) LP event that is the first time in monitoring at Unzen and increased.
Lava appearance (May 1991)1) Swarm of high frequency B-type quakes beneath the crater2) Rapid changes in EDM and tilt-meter and shallow demagnetization3) Juvenile ash involved
2. How the forecasts have been achieved?Couldn’t forecast exactly when steam explosion, but was expected. Lava effusion was forecasted by CCVEP. After lava effused (PF stage), rather qualitative assessment.
Unzen (2)
3. What kind or critical information was missed?The manual to issue the alert was not prepared 20 years ago. Probably better now…..?
4. How the scientific forecast has been used to take mitigation actions (the decision-making chain)?After lava effused, the official information flow was not useful due to slowness. Instead, communication of observatory scientists with the local governments, mass media and army was effective.
5. The interaction between scientists, decision makers, and mass media.Before lava effused, neither bad nor good.After lava effused, on-site interaction among them went well and timely.
Alert levels in Shinmoedake (Kirishima)5: Evacuation4: Prepare for evacuation3: Limit approach to volcano (~2.5 km)2: Limit approach to crater area (~1km)1: Normal
Volcanic Alert issued
Aug. 22-Oct. 29, 2008: level 2Mar. 30-Apr. 16, Mar. 6, 2010: level 2
Jan. 26: level 3 ~3km distance (bomb)..?Jan. 31: level 3 ~3km (pyroclastic flow)..?Feb. 1: level 3 ~4 km (bomb)Mar. 22: level 3 ~3 km (bomb/pyr. flow)
Volcanic phenomenon
Phreatic explosionPhreatic explosions
Magmatic eruptionSub-plinian explosionsLava accumulationVulcanian explosions
Dates
Aug. 22, 2008Mar-Jul. 20102011Jan. 19Jan. 26-27Jan. 29-31Feb. 1-
Volcanic warning introduced in 2007
Response was too slow• A village decided evacuation by themselves in the night of Jan. 30, 2011.• They lived within a few kilometers from the active crater, in the lowest side
without seeing the crater. Explosions that night were so noisy for them to be very frightened.
• In addition, effusion of “lava dome” was observed two days before. The word of “lava dome” made them to fall into a sort of panic, as they imaged pyroclastic flow events at Unzen by it.
New lava dome in the crater floor (Jan. 28)
Shinomedake (Kirishima)
1. What kind of eruption forecasting assessment was made?1) Inflation rate increased for a year2) Rate of seismicity increased, though was not noticed correctly.3) Precursory steam eruption for a few years4) juvenile ash one week before the climax.
2. How the forecasts have been achievedForecast couldn’t be done correctly.
3. What kind or critical information was missed?2) of 1 items. No one may have considered seriously.
4. How the scientific forecast has been used to take mitigation actions?Personal scientific communication was useful in part.
5. The interaction between scientists, decision makers, and mass media.Understanding and information issue were taken behind the phenomena.
Present condition of Shinmoedake
SO2
Daily cumulative time of volcanic tremor
GPS
hrs