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Unrest that led to eruption: Unzen and Kirishima, Japan Setsuya Nakada 1 and Hiroshi Shimizu 2 1. Volcano Research Center, Earthquake Research Institute,

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Presentation on theme: "Unrest that led to eruption: Unzen and Kirishima, Japan Setsuya Nakada 1 and Hiroshi Shimizu 2 1. Volcano Research Center, Earthquake Research Institute,"— Presentation transcript:

1 Unrest that led to eruption: Unzen and Kirishima, Japan Setsuya Nakada 1 and Hiroshi Shimizu 2 1. Volcano Research Center, Earthquake Research Institute, The University of Tokyo 2. Institute of Seismology and Volcanology. Kyushu University Volcano Observatory Best Practice Workshop - Near Term Eruption Forecasting Erice, Sicily (IT), September 2011

2 : 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 : Lava effusion continued for almost 4 years. (2x10 8 m 3 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

3 Nov. ‘89 Dec. ‘89 July ‘90 Oct. ‘90 Nov. 19, 1990 Precursor of eruption (seismicity)

4 Micro-pumice in phreatic eruption products in February 1991 May 3, 1991 Earthquake Volcanic Tremor Precursors of first eruptions

5 EDM Ground tilt Magnetic total Force Precursors of lava dome emergence These were reported to the Coordinating Committee for Prediction of Volcanic Eruptions (CCVEP) May 20, 1991

6 GPS at Unzen Nishi et al, (1999) JVGR v.89

7 Japan Meteorological Agency (JMA) Coordinating Committee for Prediction of Volcanic Eruptions (CCPVE) JMA Observatories of universities National Institutes Local government Mass media The public / concerned inhabitants Transmission of volcanic information in Japan Observation data/results are reported to CCPVE which assesses the unrest. JMA only can issue official statements on volcanic activity. Volcanic information is transmitted to The public through local government/ mass media. Monitoring data Volcanic Information Volc. Inform.

8 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, 1993 June 3, 1991

9 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.

10 Japan Meteorological Agency Coordinating Committee for Prediction of Volcanic Eruptions (CCPVE) Local governments Mass media Inhabitants Transmission of volcanic information at Unzen Volcano Official information Mass media Self Defense Force Police Local government Cable TV Shimabara Observatory 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.

11 SDF Police 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.

12 In addition, volcanologists shared the observation data to SDF, police, local government and mass media soon after helicopter flights every day. Mass media Prof. Ohta Local government official SDF Daily observation flight by SDF-helicopter Mass media braodcasted volcanologists’ comments soon after the daily inspection flight.

13 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

14 (Courtesy by Kazuo Shimousuki) Jan.26 pm Eruption at Shinmoedake (Kirishima) in 2011 IUGG (Melbourne) on July 4, 2011

15 Location of Kirishima Volcano Group Kirishima Pumice eruption in Shinmoedake crater after about 300 yrs silence. In , plinian explosions with pyrolcastic flows continued for two years

16 Three sub-plinian explosions in Jan. 26 and 27, 2011 Courtesy by Kazuo Shimousuki Jan 27, 15:41 explosion Jan 26 evening

17 Lava accumulation in crater for Jan , 2011 Explosion crater was sealed with new lava. Taken by Tetsuo Kobayashi on Jan 31, 2011

18 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

19 Data of extensometer (Isa Observation Station of DPRI, Kyoto Univ.) Vulcanian St. Subplinian explosions Lava accum. stage Normal direction toward the source Direction toward the source Strain change & magma volume

20 Typical subplinian Shinmoedake 2011 Intensity~10 6 kg/s Magnitude~10 11 kg x10 10 kg Column height<20 km7-9 km Eruption rates change Typical subplinian explosion data from Cioni et al. (2000) Vulcanian St.Lava accum. St Plinian St.

21 Temporal change in seismicity in Kirishima Volcano Yakiwara and others (2011) The rate increased with time 3, /01/01 to 2011/06/30 Earthquakes The rate increase in mid-2006 and the end of 2009.

22 Inflation slowly during 2006 to 2007, accelerated after the end of 2009 Geogr. Surv. Inst. (Data for 119 th CCVEP) Temporal changes of GPS baselines Graphs after reducing the effects of vapor in air and regional tectonic movement.

23 Pumice found in tephra of Jan 19 (0.5 mm across) Juvenile in tephra Phreatic explosions began in 2008, and repeated in % of pumice were observed in the Jan 19, 2011 product, a week before sub-plinian explosions.

24 Unzen (1) 1. What kind of eruption forecasting assessment? Start of eruption (Nov 1990) 1) Elevated seismicity and its migration 2) Clear attenuation of seismic waves passing under the summit 3) 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 crater 2) Rapid changes in EDM and tilt-meter and shallow demagnetization 3) 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.

25 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.

26 Alert levels in Shinmoedake (Kirishima) 5: Evacuation 4: Prepare for evacuation 3: 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 2 Mar. 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 explosion Phreatic explosions Magmatic eruption Sub-plinian explosions Lava accumulation Vulcanian explosions Dates Aug. 22, 2008 Mar-Jul Jan. 19 Jan Jan Feb. 1- Volcanic warning introduced in 2007

27 Response was too slow A village decided evacuation by themselves in the night of Jan. 30, 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)

28 Shinomedake (Kirishima) 1. What kind of eruption forecasting assessment was made? 1) Inflation rate increased for a year 2) Rate of seismicity increased, though was not noticed correctly. 3) Precursory steam eruption for a few years 4) juvenile ash one week before the climax. 2. How the forecasts have been achieved Forecast 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.

29 Present condition of Shinmoedake SO 2 Daily cumulative time of volcanic tremor GPS hrs


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