Presentation on theme: "Unrest that led to eruption: Unzen and Kirishima, Japan"— Presentation transcript:
1 Unrest that led to eruption: Unzen and Kirishima, Japan Volcano Observatory Best Practice Workshop- Near Term Eruption ForecastingErice, Sicily (IT), September 2011Unrest that led to eruption: Unzen and Kirishima, JapanSetsuya Nakada1 and Hiroshi Shimizu21. Volcano Research Center, Earthquake Research Institute, The University of Tokyo2. Institute of Seismology and Volcanology. Kyushu University
2 Eruption history at Mount Unzen : More than 30 people were killed by earthquakes anddebris flows.1792: Failure of Mt. Mayuyama (old lava dome) generated tsunami.About 15,000 people were killed.: 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 ofUnzen Volcano)Mt. MayuyamaShimabara City
7 Transmission of volcanic information in Japan JMA only can issue official statements on volcanic activity.Japan Meteorological Agency (JMA)Coordinating Committee for Prediction of Volcanic Eruptions (CCPVE)JMAObservatoriesof universitiesNationalInstitutesLocalgovernmentMassmediaThe public /concerned inhabitantsVolcanic InformationMonitoringdataVolc. Inform.Observation data/results are reported toCCPVE which assesses the unrest.Volcanic information is transmitted toThe public through local government/mass media.
8 Pyroclastic flow event The YomiuriPyroclastic flow eventDome collapse started on May 24, 1991Pyroclastic surges attacked mass media and fire station staffs. June 3, 1991/The June 3rd pyroclastic flow had been largest by that time./Fireman and fire car were running away from cloud of pyroclastic flow./They could escape from the attack./After passing of pyroclastic cloud, large trees are completely cut down, but this is only the pathway of cloud of pyroclastic flow.June 24, 1993June 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 Transmission of volcanic information at Unzen Volcano Cooperation between organizations concerned made it possible to transmit unofficial but useful volcanic information: more quickly, accurately and understandably.Official informationJapan Meteorological AgencyCoordinating Committee for Prediction of Volcanic Eruptions (CCPVE)LocalgovernmentsMassmediaUnofficial information (real-time)CommentsSelfDefenseForceShimabaraObservatoryMassmediaInhabitantsPoliceAdvicesLocal governmentCable TVUnofficial information (real-time)
11 Volcanologist SDF Police 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.VolcanologistSDFPoliceSDF, police, local governments and inhabitants were able to be informed immediately what was monitored.
12 Daily observation flight by SDF-helicopter In addition, volcanologists shared the observation data to SDF, police, local government and mass media soon after helicopter flights every day.Prof. OhtaLocal government officialSDFMass mediaMass 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 Eruption at Shinmoedake (Kirishima) in 2011 IUGG (Melbourne) on July 4, 2011Today’s my talk is on the newest volcanic eruption in Japan which started at Kirishima volcano this January.The background photo of this slide shows the subplinian explosion of January.Volcanic ash was drifted eastward, so that several airplain flights were cancelled or forced to detour from the normal flight courses.Eruption at Shinmoedake (Kirishima) in 2011Jan.26 pm(Courtesy by Kazuo Shimousuki)
15 Location of Kirishima Volcano Group Pumice eruption in Shinmoedake crater after about 300 yrs silence.In , plinian explosions with pyrolcastic flows continued for two yearsKirishim locates in southern Kyushu and north of Sakurajima.It is a group of volcanoes, including two most active centers; one is Ohachi and Shinmoedake.Eruption occurred in Shimoedake.Pumice eruption occurred in Shinmoedake about 300 years ago.The January eruption was reproduction of pumice eruption.ShinmoedakeOhachi
16 Three sub-plinian explosions in Jan. 26 and 27, 2011 Jan 26 eveningThe explosion continued for a few hours. Height of ash column was 7-9 km above the crater.In the downwind side, small scale pyroclastic flow was generated.Courtesy by Kazuo ShimousukiJan 27, 15:41 explosion
17 Lava accumulation in crater for Jan. 28-31, 2011 The lava dome grew rapidly and it filled the crater in the following 4 days.During the growth very beautiful growing rings or wrinkles were observed on the surface.The form of this lava accumulation was flattened when the magma supply declined.Explosion crater was sealed with new lava.Taken by Tetsuo Kobayashi on Jan 31, 2011
18 SAR images with a few days interval were very effective Explosion crater was covered completely with new lava|Insufficient degassingHighly possible strong explosionsThis observation data were not reflected to evacuation plan.The lava growing manner could be clearly followed by satellite SAR images. This is the example of lava accumulation within the crater.Growing wrinkles of lava surface is clearly visible. This kind of image was very effective to give warning to the local people.That is; the rate of lava accumulation was very fast, covering the explosion craters, so that we worried about imperfect degassing which may trigger sudden explosion.TerraSAR-XEntered into vulcanian stageCourtesy by PASCO Co., Ltd.
19 Strain change & magma volume Vulcanian St.SubplinianexplosionsLavaaccum.stageDirection toward the sourceNormal direction toward the sourceThe extensometer and tiltmeter records were too important during explosions.This shows data of extesometer near the volcano.Before the onset of explosion, the data show daily drift.When subbplinian explosion occur the deflation of summit area marked.Three deflation crealy match the time of explosions.During lava accumlation at the crater, slow deflation was recorded continuously.As we can know the volume of lava accumulated in the crater with photographic measurement, we can know how much magma was issued during eruption by using the relationship between the extent of deflation and erupted magma volume..The total volume of eruption ranges 21 million cubic meters in geological estimation.And the volume of magma which can be calculated from the extensometer is close to the geological value.MethodsTephraDRE,x104 m3Lava accum.Total DRE,Deposit730~110014002100~2500Strain13001400*2600Data of extensometer (Isa Observation Station of DPRI, Kyoto Univ.)
20 Eruption rates change Lava accum. St Vulcanian St. Plinian St.Lava accum. StVulcanian St.As we know the duration of each explosion or lava accumulation, we can calculate the eruption rates.This diagram shows the temporal change of eruption rate.The rate of subplinian explosion ranges 0.5 to 1.5 million kg per second. These values are typical to the eruption rate of typical subplinian explosions.Typical subplinianShinmoedake 2011Intensity~106 kg/sMagnitude~1011 kgx1010 kgColumn height<20 km7-9 kmTypical subplinian explosion data from Cioni et al. (2000)
21 Temporal change in seismicity in Kirishima Volcano Yakiwara and others (2011)2001/01/01 to 2011/06/303,401The rate increased with timeEarthquakesThe rate increase in mid-2006 and the end of 2009.
22 Temporal changes of GPS baselines Graphs after reducing the effects of vapor in air and regional tectonic movement.Geogr. Surv. Inst. (Data for 119th CCVEP)Inflation slowly during 2006 to 2007,accelerated after the end of 2009
23 Pumice found in tephra of Jan 19 (0.5 mm across) Juvenile in tephraPhreatic 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.Juvenile materials were found in the products of phreatic eruptions a week before the first subplinian explosion.
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 Volcanic warning introduced in 2007 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: NormalDatesAug. 22, 2008Mar-Jul. 20102011Jan. 19JanJanFeb. 1-Volcanic phenomenonPhreatic explosionPhreatic explosionsMagmatic eruptionSub-plinian explosionsLava accumulationVulcanian explosionsVolcanic Alert issuedAug. 22-Oct. 29, 2008: level 2Mar. 30-Apr. 16, Mar. 6, 2010: level 2Jan. 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)This was established in order to take rapid response to the public based on the agreement between JMA and local municipalities.
27 Response was too slowA 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)
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 GPSDaily cumulative time of volcanic tremorhrsSO2