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F.Imamura, DRCR 1
Mechanism of tsunamigeneration,propagation and runup
-sharing experiences with Japanese
■Mechanism of tsunami generation
■Predicting the propagation, runup and inundation oftsunamis
■Near and far-field tsunamis
■Countermeasure; hard and soft type
■Tsunami warining system
■Community based workshop to make Hazard map
Fumihiko Imamura, DCRC, Tohoku Univ.
F.Imamura, DRCR 2
What is a tsunami ? 津波とは?• harbor+wave 津+波• International word in 1946 academically• Tsunami committee in IUGG started in 1960
Historical Tsunamis• BC.14th Santorini, the oldest in the world records• The tsunami documented in Japan Well documented and more than 195 tsunamis over
1,313 years. 684年南海道、白鴎地震、Tonanaki
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Several reasons to generate tsunami;seismic and non-seismic
• Fault• Landslide• Volcano• Comet compact
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Seismicity in the Pacific & world
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Estimation of a seabed movement(deformation)
A fault movement is described by its location including its depth,•Mechanical characteristics; (strike, dip- and slip-angles of the fault plane),•Geometrical characteristics (length, width and dislocation of the fault plane), and•Dynamic characteristics(rupture direction, rupture velocity and rise time of the faultmovement). •Earthquake magnitude
•Depth of the fault•Length and width of the fault plane•Strike and dip angle of the fault plane•Dislocation and slip angle
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Earthquake induced tsunamis
Tsunamis can be generated when the sea floor abruptly deforms andvertically displaces the overlying water.
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Landslide/volcano induced Tsunamis
Caldera formation; surrounding water rushing into a cavity
Landslide flowing into water
10% of tsunamis over 100 years
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Tsunami Wave System• Generation
– A seafloor disturbance, such as motion along a fault, pushes upthe overlying water.
• Propagation– The wave propagates across the deep ocean at jetliner speeds– Shoaling and refraction to amplify the wave
• Inundation– As the wave moves into shallower water, increased energy
density increases both the wave height and the currents.– Runup on a land and run-down
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Propagation : Shoaling effect
The deeper the water and the longer the wave, the faster the tsunami propagate.
The back of wave overtakeanother,decreasing thedistance between them
larger disatance
larger larger disatancedisatanceshorter disatance
shorter shorter disatancedisatancedicreasing of wave leng,amlificaton of wave height
dicreasingdicreasing of wave of wave leng,leng,amlificatonamlificaton of wave height of wave heightFaster wave propagatingspeed in a deep sea
Faster wave propagatingFaster wave propagatingspeed in a deep seaspeed in a deep seaslower wave propagatingspeed in a shallow sea
slower wave propagatingslower wave propagatingspeed in a shallow seaspeed in a shallow seawave tail
wave tailwave tailwave front wave frontwave front
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Headland
Crest line of wave
Propagation : Refraction effect
Energy concentration
Wave fronts tend to align parallel to the shoreline so that they wrap arounda headland
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Generation and Propagation of the1896 Sanriku tsunami
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遺体の処置
釜石では筵さえ不足。
広田では、1度では多すぎ2度に分けて回収
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岩手県内踏査行程
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Functions of disaster prevention --- Function to stop drifts
Coastal forest
Tsunami direction
Cultivate rafts
Fishing boat
1960 Chileian tsunami at Kesen-numa Japan, (Izumi,1961)
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Prevention Works & Researchon Tsunamis
Before :■education/memorial■Resettlement to higher location
Recent after 1960■Structural mitigation (hard)
■sea wall, breakwater
■Integrated prevention with soft
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Local Propagation• Locally generated tsunami waves may propagate from their generating source to
the near shore area of a nuclear power plant site;• hence, the wave propagation phenomena become important.• Numerical techniques,FDM, are applied to determine modification during
propagation.• The accuracy of bottom topography has a vital effect on the computed results
TIME -project; Tsunami inundation modeling exchangeBy UNESCO/IOC and IUGG ,manual 34
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Distant Tsunamis
Wave system
The fact that the wavelength of atsunami is much longer than thewater depth leads to the system oflong waves.The wave amplitude of a tsunami inthe deep ocean is infinitesimallysmall compared to the water depth ;Linearity of the water wave .
A distant tsunami can be solved withthe aid of liner equations for longwaves with the Coriolis force ,frequency dispersion included,described in the longitude-latitudecoordinate system. 1996 Irian Jaya tsunami, made by DCRC Tohoku Univ.
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チリ地震津波1960 Chile
国際太平洋津波警報センターの設立津波防波堤の建設(大船渡)津波高潮防潮堤の建設(全国の沿岸)津波水門が初めて建設される
142名犠牲者津波警報発令されず北海道から沖縄にかけての広い地域
チリ地震津波
1960.5.24
対 策主な被害・課題津波イベント名
年月日
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F.Imamura, DRCR 21
チリ津波による被害Damage caused by the tsunami
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北上川で成長する波状段波
第一波
第二波
第三波
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新潟・十勝沖地震津波1964 Niigata &1968 Tokachi
52名犠牲者(ほとんどが地震による)防潮堤の機能発揮
十勝沖地震津波
1968.5.16
26名犠牲者津波・石油タンク被害・火事が連動した液状化による被害大
新潟地震津波
1964.6.16
対 策主な被害・課題津波イベント名
年月日
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津波による火災の発生Fire caused by a tsunami
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1964年新潟地震の場合
津波と地下水とが溜まった地域焼失区域
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Tsunami Warning System
1. Estimating the occurrence of a tsunami by seismicinformation(magnitude, location and depth)
2. Data base of the simulation with assumptions3. Real time analysis with the tentative fault model4. Revision of the tentative fault model by the observation data
JMA Tsunami warning
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The “Three Helps” of disaster measures
To reduce damage and casualties
Public help
Self help
Mutual help
The people could not see theimpact/terror of tsunami only bywarning with the tsunamiinformation; arrival time andheights.They should understand its impacthave the imagination before thetsunami attack through makinghazards map and having workshop.
workshop
Tsunami warning Risk communication
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Community-based Programs forawareness of tsunami disaster
■Location of the program leadership■Program goals and training approaches■Use of volunteers■Targeted organisational unit■Knowing what to do in the face of hazard■Curriculum intervention for disaster mitigation from the
hazard management community■Curricula for responsible citizenship
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Making the original hazard maps
■ In the past, the map was provided by the localgovernment but no use for the people
■Original information should be included■Selecting the base map■Collecting the information of risk■Discussion what information be included■Checking them by town-walking
inundation
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Hazards map and WorkShopmaking HM with the residents
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Powerful & future tool to support the awareness;Example of Hazards map and Data base Using the image fromSattelite on GIS
Safety area
Damage in past
Damage in past
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Criteria to estimate damage by tsunamis
runupheightinundation
height
inundationdepth
ground elevation
trace
distance from shoreline
tide levelat theevent
M.S.L.
Inundation depthHuman: killed >> 50cmHouse: partially damaged >> 1.0m totally damaged >> 2-3.0mBuilding: damaged >> 5.0m
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安全な避難のために
1次避難場所
For Safe Evacuation
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Integrated Tsunami Countermeasure
No system Structure & Facility;sea wall andbreakwater
Combination with ;green belt andtsunami information
PAST PRESNT FUTURE
Public education for awareness andevacuation system
with consideration of life and culture at reachregion
Memorial day, International Tsunami Mitigation day; 26 December
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