F.Imamura, DRCR 1 Tsunami Simulation for the warning and risk evaluation • Mechanism of tsunami generation • Predicting the propagation, runup and inundation of tsunamis • Runup and inundation information to be used for zoning and coastal planning Fumihiko Imamura, DCRC, Tohoku Univ.
23
Embed
Tsunami Simulation for the warning and risk evaluation
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
F.Imamura, DRCR 1
Tsunami Simulation for the warningand risk evaluation
• Mechanism of tsunami generation
• Predicting the propagation, runup and inundationof tsunamis
• Runup and inundation information to be used forzoning and coastal planning
Fumihiko Imamura, DCRC, Tohoku Univ.
F.Imamura, DRCR 2
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
F.Imamura, DRCR 3
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
F.Imamura, DRCR 4
Earthquake induced tsunamis
Tsunamis can be generated when the sea floor abruptly deforms andvertically displaces the overlying water.
F.Imamura, DRCR 5
Landslide/volcano induced Tsunamis
Caldera formation; surrounding water rushing into a cavity
Landslide flowing into water
10% of tsunamis over 100 years
F.Imamura, DRCR 6
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
F.Imamura, DRCR 7
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
F.Imamura, DRCR 8
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.
F.Imamura, DRCR 9
Trans-ocean propagation-importance of dispersion effect-
An initial tsunami profile has many components of different period, whichpropagate with different velocities. This difference results in non-negligibledeformation in wave profile, if the travel time becomes long as in case of adistant tsunami. A parameter Pa (Kajiura, 1970) is used to judge whether thefrequency dispersion effect should be included or not.
Pa =(6h/R)1/3(a/h)
where h is the water depth, a the horizontal dimension of the tsunami sourceand R the distance from the source to the site of a nuclear plant.
Pa > 4, the linear long-wave equation with the Coriolis forcePa < 4, the frequency dispersion effect should not be neglected. the linearized Boussinesq equation should be used including theCoriolis force described in the longitude-latitude coordinates.
F.Imamura, DRCR 10
Tsunami Numerical Simulation to be improve through the comparison with the several data
The 2004 Indian Oceantsunami simulation byTohoku Univ.dx=2min.(2-4km)in spherical coordinatedt=2 secondSimulation of thetsunami for 8 hoursneeds CPU time of 1hour using Pentium 4computer system
F.Imamura, DRCR 11
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
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
F.Imamura, DRCR 15
Accuracy of the simulation
Major causes of low accuracyinduced by ;
• Initial source; location andslip
• Modeling and Geometrydata
For example.
The fixed epicenterand variety oflocations in the fault
F.Imamura, DRCR 16
Mascarene Ridge
Chagos-Laccadive Ridge
Ninetyeast Ridge
South-Honshu Ridge
Possibility of the Tsunami Warning using by the Simulation
Carlsberg Ridge
Cooperated with the Deployment of Asia-Pacific-Indian Ocean Hazard-mitigation Network for Earthquakes and Volcanoes: DAPHNE Project
Under the TIME project
F.Imamura, DRCR 17
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
F.Imamura, DRCR 18
Advanced information – estimatingpotential damage
■Scenario
■Earthquake/tsunamisource
■Simulation
■Tsunami heights,velocity, wave force,inundation area
■Estimating damage onthe GIS
Population Estimated casualties (%)151,129 27,325 18.1
Tsunami Hazard Map to provide the inundationAccording to the information of JMA tsunami warning
F.Imamura, DRCR 21
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
F.Imamura, DRCR 22
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
F.Imamura, DRCR 23
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