in the wake of the 2011 tohoku tsunami: modeling of tsunami wave … · 2014. 6. 30. · 1 in the...
TRANSCRIPT
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In the wake of the 2011 Tohoku Tsunami: Modeling of Tsunami Wave Propagation and Evacuation.
Research efforts at Tohoku University and the University of Hawaii
Erick Mas1, Jeremy Bricker1, Volker Roeber1 Yoshiki Yamazaki2, Yefei Bai2, Kwok Fai Cheung2
1International Research Institute of Disaster Science (IRIDeS), Sendai, JAPAN
2Department of Ocean & Resources Engineering, University of Hawaii and Manoa, Honolulu, USA
PREDICT: A Tsunami Detection Initiative for British Columbia 27th & 28th March 2014
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Yoshiki Yamazaki, Yefei Bai, Kwok Fai Cheung, Volker Roeber Department of Ocean and Resources Engineering
University of Hawaii at Manoa
Resonance around the Hawaiian Islands from the 2011 Tohoku Tsunami
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US Coast Guard Logs Harbor OscillaPons caused by the 2011 Tohoku Tsunami
Maalaea: Emptying of harbor at 75 min intervals 10 h aTer tsunami arrival
Kahului: Largest wave in Hawaii 2 h aTer arrival and persistent 15 min oscillaPons
Nawiliwili: Minor wave acPviPes and the first harbor to reopen
Honolulu: lingering small oscillaPons Keehi : Strong surges at 15 min period for 2.5 days
Hilo: Mix of strong 5 and 30-‐min oscillaPons for 12 h
Lahaina: Strong 25-‐min oscillaPons for 1.5 days
Kauai
Oahu
Maui
Hawaii
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The 2011 Tohoku Tsunami • NEOWAVE of Yamazaki et al. (2009, 2011 IJNMF): weakly dispersive and shock-‐ capturing with mulP levels of two-‐way nested grids • Source from finite-‐fault inversion of seismic waves constrained by near-‐field tsunami observaPons (Yamazaki et al., 2011 GRL) • Dynamic tsunami generaPon illustrated in the first 5 min of animaPon
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Comparison of Computed & Measured Data at DART Buoys
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The 2011 Tohoku Tsunami around the Hawaiian Islands
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Comparison with Measurements (black lines)
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Inter-‐island Resonance Modes Spectral Energy Plots
Node
AnPnode
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Island-‐scale Resonance Mode Maui Nui
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Comparison with ADCP Measurements over Maui Nui
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Shelf/Reef Resonance Modes Kahului Bay and Harbor
Phase Angle Spectral Energy
• Progressive waves: conPnuous and gradual phase distribuPons
• Standing waves: abrupt phase transiPon of 180° apart
• The 14-‐min mode has disPnct nodal lines typical of standing waves
• The 16-‐min mode has a nodal point indicaPng “circular” standing waves
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Maximum Surface elevaPon and Flow Speed
Minor wave amplificaPon and negligible flow speed outside the 100-‐m depth contour Coherent standing wave and current paferns
AmplificaPon of currents by fringing reefs within the 20-‐m depth contour
Speed up of flows across reef edge due to formaPon of nodal lines
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Concluding Remarks
A source model consistent with seismic and ocean wave records allows reproducPon of the 2011 Tohoku Tsunami.
The validated model data provides a wealth of informaPon for studies of tsunami processes in Hawaii.
Model results in frequency domain provide an alternate view of wave dynamics and coastal processes.
The frequency-‐domain results show inter-‐island and island scale resonance in Hawaii • Coastal currents driven primarily by resonance • DelineaPon of high and low-‐hazard zones by 20 and 100 m depth
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Coastal community resilience through mul2layer protec2on and evacua2on behavior
• Erick MAS*, Bruno ADRIANO, Shunichi KOSHIMURA
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IntroducPon
Calculation results of tsunami profile at Suga in Kamaishi Port (PARI, 2011)!
Tsunami gate at Fudai village!
Rikuzentakata control forest. Before and After.!
Damage to the seawall at Yamada town!Seawall damage at Taro
(Suppasri, 2011)!
（共同通信）hfp://www.boston.com/bigpicture/2011/03/massive_earthquake_hits_japan.html
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MoPvaPon
✤ Ongoing reconstrucPon efforts
Sendai City Earthquake Disaster Reconstruction Plan!
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ObjecPve
To evaluate the contribuPon of coastal defenses for populaPon evacuaPon. The presence of breakwater, seawall and coastal forest are combined following the philosophy of tsunami mulP layer protecPon.
Method: Agent based model
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Method: Agent based model
Hypothetical Town!
Evacuation Behavior (Start time decision)!
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Model
!
Outside of inundation area (right boundary)!
A* algorithm for pathfinding!
Density recognition!
Density in grid!
Rayleigh distributed decision!Mas et. al, 2012!
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EvacuaPon Behavior (u)
Faster behavior for small wave heights can accomplish 15% ( ) of reducPon in casualPes, while for big wave heights it makes a 40% ( ) difference on populaPon safety.
Ht = 4m, Hb = 0m, Hs = 0m, Wgb = 0m, u = 15min, Tsunami arrival time= 22min!
X! X!X!
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Lesson from two different stories, the importance of educaPon: Disaster effect on schools (a comparison)
Unosumai elementary school (Kamaishi) • Very close to the shore, they absolutely knew
that the school is in the tsunami inundaPon area
• All students survived • They did not wait for evacuaPon instrucPons
from the teachers • All of 350 students successfully managed to
evacuate and survive!
Ookawa elementary school (Ishinomaki) • 3.8 km from the shore, had never
experienced a tsunami before • Only 31 of total 108 students survived • Students implemented standard earthquake
evacuaPon (leave the classroom wearing helmets) but did not evacuate to high ground since most teachers felt the area was safe from the tsunami
3.8 km
0.7 km
Powerpoint slide from
Abdul Muhari
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Breakwater
Ht = 4m, Hb = 5m, Hs = 0m, Wgb = 0m, u = 15min, Tsunami arrival time= 22min!
X!X!
✤ Breakwater size of about the wave height can reduce casualties up to 60% when evacuation behavior is fast.!
✤ Only breakwaters about three times higher than the incoming wave may ensure coastal safety, however for large tsunamis this is difficult to accomplish!
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Seawall
Ht = 4m, Hb = 0m, Hs = 5m, Wgb = 0m, u = 15min, Tsunami arrival time= 22min!
X! X!
✤ Seawall protects slightly better than breakwater, in particular after its height is twice the incoming wave height.!
✤ When the seawall is bigger than the incoming wave, the behavior of waiting to confirm inundation or overtopping shows 5% to 10% increase of casualties.!
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Greenbelt
• Greenbelt contribuPon was modeled using an equivalent roughness model
• n0 = 0.025 ; Cd = 0.996 • k = diameter of tree (0.15m) • fd = forest density (30 trees / 100m2) • θ = forest occupancy on grid size • D = flow depth
Ht = 4m, Hb = 0m, Hs = 0m, Wgb = 100m, u = 15min, Tsunami arrival time= 22min!
X! X!
(Aburaya and Imamura, 2002)!
parameter values from (Harada and Imamura, 2003)!
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MulPlayer protecPon
Ht = 4m, Hb = 5m, Hs = 5m, Wgb = 100m, u = 15min!Breakwater, Seawall & Greenbelt!
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Conclusions " It is important to show the popula2on -‐on an simple manner-‐ how investments on
new coastal defense structures during reconstruc2on will impact on their safety.
" Fast tsunami evacuaPon behavior can increase to 15% the number of survivors and in cases of large tsunami waves even to 40% under condiPons of this test.
" A seawall gives slightly beJer outcomes than a breakwater for protecPon.
" Safety of populaPon is mainly controlled by the evacua2on behavior when the height of seawall is smaller than the height of tsunami.
" Higher seawall can increase 10 to 40% on the populaPon safety outcome.
" A seawall effecPvely reduces the maximum wave height and, when bigger than the incoming wave, also the Pme to arrive.
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Tsunami early warning
NaPonal Research InsPtute for Earth Science and Disaster PrevenPon, K-‐NET ground
moPon recorders
Japan Meteorological Agency tsunami and Pde gauges
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Powerpoint slide from
Fumihiko Im
amura
Long-‐duraPon quake (about 2 minutes): updates to tsunami warning as quake conPnued and seismic informaPon was processed
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Next generaPon tsunami early
warning – dense ocean network of cabled pressure
sensors
Yomiuri Shinbun 29
