The document summarizes lessons learned from the 2011 Tohoku tsunami in Japan. It discusses the tsunami's runup pattern, failures of wharf foundations and seawalls, the effect of centrifugal forces on seawall design, and factors influencing tsunami casualties beyond runup height alone. Key features of a new tsunami risk assessment model for HAZUS-MH are outlined.

1. TSUNAMI DESIGN
Lessons Learned from the 2011 Tohuku Tsunami
Harry Yeh
Oregon State University
February 2013 EERI Meeting, Seattle

2. 1. Runup Pattern of the 2011 Tohoku Tsunami

3. Measured Runup Distribution
5907 data points
More than 300 contributors
Red contours: uplift
Blue contours: subsidence
Arrows: sea-floor geodetic observations

4. PMEL/NOAA’s Work using the DART buoy Data

5. Sanriku Coast = Rugged coastal line (“Ria Coast”) >

6. Sendai plain = flat broad farmland <

7. >
<
>
<

8. 2. On Geotechnical Issues

9. Wharf Foundation Failure in Onagawa
(38̊26.50’N 141̊26.50’E)

10. Wharf Foundation Failure: in Onagawa
The video footage shows that
there was no significant
visible damage detected prior
to the tsunami attack.
(38̊26.50’N 141̊26.50’E)

11. 1
Quay-wall collapse
Konakano, Japan: the 1960 Chilean Tsunami.
4
2
5
3

12. 1
Quay-wall collapse
Konakano, Japan: the 1960 Chilean Tsunami.
4
2
tion
efac
Liqu
ntary
M ome
5
3

13. 3. Seawalls and Coastal Dikes

14. Upright (nearly-vertical) Seawalls

15. Kirikiri, Iwate Prefecture
39˚22’15.4”N 141˚56’45.0”E

16. Kirikiri
Tsunami height: 17.2 m
The crown elevation: 6.3 m
39˚22’15.4”N 141˚56’45.0”E

17. Kirikiri
Tsunami height: 17.2 m
The crown elevation: 6.3 m
Scour
Flipping failure by the underfoot
rotation
Scour
Deep scour hole at the shore side
39˚22’15.4”N 141˚56’45.0”E

19. Total failure

20. Total failure during the drawdown phase.

21. Hakozaki, Iwate Prefecture
39˚19’24.3”N 141˚54’50.2”E

22. Hakozaki
Tsunami height: 15.4 m.
The crown elevation is 5.6 m
Seawall with flange
The seawall itself was undamaged
39˚19’24.3”N 141˚54’50.2”E

24. No Failure

25. Mound-Type Coastal Dikes

26. Kanahama, Iwate
39˚35’33.3”N 141˚56’48.2”E

27. Kanahama
Tsunami Height:11.3 m
The crown height: 8.5 m
The front side is undamaged
Concrete panels on the rear side
were ripped.
39˚35’33.3”N 141˚56’48.2”E

28. Kanahama
Elongated scour hole behind the dike
39˚35’33.3”N 141˚56’48.2”E

30. Damage near the crown
Severe scour hole that could lead to failure

31. Tsunobeuchi, Fukushima
37˚32.7916N 141˚1.7053E

32. Tsunobeuchi
Tsunami Height: 17.2m
Crown Elevation: 6.2 m
The rear face of this dike was unlined and covered with vegetation. The slope of
this earthen surface is mild. There are scours on the earthen surface but is still in
tact. The slope of the rear surface may play a role in preventing the total failure.
37˚32.7916N 141˚1.7053E

33. Minor damage in spite of the unlined earthen back face

34. Consideration of the Flow Induced Centrifugal Forces
− Flow over the crown −

35. Consideration of the Flow Induced Centrifugal Forces
− Flow over the crown −
• Assume the flow is quasi-steady and irrotational, and forms
concentric circular streamlines around ‘o’: vs = c/Rs; vb = c/Rb.
• Assume the flow depth at ‘o’ is critical, hence y0 ≈ 2/3 H
• vs = 2 g(H − y0 ) along the streamline on the water surface.

36. ⎧2 Rs
⎪ 3 H = Rs log R (*)
⎪ b
⎪ Rs
⎨ vb = 3 g H
2
⎪ Rb
⎪ p = 1 ρ v2 − 1 ρ v2 + ρ g y
⎪ b 2 s 2 b 0
⎩
In Kanahama:
Tsunami height ~ 11.6 m and the crown elevation ~ 8.5 m.
Hence H ≈ 3 m. If Rb ≈ 1.5 m, we find Rs = 2.95 m from (*).
Then we find pb = – 8.6 kN/m2 or pb/ρg = – 0.88 m of H2O.
This negative pressure can easily lift a concrete slab with 25 cm
thick.

37. − Flow at the Rear Toe of the Dike −
Z
• Again assume the flow is quasi-steady and irrotational and forms
concentric circular streamlines around ‘t’: v1 = c/R1; vt = c/R.
• v1 = 2 g(H + z − y1 ) along the streamline on the water surface.
• y1 = yt; q= 2H
3
2
3 gH

38. ⎧2 R
⎪ 3 H 2 g H = R1 2 g ( H + Z − (R − R1 ) log
3
R1
⎨
⎪ p = 1 ρ v 2 ⎡1− ( R R )2 ⎤ + ρ g(R − R )
⎩ t 2 1⎣ 1 ⎦ 1
Kanahama:
Tsunami height ~ 11.6 m and the crown elevation ~ 8.5 m.
Hence H ≈ 3 m. Z = 8.5 m and if R ≈ 2 m, we find R1 = 1.2 m.
Then pt = 74.8 kN/m2 or p0/ρg =7.62 m of water head.
This large positive pressure together with vt = 14.5 m/s can
scoop the soils in the rear toe of the dike: scour.

39. A preferred seawall design against severe overtopping flows ?
Small curvature (large radius)
This design concept should be applicable for dikes, seawalls,
levees, and alike for the consideration of overtopping flows
caused by tsunamis, storm surges, or riverine floods.

40. 4. On Casualty

41. Indication from the Statistics (Suppasri et al. 2011)
2011 Tohoku Tsunami

42. Indication from the Statistics (Suppasri et al. 2011)
Data from Koshimura of Tohoku University

43. Indication from the Statistics (Suppasri et al. 2011)
Only trend that we can detect from the figure is that tsunami fatality rate diminishes
when maximum tsunami “height” is less than 1.5 m.
Data from Koshimura of Tohoku University

44. Indication from the Statistics (Suppasri et al. 2011)
Although there is a weak trend that fatality rate increases
with tsunami’s runup height, the runup height is not the
primary controlling factor.
More likely, people’s prior knowledge to tsunami hazard
(i.e. education), notifications of tsunami warnings and
their response made the significant difference.
Data from Koshimura of Tohoku University

45. Development of a Tsunami Risk Assessment Model
for HAZUS-MH

46. Methodology Overview – Local EQ Event
Potential Hazards
Local EQ Event
Earthquake Tsunami
Hazard Hazard
Analysis Analysis
Damage
I
n
v Earthquake Tsunami
e Damage Damage
n
t Assessment Assessment
o
r Combined Tsunami
y and Earthquake
. Damage-State
Probabilities
E
x Impacts
p
o
s Social
u
r
e
Shelter Casualty
Estimates Estimates
Economic Other
Direct Losses Debris

47. Methodology Overview – Distant EQ Event
Potential Hazards
Distant EQ Event
Tsunami
Hazard
Analysis
Damage
I
n
v Tsunami
e Damage
n
t Assessment
o
r
y
.
E
x Impacts
p
o
s Social
u
r
e
Shelter Casualty
Estimates Estimates
Economic Other
Direct Losses Debris

48. Key Features
• Probabilistic approach for combining tsunami and earthquake
damage
• Hazard → characterized by inundation depth, velocity, and
momentum flux and to be compatible with NOAA’s SIFT output
• Damage → performance-based engineering approach
• Debris → transport model that predicts final position of the debris
(cars, trucks, shipping containers, boats, building debris)
• Casualties → model reflects warning time, time of day and time of
year, evacuation conditions (e.g., rainy and nighttime), community
characteristics and preparedness, slope of terrain, age, etc.
• Shelter → model reflects those seeking shelter because of damaged
homes, flooded roadways, or being ordered to evacuate.