Proceedings of Coastal Engineering, JSCE, Vol.3, 2012, November

ANALYSIS ON THE TSUNAMI FLOW VELOCITY
DURING THE PACIFIC COAST OF TOHOKU
EARTHQUAKE AND TSUNAMI
Piyawat Foytong1, Yoshiyuki Ezura2, Yu Hiraki3 and Gaku Shoji4
1Dept. of Civil Engineering, Chulalongkorn University, Bangkok, Thailand, piyawat_pwf@yahoo.com
2Dept. of Engineering Mechanics and Energy, University of Tsukuba, Ibaraki, Japan, s1220859@u.tsukuba.ac.jp
3Central Japan Railway Company, Aichi, Japan, s1021008@u.tsukuba.ac.jp
4Faculty of Engineering, Information and Systems, University of Tsukuba, Ibaraki, Japan, gshoji@kz.tsukuba.ac.jp

The March 11, 2011 tsunami caused serious damage to many buildings, bridges and lifelines, and18,771 people were killed and missing in Japan (data on 2012, July 25). From this event, the digital
videos on the damage of structures and the tsunami flows were recorded and uploaded to open web sites.
The tsunami flow velocity on land is estimated by using image processing of videos and estimating thedimension of the moving and reference objects. The analyzed tsunami flow velocities range about 2.9 4.9 m/s in Kamaishi town, 2.1 - 2.8 m/s in Ofunato town, 2.6 - 5.4 m/s in Kesennuma town, 1.4 m/s in
Iwaki town and 2.6 m/s in Oarai town. Finally, the analyzed tsunami flow velocities are used to validate
the tsunami velocity from the tsunami inundation simulation for this event. The tsunami flow velocities
from the simulation results have the similar trend with the tsunami flow velocities by image processing ofvideos; however, most of them are less than the results by image processing of videos.
Key Words : Tsunami, tsunami wave velocity, tsunami videos, tsunami simulation

1. INTRODUCTION
The March 11, 2011 tsunami caused serious
damage to many buildings, bridges and lifelines,
and 18,771 people were killed and missing in Japan(data on 2012, July 25). From this event, the digital
videos on the damage of structures and the tsunami
flows were recorded and uploaded to open web
sites. To analyze the structural damage due to thetsunami, the tsunami flow velocity and the tsunami
inundation height are needed to estimate thehydrodynamic force acting on the structures (CCH,
2000; FEMA55, 2000; Yeh, 2007; Lukkunaprasit etal., 2009).
Many researches proposed the way to estimate
the tsunami inundation flow velocity. Fritz et al.
(2006) analyzed the tsunami velocities from the2004 Indian Ocean tsunami by using recorded
videos by the survivors in Banda Aceh, Indonesia.
The particle image velocimetry analysis was applied
to rectify the video images. The tsunami velocities
in Banda Aceh were about 2 - 5 m/s. Matsutomi etal. (2006) reported the results of field surveys inSouthern Thailand and Northern Sumatra from the2004 tsunami. The approximated tsunami velocities

were about 3 - 4 m/s in Patong beach area, Thailand,
6 - 8 m/s in Khao Lak area, Thailand and 5 - 16 m/s
in Northern Sumatra, Indonesia. Matsutomi andOkamoto (2010) proposed the relationship of theinundation flow velocity and inundation depth. The
inundation flow velocity was estimated by using
Bernoulli’s theorem and the inundation depth, andexamined with the experiments. Koshimura andHayashi (2012) analyzed the tsunami flow velocity
and estimated the tsunami force of the 2011 tsunami
in Miyagi Prefecture, Tohoku, Japan by using image
processing of recorded videos. The proposed
tsunami flow velocity of the tsunami front was
faster than 6 m/s. The tsunami hydrodynamic force
was roughly estimated as 100 kN/m.
In this research, the tsunami flow velocities onland are analyzed by using image processing ofrecorded videos and estimating the dimension of themoving objects and reference distances in Kamaishi
town, Ofunato town, Kesennuma town, Iwaki town
and Oarai town. The analyzed tsunami flow
velocities are used to validate the tsunami velocities
from the tsunami inundation simulation for thisevent in Kamaishi town, Ofunato town and
Kesennuma town.

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2. TSUNAMI FLOW VELOCITY FROMVIDEOS(1) Location of recorded videos
The videos were recorded with handheld
amateur video cameras by survivors. Among 9
recorded videos, 3 datasets were recorded in
Kamaishi town, 3 datasets in Kesennuma town, 1
dataset in Ofunato town, 1 dataset in Iwaki town and
1 dataset in Oarai town. 15 points are considered asshown in Table 1(Video No.1-15). The recorded
videos locations are specified by comparing thebuilding landmarks in the videos with the Google
Street View (Street View for Google Maps, 2011). The
criteria for selecting video frames are that 1) the
location of the considered objects should be
perpendicular with the video camera angle, 2) themoving object should be parallel to the reference
distance and 3) the moving object should flow withthe same speed as the tsunami.
(2) Estimation of tsunami flow velocity
The examples of the moving object and thereference distance are shown in Fig.1 to Fig.3. Fig.1
shows the moving object, the wave front, and thereference distance, car parking channel, of the point
No. 3 in Kamaishi town. Fig.2 shows the moving
car and the reference distance between 2 poles of thepoint No. 7 in Ofunato town. Fig.3 shows themoving car and the reference distance on thebuilding of the point No. 10 in Kesennuma town.
The reference distance is estimated by the size ofthe car and drain cover. For the point No. 3, thewidth of the car parking channel is general size thatcan be measured from other places. For the point
No. 7, the distance between 2 poles can be estimatedby the size of the moving car. As shown in Fig.4,
the width of the building for the point No. 10 can be
estimated by using the photo from the Google Street
View.
The number of frames and the lengths of thereference distance of each point are shown in Table
1. The frame rate of all videos is 30 frames per
second. Therefore, the tsunami flow velocity ve canbe computed by Eq.(1). The tsunami flow velocities
from the video analysis of all points are also shownin Table 1. The tsunami flow velocities are ranging
about 2.9 - 4.9 m/s in Kamaishi town, 2.1 - 2.8 m/s
in Ofunato town, 2.6 - 5.4 m/s in Kesennuma town,
1.4 m/s in Iwaki town and 2.6 m/s in Oarai town.
ve =Reference distance
No. of frameൗ
Frame rate

Wave Front

Distance

Fig.1 Frame of the point No. 3 in Kamaishi town.

Distance
Moving Car

Fig.2 Frame of the point No. 7 in Ofunato town.

Distance
Moving Car

Fig.3 Frame of the point No. 10 in Kesennuma town.



L2

L1



Fig.4 The estimation of the building width of the point No. 10
from the Google Street View.

(1)- 52 -



Table 1 The locations and the tsunami flow velocities by image processing of videos.



3. TSUNAMI FLOW VELOCITY FROMTSUNAMI SIMULATION(1) Computation boundary and calculation of thetsunami simulation
The tsunami flow is computed by using
TUNAMI model (Tohoku University’s Numerical
Analysis Model for Investigation of Tsunami)(DCRC, Tohoku University). The governing
equations of the non-linear shallow water theory as
shown in Eq.(2)-(4) are discretized using the finite
difference method with a staggered leap-frog
scheme.
∂η ∂M ∂N
+
+
=0
∂t
∂x ∂y

(2)

∂M ∂ § M 2 · ∂ § MN ·
+ ¨
¸+ ¨
¸
∂t ∂x © D ¹ ∂y © D ¹= − gD∂η gn 2−M M 2 + N2
∂x D 7 3(3)∂N ∂ § MN · ∂ § N 2 ·
+ ¨
¸
¸+ ¨
∂t ∂x © D ¹ ∂y © D ¹∂η gn−
N M 2 + N2
∂y D 7 3
2= − gD(4)

where D is the total water depth (η+h), η is thetsunami wave height, h is the water depth, g is thegravitational acceleration, M is the discharge flux ofx direction and N is the discharge flux of y direction.
In this research, 3 areas are considered in
Kamaishi area, Ofunato area and Kesennuma area.
Six computational nested-grid regions are used in
the nested grid system. Region 1, region 2 andregion 3 are the same for all 3 areas. Region 4,
region 5 and region 6 are generated for each area
separately. Region 1 and region 2 are generated byusing GEBCO 30-arcsecond-grid data (2009) for
both topography and bathymetry with a grid size of
1,350 m and 450 m, respectively. Region 3 isgenerated by using GEBCO 30-arcsecond-grid data
for topography and JHA data for bathymetry with agrid size of 150 m. Region 4, region 5 and region 6
are generated by using GSI data for topography andJHA data for bathymetry with grid sizes of 50 m,
50/3 m and 50/9 m, respectively. The time step of
the computation is 0.1 second for all areas, and thetsunami inundation and propagation on dry land isconsidered in all regions.
(2) Tsunami source model
The tsunami fault model proposed by Imamura
et al. (2011) is used to simulate the 2011 tsunamithat is consisted of 10 faults. The fault parameters
are shown in Table 2. For all fault segments, thelength and the width are 100 km, the strike angle is
193.0 degree, the dip angle is 14 degree and the rake
angle is 81 degree.
(3) Validation of tsunami simulation
The tsunami simulation results are validatedwith observed data which are tidal data, tsunami
inundation heights and inundation area. The datafrom 3 coastal wave gauge stations along the shore
line of Iwate, which are Iwate-Chubu-Oki coastal
wave gauge, Iwate-Nanbu-Oki coastal wave gauge
and Miyagi-Hokubu-Oki coastal wave gauge (PARI,
2011), are used to compare with the tsunami
simulation. Fig.5 shows the comparison of theinundation heights of the tsunami simulation resultswith the observed tsunami inundation heights that
corrected by the astronomical tide at the time of theevent with reliability level A (The 2011 Tohoku
Earthquake Tsunami Joint Survey Group, 2011) atthe same points. There are 34 data points in- 53 -Kamaishi area, 15 data points in Ofunato area and57 data points in Kesennuma area. The simulation
results at the points in Ofunato area and Kesennuma
area agree well with the observed data; however, for
Kamaishi area, the simulation results are larger thanthe observed data by about 50%.
Table 2 Fault parameter for the 2011 off the Pacific coast of
Tohoku tsunami (Imamura et al., 2011).

1.7-4.4 m/s in Kamaishi area, 2.0 m/s in Ofunato
area and about 1.3-4.3 m/s in Kesennuma area.
Fig.6 shows the comparison of the tsunami flow
velocities from image processing of videos with thatfrom the tsunami simulation. The simulation results
have the similar trend with the results by image
processing of videos; however, most of them areless than the results by image processing of videos.
Table 3 The estimated inundation depth from the recorded
videos and the tsunami flow velocities.

15



10

6.0

Kamaishi Area
5

Kamaishi Area

Ofunato Area

Velocity from Analysis (m/s)

Analyzed Inundation Height (m)120

Kesennuma Area
0
0

5

10
15
Observed Inundation Height (m)20

Fig.5 The comparison of the tsunami inundation heights.



4. COMPARISON OF RESULTS
The tsunami flow velocities by the tsunami
simulation are estimated at the same locations of thevelocities by image processing of videos in thecomputational region 6 of each area. To analyze thetsunami flow velocities from the tsunami
simulation, the inundation depths are needed, andestimated from the recorded videos. The inundation
depths are estimated by two methods; visualized
estimating from the recorded video (A), andmeasuring in the Google Street View (B). For thevisualized estimating method, the tsunami
inundation depths are estimated by the tsunami levelon the building (A1) and on the submerged car (A2)with the assumption that, there is no buoyancy ofthe building and the car. The estimated method, theestimated inundation depths from the recorded
videos and the tsunami flow velocities are shown in
Table 3. The tsunami flow velocities are about

5.0

Ofunato Area
Kesennuma Area

4.0
3.0
2.0
1.0
0.0
0.0

1.0

2.0
3.0
4.0
5.0
Velocity from Image Processing (m/s)

6.0

Fig.6 The comparison of the tsunami flow velocities fromimage processing of video with tsunami simulation.



5. CONCLUSIONSThe March 11, 2011 Pacific Coast of Tohoku
tsunami caused serious damage to many buildings,
bridges and lifelines and killed many people in
Miyagi and Iwate prefectures, Tohoku, Japan. The
tsunami flow velocities are analyzed from therecorded videos in Kamaishi town, Ofunato town,
Kesennuma town Iwaki town and Oarai town. The
analyzed tsunami flow velocities are used tovalidate the tsunami velocities from the tsunami
inundation simulation for this event in Kamaishi- 54 -

town, Ofunato town and Kesennuma town. Findings
can be summarized as follows:
1. The tsunami flow velocities are analyzed by using
image processing of recorded videos andestimating the dimension of the moving objects
and reference distances. The analyzed tsunami
flow velocities are about 2.9-4.9 m/s in Kamaishi
town, 2.1-2.8 m/s in Ofunato town, 2.6-5.4 m/s in
Kesennuma town, 1.42 m/s in Iwaki town and2.55 m/s in Oarai town.
2. The tsunami simulation is carried out in 3 areas toestimate the tsunami flow velocities and tocompare with the observed data. The arrival times
from tsunami simulation results are longer thanthe observed data from wave gauges for about 3
minutes for Iwate-Chubu-Oki coastal wave gauge
and Iwate-Nanbu-Oki coastal wave gauge, and 4
minutes for Miyagi-Hokubu-Oki coastal wave
gauge. The comparisons of the tsunami
inundation heights at the same points are agreed
well with the observed data in Ofunato area andKesennuma area; however, for Kamaishi area, thesimulation results are larger than the observed
data by about 50%.
3. The tsunami flow velocities from the tsunami
simulation are estimated at the same points of
those from recorded videos by using the estimatedinundation depths from the recorded videos. The
tsunami flow velocities are about 1.7-4.4 m/s in
Kamaishi area, 2.0 m/s in Ofunato area and about
1.3-4.3 m/s in Kesennuma area. The simulation
results have the similar trend with the results byimage processing of videos; however, most ofthem are less than the results by image processingof videos.
ACKNOWLEDGMENT:The
authors
acknowledge support from the Office of the Higher
Education Commission, Ministry of Education,
Thailand, Chulalongkorn University, Bangkok,
Thailand, University of Tsukuba, Ibaraki, Japan, andDisaster Control Research Center, Tohoku
University (Professor Imamura, F., and Professor
Koshimura, S. ).
REFERENCES
City and County of Honolulu Building Code (CCH) (2000):
Department of Planning and Permitting of Honolulu
Hawaii, Chapter 16 Article 11, Honolulu, Hawaii.
Disaster Control Research Center (DCRC), Tohoku University:
TUNAMI-CODE Tohoku University’s Numerical Analysis
Model for Investigation of Tsunami, School of Engineering,Tohoku University, Japan.
Federal Emergency Management Agency 55 (FEMA 55)(2000): Coastal Construction Manual, Edition 3,
Washington, D.C.
Fritz, H.M., J.C. Borrero, C.E. Synolakis, and J. Yoo (2006):
2004 Indian Ocean tsunami flow velocity measurementsfrom survivor videos, Geophysical Researh Letters, Vol.33,
L24605.
Geospatial Information Authority of Japan (GSI): Digital
Elevation Model, (accessed on 16 December 2011).
http://saigai.gsi.go.jp/fgd/download/download.html
Imamura, F., S. Koshimura, Y. Murashima, Y. Akita, and Y.
Aratani (2011): Tohoku University Model (version1.1),
Disaster
Control
ResearchCenter(DCRC),
http://www.tsunami.civil.tohoku.ac.jp/hokusai3/J/events/to
hoku_2011/model/dcrc_ver1.1_111107.pdf (accessed on 10
Dec. 2011).
Japan Hydrographic Association (JHA) (2010): Digital
Topography of Ocean Floor M7000 Series.
Japan Meteorological Agency (JMA) (2011): The 2011 off the
Pacific Coast of Tohoku Earthquake. (accessed on 5 Dec.
2011) http://www.jma.go.jp/jma/en/2011_Earthquake.html
Joint Research Group of the 2011 off the Pacific Coast of
Tohoku Earthquake Tsunami (2011): Filed Survey Results.
http://www.coastal.jp.ttjt (accessed on 10 Dec. 2011).
Koshimura, S. and S. Hayashi (2012): Interpretation of tsunami
flow characteristics by video analysis, 9th International
Conference on Urban Earthquake Engineering/ 4th Asia
Conference on Earthquake Engineering, March 6-8, 2012,
Tokyo Institute of Technology, Tokyo, Japan,
pp.1987-1990.
Lukkunaprasit, P., N. Thanasisathit, and H. Yeh (2009):
Experimental verification of FEMA P646 tsunami loading,
Journal of Disaster Research, Vol.4, pp.45-53.
Matsutomi, H., T. Sakakiyama, S. Nugroho, and M. Matsuyama(2006): Aspects of inundated flow due to the 2004 Indian
Ocean tsunami, Coastal Engineering Journal, Vol.48, No.2,
pp.167-195.
Matsutomi, H. and K. Okamoto (2010): Inundation flow
velocity of tsunami on land, Island Arc, Vol.19,
pp.443-457.
National Police Agency: Damage Situation and Police Cou
ntermeasures, http://www.npa.go.jp/archive/keibi/biki/higa
ijokyo.pdf (accessed on 25 July. 2012).
Port and Airport Research Institute (PARI) (2011): Nationwide
ocean wave information network for ports and harbors data,
http://nowphas.mlit.go.jp/nowphasdata/sub301.htm.
(accessed on 18 December 2011).
Street View for Google Maps (2011), https://maps.google.co.
jp/ (accessed on 10 Dec. 2011).
The General Bathymetric Chart of the Oceans (GEBCO)(2009),
http://www.gebco.net/ (accessed on 28 November 2011).
Video No.1-2, http://www.guardian.co.uk/world/video/2011/m
ar/14/japan-tsunami-amateur-footage-video (accessed on
10 Dec. 2011).
Video No.3-4, http://www.youtube.com/watch?v=Nnu4K7mvJ
wY (accessed on 10 Dec. 2011).
Video No.5, http://www.youtube.com/watch?v=M535NGr9vbo (accessed on 10 Dec. 2011).
Video No.6-7, http://www.youtube.com/watch?v=oKzEQwAx
0m8 (accessed on 10 Dec. 2011).
Video No.8-11, http://www.youtube.com/watch?v=j5upJN7Sg
zs (accessed on 10 Dec. 2011).
Video No.12, http://www.youtube.com/watch?v=hK1zBRA9T
3k (accessed on 10 Dec. 2011).
Video No.13, http://www.youtube.com/watch?v=2uJN3Z1ryc
k&feature=related (accessed on 10 Dec. 2011).
Video No.14, http://www.youtube.com/watch?v=q8ufzRIVipI(accessed on 10 Dec. 2011).
Video No.15, http://www.youtube.com/watch?v=oFZDDifrycc(accessed on 10 Dec. 2011).
Yeh, H. (2007): Design tsunami forces for onshore structur
es, Journal of Disaster Research, Vol.2, No.6, pp.531536.

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