Proceedings of the International Symposium on Engineering Lessons Learned fromthe 2011 Great East Japan Earthquake, March 1-4, 2012, Tokyo, JapanTSUNAMI DAMAGE IN PORTS BY THE 2011 OFF
PACIFIC COAST OF TOHOKU EARTHQUAKE
Takashi TOMITA1 and Gyeong-Seon YOEM2
1

Research Director, Asia-Pacific Center for Coastal Disaster Research, Port and Airport ResearchInstitute, Yokosuka, Japan, tomita@pari.go.jp
2Researcher, Asia-Pacific Center for Coastal Disaster Research, Port and Airport Research Institute,Yokosuka, Japan, yon-g@pari.go.jp

ABSTRACT: The tsunami generated by the 2011 off Pacific Coast of Tohoku
Earthquake caused devastated damage in wide areas by not only inundation but also
tsunami^-debris. We cannot control generation of earthquake even with state-of-arts
technologies. However, we can surely mitigate possible disasters with adequate human
responses. To fear tsunamis appropriately and to prepare adequate measure with local
characteristics are important to preparing possible tsunamis/
Key Words: Great East Japan Earthquake, tsunami, port, inundation, destruction,
debris, estimation, disaster mitigation, disaster prevention

INTRODUCTION
Japan has many experiences of tsunami disasters such as the 1896 Meiji Sanriku tsunami that caused
22,000 dead and missing. Even after improvement of coastal defense systems which have beensignificantly implemented since the 1960s, the 1983 Nihon-kai Chubu earthquake tsunami (the JapanSea tsunami) killed 100 persons, and 1993 Hokkaido Nansei-oki earthquake tsunami (the Okushiritsunami) caused 230 dead and missing including casualties by the seismic damage. In the case ofOkushiri tsunami, many residents in Okushiri Island escaped to hills soon after the earthquake shockand saved their lives, because the residents had a disaster experience of the 1983 Japan Sea tsunami
which hit and inundated the southern part of the island and caused two missing persons. However, theOkushiri tsunami came several minutes after the earthquake: for example, tsunami arrived the northernpart of the island 5 minutes or less because it was near the epicenter. Some residents, therefore, did nothave enough time for evacuation. In the 2003 Tokachi-oki earthquake tsunami, two anglers weremissing in the mouth of a river. Since the 2003 tsunami tsunamis have caused no dead or missing inJapan. However, the 2011 Off the Pacific Coast of Tohoku Earthquake generated a higher tsunami (the3.11 tsunami) than the tsunami level determined for tsunami disaster management in communities
such as the 1896 Meiji Sanriku tsunami. As the result, the number of dead and missing reached about
20,000 people.
The 2011 Off the Pacific Coast of Tohoku Earthquake occurred in the subduction zone where thePacific plate subducts beneath the North American plate or the Okhotsk plate. The magnitude ofearthquake was Mw 9.0. The earthquake-induced tsunami was high and caused devastating disasters
along the coast in the Tohoku and Kanto regions. According to the National Police Agency (NPA), as454

of 30 December 2011, the confirmed death was 15,844 persons and the missing was 3,451, the numberof completely-damaged houses was 127,185. Further, 84,537 people were in 1,328 refuges as of 13
June 2011, according to NPA. The Fishery Agency reported 25,008 fishing boats were damaged.

TSUNAMI HEIGHT
Offshore Tsunami
Buoys with a GPS sensor off the coast in the Tohoku region successfully measured the tsunami
propagating to Japan in the Pacific Ocean. Figure 1 indicates a profile of the 3.11 tsunami measured
off the Port of Kamaishi with a GPS-installed buoy. Even in the water of 204 m deep, the maximum
tsunami of 6.5 m high was measured, which appeared in the first tsunami wave. This high tsunami inthe offshore region is furthermore enlarged due to wave transformation in shallower water depth.
) 7m(i6mansut 5ehtyb 4
notia 3veleec 2
farus 1
reta 0W-1
14:40

14:50

14:50
15:00
March 11, 2011

15:10

15:20

Fig. 1 Tsunami profile measured with a GPS-installed buoy off the Port of Kamaishi (Kawai et al.,2011)
Tsunami Trace HeightMany teams have conducted field surveys to measure heights of tsunami trace and understand tsunami
damage. The tsunami inundation and runup heights have been measured at more than 5,000 points andare summarized in a web page of the 2011 Tohoku Earthquake Tsunami Joint Survey Group(http://www.coastal.jp/ttjt/). Figure 2 indicates tsunami trace heights measured by teams dispatched todamaged major ports by the Port and Airport Research Institute of Japan. In the figure, (I) and (R)indicate inundation height and runup height, respectively. These values are height above the estimatedtide level at the time of tsunami arrival. Records of the historical tsunamis (Watanabe, 1998) are also
indicated in the figure.
In the Sanriku coast from Kuji to Kesen-numa, which is formed by a series of inlets, tsunami
inundation and runup heights were greater than those of Hachinohe and the southern part fromIshinomaki which lie on plains. The maximum inundation and runup heights in damaged areas so far
were broken by the 3.11 tsunami. The maximum runup height among the measurements of the 2011
Tohoku Earthquake Tsunami Joint Survey Group is about 40.0 m in Ofunato city. Even in Ishinomaki
and Sendai where the tsunami records were 5 m or less, the inundation height by the 3.11 tsunami wasmore than 10 m.

455

Hachinohe
Kuji
MiyakoKamaishi
OfunatoKesennuma
Ishinomaki
Sendai
SomaOnahama

The 3.11 tsunami△：Inundation height●： Run-up height

Hitachinaka：1896 Meji-Sanriku：1933 Showa-Sanriku：1960 ChileKashima

Fig. 2 Heights of tsunami trace measured in major ports
TSUNAMI DAMAGE
In the Port of Hachinohe, inundation heights are 5.4 to 6.4 m (2.5 to 2.9 m in the inundation depthabove the ground surface) at points behind breakwaters. On the contrary, they are 8.3 to 8.4 m at thepoints directly facing the Pacific Ocean. The difference of the inundation heights indicates an effect ofbreakwater to reduce tsunami. Boats were moved and landed by tsunami action, as shown in Fig. 3,
because the inundation depth is deeper than draft of the boats. Boats and ships with deeper draft were
not able to be landed but moved on the sea surface in the port, following the tsunami flow.
Even in the outside of the protected area by the breakwater, inundation height of 6.0 m wasmeasured behind a coastal green belt consisting of pine trees. The green belt also mitigated tsunami
flooding and further caught boats to prevent them from hitting houses as shown in Fig. 4.

Fig. 3 Boats landed on a wharf in Port ofHachinohe

Fig. 4 Boats caught by a coastal green belt
in Hachinohe

456Among the North Hattaro Breakwater of 3,504 m long, caissons of total 1,437 m long were moved andsubmerged, as shown in Fig. 5. In the figure many caissons are moved and submerged, and parts ofwave-absorbing blocks installed in front of caissons can be seen above the sea surface. Figure 6 shows
the tsunami overtopping the breakwater. According to the depth survey around the breakwaters after
the event, parts of mound of the breakwater were scoured. Therefore, the breakwater may be damaged
by not only the tsunami forces induced by difference of the water surface level in the front-side of thebreakwater from that of rear side but also lack of stability of caisson induced by foundation failure dueto the overtopping tsunami.
Significant seabed scours were also measured around a corner of a reclaimed island in the port aswell as opening sections of breakwaters. The scoured depth there was about 11 m.

Fig. 5 Breakwater damaged in the Port of Hachinohe

Fig. 6 Tsunami overtopping a breakwater (Courtesy of Tohoku Grain Terminal Co. Ltd.)In the Port of Kuji the tsunami overtopped a line of tide protection wall of 3.6 m high, and flooded
residential area with inundation depth of 4.4 m. Furthermore, the tsunami push oil tanks over sideways
as shown in Fig. 7. The depth of water mark on the upright standing tank, which is at the center of thefigure, indicates inundation depth of 4.4 m. In another city of Kesen-numa, 21 oil tanks were also
damaged, floated and moved by the tsunami. The estimated amount of oil leaking from the damaged
tank was 12,810 m3, according to a report of City of Kesen-numa. The oil was one of causes of fire inthe city.

Fig. 7 Oil tanks damaged in the Port of Kuji

457

In the Port of Kamaishi, the tsunami inundation heights were 7.0 and 8.1 m (5.7 m and 3.5 m ininundation depth respectively) near coasts. The deep tsunami on land floated and crushed wooden
houses, as shown in Fig. 8, which was a scene of the video taken by the Kamaishi Port Office of MLIT.
Reinforced concrete (RC) buildings and large-scale grain silos were also damaged but not collapsed.
Many vehicles together with debris from the destroyed houses filled roads, as shown in Fig. 9.

Fig. 8 Destruction of houses in Kamaishi

Fig. 9 Tsunami debris in Kamaishi

An offshore breakwater installed in the mouth of the Kamaishi Bay, which protected residential andindustrial area in the bay together with seawalls along costal lines against the tsunami whose height
was the same as the 1896 Meiji Sanriku tsunami, was damaged by the tsunami as shown in Fig. 10.
Caissons were moved and submerged by horizontal force caused by the difference of the water surface
levels in the front-side of the breakwater from that of the rear side (Takahashi et al., 2011). Photo
analysis indicates that the water surface rose up to T. P. +11.8 m at least and overtopped the breakwater
whose crown height was T. P. +5 m, in which T. P. is the datum of altitude in Japan.

T. P. +16.1m approx.

4.3 m

Fig. 10 North offshore breakwater damaged
in the Port of Kamaishi

Fig. 11 Tsunami overtopping the north offshore
breakwater in the Port of Kamaishi(Photo courtesy of Japan Coast Guard)

Tsunami inundation heights were almost same in the Miyako bay, as shown in Fig. 12. The tsunami of
10 m high overtopped a protection dike along the coast and inundated residential areas as shown in Fig.
12. Boats were landed on wharfs in the Port of Miyako. Logs and vehicles were also floated andimpacted houses, as shown in Fig. 13.

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8.7m (I)

9.8 m (I)15.6 m (R)Fig. 13 Destruction of residential area
behind a protection dike10.3 m (I)

10.4 m (I)

Fig. 12 Tsunami heights in Miyako Bay

Fig. 14 Debris impact
Tsunami debris is not only vessels, automobiles, oil tanks, logs but also shipping containers. In thePort of Sendai-Shiogama, many containers were scattered by the action of tsunami, as shown in Fig.
15. In the Port of Hachinohe, about 700 containers were also floated and moved, as shown in Fig. 16.

Fig. 15 Scattered containers in the Port ofSendai-Shiogama

Fig. 14 Floated containers in the Portof Hachinohe (Courtesy ofTohoku Grain Terminal, Co. Ltd.)459

NUMERICAL SIMULATIONS ON THE TSUNAMI IN KAMAISHI
The tsunami propagation and inundation is calculated with the model of STOC (Tomita et al., 2007) withthe eighth nested grid system in which the smallest grid size of 12.5 m is allocated in the Port ofKamaishi. The tsunami source is basically estimated with the fault model proposed by Fujii et al. (2011),
but the fault dislocation is 1.5 times original amount so as to fit the calculated first peak of the tsunami to
the the measured one offshore the coast of Kamaishi with a GPS-mounted buoy, as shown in Fig. 15.
Water surface elevation (m) by the tsunami
6Measured

4Calculated

20-2-4020406080100120140160180

Time (minutes) after the earthquake occurrence

Fig. 15 Comparison of the calculated tsunami to the observed one offshore the coast of Kamaishi
Figure 16 indicates the distribution of the maximum inundation height in the case of no-damaged
breakwater. The values in the figure indicate the measured inundation depth in the field survey and thecalculated one at the same points. In this case, the function of breakwater to reduce the tsunami isslightly strong in the calculation. On the contrary, in the case of breakwater damaged initially, thetsunami reduction due to the breakwater is smaller than actual reduction, as shown in Fig. 17, because
the calculated inundation heights are greater than the measured. Therefore, the breakwater may befunctional until around the time of the first and largest peak of the tsunami hitting. In the case of no
breakwaters showed in Fig. 18, the inundation depth is greater than that of case with the breakwater.
Especially, at the point with the measured inundation depth of 8.1 m, residents escaped a three-stories
building. If there are no breakwaters, the tsunami surely overtops the building and the escaping people
may be exposed to danger to lose their lives.
242

Meas.: 6.9-9.0 m
Cal. : 8.6 m

45
4242

Meas. : 6.9‐9.0 m
Cal. ：10.6 m

45
4283

283

Meas. : 8.1 m
Cal. : 8.2 m

Meas. : 8.1 m
Cal. : 10.1 m

Meas. : 7.4-7.8 m
Cal. : 7.4 m

Meas. : 7.4‐7.8 m
Cal. : 11.4 m
24 924 945

45

Fig. 16 Distribution of the calculated maximum
Fig. 17 Distribution of the calculated maximum
inundation height in the case of no-damaged
inundation height in the case of the breakbreakwaters
water damaged before the tsunami attack

460

242

Meas. : 6.9-9.0 m
Cal. : 14.5 m

45
4283

Meas. : 8.1 m
Cal. : 13.6 m
Meas. :7.4-7.8 m
Cal. : 14.4 m
249

45

Fig. 18 Distribution of the calculated maximum inundation height in the case of no breakwaters

LESSONS LEARNT FROM THE MARCH 11 TSUNAMI
From the devastating and cruel tsunami disaster on March 11, 2011, the following three concepts arepointed out to prepare possible tsunamis.
The first is to fear possible earthquakes and tsunamis appropriately. At the event of the 3.11
tsunami, inundation was reduced behind areas of infrastructures such as breakwaters, seawalls andhighly-mounted roads. On the contrast, the large tsunami overtopping or breaking such aninfrastructure caused deadly inundation. Thus, we should predict possible earthquakes and tsunamis
with various sciences and technologies. At least, we should understand the maximum level to attain nocasualties. A useful way to find out the maximum level of tsunami is investigation of paleo-tsunamis
with tsunami descriptions in archives and tsunami depositions under the ground. This level may be
inconformity with the design level of infrastructures such as a seawall.
After the estimation of possible tsunamis, to image its-induced damage in an objective area isimportant to fear the tsunamis appropriately. To enhance images of tsunami damage, physical andmathematical simulations are available as well as experiences of the past disasters. These tools provide
virtual reality experiences that we undergo in a virtual field. Base on such an image, to mitigate
tsunami disasters with no causalities, we can adequately integrate structural measures like a seawall
and non-structural measures like an evacuation plan.
The second is risk communication. It is essential that all stakeholders at levels of the nation, region,province, municipality and resident share correct knowledge and damage image. The disaster risk will
be fully able to be reduced if many related persons correctly understand disaster risk and its
management measures.
The third is to live with the sea. A tsunami is a hazard originated in the sea. However, people have
lived with the sea and received many benefits from the sea such as fishery, marine traffic and richcoastal environment. We cannot live without the sea. Thus, some people have to have their activities
near the sea to continue our livelihoods. To save their lives, we should develop the way to mitigate
tsunami disasters taking the living with the sea into consideration.

CONCLUSIONS
Tsunami-resilient communities and people should be built through integration of town/city planning,
public education including evacuation drill, tsunami disaster mitigation structures, warning system andevacuation system including arrangement of emergency shelters. Regarding tsunami reduction
structures such as breakwaters and seawall, they should have a function that prevents lives andproperties from being lost by a certain level of tsunami or lower. Even for the maximum level of461

tsunami, systems and measures should be enhanced and developed to attain no casualties and to makeits-induced damage be as little as possible. We should also have systems and measures to restore andrehabilitate damage easily if the damage occurs. To implement them, it is important to estimate
possible tsunamis and their-induced damage, and share knowledge and damage image among
stakeholders in all levels.
Finally, I would like to express my deepest sympathy to victims of the 2011 Great East Japan
Earthquake
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Takahashi S. et al. (2011). "Urgent Survey for 2011 Great East Japan Earthquake and Tsunami
Disaster in Ports and Coasts." Technical Note of PARI, No. 1231.
Tomita, T., Honda, K. and Kakinuma, T. (2007). "Application of three-dimensional tsunami simulator
to estimation of tsunami behavior around structures," Proceedings of 30th International Conference
on Coastal Engineering, ASCE, 1677-1688.
Watanabe, H. (1998). "List of Damaging Japanese tsunami (2nd edition)." Tokyo University
Publishing (in Japanese).

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