Proceedings of the International Symposium on Engineering Lessons Learned fromthe 2011 Great East Japan Earthquake, March 1-4, 2012, Tokyo, JapanDAMAGES OF WOODEN HOUSESCAUSED BY 2011 GREAT EAST JAPAN
EARTHQUAKE AND TSUNAMI
Mikio KOSHIHARA1, Naohito KAWAI2, Hiroshi ISODA3 and Takahiro TSUCHIMOTO4
1

Associate Professor, Institute of Industrial Science, The University of Tokyo,
Tokyo, Japan, kos@iis.u-tokyo.ac.jp
2
Professor, School of Architecture, Kogakuin University,
Tokyo, Japan, kawai-nk@cc.kogakuin.ac.jp
3
Professor, Department of Architecture, Faculty of Engineering, Shinshu University,
Nagano, Japan, hisoda@shinshu-u.ac.jp
3
Head, Research Center for Land and Construction Management, NILIM,
Ibaraki, Japan, tsuchimoto-t92ta@nilim.go.jp
ABSTRACT: Substantial earthquake damage of wooden buildings and structures,
including collapse or other heavy damage to houses, occurred over a wide swath fromTohoku down to northern Kanto, although in only a fairly limited number of clusters. The
type of damage is extremely diverse due to differences in site amplification of the groundmotion characteristics.
The summary of damage is broadly divided by the cause of damage, either the damage
due ground deformation or damage due to the vibration of the wooden building.
Key Words: wooden house, heavy timber structure, vibrational damage, liquefaction

INTRODUCTION
In Japan there are many types of wooden buildings. The first category, traditional wooden buildings,
includes temple, shrines, folk house and town house. The second category includes single-family
detached wooden houses. Japan has a stock of about 30 million units, and 600 thousand units are
newly constructed every year. This category can be divided into four types according to theclassification of construction method; conventional construction, two-by-four system, prefabricatedhouses and moment frame system. The third category is heavy timber structure, used example, to build
schools, gymnasiums and museums. There are great varieties in the structural system of heavy timber
structure. Moment-resisting frames and trusses are widely used.
Substantial earthquake damage of buildings and structures, including collapse or other heavy
damage to houses, occurred over a wide swath from Tohoku down to northern Kanto (Fig.1 ), although
in only a fairly limited number of clusters. The type of damage is extremely diverse due to differencesin site amplification of the ground motion characteristics.

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Ofunato*
Kurihara** OsakiSendaiEpicenter(JMA)**NatoriTohokuFukushima* Iwaki

Kanto

Tokyo*

Takanezawa*
Tsukuba** Katori
Chiba

Fig.1 Damaged area

DAMAGE DUE TO GROUND MOTION
The summary of damage is broadly divided by the cause of damage, either the damage due to thevibration of the superstructure or damage due to ground deformation.
Among this division, the vibration of the superstructure is arranged as minor damage (damage tofinishing materials), moderate damage (structural damage), and collapse. Buildings include houses,
stores, apartments, barns, ware-houses, school buildings, public buildings, shrines, gymnasiums, andother large buildings. They vary in construction method, number of floors, size, and shape.
The earthquake caused extensive damage including housing collapses throughout northeastern
Kanto to Tohoku in broad area. In areas such as river basins where the ground is soft, wooden
structures are subjected to larger damage due to the longer natural periods. In addition to serious
structural damage, roof tile damage and chipped wall finishes, although minor, were seen extensively
throughout northern Kanto to the Tohoku area.
In addition to vibrational damage, a large amount of destruction occurred due to grounddeformation. Wooden houses built on slopes collapsed or were heavily damaged due to landslides
and the destruction of retaining walls. Prominent damage throughout the area was due to slope orland subsidence due to liquefaction of the upper structure of the sandy ground. The liquefaction often
tilted the whole superstructure if it did not collapse. In addition, the areas where damage occurred
were often on soft soil so the origin of the damage may not be clearly due to ground deformation or
vibration.
In particular, the building members in Fig. 2 showed extensive termite damage. Numerous
communities have reported serious damage to houses. This damage is reported in Ishinomaki, Osaki,
Kurihara, Kesennuma, Sendai and Misato, in Miyagi Prefecture, Sukagawa in Fukushima Prefecture,
Nasu Karasuyama, Nasu, Takanezawa and Haga in Tochigi Prefecture and Mito, Ibaraki, Sakuragawa,Naka, and Hitachiota in Ibaraki Prefecture. In addition, sporadic cases of deteriorated housing collapse
have been reported in other cities such as Katori, Chiba Prefecture and Kounosu Saitama Prefecture.
Fig. 2 – Fig. 5 illustrate some of this damage. Most of the extensive damage occurred in relatively
old housing construction, often obsolete buildings, with decay and termite damage. In particular, the207

Fig.2 Collapse of wooden house in Osaki

Fig.3 Partial collapse of wooden house in
Kurihara

Fig.4 Collapse of wooden house with store
attached in Misato

Fig.5 Severe damage of wooden house withstore in Osaki

building members in Fig. 5 showed extensive termite damage.
The wooden houses typically have large openings facing the street, which is inadequate forearthquake resistance. Exterior walls often showed chipped mortar and glass as well as ants in thewood sheathing, which sometimes spread into the structural members. Therefore, the damage of mostdwellings was amplified due to the termite damage.
In contrast, one distinct example of vibration damage is found in Fig. 6, which shows the partial
collapse of the high stone foundation near the city of Nasu Karasuyama and the town of Ichigai in
Tochigi Prefecture. This vibrational failure of the foundation was often found and would lead to thecollapse of the wooden structure above.

Fig. 6 Collapse of wooden house with high stone foundation

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Vibrational damage to storehouses, ‘DOZO’
A wide array of damage to storehouse buildings was observed from Kanto to Tohoku, many of whichhave attached dwellings. Examples of storehouse damage are in Fig. 7 through Fig. 9
The primary type of damage was in the form of fallen roof tiles or chipped exterior wall coatings.
Major damage, demonstrated in Fig. 7, was evident in the form of permanent inclination of thebuilding. The group of store-houses in Osaki, as seen in Fig. 8, was over 200 years old and had
obvious structural deficiencies. Although there is no deformation to the columns and other structuralmembers, the termite decay is extensive within the members and would be difficult to repair. Fig. 9shows a building on the same property as the warehouses. A retrofit was performed on the interior
wooden bearing walls and reinforced concrete masonry foundation inside. The structural timbers werestill intact but the roof collapsed.

Fig.7 Permanent inclination of a storehouse

Fig.8 Damage of older storehouses in Osaki

Fig.9 Retrofitted storehouse in Osaki

Fig.10 Damage of storehouse with heavy mud Fig.11 Damage of three storehouses with heavy
walls in Tsukuba
mud walls

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Fig. 10 and Fig. 11 show the damage of residential storehouses. Residual deformations were small
and the damage was primarily in the form of cracks and spalling of the mud wall as well as falling roof
tiles.
Vibrational damage to barns
In residential areas, many structures such as barns and small storage buildings collapsed. These
structures did not have adequate seismic considerations. Examples of such damage are in Fig. 12 andFig. 13.

Fig. 12 Collapse of shed in Kurihara

Fig.13Collapse of shed in Kurihara

Vibrational damage to schools
School buildings were a mixture of old timber construction methods and new laminated timber
structures. A schoolhouse using older timber construction was reported to have a partial second floor
collapse and large deformations in Osaki city as well as traces of sand boiling in the schoolyard,caused by liquefaction of the sandy ground. Fig. 14 shows the markings indicating sand boiling. In
Iwaki timber schoolhouses are heavily damaged as shown in Fig. 15.
School buildings using laminated wood construction, such as an elementary school gymnasium inNaka-city, only experienced minor damage to the concrete foundation and timber braces.

Fig.14 Damage of school building and markings Fig.15 Severe damage of school building inof sand boiling in Osaki
Iwaki

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Vibrational damage to shrines
Damage to shrines are widely reported across the Northeast of Japan with a notable collapse of themain building of a temple in Takanezewa town, seen in Fig. 16.
In addition, Fig. 17 shows the severe damage of the gate to a shrine in Osaki-city. Marks aroundthe site seem to indicate sand boiling caused by the liquefaction of the sandy ground. These shrines
used traditional wooden construction methods and were located on soft soils.

Fig.16 Collapse of the main building of temple Fig.17 Severe damage to the gate of a shrine in
Osaki
in Takanezawa

Vibrational damage of other wooden buildings
In addition to other building types discussed, a renovated theater in Kurihara-city experienced large
residual deformation, evident in Figure 18.
Other examples of damaged timber buildings included houses that used logs assembly.
Although this is a rare construction method, there are reports of damage at the intersection of the logs
in houses in Nasushiobara-city.

Fig. 18 Severe damage of old cinema in Kurihara-city
Building damage due to landslides
This earthquake caused many landslides and destruction of retaining walls, leading to the destructionof many houses built on the slopes.
Areas of intense damage were found in Aoba-ku Sendai-city, Izumi-ku Sendai-city,
Wakabayashi-ku Sendail-city, Fukushima-city, Kagamiishi town, Iwaki-city in Fukushima Prefecture,211

and Nasu-karasuyama-city in Tochigi Prefecture.
through Fig. 22.

Examples of such damage are found in Fig. 19

Fig. 19 Collapse of hotel due to landslide in Fig. 20 Severe of a house due to landslide in
Sendai-city
Sendai-city

Fig. 21 Severe damage of a house due to Fig. 22 Severe damage of a house due tolandslide in Sendai-city
landslide in Iwaki-city

Fig.23 Damage due to liquefaction in Katori-city

Damage due to liquefaction
Soil liquefaction occurred rapidly in a wide range of places due to the sandy soil. Ground subsidence
lead to serious damage or a tilt of the superstructure.
This damage was evident in Kashima, Kamisu, Itako city, Inashiki, Kawachi-machi in Ibaraki
Prefecture, Asahi city, Urayasu, Funabashi, Narashino, Chiba, Abiko, Katori (Fig. 23) in Chiba212

Prefecture and Kuki city in Saitama Prefecture. The structural damage to the superstructure due toliquefaction was rather small if it used a reinforced concrete foundation. Damage was typically inthe form of structural inclination and subsidence.
Ground deformation and other damage
In flat ground, even though liquefaction does not occur, the soft ground will result in land and soil
cracks. Damage to the superstructure from differential settlement is reported in Sakura, and Narita in
Chiba Prefecture. Similar damage may have happened in the other regions. This type of the damage
occurred to old houses, so the origin of the damage may not be clearly due to ground deformation or
vibration.

DAMAGE DUE TO THE TSUNAMI
Tsunami-affected area and study sites
The earthquake triggered a tsunami that flooded areas in the Aomori, Iwate, Miyagi, Fukushima,
Ibaraki, and Chiba Prefectures. The reconnaissance was conducted in two parts, as indicated in Table
1 due to limitations of time and human resources. A brief summary of the damage is contained
within this re-port.
In addition, some results were calculated introducing the relationship between strength ofwooden buildings and the horizontal distribution of the tsunami wave.
Table 1 Survey of the tsunami damage to wood buildings
Classification
Lowland

Sloping land

Municipality
Study Dates
Wakabayashi-ku, Sendai, Natori,
April 6th, 2011- April 8th,
Iwanuma, Watari, and Yamamoto in 2011
Miyagi Prefecture
Ootsuchi, Kamaishi, Ofunato, andRikuzentakada, in Iwate Prefecture
May 25th, 2011 – May 27th,and Kesennuma Minamisanriku,
2011
Onagawa and Higashimatsushima in
Miyagi Prefecture

Damage to lowland areas
The lowlands, often with nothing blocking the force of tsunami, had extensive damage reaching
locations far inland. The following provides an overview of this damage.
Wakabayashi-ku, Sendai-city, Miyagi PrefectureWith a few exceptions, most wood houses were completely washed away by the tsunami. Fig.24
shows one of the few wooden houses left standing, due to a location downstream of a reinforced
concrete building. Inundation depth estimated from remaining reinforced concrete buildings reached
6 to 8 meters.
In an area approximately 1.5 km away from the shoreline in Arahama district, many low-risebuildings and dozens of hotels were washed away. In this area, some wooden houses situated in aline the direction of the water flow withstood damage, as shown in Fig. 25. Inundation depth in thisarea was estimated to be about 4 to 5 meters, with the remaining wooden houses being low-rise andnon-residential. On the other hand, there were several cases identified that no buildings were left
standing in the direction of the tsunami waves.

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Fig. 26 shows one of the few wooden structures left standing, with damage limited to the walls in the
direction of floodwater. The method of construction was relatively new, involving joints with moremetal than traditional construction.

Fig. 24 Wood house remained downstream of RC
building

Fig. 25 Wooden houses remained in a line

Fig. 26 Wooden building escaping complete
devastation

Yuriage, Natori-city, Miyagi Prefecture
In general, this area experienced widespread catastrophic damage. Fig. 27 shows an aerial photo(from 3/13/2011) of the area surveyed, with the locations of the properties surveyed circled.
Initial investigation was conducted on the house in Fig. 28 at location(Circled numbers in
Fig.27 and so on), which had been carried away with the foundation attached. The junction of thefoundation to the steel pile failed due to the force of the tsunami, leaving the steel pipe piles in thesand since in Fig. 29 at location (2). This would indicate that the tsunami wave was moving east to
west-southwest.
In this same vicinity, the temple and steel building at locations (3) and (4) respectively, wereseverely damaged but remained in place. The wooden shop with dwelling at location (5) only
received slight damage presumably due to being downstream to the temple and steel building.
Fig. 30 shows a wooden house in location (10) that withstood the tsunami force without the protection
from trees at location (7). This is probably due to the relatively new construction of the house, which
was built in the last few years.

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Fig. 27 Aerial photograph and the position of investigated buildings in Yuriage, Natori-City

Fig. 28 Wooden house that was carried awaywith foundation

Fig. 29 Steel pile left at the original position of
Figure 28

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Fig. 30 Wood house remaining without theprotection of the forest (Location (10))
A few wooden houses remained around location (11), downstream of a factory building.
Inundation depth is estimated at about 3.5 meters in this area. These buildings are pictured in Fig. 31
and Fig. 32 (Picture taken from location (12)).
Fig. 33 in location (14) shows a group of houses that remained down-stream of a large factory building.
The buildings that survived were a mix of older and newly constructed wooden houses. In addition,
the factory building in location (15) protected wooden houses for an even further distance. This is
expected to be due to the relatively new construction of these houses that had superior structural
specifications. These houses are seen in Fig. 34 taken from location (11). Another wooden house,at location (17), was spared from catastrophic damage presumably due to superior construction.

Fig.31 Japanese conventional post and beam
wood house remaining (Location (11))

Fig. 32 One of few light frame construction woodhouses remaining (Location (11))

Fig. 33 Group of wooden houses that escaped
damage downstream of a RC structure(Location (14))

Fig. 34 Wooden houses which avoided being
carried away downstream of the factory building(Location (11))

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Araham, Watari-town, Miyagi Prefecture
The Araham, Watari-town area is surrounded by the Pacific Ocean on the west and a lake to the South,
with a harbor off of the lake, as shown in Fig. 35. The tsunami washed away many of the wooden
houses, leaving only the foundation.

Fig. 35 Aerial photograph in Arahama, Watari-machi
The extent of the severe damage was mostly on the eastern peninsular region. One woodenbuilding, as pictured in Fig. 36, was previously “L” shaped in plan. The part of the house that had
the largest amount of area exposed to the tsunami wave washed away while the shorter side remained.
Judging from the connection in Fig. 37, the estimated date of construction was after 2000, revisedbuilding standard in Japan.
Fig. 38 shows a hybrid construction building that withstood the tsunami force. This building
uses reinforced concrete stilts for the first floor and wooden construction on the second floor. Fig. 39
shows a one-story heavy timber structure with glulam frame in which the wooden structure remained
intact, but the building was filled with wreckage and building materials.
North of the harbor, estimated to have been in 6 meters of floodwater, mostly consisted of
detached wooden houses. Fig. 35 shows the impacted area, with very few houses remaining on thenorth side of the harbor. One of the few that remained, pictured in Fig. 40, was a three-story wooden
house that had been design for superior seismic protection. This extra strength is probably
responsible for the survival of the building. West of the harbor, estimated to have been in 4 meters offloodwater, had a number of buildings withstand the tsunami force. One of the wooden houses,
pictured in Fig. 41, also withstood contact from a ship. This is probably due to relative young age ofthe house, which presumably has superior structural specification.

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Fig. 36 A portion of a wood house that was Fig. 37 Fastener of joint in the house of Fig. 36
washed away

Fig. 38 Hybrid construction consisting of RC on
the 1st floor and wooden construction on thesecond floor

Fig. 39 Heavy timber structure with Glulam
frame remaining

Fig. 40 3-story wooden house remaining

Fig. 41 Wooden house remaining even after
collision with ship218

Summary of damage to the lowlands
The following conclusions were drawn about wooden building in the lowlands.
•Overall damage was quite severe•If a building did withstand the tsunami, the wooden buildings downstream often stayed
intact.
•The wooden buildings that stayed intact downstream of other buildings showed newer andsuperior structural construction.
•Even if there was no building blocking the force of the tsunami, there are a few examples of
low-rise wooden buildings that remained intact due to newer construction specifications.
However, the buildings that remained had severe damage to the lower level walls
perpendicular to the tsunami direction.
Damage to wooden buildings on slopes
In this section, the damage survey results are only given for Akasaki-machi, Ofunato-city, a village on
the east side of the bay of Ofunato situated on a gradual slope. Fig. 42 shows the aerial photographof the district with the locations of the buildings surveyed.

Fig. 42 Aerial photograph in Ofunato-City

A house in location (1) (Fig. 43), according to residents, was almost completely submerged withinundation depth over 7 meters. The house had some damage but was largely spared overall. An
adjacent work shed in location (2) was disconnected from the concrete foundation and moved. The
two-story wooden house across the street in location (3) on the ocean side received very little damage(Fig. 44). The hill to the north of these buildings probably reduced the magnitude of the tsunami
force.
Fig. 45 shows a traditional Japanese wood house in location (5) that survived the inundation
depth of about 5-6 meters and it was located 1.5 meters above the road level. Although the walls
were destroyed the structure was intact, and there seemed to be little residual deformation in the house.
Fig. 46 in location (6) was about 2 meters above the road level. The house was spared de-spite
floodwater levels reaching 6 meters, damaging parts of the roof as well as the house. A relatively
new house to the northeast was washed away. This house was equipped with significant tie-down
hardware and large partial corrosive pores were observed. This indicates that the tie-down hardware
was not sufficient to fix the house to the foundation.
Along the prefecture road up the hill from these buildings, a lightweight steel frame house inlocation (9) withstood floodwaters up to 5 meters. Adjacent to this building in location (10), a small
one-story building that had minor structural specifications survived, pictured in Fig. 47. The house219

was con-firmed to have one brace with nailed joints and anchor bolts into the foundation. In addition,
despite a 3.8-meter inundation depth, a dilapidated warehouse in location (11) remained standing (Fig.
48). Just to the East in location (12), old houses were rotated about 30 degrees clockwise (Fig. 49).
The fact that some of these older buildings withstood these floodwaters suggests that the slope reduced
the force of the tsunami in contrast to the lowlands.

Fig. 43 Wooden house intact with 7m wave
depth

Fig. 44 Wood house without damage with over
7m wave depth

Fig. 45 Traditional wooden house that avoided
being carried away under 5-6 m wave depth

Fig. 46 Wooden house that avoided being carriedaway even with flood damage up to the 1st floor
roof

Fig. 47 House that survived with minor
structural specifications

Fig. 48 Warehouse that survived with minor
structural specifications

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Fig. 49 Survived old house which was rotated

CONCLUSIONSThe summary of damage is broadly divided by the cause of damage, either the damage due grounddeformation or damage due to the vibration of the wooden building.
Among this division, the vibration of the wooden building is arranged as minor damage(damage to finishing materials), moderate damage (structural damage), and collapse. Buildings
include houses, stores, apartments, ware-houses, school buildings, public buildings, shrines,
gymnasiums, and other large buildings. They vary in construction method, number of floors, size,and shape.
Collapse and other heavy damage affecting wooden houses, which tend to have long natural
period and little seismic protection, were extensive in areas having soft ground (along river beds, etc.).
Also reported was damage to earth wall storehouses, ‘DOZO’, not only in areas where houses ingeneral suffered severe damage, but also in areas where they suffered little damage.
Slight damage, typically to roof tiles (especially fallen ridge tiles) and exterior wallcoverings (peeling, etc.) was observed over a wide area extending from Tohoku to Kanto.
Particularly conspicuous in the aftermath of this earthquake are (1) collapse or other severe
damage to houses and other structures as a result of landslides or failure of retaining wall on slopes,
especially on land developed for residential use, and (2) tilting or sinking of entire structures as aresult of the liquefaction of sandy soils. Furthermore, many of the areas that experienced significant
vibrational stress are characterized by soft ground, and in several cases it is not entirely clear whether
damage to structures there should be attributed to vibration or to ground deformation.
As for tsunami damage, many wooden houses were swept away within areas struck
particularly hard. There were cases, however, of wooden houses that, because they were shielded fromdirect tsunami impacts by relatively large surviving structures, remained in place. There were also
cases where wooden houses presumably having excellent structural specifications remained in place
despite the lack of a shielding building, although some did suffer severe damage to their walls orframes. The use of hold-down connectors appeared not to be an important factor in determining
whether a wooden house was swept away.
ACKNOWLEDGMENTS
The authors thank the editorial committee of ‘Preminary Reconnaissance Report of the 2011
Tohoku-Chiho Taiheiyo-Oki Earthquake’ in Architectural Institute of Japan (AIJ) and the editorialcommittee of that in English. A part of this research was supported by Managing Committee on
Wooden Structures of AIJ.

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