Proceedings of the International Symposium on Engineering Lessons Learned fromthe 2011 Great East Japan Earthquake, March 1-4, 2012, Tokyo, Japan

BUILDING DAMAGE IN NARITA, SAKURAAND THE TONE RIVER BASIN IN CHIBAPREFECTURE
Yukiko NAKAMURA1, Tomofusa AKITA2, Yuko SHIMADA3,Toru TAKAHASHI4 and Nobuyuki IZUMI5
1Associate Professor, Department of Architecture, Chiba University,Chiba, Japan, nakamura.yukiko@faculty.chiba-u.jp
2Assistant Professor, Department of Architecture, Chiba University,Chiba, Japan, akita@faculty.chiba-u.jp
3Assistant Professor, Department of Architecture, Chiba University,Chiba, Japan, yshimada@faculty.chiba-u.jp
4Professor, Department of Architecture, Chiba University,Chiba, Japan, takahashi.toru@faculty.chiba-u.jp
5Professor, Department of Architecture, Chiba University,Chiba, Japan, nobuyuki.izumi@faculty.chiba-u.jp

ABSTRACT: The 2011 Tohoku-chiho Taiheiyo-oki Earthquake that occurred on March
11 caused severe damage to buildings. In Chiba Prefecture, a Japanese MeteorologicalAgency (JMA) seismic intensity scale (IJMA) of six-minor was recorded at Narita,Inzai-sasagami and Inzai-ohmori. Tsunami damage on the Pacific side and liquefaction
damage on the Tokyo Bay side and along the Tone River of Chiba were severe. Inaddition to this damage, there was building damage by liquefaction. We report here on
the building damage in Chiba Prefecture.
Key Words: Great East Japan earthquake, building damage, Chiba Prefecture

INTRODUCTION
The 2011 Tohoku-chiho Taiheiyo-oki Earthquake, Japan that occurred on March 11 2011, caused
severe damage over a wide area of Japan including Chiba Prefecture. A Japanese MeteorologicalAgency (JMA) seismic intensity scale (IJMA) six-minor earthquake motion was recorded at Narita andInzai cities in Chiba Prefecture, Kanto region.
As a result of the earthquake twenty people died and two people are missing in Chiba Prefecture.
There were 799 collapsed buildings, 9,810 partially collapsed buildings and more than 43,000
damaged buildings in Chiba (Chiba Prefecture).
In addition to the damage caused by earthquake movement, a tsunami affected the Pacific Oceanside and massive liquefaction occurred in the plain area along the Tone River and the Tokyo bay area.
We carried out a damage investigation of Chiba between March 22 and April 17. We surveyed
mainly Abiko and Katori cities along the Tone River and Narita and Sakura cities around Inba-numa.
Figure 1 shows the surveyed areas on a map of Chiba Prefecture.

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AbikoKatori
NaritaSakuraFigure 1 Survey area map (Chiba Prefecture)

DAMAGE IN KATORI CITY
Katori is located along the Tone River, which was subjected to a JMA seismic intensity of scale
five-upper. We surveyed the Sawara and Omigawa area in Katori between March 22 and April 17.
The major building damage in this area was caused mainly by soil failure and liquefaction.
Collapsed buildings were typically dilapidated timber houses and warehouses. Nonstructural wallsof buildings fell down. The collapse of concrete block walls and roof tile damage occurred over a widearea, not only in areas subject to soil failure and liquefaction.
Sawara area
Liquefaction damage was severe on the west side of Katori city hall. Timber houses and power
poles were leaning, concrete block walls had collapsed and road surfaces were deformed (Figures 2and 3). Attached buildings were separated from main buildings by soil failure. A tank was unseated byland subsidence(Figures 4 and 5).
Revetment along the Ono River was damaged (Figure 6). The Ono River dried up by erupting
sand leaving boats stranded. Many buildings along the Ono River sank.
In the important traditional building preservation area of Sawara, the roof tiles and plaster walls oftraditional buildings were dislodged and collapsed (Figures 7 and 8). The government-designatedexcavation of the ruins of the old Ino Tadataka residence was closed and its roof was covered withblue tarpaulins (Figures 9 and 10). Mitsubishi-kan, which is a significant cultural property of Chiba,
had no structural damage (Figure 11).

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Figure 2 Damage of a masonry garden wall

Figure 3 Leaning power pole

Figure 4 Damage of a tank by land subsidence

Figure 5 Attached building separated fromthe main building

Figure 6 Damage to the revetment along
Ono River

Figure 7 Timber house damage fromliquefaction1193

Figure 8 Collapsed timber house near theOno River Drainage Pump Station

Figure 9 Old Ino Tadataka residence

Figure 10 Important traditional buildingin the Sawara preservation area

Figure 11 Mitsubishi-kan (no damage)

Omigawa area
Around Omigawa station there was less liquefaction and soil failure. There were collapsed
concrete block walls and fallen exterior walls. Figure 12 shows the collapsed warehouse near theKurobe River. The warehouse collapsed because of fallen lumber.
The Shinkai-cho area of Omigawa near the Tone River was severely damaged by soil failure. Amanhole and a water storage tank were uplifted by liquefaction as seen in Figure 13. Only one blockof land collapsed to the west and a timber house tilted because of soil failure (Figures 14-16).
Figure 17 shows a large sand eruption point in the next block. A water tank was uplifted about 30 cm
by liquefaction. (Figure 18)
The two adjoining blocks responded differently. One manhole was uplifted, but the others were
not damaged as shown in Figure 19.

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Figure 12 Collapsed warehouse

Figure 13 Shinkai-cho area

Figure 14 Subsidence damage

Figure 15 Tilted timber house

Figure 16 Tilted timber house

Figure 17 Sand eruption point1195

Figure 18 Water tank uplifted by liquefaction

Figure 19 Shinkai-cho, Omigawa areaDAMAGE IN ABIKO CITY
We surveyed the Fusa and Abiko station area in Abiko on March 22. The JMA seismic intensity
scale (IJMA) in Abiko was five-minor. The IJMA in Inzai, which is close to the Fusa area was six-minor.
The major damage around Abiko Station was fallen roof tiles. The damage in Abiko was minor
excluding the damage caused by liquefaction in the Fusa area. Liquefaction was limited to the Miyako
area of Fusa (Figures 20 and 21). This liquefaction area was consistent with its swamp-like origins.
There were the leaning power poles and an uplifted manhole (Figures 22 and 23). Many timberbuildings in the liquefaction area were tilted and had settled because of subsidence (Figures 24 and 25).
The maximum total settlement was about 1 m and the tilt or inclination angle was about 1/100. A
reinforced concrete structure apartment in Miyako had no structural damage but did have damage topipes.

Figure 20 Liquefaction in Miyako

Figure 21 Sand eruption

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Figure 22 Inclination of power poles

Figure 23 Uplifted manhole

Figure 24 Settling of a timber house
due to liquefaction

Figure 25 Inclination of a building due toliquefaction

DAMAGE AROUND INBA-NUMA
Inba-numa is on the right bank of the Tone River. There were early reports of damage to andcollapse of buildings in Narita and Sakura cities around Inba-numa. We surveyed Narita and Sakura on
March 24 and April 16.
Narita city
A JMA seismic intensity scale (IJMA) six-minor earthquake was recorded at JMA Narita. The levelsix-minor was the maximum IJMA recorded in Chiba Prefecture. The JMA Narita station was set up on
higher ground than the neighboring area. Figure 26 shows the JMA Narita station and Narita city hall.
Damage to exterior walls was observed in a steel structure near the JR Narita station (Figure 27). No
other damage was observed apart from fallen roof tiles. Damage to housing was mainly unevensettling over a limited area caused by land failure. A collapsed ceiling in a public building was also
reported.
Timber buildings in the Naritasan Shinsho-ji Temple had no structural damage but many stonestructures, such as a stone lantern, had fallen.

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Figure 26 JMA Narita station and Narita
city hall.

Figure 27 Fallen exterior walls

Figure 28 Naritasan Shinsho-ji Temple

Figure 29 Damage to a stone structure

Sakura city
A peak ground acceleration of 1,053 cm/s/s was recorded at the K-NET Sakura station (NIED).
The station is set on a slope above the city hall. Figure 30 shows the K-NET Sakura station and city
hall. Figure 31 shows the cityscape from Sakura city hall. The damaged roof tiles were covered in blue
plastic tarpaulins. There were cracks in the stairs of a building near Keisei-Sakura station located in
the low-lying area.
Damage to buildings was reported in the north of the city where the low-lying area and plateau
meet. Damage to housing was mainly uneven settling. One of the area concentrated damage was indeveloped land in the low-lying area. The houses settled about 10 cm.

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Figure 30 K-NET station and Sakura city hallon the hill.

Figure 31 Cityscape from Sakura city hall

Figure 32 Settling of a timber house

Figure 33 Damage to a column base of thestairs in Keisei-Sakura Station.

CONCLUSIONS
We conducted a preliminary damage investigation of the area along the Tone River and aroundInba-numa in Chiba Prefecture.
The damage caused by earthquake movement was low. The major damage was to timber housing
caused by liquefaction or soil failure. There were fallen roof tiles and exterior walls, collapsed
concrete block walls and equipment damage. Old timber houses and warehouses had collapsed. The
damaged buildings were mainly timber structures. Steel structure buildings and reinforced concrete
structure buildings showed no or minor damage without any structural failures.

REFERENCES
Chiba Prefecture (2012) “Great East Japan Earthquake Information part 198 (in Japanese)”
http://www.pref.chiba.lg.jp/bousai/h23touhoku/20120104-198.html
Chiba Prefecture “municipality map of Chiba (in Japanese)”
http://www.pref.chiba.lg.jp/kouhou/map.html
National Research Institute for Earth Science and Disaster Prevention (NIED) “Kyoshin Network
K-NET” http://www.k-net.bosai.go.jp/1199