Scholarly article on topic 'Liquefaction in Tohoku district during the 2011 off the Pacific Coast of Tohoku Earthquake'

Liquefaction in Tohoku district during the 2011 off the Pacific Coast of Tohoku Earthquake Academic research paper on "Earth and related environmental sciences"

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{Liquefaction / "The 2011 off the Pacific Coast of Tohoku Earthquake" / "Sand boils" / "Uplift of manhole" / "Land condition map (E8)"}

Abstract of research paper on Earth and related environmental sciences, author of scientific article — A. Yamaguchi, T. Mori, M. Kazama, N. Yoshida

Abstract Information on the liquefaction and the liquefaction-induced damage in the Tohoku district during the 2011 off the Pacific Coast of Tohoku Earthquake has been compiled. The liquefaction in this report was mainly identified by sand boils. It caused damage to earth structures and residential houses, as well as the uplift of manholes. A comparison of geological maps and aerial photos, before and after the earthquake, shows that many of the liquefied sites were old river beds and developed areas. Liquefaction in the tsunami-affected areas was difficult to identify as the evidence of liquefaction had been washed away by the tsunami. However, the liquefaction was identified through interviews with residents and by photos and videos taken before the arrival of the tsunami. Liquefaction was also observed at Sendai Airport, but the runaway was not damaged because it had been remediated against soil liquefaction.

Academic research paper on topic "Liquefaction in Tohoku district during the 2011 off the Pacific Coast of Tohoku Earthquake"

The Japanese Geotechnical Society

Soils and Foundations

www.sciencedirect.com journal homepage: www.elsevier.com/locate/sandf

SOILS AND

FOUNDATIONS

Liquefaction in Tohoku district during the 2011 off the Pacific Coast

of Tohoku Earthquake

A. Yamaguchi*, T. Mori, M. Kazama, N. Yoshida

Received 28 February 2012; received in revised form 30 July 2012; accepted 1 September 2012 Available online 27 December 2012

Abstract

Information on the liquefaction and the liquefaction-induced damage in the Tohoku district during the 2011 off the Pacific Coast of Tohoku Earthquake has been compiled. The liquefaction in this report was mainly identified by sand boils. It caused damage to earth structures and residential houses, as well as the uplift of manholes. A comparison of geological maps and aerial photos, before and after the earthquake, shows that many of the liquefied sites were old river beds and developed areas. Liquefaction in the tsunami-affected areas was difficult to identify as the evidence of liquefaction had been washed away by the tsunami. However, the liquefaction was identified through interviews with residents and by photos and videos taken before the arrival of the tsunami. Liquefaction was also observed at Sendai Airport, but the runaway was not damaged because it had been remediated against soil liquefaction. © 2012 The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved.

Keywords: Liquefaction; The 2011 off the Pacific Coast of Tohoku Earthquake; Sand boils; Uplift of manhole; Land condition map (E8)

1. Introduction

An earthquake with a moment magnitude of 9.0 occurred in the off Sanriku area of the Tohoku district on March 11, 2011. This earthquake was an ocean trench type of earthquake and its focus was located at a depth of about 24 km. The earthquake was named the 2011 off the Pacific Coast of Tohoku Earthquake (Japan Meteorological Agency, 2011a), which measured the maximum of 7 on the Japanese seismic intensity scale in Kurihara, Miyagi Prefecture and measured over a low 6 on the Japanese seismic intensity scale of 7 in

Miyagi, Fukushima, Ibaraki, Tochigi, Iwate, Gunma, Saitama and Chiba Prefectures (Japan Meteorological Agency, 2011b).

One of the characteristics of this earthquake is the tsunami that followed it and the significant damage that resulted from it. Liquefaction can also be counted as another characteristic of this earthquake because it occurred over such a wide area, from the Tohoku district to the Kanto district, and caused significant damage. Case histories of liquefaction in the Tohoku district are reported in this paper.

*Corresponding author. E-mail address: yamaguti@tjcc.tohoku-gakuin.ac.jp (A. Yamaguchi). Peer review under responsibility of The Japanese Geotechnical Society.

2. General features of liquefaction in Tohoku district and liquefied sites

The liquefied sites in Iwate, Miyagi and Fukushima Prefectures are shown in Fig. 1 and Table 1. There are 93 liquefied sites, which include not only the sites identified by the authors, but also those identified through interviews, published matter, the web, etc. The identification of liquefaction was

0038-0806 © 2012 The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.sandf.2012.11.005

Fig. 1. Location of liquefied sites (modified from Google (2011)). Blue, red, yellow and green circles denote sand boils without structural damage, uplift of underground structures, damage to residential houses and others, respectively. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

based on clear evidence, such as sand boils and the large uplift of manholes. There were not many sites with evidence in the area where the tsunami hit, because the evidence of liquefaction had been washed away. In these cases, the liquefaction was identified based on photos and videos taken before the arrival of the tsunami. The Tohoku district also includes Yamagata, Akita and Aomori Prefectures, but there were no reports of liquefaction in those areas. The longitude and latitude in Table 1 were taken from Google (2011). The distances from the epicenter to the sites of liquefaction are shown in the table.

The appearance of soil liquefaction is classified into four types, namely, sand boils without damage to structures, the uplift of underground structures such as manholes, damage to residential houses, and others. The four types are distinguished in Fig. 1 as blue, red, yellow and green

symbols, respectively. The apparent uplift of manholes may have occurred when the surrounding ground subsided due to the densification of soil. In order to distinguish this phenomenon from liquefaction, the uplift of manholes by more than about 30 cm is identified as liquefaction in Table 1.

3. Overview of liquefaction-induced damage

The damage caused by the soil liquefaction is shown in this section by focusing on its relation to ground failure.

3.1. River dikes and their vicinities

Two types of liquefaction were observed along river dikes. One type is the sand boils found in the farm land

Table 1

Liquefaction sites.

No. Damage type Site Latitude Longitude Epicentral Reporter

distance

1 Uplift of manhole Hotel Toyoko, Furukawa 38°34'16.32''N 140°57'56.21 ''E 167.3 Tohoku Gakuin University

2 Uplift of manhole Furukawa 38°34'18.39''N 140°57'57.80''E 173.8 Tohoku Gakuin University

3 Inclining of apartment FINE COURT FURUKAWA, Furukawa 38°34'18.33''N 140°57'46.22''E 174.0 Tohoku Gakuin University

4 Damage of embankment Takakawa Bridge 38°34'25.24''N 140°53'2.17''E 180.7 Tohoku Gakuin University

5 Sand boiling Shimoshinden, Naruse River 38°32'47.23''N 140°52' 30.46''E 180.6 Tohoku Gakuin University

6 Dike collapse Shimoshinden, Naruse River 38°32'12.54''N 140°53' 14.00''E 180.3 Tohoku Gakuin University

7 Sand boiling Nakaniida, Naruse River 38°32'6.43''N 140°53' 31.46''E 178.9 Tohoku Gakuin University

8 Sand boiling Confluent point with Zen River, Yoshi River and Yoshida River 38°25'50.65''N 140°55'33.23''E 173.3 Tohoku Gakuin University

9 Sand boiling Downstream 1 km from No. 8, Yoshida River 38°25'34.66''N 140°56'19.75''E 172.1 Tohoku Gakuin University

10 Sand boiling Nakayashiki, Yoshida River 38°25'40.06''N 140°58'8.36''E 169.6 Tohoku Gakuin University

11 Sand boiling Nakayashiki, Yoshida River 38°25'42.89''N 140°58'18.16''E 169.4 Tohoku Gakuin University

12 Dike collapse Kamishida, Yoshida River 38°26'49.80''N 141°1'54.08''E 164.7 Tohoku Gakuin University

13 Sand boiling Kamishida, Yoshida River 38°26'50.09''N 141°2'2.32''E 164.5 Tohoku Gakuin University

14 Sand boiling Kamishida, Yoshida River 38°26'49.33''N 141°2'2.89''E 164.5 Tohoku Gakuin University

15 Dike collapse Kamishida, Yoshida River 38°26'47.05''N 141°2'17.06''E 164.1 Tohoku Gakuin University

16 Dike collapse Shimoshida, Yoshida River 38°26'39.08''N 141°2'51.25''E 163.2 Tohoku Gakuin University

17 Dike collapse Shimoshida, Yoshida River 38°26'40.67''N 141°2'52.32''E 163.2 Tohoku Gakuin University

18 Dike collapse Shimoshida, Yoshida River 38°26'39.80''N 141°2'52.25''E 169.4 Tohoku Gakuin University

19 Dike collapse Shimoshida, Yoshida River 38°26'36.06''N 141°3'19.63''E 162.5 Tohoku Gakuin University

20 Uplift of manhole Iwakiri, Sendai City, 38°18'12.87''N 140°57'17.54''E 168.5 Tohoku Gakuin University

21 Damage of house Jingahara, Sendai City 38°18'1.51''N 140°54'26.42''E 172.7 Tohoku Gakuin University

22 Road collapse Shida Bridge, Naruse River 38°31'49.50''N 141°0'19.70''E 170.8 Tohoku Gakuin University

23 Dike collapse Naruse River 38°27'13.80''N 141°6'30.49''E 158.3 Tohoku Gakuin University

24 Sand boiling Naruse River 38°26'47.03''N 141°6'24.78''E 158.2 Tohoku Gakuin University

25 Sand boiling Naruse River 38°26'59.42''N 141°6'34.44''E 157.9 Tohoku Gakuin University

26 Road sagging Nagamachi 38°13'28.97''N 140°52' 33.74''E 174.6 Tohoku Gakuin University

27 Sand boiling and Torinoumi 38°2'15.35''N 140°54' 4.42''E 172.3 Hashimototen

Road liquefaction Shed liquefaction Sand boiling

31 Sand boiling

32 Uplift of manhole

33 Uplift of manhole

34 Uplift of manhole

35 Sand boiling

36 Uplift of septic tank

37 Sand boiling

38 Uplift of manhole

39 Uplift of manhole

40 Uplift of manhole

41 Inclining of power pole

42 Uplift of manhole

43 Uplift of septic tank

44 House damage

45 Sand boiling

46 Road liquefaction

47 Sand boiling

48 Sand boiling

49 Inclining of power pole

50 Sand boiling

51 Sand boiling

52 Dike collapse

by Sendai Airport, Iwanuma by Sendai Airport, Iwanuma Sendai Airport

Sendai Airport

Takanosuhigashi, Shiroisi Takanosu, Shiroisi Takanosunishi, Shiroisi Hukuro, Kurihara City Town Office, Kunimi-cho Kooriyama City Sukagawa City Akaike, Sukagawa City Sukagawa City Kagamisihi Station, Sukagawa City Sukagawa City Sukagawa City Minakamityo, Sukagawa City Iwaki City Iwaki City Iwaki City

Ueda Station, Iwaki City Iwasaki, Iwaki City

Ishinomaki City Ishinomaki City Ishinomaki City

38°7'31.62"N 38°7'24.01"N 38°8'24.38''N

140°54' 59.78''E 140°55' 5.65''E 140°55' 58.08''E

170.7 170.5 169.3

38°8'20.45''N 140°55' 54.13''E 169.4

37°59'54.14''N

37°59'49.75''N

37°59'57.49''N

38°48'11.26''N

37°52'37.46''N

37°22'1.44''N

37°18'28.98''N

37°16'48.57''N

37°16'46.39''N

37°15'3.64''N

140°38'35. 140°38'13. 140°37'59. 140°57'40. 140°32'56. 140°23'13. 140°17' 17. 140° 16' 31. 140°17' 55. 140°20'47.

53''E 85''E 77''E 14''E 73''E 36''E 34''E 84''E 15''E 85''E

37°17'40. 37°18'26. 37°16'55. 36°55'24. 36°54'24. 36°54'35. 36°55'16. 36°58'45.

00''N 72''N 05''N 87''N

74''N 69''N 90''N

140°21' 140°21' 140°23' 140°45' 140°47' 140°47' 140°47' 140°51'

24.92''E

58.47''E

7.06''E

44.32''E

34.26''E

53.75''E

54.88''E

1.67''E

38°31'51.88''N 38°26'30.53''N 38°30'42.32''N

141°13' 10.74''E 141°18' 56.97''E 141°14' 1.75''E

233.1 243.6 245.8

238.6 237.3 236.8

226.1 225.5

140.4 149.4

Fodo Tetra, Ando Fodo Tetra, Ando Tohoku Regional Bureau Ministry of Land

Tohoku Regional Bureau Ministry of Land

Tohoku Gakuin University Tohoku Gakuin University Tohoku Gakuin University NihonUniversity, Sento NihonUniversity, Sento NihonUniversity, Sento NihonUniversity, Sento NihonUniversity, Sento NihonUniversity, Sento NihonUniversity, Sento

NihonUniversity, NihonUniversity, NihonUniversity, NihonUniversity, NihonUniversity, NihonUniversity, NihonUniversity, Nihon University,

Sento Sento Sento Sento Sento Sento Sento Sento

Tohoku University, Yamakawa Tohoku University, Yamakawa Tohoku University, Yamakawa

Table 1 (continued)

No. Damage type Site Latitude Longitude Epicentral distance (km) Reporter

53 Dike collapse Tome City 38°36'9.68"N 141°17'28.15'' E 148.1 Tohoku University, Yamakawa

54 Liquefaction Onahama Port, Iwaki City 36°56'28.10"N 140°53'47.70'' E 216.4 Tohoku University, Mori

55 Dike collapse Oosaki City 38°35'26.94''N 140°58'26.35'' E 173.7 *a

56 Dike collapse Matsugasaki, Oosaki City 38°31'58.72''N 141°0'16.06''E 169.3 *a

57 Sand boiling Nankoudai Higashi Elementary 38°17'54.24''N 140°54'42.07'' E 172.2 Tohoku University, Mori

School, Sendai City

58 Sand boiling Arahama, Watari-cho 38°2'48.61''N 140°54'44.57'' E 171.2 *b

59 Sand boiling Yuriage, Natori City 38°10'34.21''N 140°57'21.24'' E 167.3 Tohoku University, Mori

60 Road sagging Asahityo, Shiroishi City 37°59'38.02''N 140°38'4.87''E 195.9 Tohoku University, Mori

61 Dike collapse Kakuda City 37°56'8.35''N 140°47'45.95'' E 182.4 *a

62 Sand boiling Natori City 38°10'20.13''N 140°57'14.73'' E 167.5 Tohoku University, Mori

63 Sand boiling Natori City 38°10'17.97''N 140°57'12.54'' E 167.5 Tohoku University, Mori

64 Sand boiling Natori City 38°10'15.13''N 140°57'5.49''E 167.7 Tohoku University, Mori

65 Sand boiling Natori City 38°10'38.22''N 140°57'10.70''E 167.6 Tohoku University, Mori

66 Sand boiling Kozurushinden, Sendai City 38°16'31.04''N 140°56'3.28''E 170.0 Tohoku University, Mori

67 Road sagging Sendai City 38°13'58.06''N 140°53'12.17'' E 173.7 Tohoku University, Mori

68 Sand boiling Matsunami, Shirakawa City 37°7'6.21'' N 140°12'10.33'' E 259.1 *c

69 Sand boiling Natori City 38°10'31.57''N 140°57'27.78'' E 167.2 Tohoku University, Mori

70 Uplift of manhole Higasimachi, Shiroishi City 37°59'44.95''N 140°37'40.86'' E 196.5 Tohoku Gakuin University

71 Uplift of manhole Higasimachi, Shiroishi City 37°59'44.72''N 140°37'42.75'' E 196.5 Tohoku Gakuin University

72 Uplift of manhole Higasimachi, Shiroishi City 37°59'36.64''N 140°37'30.38''E 196.8 Tohoku Gakuin University

73 Uplift of manhole Higasimachi, Shiroishi City 37°59'22.24''N 140°37'25.31'' E 197.0 Tohoku Gakuin University

74 Sand boiling Rikuzentakata City 39°0'22.00''N 141°38'6.59''E 146.5 *d

75 Uplift of manhole Ishinomaki Station, Ishinomaki 38°26'0.51''N 141°18'12.16'' E 141.2 *e

76 Liquefaction City Ishinomaki New Port 38°25'0.20''N 141°17'14.37'' E 142.1 *f

77 Sand boiling Takasago International Terminal, 38°16'1.06''N 141°1'23.56''E 162.1 Tohoku University, Mori

Sendai Shiogama Port

78 Liquefaction Sakaetyo, Ofunato City 39°5'17.88''N 141°42'27.83'' E 148.5 *g

79 Road sagging Yokkamachi, Hanamaki City 39°24'3.96''N 141°7'1.33''E 209.2 nh

80 Uplift of manhole Yokkamachi, Hanamaki City 39°23'53.82''N 141°6'46.81''E 209.3 *

81 Sand boiling Sendai City Miyagino Fire Station 38°15'57.83''N 140°55'44.42'' E 170.4 Touhoku Gakuin University

82 Sand boiling Shimomasuda, Natori City 38°8'9.05''N 140°55'58.58''E 169.2 Kahokushinpou Publication Center

83 Sand boiling Yakata Post Office, Sendai City 38°18'46.76''N 140°47'50.76''E 182.4 Tohoku University, Kazama

84 Liquefaction Ohya Mine, Motoyoshi-cho, Iwate 38°48'52.95''N 141°31'57.66''E 140.3 Tohoku University, Kazama

Prefecture

85 Sand boiling Narita Chuo Kindergarten, 38°22'1.96''N 140°53'46.85'' E 174.6 Tohoku Gakuin University,

Tomiyatyo Yamaguchi

86 Dike collapse Marumori-cho, 37°55'8.22''N 140°48'31.83'' E 181.5 Tohoku Regional Development

Bureau*1

87 Uplift of manhole Sendai City 38°13'16.59''N 140°56'15.00''E 169.2 Sendai City Construction Bureau

88 Uplift of manhole Sendai City 38°13'22.34''N 140°55'24.10'' E 170.5 Sendai City Construction Bureau

89 Uplift of manhole Sendai City 38°13'40.71''N 140°56'10.77''E 169.4 Sendai City Construction Bureau

90 Uplift of manhole Sendai City 38°16'47.36''N 140°55'58.31''E 170.2 Sendai City Construction Bureau

91 Road sagging Sendai City 38°16'28.08''N 140°55'47.49'' E 170.4 Sendai City Construction Bureau

92 Sand boiling Rikuzentakata City 39°3'9.50''N 141°35'45.10'' E 151.3 Okuyama Boring Co., Ltd.

93 Road sagging Kitakami Station, Iwate Prefecture 39°16'56.94''N 141°7'14.75''E 200.2 Okuyama Boring Co., Ltd.

ahttp://www.thr.mlit.go.jp/Bumon/B00097/k00360/taiheiyouokijishinn/kasennkannkeishisetu/daiippou.pdf

bhttp://www.youtube.com/watch?v = Baw7Pe6uEdg

chttp://cds.nagaokaut.ac.jp/houkokusyo/

dhttp://sankei.jp.msn.com/affairs/news/110730/dst11073023270029-n2.htm ehttp://maoym.blog27.fc2.com/blog-entry-113.html

fhttp://archive.shinsai.yahoo.co.jp/user/H7DMXGMI7FRQK6IJQNTLZ3LVWI/entry/7983/?s=5 ghttp://archive.shinsai.yahoo.co.jp/user/H7DMXGMI7FRQK6IJQNTLZ3LVWI/entry/7983/?s = 5 hhttp://kimura-yukihiro .com/sinsai.html

ihttp://archive.shinsai.yahoo.co.jp/entry/14158/?s = 3 = %E5%B2%A9%E6%89%8B%E3%80%80%E6%B6%B2%E7%8A%B6%E5%8C%96&x = 0 Jhttp://www.thr.mht.go.jp/Bumon/B00097/K00360/taiheiyouokijishinn/kenntoukai/111007/03shiryou2.pdf

VI - vuui^ity M

N 4 "r r No.55

0 2 km

No.9 No.10 I Jm i i ■

Fig. 2. Liquefied sites along the Naruse and Yoshida Rivers (modified from Google (2011) map,).

Photo 1. Sand boil at Nakaniida (No. 7 site).

and/or the flood channels around the dikes. Ground cracks were observed only in places where sand boils had been observed, but no ground deformation was seen. In many cases, no damage to the dikes was observed. The other type is sand boils found at the toe or in the middle of the slopes of dikes. The failure of dikes, such as subsidence at the top of the dike and/or cracks in a longitudinal direction, was frequently observed at these sites.

3.1.1. Sand boils in farm land and flood channels

The liquefied sites along the Naruse River and the Yoshida River, first-grade rivers, are shown in Fig. 2. Among the sites, two typical examples are shown here.

Photo 1 shows sand boils in a dry field at Nakaniida (No. 7 site). As seen in the aerial photo in Photo 2(a), the sand boils are lined up in a circle. Photo 2(b) gives an

Steel tower

Water channel /

Photo 2. Arial photo at the site in Photo 1. (a) 2011 (modified from Google (2011) earth) and (b) 1975 (modified from Geospatial Information Authority of Japan, Archive of Japanese land translation (2011)).

aerial view of the same site taken in 1975; the same steel tower appears in both photos. The locations of the sand boils trace the water channel, which suggests the liquefaction of the fill material or the material at the old river bed.

Sand boils in the flood channel near the junction of the Zen River, a tributary river of the Yoshida River, and the Yoshida River (No. 8 site) are shown in Photo 3, while Photo 4(a) gives an aerial view of this site. Sand boils are lined up in a circular shape. This shape agrees with the old

Photo 3. Sand boil at No. 8 site.

channel shown in Photo 4(b). Therefore, the fill material or the old riverbed should have liquefied, too.

No damage to the river dikes was observed at either of these two sites.

As typically shown in these examples, no significant settlement or upheave was observed near the sand boils. The liquefied area was very limited to the fill material or the old riverbed of the small water channel.

3.1.2. Liquefaction near failed river dikes

Significant damage to river dikes was observed in several places, among which two typical cases (Nos. 4 and 6 in Fig. 2) are discussed here.

Damage to a river dike near the Takakawa Bridge that crosses the Tada River, a tributary of the Naruse River, is shown in Photo 5. This failure extends about 100 m along the river, as shown by the solid red line in the center of Fig. 3. A lateral spread of the slope was also observed in addition to the settlement of the dike. This failure caused damage to the nearby house shown in Photo 6. Judging from the land condition map in Fig. 3, the foundation ground of the river dike near the Takakawa Bridge was sand and it liquefied.

The failure of the river dike of the Naruse River at the No. 6 site, located about 40 km from the river mouth, is shown in Photo 7. A longitudinal crack was observed about 500 m along the dike, which is shown by the solid red line on the land condition map at this site in Fig. 4. Sand covers the bottom of the crack, which is supposed to be liquefied sand. Significant lateral spread occurred at the dike, and the height of the dike fell to about 2/3 of its original height. No deformation of the small water channel was observed beside the dike, as can be seen in Photo 8, nor was any ground deformation observed in the vicinity of the dike. Laterally spread soil covered the water channel, as shown in the back of Photo 8. According to the land condition map, an old river runs in the north and a natural levee extends outside of it. Therefore, the failed

Photo 4. Arial photo at the site in Photo 3. (a) 2011 (modified from Google earth) and (b) 1975 (modified from Archive of Japanese land translation).

Photo 5. Ground failure near Takakawa Bridge.

dike is located between the old river and the current river; it is supposed to be a flood plain. According to a trenching survey (Tohoku Area Developing Bureau, Ministry of Land, Infrastructure, Transport and Tourism, 2012), the dike at the No. 22 site liquefied during the earthquake, since the bottom of the dike (sandy liquefiable soil) had sunk into the natural ground under the water table. The same phenomenon is supposed to have occurred at this site.

3.2. Uplift of manholes at Iwakiri and Shiroishi

3.2.1. Iwakiri area

The uplift of manholes was observed for a length of about 200 m along the pavement near Iwakiri Station (No. 20 site). A detailed map is given in Fig. 5. Photo 9

□ Old riverbed

□ Back swamp

□ Coastal plain

Flood plain

□ Natural levee, sand bank, gravel

m Fill

1 1 Thick fill

Fig. 3. Land condition map near Takakawa Bridge (modified from Geospatial Information Authority of Japan, land condition map (2011)). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Vr' I ?

Photo 6. Damage to residential house near Takakawa Bridge.

Photo 7. Left side bank of Naruse River about 40 km from river mouth.

shows one of the uplifted manholes. A total of 6 manholes were uplifted, among which the maximum uplift was about 50 cm. The only observed uplifted manholes were those for sewage use; manholes for rainfall use were not uplifted, as shown in Photo 9.

Fig. 4. Land condition map near No. 6 site (modified from Geospatial Information Authority of Japan, land condition map (2011)). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Photo 8. Toe of slope of dike of Naruse River.

The site is a silty clay layer deposited at the ground surface up to G.L.-3 m with an organic clay layer deposited below it. The water table is G.L.-1 m. As these silty

______^ JT tfgSrV

j--a . I ""JJ^ »«

.. . i L j * 'J*-L

O ' i- «C1I

Fig. 5. Map in the vicinity of Ishikiri and sites of uplifted manholes (No. 20) (modified from Google map).

Photo 9. Uplift of manhole at Iwakiri.

and organic clays have a low potential for liquefaction, the backfill soil is supposed to have liquefied. Since the sewage pile was buried at a depth of about 3 m, whereas the rainfall pile was buried at a depth of only about 1.5 m, liquefaction is supposed to have occurred at a depth of around 3 m.

3.2.2. Vicinity of Shiroishi Zao Station

The uplift of manholes was observed at the sites of Nos. 32 to 34 and Nos. 70 to 73 in Fig. 6, which are located near Shiroishi-Zao Station in Shiroishi City.

Photo 10 shows the uplift of a manhole at the No. 34 site, which reaches 1.15m. Since the ground subsided along the sewage line, fill at the construction of the sewage line is supposed to have liquefied.

The manhole at the No. 70 site is shown in Photo 11. The uplift of manholes at the sites of Nos. 70 and 71, located about 30 m from the No. 70 site, is 1.15m.

The uplift of other manholes was also more than 1 m. As seen in the photo, the settlement of the road occurred along the sewage line and it was already fixed at the time of the reconnaissance. As shown in the aerial photo in Fig. 7, taken near this site in 1976, the site was originally a paddy field that was later reclaimed. The ground is supposed to be soft and the water table is high.

3.2.3. Furukawa city

Manholes uplifted near Osaki Station in Osaki City. Photo 12 shows a manhole at the No. 1 site in Fig. 8. It is uplifted for about 40 cm, which suggests the onset of liquefaction, although no sand boils were observed nearby. The manhole at the No. 2 site, which is about 100 m from the No. 1 site, also uplifted about 60 cm. Ground deformation was observed on the pavement near the No. 2 site, and blocks on the pavement tilted or settled about 5 m from the manhole along the pavement. Significant damage caused by liquefaction was observed only at these two sites, although small ground deformation was also sometimes observed elsewhere.

A 4-story reinforced concrete apartment house settled at the No. 3 site in Fig. 8 and the surrounding ground deformed. This site is located about 250 m east from the site of the manhole uplift. The building, built in 1981, is shown in Photo 13. Sand boils were observed just at the right side (west side) of the building in this photo. In addition, the pavement deformed significantly. Damage caused by the liquefaction was observed only at this building and in the immediately surrounding area.

3.3. Damage to residential houses

Damage to the residential area at Jingahara in Sendai City, the No. 21 site in Fig. 5, is shown here as an example of the damage to residential houses due to liquefaction. This is an area of small reclaimed land developed during

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the first decade of 2000. It is located just next to the large-scale reclaimed land in the upstream direction, in the shorefront of a regulating pond. Liquefaction occurred in the foundation ground and liquefaction-induced lateral displacement or flow occurred, which caused significant damage to residential houses. The plan of the damaged area is shown in Fig. 9, where the upstream side is toward the bottom of the figure. This area has a concave ground surface and it is lower than the residential area on the upstream side by about 8 m. Large cracks appeared in the

east shore of the regulating pond as well as uneven settlement and lateral displacement. Sand boils were observed on the right side of the figure. The ground deformation in this area is shown in Photo 14, where a crack with a difference in height of 0.5 m and a width of 0.3 m appeared, and a residential house moved towards the pond (right side).

The estimated cross section of this area, based on the borehole investigation, is shown in Fig. 10. A Holocene clay layer lies on the weathered rock. Fill with sandy soil

Photo 12. Uplift of manhole No. 1 near Furukawa Station.

and gravelly sandy soil lie on it. The SPT-N value of the fill ranges between 2 and 4; the fill is soft soil. Judging from the A-A' cross section, liquefaction is supposed to have occurred in the sandy soil in the fill. Ground failure occurred as the bearing capacity of the gravelly sandy soil was lost. This gravelly sandy soil also liquefied, which can be recognized from the sand boils observed on the right side of the A-A' section where the water table is shallow.

Large cracks were observed at the shore of the regulating pond. The crack was smaller in size on the mountain side than on the pond side, probably because lateral movement was predominant near the pond, whereas densification due to ground shaking was predominant on the upstream side.

The foundation ground of the house in the B-B' section was improved by the column type of mixing soil method, as shown in Photo 15, which suggests that the softness of the ground in this area had been recognized before the construction of the house. The diameter of the improved soil column is 500 mm. Although the improved soil remains, the ground nearby the remediated column deformed significantly; settlement and horizontal displacement reached 0.8 m and 0.4 m, respectively. However, damage to this house was less than that of the houses nearby.

3.4. Harbor and airport

3.4.1. Yuriage district

As the Yuriage district was hit by the tsunami, any evidence of ground failure had been washed away. The onset of liquefaction, however, was reported from observations made before the arrival of the tsunami. The locations of the liquefied sites are shown in Fig. 11.

Photo 16 shows the liquefaction near the dike at the mouth of the Natori River just after the earthquake. Sand

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Photo 13. Differential settlement of 4 story RC apartment house due to liquefaction.

boils covered the road, and the wheels of cars were covered by the boiled sand at the toe of the river dike. Photo 17 shows the same location on June 21, 2011. Clear evidence of liquefaction cannot be observed as the ground surface had been washed away by the tsunami. Judging from the observation in which the settlement or the caving of the ground occurred only near the catchment channel, placed at the toe of the slope, liquefaction occurred only near the toe of the dike because damage to the river dike was

expected if the ground liquefied widely. In other words, liquefaction occurred only in the fill during the construction of the catchment channel.

Photo 18 (Modified from Coastal Development Institute of Technology (2011)) shows the ground when the tsunami had just arrived at the shores of the Yuriage area. The muddy water that covered the ground is supposed to be liquefied material, because the weather on the day of the earthquake was fine. Sand boils are observed at three sites shown by the red hollow circles in the photo, namely, an open space to the east of the Hiyori miniature hill (elevation = 6.05 m, width = 40 m x 20 m), an open space to the south of the Hiyori miniature hill and a field with a 3-story reinforced concrete housing complex. East of the Hiyori miniature hill was known to be a wet area with a shallow water table. A drainage pump had been installed near the open space. As no uneven deformation was observed on the nearby roads by the field investigation, liquefaction is supposed to have occurred locally.

The land condition map near Yuriage is shown in Fig. 12. The liquefied sites of Nos. 59 and 65 were water channels in 1971 when this map was compiled. The sites at Nos. 62, 63 and 70 are located in the fill area. Therefore, the fill material is supposed to have liquefied.

3.4.2. Onahama Port

Onahama Port has been designated as an important harbor. Eight docks have been constructed starting from

Photo 14. Damage in Jingahara district (from Photo ©).

the No. 1 dock in 1957, and construction is still undergoing at present. Fig. 13 presents a geological classification map near Onahama Port and the liquefied sites, which were identified by the author's field survey on June 28, 2011.

Sand boils and differential settlement were observed on the road and the pavement, and the maximum settlement for the road surface was about 40 cm. Onahama Port was a filled ground developed south of the urban area of Onahama City. It is located at the sandbar of the Fujiwara River. Evidence of liquefaction was observed in the fill of the port, but no evidence was observed in the downtown area. Photo 19 shows the sand boils caused by the aftershock of April 7 at the No. 3 dock. The maximum thickness of the sand boil was about 40 cm. Evidence of liquefaction due to the main shock was lost by the tsunami.

Soil profiles near Onahama Port are shown in Fig. 14; the locations of the sites are shown in Fig. 13. There are two fill layers with different blow counts at Onahama Port (No. 3 borehole data), which probably indicates different developing ages. The new fill above GL-4 m is supposed to have liquefied because the water table must have been less than 2.8 m, as the ground surface is about 2.8 m in elevation.

3.4.3. Sendai Port area of Sendai-Shiogama Port

Sendai-Shiogama Port is located to the east of Sendai City, near the boundary between Tagajo City and Sendai

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Photo 15. Improved soil column at residential house in Jingahara district (from Photo ©).

City. It is an international port facility that supports the greater Sendai urban area.

The Sendai Plain is a Holocene plain developed by the Nanakita and the Natori Rivers. The Sendai Port area is a roadside canal port area developed from 1976; it is located near the boundary of the Holocene plain and the sea.

Takasago International Dock at Sendai Port was located on the beach ridge. Liquefaction was observed only near the sheet pile quay wall of the No. 2 pier among two piers, probably because the background was developed by the filling in of crushed rock and split stone, whereas the No. 1 pier was developed by concreting the natural ground. The settlement of the ground, the movement of the quay wall toward the sea, and the opening of cracks in the backyard of the quay wall were observed. Differential settlement between the crane rail, supported by steel piles, and the ground surface was about 10 cm in the No. 1 pier, whereas it reached 88 cm in the No. 2 pier. Sand boils caused by the aftershock were also observed. The No. 2 pier consisted of two blocks, Block 1 and Block 2, as shown in Fig. 15, and damage was more severe in Block 2 (Tohoku Area Developing Bureau, Ministry of Land, Infrastructure, Transport and Tourism, 2011a).

The soil profiles for these two blocks are shown in Fig. 16 (Tohoku Area Developing Bureau, Ministry of Land, Infrastructure, Transport and Tourism, 2011b). The ground surface is 3.87 m from the sea water in Block 1 and 3.23 m in Block 2. There is a crusher run layer with an SPT-N value between 10 and 20 at Block 2. This crusher run is composed of gravel with diameters between 10 mm and 40 mm and is loose, which may be the reason why the damage in Block 2 was more severe. Actually, the

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Photo 17. Evidence of liquefaction near river mouth of Natori River.

Fig. 12. Land condition map for Yuriage district (modified from Geospatial Information Authority of Japan, land condition map (2011)).

Photo 19. Liquefaction at No. 3 pier of Onahama Port (courtesy of Tohoku Area Developing Bureau).

damage was more severe as the thickness of this layer increased.

Photo 20 shows the sand boil in the No. 2 pier during an aftershock. This sand is supposed to be the fill beneath the asphalt pavement. However, the water table is GL-4 m, as shown in Fig. 16, and there is little fill material below the water table. This water table was measured on April 11 to 14, about a month after the earthquake and very close to the day of the aftershock. Therefore, the mechanism of the liquefaction is not clear.

One of the possible mechanisms at this site is as follows. Due to dilatancy, a significant change in volume occurred in the crusher run layer, and drained water flowed up into the fill layer resulting in a higher water table. If the duration of this earthquake had been sufficiently long, the fill layer would have

been liquefied not by the main shock, but by the subsequent shock. This mechanism can explain the observation in which the damage was more severe when the thickness of the crusher run layer was larger.

3.4.4. Ishinomaki Port

A crack in the quay wall was observed at Ishinomaki Port, and caving with a width of 5 m to 15 m and with a depth of 2.2 m at maximum occurred in the back of the caisson. The reason has not been clarified, but liquefaction has not been reported (Tohoku Area Developing Bureau, Ministry of Land, Infrastructure, Transport and Tourism, 2011c).

3.4.5. Sendai Airport

Sendai Airport is located in Natori and Iwanuma Cities. It was hit by the tsunami, but liquefaction is reported to have occurred at the apron.

The locations of the liquefied sites of Sendai Airport are shown in Fig. 17. Photo 21 shows a sand boil; the photo was taken before the arrival of the tsunami. Cracks were observed at these locations after the tsunami, and water pools formed easily because of the ground subsidence.

The soil profiles for the apron are shown in Fig. 18, sites A and B in Fig. 17, respectively. Site A is very close to the No. 30 site where cracks and subsidence were observed, and site B is at the west end of the apron where no liquefaction-induced damage was observed. Considering the damage at these two sites and the fact that the As1 _0 layer does not exist at site B, liquefaction occurred in the As1 _ 0 layer (Tohoku Area Developing Bureau, Ministry of Land, Infrastructure, Transport and Tourism, 2011d). The water table is

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Fig. 14. Soil profile near Onahama Port before earthquake.

Fig. 15. Map near No. 77 site (modified from Google map).

high, namely, GL-1.35m, at Point A. The fill material Ministry of Land, Infrastructure, Transport and between GL-1.25m and GL-3.7 m includes much silt Tourism, 2011e). Therefore, the fill material may also have and is very loose (Tohoku Area Developing Bureau, liquefied.

Fig. 16. Soil profile at No. 2 pier.

It is noted that remedial measures were taken at the runway by infiltration solidification and the X-jet grouting method. The runway maintained serviceability and was able to be used 5 days after the earthquake after removing the debris caused by the tsunami. On the other hand, uneven settlement occurred on the taxi way where remediation had been prepared, but had not been finished (Sugano, 2011).

4. Concluding remarks

The liquefied sites in the Tohoku district have been shown and the causes of liquefaction have been explained

from the viewpoint of topology and geology. They are summarized as follows:

Damage to river dikes, due to liquefaction, was not observed near dry fields, paddy fields or flood channels near the dikes. Sand boils occurred along old rivers and water channels. On the other hand, severe damage did occur when there was liquefaction at the bottom of the dikes, as the reclaimed dike material subsided under the water table because of the consolidation of the soft clayey layer below it.

The uplift of manholes occurred only for sewage manholes. The maximum uplift of the manholes was 50 cm or less when there was no deformation of the nearby ground.

Fig. 17. Liquefied sites at Sendai Airport and vicinity (modified from Google map).

Photo 21. Sand boil at Sendai Airport (after Sugano, 2011).

On the other hand, the uplift grew to more than 1 m at maximum when ground deformation was observed near the manholes.

Damage to residential houses, such as tilt and settlement, was observed in some places, but there were not many damaged houses.

Damage to port and airport facilities occurred at Onahama Port, Sendai-Shiogama Port and Sendai Airport, which can be identified by the photos taken before the arrival of the tsunami. Liquefaction may have occurred at more sites along the water front, but this cannot be identified because the tsunami washed away the evidence.

Fig. 18. Soil profile at apron. Acknowledgments

Data on the damage and the soil at Onahama Port were provided by the Sendai Research and Engineering Office for Port and Airport, Tohoku Regional Development

Bureau, Ministry of Land, Infrastructure, Transport and Tourism. Data on the damage in the Jingahara area were given by the Sendai City Development Bureau. Data on the damage and the soil of both Sendai-Shiogama Port and Sendai Airport were provided by the Tohoku District Development Bureau. The authors wish to thank these organizations for their information and assistance.

Thanks are also extended to Professor Yasuda of Tokyo Denki University, Professor Yamakawa of Tohoku University, Mr. Ando of Fudo Tetra Corp., Mr. Fujii of Okumura Boring Corp., Professor Sento of Nihon University and Professor Tobita of Tohoku Gakuin University for the data on the liquefied sites and to the students of Tobita and Yamaguchi Laboratories for joining the field investigation.

References

Coastal Development Institute of Technology (2011): CDIT, 35, 2011, 1. Google (2011): Google Earth, /http://www.google.co.jp/intl/ja/earth/ index.html >.

Geospatial Information Authority of Japan (2011): Archive of Japanese Land Translation, /http://archive.gsi.go.jp/airphoto/> (in Japanese). Geospatial Information Authority of Japan, land condition map (2011): /http://www1.gsi.go.jp/geowww/themap/lcm/sendai.html> (in Japanese). Japan Meteorological Agency (2011a): The 2011 off the Pacific Coast of Tohoku Earthquake, / http://www.jma.go.jp/jma/menu/jishin-portal. html#b> (in Japanese).

Japan Meteorological Agency (2011b): The 2011 off the Pacific Coast of Tohoku Earthquake, /http://www.seisvol.kishou.go.jp/eq/2011_03_11_ tohoku/0311_shindo.pdf>.

Sugano, T. (2011): Damage to Port and Airport Facilities During the 2011 off the Pacific Coast of Tohoku earthquake, Port and Airport Research Institute, 28 (in Japanese).

Tohoku Area Developing Bureau, Ministry of Land, Infrastructure, Transport and Tourism (2011a): 2010 Annual Report of Damage on Outer Harbor of Sendai-Shiogama Port (Sendai Port Area), Sendai port, 13-16, (in Japanese).

Tohoku Area Developing Bureau, Ministry of Land, Infrastructure, Transport and Tourism (2011b): 2010 Annual Report of Damage on Outer Harbor of Sendai-Shiogama Port (Sendai Port Area), Sendai Port, 80 (in Japanese).

Tohoku Area Developing Bureau, Ministry of Land, Infrastructure, Transport and Tourism (2011c): 2010 Annual Report of Damage on Outer Harbor of Sendai-Shiogama Port (Sendai Port Area), Ishino-maki Port, 94. (in Japanese).

Tohoku Area Developing Bureau, Ministry of Land, Infrastructure, Transport and Tourism (2011d): 2011 Annual Report on Damage Investigation of Facilities of Sendai Airport III Soil Investigation, 107. (in Japanese).

Tohoku Area Developing Bureau, Ministry of Land, Infrastructure, Transport and Tourism (2011e): 2011 Annual Report on Damage Investigation of Facilities of Sendai Airport III Soil Investigation, 114. (in Japanese).

Tohoku Area Developing Bureau, Ministry of Land, Infrastructure, Transport and Tourism (2012): Transactions of Investigate Commission of Restoration Technique for Dike of the Kitakami River, etc. on Oct.7, 20. (in Japanese).