Proceedings of the International Symposium on Engineering Lessons Learned fromthe 2011 Great East Japan Earthquake, March 1-4, 2012, Tokyo, JapanDAMAGE ASSESSMET O WATER SUPPLYSYSTEM AD SEWERAGE SYSTEM AT THE 2011
OFF THE PACIFIC COAST OF TOHOKU
EARTHQUAKE - CASE STUDY FOR THE DATAAT IBARAKI AD CHIBA PREFECTURES Satoshi NABA1, Takuya TSUKIJI2, Gaku SHOJI3 and Shigeru NAGATA4
1

Graduate Student, Graduate School of Systems and Information Engineering,
University of Tsukuba, Ibaraki, Japan, s1021001@u.tsukuba.ac.jp
2
Collage of Engineering Systems, University of Tsukuba, Ibaraki, Japan, s0811228@u.tsukuba.ac.jp
3
Associate Professor, Faculty of Engineering, Information and Systems,
University of Tsukuba, Ibaraki, Japan, gshoji@kz.tsukuba.ac.jp
4
Kajima Technical Research Institute, Tokyo, Japan, nagata-shigeru@kajima.com

ABSTRACT: We evaluate the dependency of damage and restoration of water supply
systems and sewerage systems on the seismic hazards in the 2011 off the Pacific Coast of
Tohoku earthquake focusing on the damage at Ibaraki and Chiba prefectures. We collectthe damage data of the systems by carrying out interviews for related local government
sectors. We quantify two damage ratios R on physical damage points and RL on
disrupted pipeline lengths, for 14 municipalities in Ibaraki prefecture and 8
municipalities in Chiba prefecture.
Key Words: The 2011 off the Pacific Coast of Tohoku earthquake, water supply system,
sewerage system, damage ratio, fragility curve

ITRODUCTIO
Water supply systems and sewerage systems were severely damaged at the 2011 off the Pacific Coastof Tohoku earthquake and tsunami which occurred on March 11, 2011. It caused large influence tosocial and economic activities since our society is strongly dependent on water treatment systems.
Water outages occurred at maximumly 2,105,091 houses as of March 11, 2011 in 187 municipalities
such as 616,480 houses in Miyagi prefecture, 444,288 houses in Ibaraki prefecture and 373,069 houses
in Chiba prefecture (Ministry of Health, Labour and Welfare 2011). Sewerage damage occurred at 120
treatment facilities, 112 pump stations, 1,061 km pipelines and 20,730 manholes (Ministry of Land,
Infrastructure, Transport and Tourism 2011). The reason of these vast damage is that the related
facilities and buried pipelines subjected to severe tsunami waves, strong ground excitations and large
liquefaction. For predicting damage caused by future extreme earthquakes and tsunamis and planningeffective restoration strategy for water treatment systems, it is much significant to analyze damage

1487

6強
6.0-6.4

35°40'0"N

36°38'0"N

HitachiHokotaKashima
Itako
KamisuInashiki Katori

Tsukuba
TorideIchikawa
Funabashi

Abiko
SakuraUrayasu
Narashino
139°5'0"E

141°25'0"E

Mito
Hitachinaka
Oarai
Omitama

6弱
5.5-5.976.5-

35°11'0"N

140°50'0"E

139°40'0"E

Chiba
140°15'0"E

0 12.5 25

36°9'0"N

140°15'0"E

35°40'0"N

139°40'0"E

35°11'0"N

36°9'0"N

36°38'0"N

139°5'0"E

震度階級
Seismic
Intensity
Kasama3 -3.443.4-4.4
5弱
4.5-4.9
Shimotsuma
5強
5.0-5.450

140°50'0"E

75

100
km
141°25'0"E

Fig. 1 Subject municipalities and seismic hazards distribution
data due to the earthquakes and tsunamis. From the reason above, we collect the damage data by
carrying out interviews for related local government sectors focusing on the damage areas at Ibaraki
and Chiba prefectures and evaluate the dependency of damage and restoration of water supply systems
and sewerage systems on the induced seismic hazards. In addition, we compare the damage ratios insubject municipalities with estimated ones derived by our previously proposed seismic fragility
curves.

SETTIG OF AALYZED DATA
Fig.1 shows subject municipalities at Ibaraki and Chiba prefectures. For analysis of water supply
systems, we select 21 municipalities: Hitachi, Hitachinaka, Mito, Kasama, Oarai, Hokota, Omitama,
Shimotsuma, Tsukuba, Kashima, Inashiki, Toride, Kamisu at Ibaraki prefecture and Katori, Abiko,
Funabashi, Ichikawa, Sakura, Chiba, Narashino, Urayasu at Chiba prefecture. Among them, Toride
data includes the damage data at the areas managed by South Ibaraki Waterworks Agency. For analysisof sewerage systems, we select 19 municipalities: Hitachinaka, Mito, Kasama, Oarai, Hokota,
Omitama, Shimotsuma, Tsukuba, Kashima, Itako, Inashiki, Kamisu at Ibaraki prefecture and Katori,
Abiko, Funabashi, Sakura, Chiba, Narashino, Urayasu at Chiba prefecture. For total 22 municipalities,
we carried out field surveys and interviews at Hitachinaka (6/1, 6/29, 12/26, 2011), Mito (1/10, 2012),
Kasama (12/8, 2011), Oarai (12/22, 2011), Tsukuba (12/22, 2011), Kashima (12/20, 2011 and 1/6,
2012), Itako (6/28, 9/26,11/16, 2011 and 1/6, 2012), Toride (5/31, 2011), Kamisu (6/28, 9/26, 12/20,
2011 and 1/6, 2012) at Ibaraki prefecture and Katori (6/28, 2011), Abiko (5/31, 12/26, 2011),
Funabashi (12/6, 2011), Sakura (12/26, 2011), Chiba (6/3, 9/2, 2011 and 1/13, 2012), Urayasu (6/3,
2011) at Chiba prefecture.
For water supply systems, we analyze total pipeline lengths L, disrupted pipeline lengths Ld, thenumber of physical damage points p, their damage modes and the restoration periods for districts of a
town in the relevant municipalities. We distinguish types of pipelines and diameters of pipelines on
conduits, transmission pipes, distribution pipes and service pipes. Similarly, for sewerage systems, weanalyze total pipeline lengths L, disrupted pipeline lengths Ld, the number of physical damage points
p, their damage modes, the periods of restriction for use for sewerage systems and temporary
restoration periods for districts of a town in the relevant municipalities. We distinguish types ofpipelines and diameters of pipelines on sanitary pipes, rainwater pipes and combined sewer pipes.
We quantify two damage ratios R and RL: R defined by the ratio of number of physical damage
points p divided by total lengths L of the systems as following equation,

1488

R =

p
L

(1)

and RL defined by the ratio of disrupted lengths Ld divided by total lengths L of the systems asfollowing equation,

RL =

Ld
L

(2)

In order to analyze relation of damage ratios R and RL with related seismic hazards, we computeseismic hazards distribution on seismic intensity with third meshes by spatial interpolation based on
simple kriging method (Cressie 1993) by using the observed strong ground motions data by Japan
Meteorological Agency (2011), and National Research Institute for Earth Science and Disaster
Prevention (2011), and by using information of moment magnitude Mw and location of hypocenter byJapan Meteorological Agency (2011). For estimating seismic intensity IJb at the layer with Vs of
500m/s for subject areas, we use mean values derived by attenuation relationship proposed by Si andMidorikawa (1999) and for estimating amplification factor of seismic intensity at the ground surface
with seismic intensity IJb we use the relationship proposed by Fujimoto and Midorikawa (2006). For
the following analysis, we use median of estimated seismic intensities IJm for third meshes overlapped
to the areas of subject municipalities.

DAMAGE OF WATER SUPPLY SYSTEMS AD SEWERAGE SYSTEMS
Analysis on damage ratios
Fig. 2 shows the relation between the damage ratios R and IJm for subject municipalities. Fig. 3 shows
the relation between the damage ratios RL and IJm for same ones. We compute R and RL for
distribution pipes of water supply systems. We compute R and RL for sanitary pipes of seweragesystems except for the values for Tsukuba data which include sanitary pipes and rainwater pipes,
except for Katori data which include sanitary pipes and combined sewer pipes and except for
Narashino data which include sanitary pipes, rainwater pipes and combined sewer pipes.
In terms of water supply systems, from Fig. 2(a), the values of R are classified into the following
4 ranges. R for Urayasu data with IJm of 5.1 shows the remarkably largest value of 1.081/km and R
for Kashima data with IJm of 5.8 shows the next largest value of 0.654/km. These two cities areclassified into extremely severe affected municipalities. R for Inashiki and Kamisu data with IJm of
5.3 to 5.5 show relatively larger values of 0.247/km to 0.316/km which are classified into severe
damage. R for Hitachi, Hitachinaka, Mito, Oarai, Hokota and Narashino data with IJm of 5.2 to 5.8
show the values in the relatively middle range of 0.0571/km to 0.136/km. R for Kasama, Omitama,
Shimotsuma, Tsukuba, South Ibaraki Waterworks Agency, Funabashi, Ichikawa, Sakura and Chiba
data with IJm of 4.9 to 5.8 show relatively smaller values of 0.0130/km to 0.0416/km. In the above,
Kashima and Inashiki data show large R due to strong seismic intensities of 5.5 to 6.0. In contrast,
Kamisu and Urayasu data show also large R in spite of relatively lower seismic intensities of 5.0 to
5.5. The reason of the damage is possibly due to the large-scaled liquefaction at the areas.
From Fig. 3(a), the values of RL for water supply systems are classified into the following 2 ranges.
RL for Katori data with IJm of 5.2 shows the remarkably largest value of 0.0317km/km. RL for Hokota,
Shimotsuma, Tsukuba and Abiko data with IJm of 5.0 to 5.8 show relatively smaller values of
0.0000573km/km to 0.00124km/km. The trends of R and RL for both Shimotsuma and Tsukuba data
are same.
In terms of sewerage systems, from Fig. 2(b), the values of R are classified into the following 4
ranges. R for Katori data with IJm of 5.2 shows the remarkably largest value of 2.484/km and R for
Narashino data with IJm of 5.2 shows the next largest value of 0.930/km. These two cities are

1489

3.0

1.0

2.5

0.8

2.0

R [/km]R [/km]

1.2

0.6

1.5

0.4

1.0

0.2

0.5

0
4.5

5.0

5.5

0
4.5

6.0

5.0

Ichikawa
Chiba
Inashiki
OmitamaKamisuHitachi
Mito

5.5

6.0

IJm

IJm
Urayasu
NarashinoSouth Ibaraki
KasamaShimotsuma
Hitachinaka

Katori
Funabashi, Takase
Oarai
KamisuTsukuba

SakuraFunabashi
Oarai
Kashima
Tsukuba
Hokota(a) Water supply systems

Narashino
Inashiki
Omitama
Shimotsuma(b) Sewerage systems

Fig. 2 Relation between damage ratio R and IJm
0.6

0.04

0.5

RL [km/km]

RL [km/km]

0.03

0.02

0.4
0.3
0.2

0.01

0.1
0
4.5

5.0

5.5

6.0

0
4.5

5.0

Abiko
Shimotsuma
HokotaKatoriTsukuba

5.5

6.0

IJm

IJm
Abiko
SakuraChiba, Inba
Itako, Hinode
OmitamaKasama, Iwama
Shimotsuma
Hokota(a) Water supply systems

Urayasu
Chiba, Chuo
Narashino
Inashiki
Kasama, Kasama
Kashima
Tsukuba
Mito

Katori
Chiba, Nanbu
Funabashi, Takase
Oarai
Kasama, Tomobe
KamisuHitachinaka(b) Sewerage systems

Fig. 3 Relation between damage ratio RL and IJmclassified into extremely severe affected municipalities. R for Omitama and Shimotsuma data withIJm of 5.6 to 5.8 show relatively larger values of 0.198/km to 0.237/km. R for Oarai and Inashiki data

1490

with IJm of 5.5 to 5.6 show the values in the relatively middle range of 0.0218/km to 0.0540/km. R for
Tsukuba data and for Takase treatment areas in Funabashi data with IJm of 5.0 to 5.5 show relatively
smaller values of 0.0135/km to 0.0142/km. In the above, R for Katori and Narashino data show theremarkably large values of R in spite of relatively lower seismic intensity of 5.2. The reason of thedamage is due to the large-scaled liquefaction at the reclamation areas used for water ways at Katori
and at the coastal areas at Narashino.
From Fig. 3(b), the values of RL for sewerage systems are classified into the following 5 ranges. RL
for Hinode areas in Itako data with IJm of 5.9 shows the remarkably huge value of 0.538km/km
compared with other data for subject municipalities. RL for Kashima and Urayasu data with IJm of 5.1
to 5.8 show the remarkably largest values of 0.0907km/km to 0.112km/km. RL for Kamisu, Katori data
and for Kasama treatment areas in Kasama data with IJm of 5.2 to 5.4 show the next largest values of
0.0649km/km to 0.0818km/km. RL for Hitachinaka, Hokota, Inashiki data and for Chuo treatmentareas in Chiba data with IJm of 5.0 to 5.8 show the values in the relatively middle range of
0.0228km/km to 0.0412km/km. RL for Mito, Oarai, Omitama, Shimotsuma, Tsukuba, Abiko, Sakura,
Narashino data and for Tomobe treatment areas in Kasama data, Iwama treatment areas in Kasama
data, Takase treatment areas in Funabashi data, Inba treatment areas in Chiba data with IJm of 4.9 to
5.8 show relatively smaller values of 0.000237km/km to 0.0115km/km. In the above, Hinode areas in
Itako data show the remarkably huge RL due to the strongest seismic intensity of 5.9 and the intensiveliquefaction at the reclamation areas of swamp. Kashima and Urayasu data show the remarkably
largest values due to strong seismic intensities of 5.8, and liquefaction at harbor areas at Kashima andlarge-scaled liquefaction at Urayasu.
Analysis on restoration periods
Fig.4 shows relation of restoration periods for water supply systems with seismic intensity IJm andrelation of periods of restriction for use for sewerage systems and temporary restoration periods forsewerage systems with seismic intensity IJm.
From Fig. 4(a), water supply systems (WSS) at Kamisu were restored in 57 days which show thelongest restoration periods due to larger R. WSS at Kashima, Inashiki, Katori and Urayasu show thesecond largest restoration periods of 23 days to 37 days: 26 days to 34 days at Kashima and Urayasu
due to largest R, 23 days at Inashiki due to larger R, 37 days at Katori due to largest RL. WSS at
Hitachi, Hitachinaka, Oarai, Hokota and Narashino were restored in 8 days to 14 days which show
longer restoration periods due to middle range of R. In contrast, WSS at Kasama and Funabashi were
restored in 8 days which also show longer restoration periods in spite of smaller R. In case of Kasama,
it is caused by water outages in Kasama district because of lengthening of restoration periods due towater leakages at transmission pipes managed by Ibaraki Enterprise Bureau. Furthermore, R at
Kasama becomes small since we compute R by including buried pipeline lengths L in Tomobe
treatment areas and Iwama treatment areas in addition to Kasama treatment areas. In case of Funabashi,
it is caused by lengthening of restoration periods due to the damage of large-diameter pipe of morethan 500mm at the coastal areas suffered by liquefaction. WSS at Mito, Tsukuba, Abiko and Chibashow middle range of restoration periods of 5 days to 6 days: 6 days at Mito due to middle range of R,
5 days to 6 days at Tsukuba and Chiba due to smaller R, 5 days at Abiko due to middle range of RL.
WSS at Omitama, Shimotsuma, South Ibaraki Waterworks Agency and Sakura were restored in 1 days
to 3 days which show smaller range of restoration periods due to smaller R.
From Fig. 4(b), in terms of periods of restriction for use for sewerage systems, sewerage systems(SS) at Narashino were restored in 112 days which show the longest restoration periods due to next
largest R. SS at Kamisu were restored in 83 days which show the second longest restoration periods
due to next largest RL. SS at Itako, Inashiki and Urayasu were restored in 34 days to 44 days whichshow longer restoration periods due to largest and middle range of RL. In terms of temporary
restoration periods for sewerage systems, SS at Narashino were restored in 112 days which show thelongest restoration periods due to next largest R. SS at Kamisu and Katori were restored in 83 days to
91 days which show the second longest restoration periods due to next largest RL. SS at Kashima,
Itako, Inashiki and Urayasu were restored in 34 days to 44 days which show longer restoration periods

1491Periods of restriction for use andtemporary restoration periods

60

Restoration periods

50
40
30
20
10
0
4.5

5.0

5.5

6.0

120
100
80
60
40
20
0
4.5

5.0

IJm
Abiko
SakuraFunabashi
Oarai
Kashima
Tsukuba
HokotaUrayasu
Chiba
Inashiki
OmitamaKamisuHitachi
Mito

5.5

6.0

IJm
KatoriNarashinoSouth Ibaraki
KasamaShimotsuma
Hitachinaka

Abiko (Temporary restoration)
Urayasu (Restriction for use and temporary restoration)
Katori (Temporary restoration)
Narashino (Restriction for use and temporary restoration)
Itako (Restriction for use and temporary restoration)
Inashiki (Restriction for use and temporary restoration)
120
100
Kashima (Temporary restoration)
80
60
40
20
0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
Kamisu (Restriction for use and temporary restoration)(a) Water supply systems(b) Sewerage systems

Fig. 4 Relation between restoration periods and IJm
due to largest and middle range of RL. In contrast, SS at Abiko were restored in 60 days which show
longer restoration periods in spite of smaller RL.

COMPARISO OF AALYZED DATA WITH PREVIOUS SEWERAGE DAMAGE
Fig.5 shows comparison of R and RL with estimated ones derived by our proposed seismic fragility
curves (Shoji et al. 2011).
From Fig. 5(a), R at all subject municipalities except for Katori and Narashino show good
agreement with the values by seismic fragility curve. R of 2.484/km at Katori and R of 0.930/km at
Narashino are large due to not only relatively lower seismic intensity but also huge liquefaction. Then,the values of R at Katori and Narashino do not show good agreement with the values by seismic
fragility curve since the seismic fragility curve considers no effect of liquefaction.
From Fig. 5(b), RL at Mito, Kasama treatment areas in Kasama, Tomobe treatment areas in
Kasama, Oarai, Omitama, Shimotsuma, Takase treatment areas in Funabashi, Sakura, Nanbu treatmentareas in Chiba, Inba treatment areas in Chiba and Narashino show good agreement with the values byseismic fragility curve. In contrast, RL of 0.583/km at Hinode areas in Itako with IJm of 5.9 shows
remarkably larger value than those derived by the seismic fragility curve due to the strongest groundexcitation among the subject municipalities and the intensive liquefaction at the areas. RL of 0.00994
to 0.112 at Katori, Abiko, Chuo treatment areas in Chiba and Urayasu with IJm of nearly 5.0 show
larger values than those derived by the seismic fragility curve due to damages by severe liquefaction.
On the other hand, RL at Hitachinaka, Hokota, Kashima and Inashiki with IJm of nearly 5.5 show larger
values than the values derived by the seismic fragility curve due to the strong ground motions andliquefaction. Furthermore, RL at Kasama treatment areas in Kasama with IJm of 5.4 also shows larger
values due to the damage on aged pipes.

1492

0.6

2.5

0.5

2.0

0.4

RL [km/km]

R [/km]

3.0

1.5
1.0

0.2
0.1

0.5
0
4.5

0.3

5.0

Kobe
Katori
Funabashi, Takase
Oarai
KamisuTsukuba

5.5
IJm
Fragility curve
Narashino
Inashiki
Omitama
Shimotsuma

6.0

6.5

0
4.5

Kobe
Urayasu
Chiba, Chuo
Narashino
Inashiki
Kasama, Kasama
Kashima
Tsukuba
Mito(a) For R

5.0

5.5
IJm

Fragility curve
Katori
Chiba, Nanbu
Funabashi, Takase
Oarai
Kasama, Tomobe
KamisuHitachinaka

6.0

6.5

Abiko
SakuraChiba, Inba
Itako, Hinode
OmitamaKasama, Iwama
Shimotsuma
Hokota(b) For RL

Fig. 5 Comparison of damage ratios for the Tohoku earthquake with those for the Kobe earthquake

COCLUSIOS
We evaluate the dependency of damage and restoration of water supply systems and sewerage systems
on the seismic hazards in the 2011 off the Pacific Coast of Tohoku earthquake focusing on the damage
at Ibaraki and Chiba prefectures. We collect the damage data of the systems by carrying out interviewsfor related local government sectors. We quantify two damage ratios R and RL for 14 municipalities in
Ibaraki prefecture and 8 municipalities in Chiba prefecture: R defined by the ratio of number ofphysical damage points p divided by total lengths of the buried pipelines L and RL defined by theratio of disrupted lengths Ld divided by total lengths of the buried pipelines L. In addition, we compare
the values of R and RL with estimated ones derived by previously proposed seismic fragility curves.
Following conclusions are deduced.
(1) R for water supply systems are classified into the following 4 ranges: extremely large values of
0.654/km to 1.081/km at Urayasu and Kashima data with seismic intensity IJm of 5.1 to 5.8, larger
values of 0.247/km to 0.316/km at Inashiki and Kamisu data with IJm of 5.3 to 5.5, middle valuesof 0.0571/km to 0.136/km at Hitachi, Hitachinaka, Mito, Oarai, Hokota and Narashino data withIJm of 5.2 to 5.8 and smaller values of 0.0130/km to 0.0416/km at South Ibaraki Waterworks
Agency and other municipalities data with IJm of 4.9 to 5.8. RL for water supply systems areclassified into the following 2 ranges: extremely large value of 0.0317km/km at Katori data withIJm of 5.2, smaller values of 0.0000573km/km to 0.00124km/km at Hokota and othermunicipalities data with IJm of 5.0 to 5.8.
(2) R for sewerage systems are classified into the following 4 ranges: extremely large values of
0.930/km to 2.484/km at Katori and Narashino data with IJm of 5.2, larger values of 0.198/km to
0.237/km at Omitama and Shimotsuma data with IJm of 5.6 to 5.8, middle values of 0.0218/km to0.0540/km at Oarai and Inashiki data with IJm of 5.5 to 5.6, smaller values of 0.0135/km to1493

0.0142/km at Tsukuba and Takase treatment areas in Funabashi data with IJm of 5.0 to 5.5. RL for
sewerage systems are classified into the following 5 ranges: remarkably huge value of
0.538km/km at Hinode areas in Itako data with IJm of 5.9, extremely large values of 0.0907km/km
to 0.112km/km at Kashima and Urayasu data with IJm of 5.1 to 5.8, next largest values of
0.0649km/km to 0.0818km/km at Kasama treatment area at Kasama, Kamisu and Katori data withIJm of 5.2 to 5.4, middle values of 0.0228km/km to 0.0412km/km at Hitachinaka, Hokota, Inashiki
and Chuo treatment areas in Chiba data with IJm of 5.0 to 5.8, smaller values of 0.000237km/km to
0.0115km/km at Tomobe treatment areas in Kasama and other municipalities data with IJm of 4.9
to 5.8.
(3) Water supply systems (WSS) at Kamisu were restored in longest restoration periods of 57 days
due to larger R, WSS at Kashima, Inashiki, Katori and Urayasu were restored in second longest
restoration periods of 23 days to 37 days: 26 days to 34 days at Kashima and Urayasu due tolargest R, 23 days at Inashiki due to larger R, 37 days at Katori due to largest RL. WSS at Hitachi,
Hitachinaka, Oarai, Hokota and Narashino were restored in longer restoration periods of 8 days to
14 days due to middle range of R. WSS at Kasama and Funabashi were restored in longer
restoration periods of 8 days in spite of smaller R. WSS at Mito, Tsukuba, Abiko and Chiba were
restored in middle range of restoration periods of 5 days to 6 days: 6 days at Mito due to middle
range of R, 5 days to 6 days at Tsukuba and Chiba due to smaller R, 5 days at Abiko due to
middle range of RL.
(4) In terms of periods of restriction for use for sewerage systems, sewerage systems (SS) at
Narashino were restored in the longest restoration periods of 112 days due to next largest R. SS at
Kamisu were restored in the second longest restoration periods of 83 days due to next largest RL.
SS at Itako, Inashiki and Urayasu were restored in longer restoration periods of 34 days to 44 days
due to largest and middle range of RL. In terms of temporary restoration periods for seweragesystems, SS at Narashino were restored in the longest restoration periods of 112 days due to next
largest R. SS at Kamisu and Katori were restored in the second longest restoration periods of 83
days to 91 days due to next largest RL. SS at Kashima, Itako, Inashiki and Urayasu were restored
in longer restoration periods of 34 days to 44 days due to largest and middle range of RL. SS at
Abiko were restored in longer restoration periods of 60 days in spite of smaller RL.
(5) From comparison of R with estimated ones derived by our proposed seismic fragility curves, R
at all subject municipalities except for Katori and Narashino show good agreement with the values
by seismic fragility curve. From comparison of RL with estimated ones derived by our proposed
seismic fragility curves, RL at Mito and other 10 municipalities show good agreement with thevalues by seismic fragility curve. RL at Hinode areas in Itako with IJm of 5.9 shows remarkably
larger value than the value derived by the seismic fragility curve due to the strongest groundexcitation among the subject municipalities and the intensive liquefaction at the areas. RL at Katori,
Abiko, Chuo treatment areas in Chiba and Urayasu with IJm of nearly 5.0 show larger values thanthe values derived by the seismic fragility curve due to damages by severe liquefaction. RL at
Hitachinaka, Hokota, Kashima and Inashiki with IJm of nearly 5.5 show larger values than thevalues derived by the seismic fragility curve due to the strong ground motions and liquefaction. RL
at Kasama treatment areas in Kasama with IJm of 5.4 also shows larger values due to the damage
on aged pipes.

ACKOWLEDGEMETS
We appreciate valuable cooperation of all subject municipalities. This study was sponsored by thedevelopment of restoration simulation system on seismic sewerage damage financially supported by
MLIT from 2009 to 2010 (leader, Dr. S. Nagata at Kajima Technical Research Institute), the 2011 off
the Pacific Coast of Tohoku earthquake research project at University of Tsukuba (leader, Professor T.
Kanakubo) and the integrated risk management project for complex disasters on large-scale
earthquakes at University of Tsukuba (leader, Professor Y. Yagi).

1494

REFERECES
Cressie, N. A. C. (1993). “Statistics for spatial data.” John Wiley and Sons, 356-359.
Fujimoto, K. and Midorikawa, S. (2006). “Relationship between Average Shear-Wave Velocity andSite Amplification Inferred from Strong Motion Records at Nearby Station Pairs.” Journal ofJapan association for earthquake engineering, Vol.6(1), 11-22.
Japan Meteorological Agency (2011). “Japan Meteorological Agency | Earthquake Information.”
http://www.jma.go.jp/en/quake/.
Ministry of Health, Labour and Welfare (2011). “MLIT Ministry of Land, Infrastructure, Transport andTourism.” http://www.mlit.go.jp/en/index.html.
Ministry of Land, Infrastructure, Transport and Tourism (2011). “Ministry of Health, Labour andWelfare.” http://www.mhlw.go.jp/english/.
National Research Institute for Earth Science and Disaster Prevention (2011).
“Kiban-Kyoshin Network.” http://www.kik.bosai.go.jp/kik/index_en.shtml.
“Kyoshin Network K-NET.” http://www.kyoshin.bosai.go.jp/kyoshin/.
Shoji, G., Naba, S. and Nagata, S. (2011). “Evaluation of seismic vulnerability of sewerage pipelines
based on assessment of the damage data in the 1995 Kobe earthquake.” Applications of Statistics
and Probability in Civil Engineering, Faber, M. H., Kőhler, J. and Nishijima, K. eds., Taylor andFrancis Group, London, ISBN 978-0-415-66986-3, 1415-1423.
Si, H. and Midorikawa, S. (1999). “New attenuation relationships for peak ground acceleration andvelocity considering effects of fault type and site condition.” Journal of structural and constructionengineering (Transactions of AIJ), No. 523, 63-70.

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