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

Mechanism of Slope Failures in Residential
Land on Fill during Great East Japan
Earthquake
Masayuki Hyodo1, Rolando Orense2, Shohei Noda3, Satoshi Furukawa4, Toshihiko Furui5
1

Professor, Department of Civil Engineering, Yamaguchi University,
Yamaguchi, Japan, hyodo@yamaguchi-u.ac.jp
2
Professor, Department of Civil Engineering, University of Auckland,
Auckland, New Zealand, r.orense@auckland.ac.nz
3Student, Department of Civil Engineering, Yamaguchi University,
Yamaguchi, Japan, r003wf@yamaguchi-u.ac.jp
4
Frontier Project Section, Chuden Engineering Consultants Co. Ltd.,
Hiroshima, Japan, furukawa@cecnet.co.jp
5Etajima City Office, Hiroshima Prefecture,
Hiroshima, Japan, furui@mbf.ocn.ne.jp

ABSTRACT: As a result of the Great East Japan Earthquake, five slope failuresoccurred in a residential area on artificial valley fills in Taiyo New Town, Yamamoto,
Miyagi Prefecture. The fill material is sandy, derived from the weathering of tuffaceous
sandstone which formed the natural ground. Cyclic triaxial tests showed that the fill,which has about Fc=20%, has very low liquefaction resistance, which decreased withapplication of initial shear stress. Thus, the slope failure in Taiyo New Town can be
attributed to the liquefaction of the fill material induced by the intense shaking.
Key Words: Great East Japan earthquake, slope failure, valley fill, pseudostatic analysis,
tuffaceous sandstone, liquefaction

INTRODUCTION
With moment magnitude Mw 9.0, the gigantic 2011 off the Pacific coast of Tohoku Earthquake caused
extensive damage to life and property in Tohoku and Kanto regions in eastern part of Japan. One of theworst hit areas is the coastal town of Yamamoto on southern part of Miyagi Prefecture. Almost 24 km2of the town’s 64 km2 area, or about 38%, was flooded and destroyed by the large-scale tsunami
generated by the earthquake (GSI, 2011). Most of the inundated area was on the eastern side of the
National Route 6. In addition, several slope failures occurred on the hilly areas located to the west of
Route 6. In terms of slope failures, one of the worst-hit areas was Taiyo New Town, a housing site
located on artificial valley fill just to the west of Route 6. The site was constructed by leveling the
hilly area and using the cut materials as fills for the valleys to provide viable land for residential
purposes. Following the earthquake, slope failures occurred in five different sections of the land,937

damaging houses, roads, park and pipelines. In one of the failed sites, the debris slid and covered aparking lot just on the side of Route 6.
Following the earthquake, site investigations were performed at the site in order to clarify thecauses(s) of the slope failures. Samples were obtained at several locations adjacent to the failed slopes
and laboratory tests were conducted to investigate their geotechnical properties. Finally, slope stability
analyses were conducted in order to better understand the response of the embankment to earthquake
loading. The results highlighted the seismic vulnerability of residential areas on artificial valley fills
like Taiyo New Town that are constructed with weak tuffaceous materials as fill.

DESCRIPTION OF THE AREAThe Taiyo New Town housing site is located in the central part of Yamamoto, a coastal town on thesouthern edge of Miyagi Prefecture. It is located on the hilly region to the west of Route No. 6, which
traverses the prefecture in almost northwest-southeast direction. In fact, Route 6 appears to be thedividing line between the coastal plain on the east and the 40-50m high mountains (Wariyama upliftzone) on the west of the prefecture.
The site of the residential area was developed in the 1970s by cutting and leveling off some partsof the hills and using the materials as fill for the valleys. Figure 1 shows the depth distribution of cuts
and fills in Taiyo New Town. To level off the residential land, cuts were made on the hills as high as
8-10m, while valley floors as deep as 10-15 m were filled up using the same materials that were cut
from the elevated regions. It can be observed that deep valleys existed in the central portion and inwestern boundary of the site. The eastern side of the site adjacent to Route 6 was also filled up, withembankment having slope of 1:1.5. The elevation of the filled-up residential site was about 35 m
above mean sea level. It has an area of about 0.12 km2 and when the earthquake struck, more than 200
houses have been built at the site.
Investigation of the local geology of the site revealed that the original ground consisted oftuffaceous sandstones of the Yamamoto Formation. Subsequent boring data showed that thesandstones were weakly consolidated and exhibited high degree of weathering towards the surface,with the surficial layer appearing like sandy soil. Thus, the material used to fill up the valleys
consisted of sandy soils from the weathered tuffaceous sandstones. Standard penetration tests indicatedthat the sandy material used as fill has an average N-value of 5, while the highly weathered top layer
and the weathered layer the sandstone has average N-values of 6 and 16, respectively.

Figure 1. The housing site foundation map of Taiyo New Town, showing the thickness
distribution of cut and fill sections (Fukken Gijutsu Consultant, 2008)

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STRONG MOTION STATION AND SEISMIC RECORDS
About 2km to the south of Taiyo New Town, the National Research Institute for Earth Science andDisaster Prevention (NIED) operates a KiK-Net seismic station (MYGH10: Yamamoto Station) withdigital strong-motion seismometers installed at the ground surface and at a depth of GL-205m. The
2011 Tohoku earthquake triggered many seismic stations in the area, including the one in Yamamoto,and recorded strong motions. Figure 2 shows the acceleration time histories recorded at the station,
both on the surface and at depth, while Figure 3 illustrates the corresponding Fourier spectra of theacceleration records. The peak accelerations recorded at depth were in the range of 150~220 cm/sec2
with predominant frequency of 0.35 Hz. On the ground surface, on the other hand, the peak values
were much higher, 850~870 cm/sec2, with the predominant frequency shifting to 4-6 Hz.
The soil profile at KiK-Net Yamamoto station is shown in Table 1. It can be observed that
tuffaceous sandstone with shear wave velocity Vs<770 m/sec exists in the vicinity of the seismometer
installed at the bottom of the borehole. Moreover, the upper layer generally consisted of pumiceous
tuff and tuffaceous sandstones. This profile generally amplified the seismic motion as it propagates
towards the ground surface.

Figure 2. Acceleration time histories obtained from Yamamoto KiKNet Seismic station:(a) at ground surface; (b) at GL-205m (data from KiK-Net website)

Figure 3. Fourier spectra of acceleration records obtained from Yamamoto KiKNet
Seismic station: (a) at ground surface; (b) at GL-205m

939

Table 1. Soil profile at Yamamoto Kik-Net seismic station (MYGH10) (data from Kik-Net website)
Depth (m)
2.0
3.5
8.0
18.0
34.0
42.0
114.0
142.0
178.0
208.0

Thickness
(m)
2.0
1.5
4.5
10.0
16.0
8.0
72.0
28.0
56.0
30.0

Type of soil/rock
Clay
Clay
Sandstone
Conglomerate
Sandstone
Pumiceous tuff
Tuffaceous Sandstone
Sandstone
Tuffaceous sandstone
Silt

Vp
m/s)
500
1750
1750
1750
1750
1830
1830
1920
1920
1920

Vs
(m/s)
110
250
390
390
390
590
590
770
770
770

OUTLINE OF DAMAGE
Following the 2011 earthquake, slope failures occurred at five sites within the Taiyo New Town
housing site. The locations of the slope failure are shown in Figure 4. These failed or slid blocks weresequentially numbered, starting with Failed Block 1 on the eastern boundary of the housing site, going
counterclockwise to Failed Block 5 on the western side. Block 1 consisted of two landslides, referred
to as Block 1-1 and Block 1-2, respectively. Also shown in the figure are the locations of damaged
roads due to the slope failure and damaged road pavements. Extensometers were placed on the easternboundary to monitor the movement of the fill. In addition, several standard penetrations tests were
performed within the fill and adjacent to the failed blocks.

Figure 4. Location of failed slopes in Taiyo New Town

Comparing the locations of the failed blocks in the housing site (Figure 4) with the foundation groundmap shown in Figure 1, it is clear that all failed slopes occurred either on the edge of the valley fill oron the shoulder of the embankment. This suggests that the fill material, rather than the natural ground,
was involved in the slope failures.

940

Failed Block 1
Block 1 consisted of two slope failures. The first sliding block, 1-1, caused settlement at the crest andlaterally flowed down the sloping ground, as shown schematically in Figure 5. As a result, a house
located on the laterally moving ground tilted and a 1m high vertical offset was also created.
Extensional cracks were also observed on the ground and road pavements. The adjacent failed block,
1-2, was smaller in scope and induced cracking on the road as the sliding mass slid. In both cases, thesurface of the road downslope was pushed up.

Figure 5. Cross-sectional profile of failed slope in Block 1-1

Failed Block 2
About 50m north of failed Block 1, the shoulder of the embankment collapsed, sending debris 15 m
below towards the parking lot adjacent to a convenience store. It is apparent that the failure wasconfined to the upper layer consisting of fill material. A house located at the crest of the sliding mass
was partially destroyed, while the roads positioned at the top and midway of the slope were totally
destroyed, sending cracked pavements downward. Just to the north of the failed slope and down on themain road, a reinforced retaining wall missed the landslide. This retaining wall was constructed in2008 when the section failed following a heavy rainfall; the retaining wall was not damaged by thisearthquake.

SOIL AND SITE CHARACTERISTICS
To understand the characteristics of the fill material, soil samples were obtained adjacent to the failed
blocks and geotechnical tests were performed.
Geotechnical properties
Soils samples were obtained near failed Blocks 1, 2, 3 and 5 in order to investigate the geotechnicalproperties of the soil used as fill. Figure 6 shows the grain size distribution curves for samples fromthe four sites. It can be seen that the curves were fairly similar at all three locations, indicating that thefill materials were uniform throughout the housing site The soil have fairly uniform distribution withfines content, Fc=20%.
Samples obtained from Block 1 site were quite abundant and these were used in most of thegeotechnical tests. Index property tests, based on Japanese Geotechnical Society standards (JGS,
2001) showed that the density of the particles was 2.478 g/cm3, while the maximum and minimum
densities were 1.319 and 1.079 g/cm3, respectively. The compaction curve is shown in Figure 8 where
it is seen that the optimum water content is wopt=13.8% corresponding to maximum dry density,
ρdmax=1.822 g/cm3.

941

Pe rcent finer by w eigh t (% )Percent finer by weight (%)

100

100
80
80
60

60
40

40
: Block1: Block2: Block3: Block5

20

20
0
0
0.0
01
0.01

0.01
0.1

0.1 1

1

10

10

G rsizea i n s i(mze m( m) m )Gra inFigure 6. Grain size distribution curves of samples obtained from four sites
ρ

2.0

s

: Block1: Block2: Block4: Block5

87

Block1.4

Dry density ρ d (g/cm 3 )

=2

1.9

w o p t ＝ 13.8%
ρd m a x ＝ 1.822g/cm 3

1.8

1.7

1.6
Taiyo New Town

1.5
5

25

Water contents w (%)
Figure 7. Compaction curve
Next, monotonic drained and cyclic undrained triaxial tests were conducted on the soil samples. In
these tests, the reconstituted samples were prepared such that they have dry density equal to 90% of
the maximum dry density, i.e., degree of compaction Dc=90%. Using the obtained maximum andminimum dry densities, this corresponds to a relative density Dr=188%. The results of themonotonic drained tests for confining pressure of σc’=50, 100 and 150 kPa are shown in Figure 8. The
undrained shear test was also performed for confining pressure of σc’=100kPa and presented in the
figure. The soil shows contractive behavior at all levels of applied pressure. This may be due to thecollapsible behavior of weathered tuffaceous sandstone. From the stress-strain relations, Mohr circles
of stress were drawn at residual state as shown in Figure 10, and the strength parameters were obtained.
The results indicate the following values: cohesion, c=9 kPa, and angle of internal friction φ=31.7o.
Such internal friction angle is quite low for sandy soils.

942

500

300

σc'

150kPa50kPa
100kPa150kPa100kPa

200
50kPa
100

100kPa(CU test)

0

-6
0

0

3

6

9

12

15

6

Volume strain ε v (%)

Deviator stress q

(kPa)

400

CD testAxial strain ε a (%)

Figure 8. Results of consolidated drained triaxial tests

Sh ear stress τ (kPa)

450

300

Taiyo N ew Town

c d =9.0kPa, φ d =31.7 °

150

0
0

150

300

450

600

750

Principal stress σ c ' (kPa)

Figure 9. Mohr’s stress circles and failure envelope from results by drained triaxial tests

Cyclic undrained triaxial tests were performed on reconstituted samples under isotropicallyconsolidated condition, and the liquefaction resistance curve obtained for a double amplitude axial
strain εDA=5% is shown by the solid circles in Figure 10. It is seen that the liquefaction resistance ofthe material is quite low, indicating the susceptibility of the material to large deformation when shaken
under saturated condition. This may be due to the high fines content of the soil and the density used toprepare the reconstituted specimen. Note that for soil specimens with Dc=90%, the dry density of thesoil was taken as 1.64 g/cm3. According to Yamamoto Town Office, dry densities ranging from
1.44-1.54 g/cm3 were obtained at the site based on previous site investigations. Thus, although thedensity of the specimen used in the test was higher than the in-situ values, the liquefaction resistanceof the soil was low. Although the location of the water table during the earthquake was not confirmed,
this type of material will liquefy easily when subjected to cyclic shearing induced by earthquake, andwill fail due to reduction in effective stress.
In order to simulate the presence of initial shear stress in sloping grounds, such as in the present
embankment, cyclic undrained triaxial tests were also performed on anisotropically consolidated
specimens. Results for cases with initial shear stress ratio, σs/2σc’=0.30, and 0.375 are also indicatedin Figure 10. In case of anisotropically consolidated samples, the cyclic failure was defined in terms ofpeak axial strain εp=5%. It appears that if the fill material is subjected to initial static stress, the cyclic
strength decreases; such behavior is quite different from those observed for other types of granular943

Cyclic dev iator stress ratio
σ d /2 σ c '

0.6
0.5

ε p or ε DA =5%
σ3 c '=100kPa

σs /2 σ c '

0.4

:0
: 0.3
: 0.375

0.3: ε DA =5%: ε p =5%0.2
0.1
D c =90%( ρ d =1.640g/cm 3 )

0.0
0.1

1

10

100

1000

Number of cycles N

Figure 10. Liquefaction resistance curves of isotropically and anisotropically consolidated samples

Cyclic deviator stress ratio( σ d /2 σ c ') N=200.8
ε p or ε DA =5%

0.7
0.6

: Toyoura sand (D r i =50%): Toyoura sand (D r i =70%): Taiyo New Town
(D ri =188%)(D c =90%)

0.5
0.4
0.3
0.2
0.1
Taiyo New Town
0.0
0.0

0.1

0.2
0.3
0.4
0.5
0.6
0.7
Initial shear stress ratio σ s /2 σ c '0.8

Figure 11. Variation of cyclic strength at N=20 cycles with initial shear stress ratio

Deviator stress q (kPa)

150
125
100
75
50
25
0
-25
-50
0

25 50 75 100 125 150 175 200 -10 -5

0

5

10 15

Effective mean principal stress Axial strain εa (%)
p' (kPa)

Figure 12. Cyclic stress paths and cyclic stress strain curves for isotropically and anisotropicallyconsolidated samples

944

materials (Vaid, 1983; Hyodo et al., 1991, 1994; Hosono and Yoshimine, 2004). This confirms that thefill material is indeed weak and susceptible to large deformation under earthquake loading. Figure 11
shows the cyclic deviator stress ratio to cause failure after 20 cycles. The results for Toyoura sand with
Dr=50% and Dr=70% are also shown in the figure for comparison. In the case of Toyoura sand, thecyclic strength increases with initial shear stress ratio as expected for medium to dense material.
However, in the case of the sampled soil, the cyclic strength decreased with increasing initial shear
stress ratio, although it should noted that the definition of failure changed from εDA=5% toεp=5%.
Further it should be noted that failure occurred for stress non-reversal condition at the material whilestress reversal was necessary to cause failure at dense Toyoura sand.
Figure 12 shows the stress paths and corresponding relationship between cyclic deviator stress andaxial strain for both isotropically and anisotropically consolidated samples. Examination of the cyclic
stress paths for isotropically consolidated sample shows liquefaction occurring as the stress pathcycles through zero effective confining pressure. The development of cyclic strains occurs in bothcompression and extension. The cyclic failure was defined as a strain double amplitude of 5%(εDA=5%). On the other hand, the cyclic stress paths for anisotropically consolidated samples showscyclic failure occurring as the stress path reaches to the failure envelope developed by monotonic
shear tests. The corresponding cyclic stress strain plots are shown taken to peak axial strain of
approximately 15%. It should be noted that cyclic strain amplitude becomes larger as the stress pathapproaches to failure envelope. The cyclic strength for anisotropic samples was defined as the numberof cycles to reach peak axial strain εp=5%.

SLOPE STABILITY ANALYSES
To explain the cause of failure, preliminary analyses were conducted considering the stability of theembankments during the 2011 earthquake under different scenarios. For this purpose, pseudostatic
analyses were performed. The equivalent strong motion at the top of the embankment was determinedthrough the procedure outlined in Figure 13. Firstly, the model for the 1-D soil profile at the locationof the KiK-net seismic station (Table 1) was verified using earthquake recordings obtained during
previous smaller earthquakes of 1 September 2010 and 10 February 2011. In both cases, the time
history of acceleration recorded on the ground surface was used as input and the acceleration at thebottom of the borehole (GL-205m) was simulated using the program SHAKE. Next, to incorporate thenon-linear response of the soil due to the larger amplitude of motion resulting from the 2011 Tohoku
earthquake event, the surface motion (Figure 2a) was used as input to simulate the motion at GL-205m(Figure 2b). Due to space limitation, the details of the calculations are not presented here. Suffice it to
say that the 1-D ground model at the seismic station site was sufficiently validated. From the last
analysis, the incident wave (2E) at the engineering bedrock, Point C, was calculated for both N-S and
E-W direction.
For the purpose of analysis, the cross-sectional profile for Block 1 shown in Figure 5 was used.
Using the boring data obtained from field tests and knowing that the natural period of the site is 0.7
sec, the soil profile and corresponding parameters were established, as summarized in Table 2. The
depth of the engineering bedrock from the surface of the fill was 34m.
Next, the strong motion obtained at Point C was used as input (2E) at Point B to determine thesurface acceleration at Point A. Since Point C and Point B are just 2km apart, attenuation of motion
was not considered. Again, seismic response analyses were conducted and the results obtained showed
PGAs at point A of 1322.6 and 1171.3 cm/sec2 in N-S and E-W directions, respectively. Using theequation for lateral seismic coefficient, kh, proposed by Noda et al. (1975), the obtained PGAs
correspond to kh=0.368 and 0.354, respectively.

945

Figure 13. Schematic diagram showing how the PGA on top of the fill was calculated from
KiK-Net recorded motions

Table 2. Soil profile and soil properties for failed Block 1 site used in the analysis
Soil Type

Depth
(m)
6

Fill (sandy type)
Tuffaceous sand stone
12(strongly weathered)Tuffaceous
sandstone
34(weathered

H
(m)
6

SPT
N-value4.7γt(kN/m3)17.5

γsat(kN/m3)18.9

Vs(m/sec)
128

4H/Vs
(sec)
0.19

6

6.7

18.6

20.6

149

0.16

22

32.4

18.6

20.6

252

0.35
0.70

In the pseudostatic analysis of slope stability, three cases of ground models and slip failures wereconsidered: Case A, where ground water table is low (effect not considered) with composite slip
surfaces; Case B – 1, where ground water table is near the boundary between fill and sandstone withcomposite slip surfaces; and Case B – 2 where ground water table is near the boundary between fill
and sandstone with cylindrical slip surface. In the analyses, the strength parameters obtained frommonotonic drained triaxial tests were used.
In addition to the analyses using conventional strength parameters, a supplementary analysis was
performed using the results of cyclic triaxial tests instead. In such analysis, two stages wereconsidered: static analysis prior to the application of the seismic load, and dynamic analysis using
pseudo-static approach. In the static analysis, the strength parameters (cohesion c and frictional angleφ) obtained from conventional tests were used. Since the calculated factor of safety, Fs, indicates theratio of the shear resistance, τsf, and shear stress, τs, along the slip surface (i.e., Fs = τsf /τs), it ispossible to estimate the average static shear stress along the slip plane from the known values of Fsand τsf. From Figure 11, the cyclic shear resistance ratios corresponding to N=20 cycles were readfrom the curves, and the data were used to plot the dynamic strength ratio, τd/τsf, as a function of theinitial shear stress ratio, τs/τsf, as illustrated in Figure 14. Thus, knowing the average static shear stressalong a slip plane, the corresponding cyclic resistance (or dynamic strength) can be estimated. The
cyclic resistance is added to the initial static shear stresses and then used as strength parameters in
performing the pseudo-static analysis to compute the Fs for the specified earthquake load. Note that inthis procedure, it is tacitly assumed that the earthquake loading is applied for N=20 cycles.
In all the pseudo-static analysis conducted, the yield acceleration, ky, corresponding to the limit
equilibrium condition Fs=1.0 was calculated. For simplicity, the value of ky was assumed to beconstant throughout the duration of earthquake loading.

946

Dynamic strength ratio
τ d f (N =2 0) / τ sf

1.0
0.8
0.6
0.4
0.2
0.0
0.0

0.2

0.4

0.6

0.8

1.0

2.5

1.67

1.25

1.0

Initial shear stress ratio

5.0

τ s / τ sf

Factor of safety F ss

Figure 14. Relation between dynamic strength and initial stress obtained from triaxial test results

The results of the analyses are summarized in Table 3 for all the cases considered in terms of theyield acceleration, ky, necessary for limit equilibrium condition (Fs=1.0). For cases with composite
failure surfaces, the values for the two major slip surfaces considered are also indicated. Consideringthat the results of SHAKE analysis showed kh values of 0.35-0.37, the only condition where ky is lessthan these values is the case involving the use of dynamic strength at the slip surface; all other cases
using conventional strength parameters resulted in higher value of ky than that induced by the 2011
earthquake. For the conventional analysis to hold, kh should at least be 0.39, or a PGA of 1,570
cm/sec2; this value is too large.

Case
A
B-1
B-2
B-2’

Table 3. Results of pseudo-static analysis for the failed embankment in Block 1
Yield acceleration, ky
Condition
Strength Parameters
Slip 1
Slip 2
No water table; composite slip
0.46
0.42
surfaces
With water table;
0.43
0.39
cd=9kN/m3, φ=31.7o
Composite slip surfaces
With water table:
0.42
Cylindrical slip surface
cd=9kN/m3, φ=31.7o;With water table:
then changed to dynamic 0.24
Cylindrical slip surface
strengthThus, based on the calculations presented above, it appears that the slope failure in Taiyo New Town
can be attributed to the liquefaction of the fill, especially near the interface between the top fill layer
and the highly weathered tuffaceous sandstone. With the development of excess pore water pressure,the fill underwent large deformation during the shaking induced by the gigantic Tohoku earthquake.

CONCLUSIONS
The gigantic 2011 off the Pacific coast of Tohoku Earthquake caused 5 slope failures in Taiyo New
Town, a housing site on artificial valley fill in Yamamoto town, Miyagi Prefecture. To understand themechanism of the slope failures, field inspection, strong motion record analyses, laboratory tests andslope stability analyses were conducted. The following are the major conclusions from this study:947

1. The residential site of Taiyo New Town was constructed through cut and fill method. The original
hilly ground consisted of weakly consolidated tuffaceous sandstone, which showed high degree of
weathering towards the surface and manifested itself as sand on the surface. Thus, the fill material
used to fill-up the valleys was generally sandy soil.
2. The maximum surface acceleration recorded in Yamamoto seismic station was 850-870 cm/sec2
with predominant period of 4-6Hz. The estimated maximum acceleration on top of the fill basedon seismic response analyses was 1170-1300 cm/sec2.
3. Each of the five slope failures at the housing site was observed to occur at the boundary between
the filled-up valley and the fill or on the shoulder of the embankment.
4. The sandy fill material has fines content Fc=20%. Even when compacted at 90% degree ofcompaction, the fill material showed very low internal friction angle and low liquefaction
resistance. Moreover, the liquefaction resistance decreased with application of initial shear stress.
5. Pseudo-static slope stability analysis using conventional strength parameters cannot explain theslope failure in Block 1. However, when dynamic strength (or liquefaction resistance) was used torepresent the soil strength at the slip surface, the yield seismic coefficient required to induce
failure was lower than the estimated seismic coefficient on top of the fill.
6. The slope failure in Taiyo New Town can be attributed to the liquefaction of the fill material
induced by the intense shaking. It was possible that during the earthquake, the ground water level
was near the boundary of the original ground and the fill, making liquefaction possible.

ACKNOWLEDGMENTS
The authors would like to acknowledge the assistance of the engineering staff of Yamamoto Town
Office for providing access to the site for inspection and for the valuable information during
subsequent meetings. The strong motion data was obtained from K-Net.

REFERENCES
Geospatial Information Agency of Japan, GSI (2011). Area Flooded by the Tsunami (Approximate),
http://www.gsi.go.jp/common/000059734.pdf (in Japanese).
KiK-Net (2011). Digital Strong Motion Network, http://www.kik.bosai,go,jp/
Fukken Gijutsu Consultant Co. Ltd. (2008). Ground Map of Built-up Residential Land, 1:25,000 scale
Nakamura, Y., (1989). “A method for dynamic characteristics estimation of subsurface using
microtremor on the ground surface,” Quarterly Report of Railway Technical Research Iinstitute,Vol. 30, No. 1, 25 to 33.
Noda, S., Uwabe, T. and Chiba, T. (1975). “Relation between seismic coefficient and groundacceleration for gravity quay wall,” Report of the Port and Harbour Research Institute, 14 (4) (inJapanese).
Hosono,Y. and Yoshimine, M. (2004). “Liquefaction of sand in simple shear condition,” Proc.,
International Conference on Cyclic Behaviour of Soils and Liquefaction Phenomena, Bochum,
Germany, 129-136.
Vaid, Y.P., Chung, E.K.F. and Kuerbis, R.H. (1990). “Stress path and steady state,” Canadian
Geotechnical Journal, 27(1): 1-7.
Hyodo, M., Murata, H., Yasufuku, N. and Fujii, T. (1991). “Undrained cyclic shear strength andresidual strength of saturated sand by cyclic triaxial tests,” Soils and Foundations, Vol. 31, No. 3,
60-76.
Hyodo, M., Tanimisu, H., Yasufuku, N. and Murata, H. (1994). “Undrained cyclic and monotonic
behavior of saturated loose sand,” Soils and Foundations, Vol. 34, No. 1, 19-32.
Japanese Geotechnical Society (2001). Soil Testing Procedure and Commentary, (in Japanese).

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