Tsukuba, Japan
International Institute of Seismology and Earthquake
Engineering
Building Research Institute

STUDY TRIP TO ITAKO CITY

A Technical Report

By MARTINEZ BRAVO Delvin Abdiel (MEE10515)
Disaster Management Policy Program （2010-2011)(Earthquake Engineering)

April 20th 2011

Introduction
With the objective of to observe the damage caused due to earthquake occurred on
March 11th, the E-Course went to Itako city,
Itako city is located in Ibaraki prefecture, Japan (Figure 1), 85 Km to North-East fromTokyo, approximately, and 315 Km to South-West from the epicenter of the Tohoku
Earthquake (March 11th, 2011).
We visited specifically Hinode-district (Figure 1) (Housing area), located 3 Km to SouthWest, approximately, from the center of the city.
In this place the major of the damage was caused because the liquefaction
phenomenon, been this the principal objective of our visit.
This study trip was organized by the BRI/IISEE staff and JICA-Tsukuba, as part of theMaster program of the Training course of Seismology, Earthquake Engineering andDisaster Management Policy.
*The objective was to visit Itako city, however on the way we took advantages for see several
damages at Inashiki city

Damage observed and comments
INASHIKI CITY
1. - Road
Photo 1. Crack at the middleof the road. Many time thiskind of damage is presented
when earthquake occur due tochange of level of the ground(down or uplift of the ground).
The localization of the crack, at
the middle of the road, can be
due to separate construction ofeach way, different level ofcompaction

Photo 2. Crack at the border of theroad. This kind of damage can beoccasioned due lateral displacement not
uniform of the ground, because theshaking from the earthquake.

Photo 3. Settlement of thesidewalk. Difference of level,duetoliquefaction
phenomenon. In this case thesettlement of the sidewalk wasaround 16 cm. This kind ofdamage is common in area withsoil condition susceptible toliquefaction. At this site waspossible
toobserve
theliquefaction phenomenon, so, issure about the cause of thiskind of damage.

Photo 4. Uplift of the drainage
structure. Due to liquefaction
phenomenon the structure of theconcrete utilized for drainage
system was uplifted around
15cm from the original level.

Photo 5. Inclination andcollapse of electric post.
Duetoliquefaction
phenomenon the loss of theshear strength of the soil, theelectric post is impossible tokeep straight. In this photo wecan see also, the water fromthe ground that indicates thatliquefaction was occurred.

2. - Fence and Wall, and ground condition

6a6bPhoto 6a) and 6b). Crack and displacement (vertical and horizontal) in the fence
retaining wall (concrete block). Damage due to liquefaction phenomenon, the dashline show the direction of the crack on the ground, the fine sand is evidence ofliquefaction, the lateral and vertical displacement on the retaining wall is showed(orange dash circle).

7a
Photo7a)and7b).
Crackanddisplacement (vertical and horizontal) in
7b
the fence wall. The left photo (7a) show of
the continuation of the crack (black dash line) and the damage in the fence wall (reddash ellipse). Horizontal and vertical displacement, due to liquefaction phenomenon.
Also, the right photo (7b) show the effect of liquefaction, lateral and verticaldisplacement, tilted wall, crack on the bottom of the wall and separation between theroad and the fence wall (yellow dash ellipse).

3. - Damage at Building (directly)

8aPhoto 8a) and 8b). Settlement of thebuilding. Due to liquefaction phenomenon,
several building suffered severe settlement likethis building of two stories at Inashiki city. The
settlement was around 1.8m, this is enough forbecome useless the building, the message infront side (8b) indicate that the building is“UNSAFE”. This message was collocated after
the earthquake by the inspector from the local
government.

8b

ITAKO CITY
The Figure 1, show the localization of the affected area visited, Hinode District in Itakocity, in Japan map, is showed the localization of the epicenter of the earthquake
occurred on March 11th, 2011(orange arrow line).
The site is located in near to the Tone River and Kasumigara Lake in Ibaraki (in the pastthis area was cover with water from the lake), so the soil is susceptible to sufferliquefaction when is excited by shaking from the earthquake in this case, so the major ofthe damage at this site was due to liquefaction. Also, before that built house in this area,
was used for cultivate rice, that means that this land during long time was saturated withwater (the level of the water ground varies between 1 to 2 meter).

Figure 1. Geographic localization of the affected area visited (Hinode district) andepicenter of the Tohoku earthquake.
Source: Google Earth, commercial version.

Damage observed and comments
1. – Road
Photo 9. Distortion of thegroundsurface.
Thesidewalk went up and theroad went down, crack at
the road, this is clear
evidence of the occurrenceofliquefaction
phenomenon.

Photo 10. Inclination of theelectric post and tree.
Whe liquefaction occurre, themanly effect on the ground isthe loss of the of the capacity
shear strength, so the slender
structure, like electric post, cannotkeep
straigth,
andsometimes fail down (includingtree)

11a)

11b)
Photo 11a) and 11b). Distortion of the ground surface under the sidewalk. The
Photo 11b) shows the sidewalk after the earthquake, before the seismic event thissidewalk was like Photo 11a). This photo was took in the middle on two segment ofsidewalk, so this indicate different effect of the ground motion over the structure, thiscan be due to different soil condition in each side or different construction method ordifferent quality of the construction or the combination between these and anotherfactors.
Photo 12. Distortion of theground surface on the road. This
point is between two segment ofsidewalk showed on the Photo11a) and 11b). The undergroundwent up, around 10cm, and thelateral inclination is 7.6 degre. (Inthe photo, Rusli-san, take theinclination measure)Photo 13. Down ofground level. In this casethe manhole went down
duetoliquefaction
phenomenon.

Photo 14. The pipe
waterwentup.
After theearthquake the water
service remained outof service, this kind ofdamage is due toliquefaction also.

15a15bPhoto 15a) and 15b). Fall down of the small structure for “road signs”. In the caseof the slender structure is very easy fall down when occur the liquefaction phenomenon,
like the electric post, tower structure, but in case of small structure, like as the shown on
the photo 15b, is not common, and also is very difficult fall down due to the large(height) is relative small, so the momentum force necessary for become fall down is big,
however is necessary to take account, also, the foundation condition of the structure. In
this case, we can see a weak foundation, combined with the liquefaction phenomenon,
the soil behavior, like water, without shear strength, all these factors combined can be
the cause of several damages.

2. - Surrounding area of building

16a16bPhoto 16a) and 15b). Distortion of the ground in the surrounding area of building.
Down of ground level causing severe damage (crack on the sidewalk) and differential
settlement on the structure around of the building.
Photo17.
Settlement
around of the building.
Somecasedifferential
settlement can cause thetotal collapse of the building,however when the settlement
is uniform, the building cankeep straight, in this case thephoto shown good behaviorof the building against
differential settlement, duethat the structure around thebuilding suffered settlementwith different magnitude,
maybe due to kind offoundation .

3. - Fence and Wall
Photo 18. Settlement ofretaining wall. The engineer
indicates the original level ofthe retaining wall before of
the earthquake; in this casethe settlement was around
50 cm.

Photo 19. Crack and difference level at theretaining wall. In this case was difficult see, if
this wall has steel reinforce, because the crack is
not perpendicular to the longitudinal section. On
the top of the wall the wide of the crack is around
1.5 cm.

Photo 20. Crack and difference level at fence
brick wall. In this case is very clear that the fence
wall don’t have steel reinforce, for this reason isvery weak against lateral and vertical force.

Photo 21. Crack and horizontal displacement on the fence concrete block wall.
Without steel reinforce.

22a)

22b)

22c)

22d)
Photo 22a), 22b), 22c) and 22d). Differential settlement: crack and different levelon fence brick wall and retaining wall. Due to liquefaction phenomenon, this wall
suffered higher differential settlement, causing lateral-vertical displacement and crack.
The photo 22d) show that the wall don’t have steel reinforce, so is very weak inhorizontal direction. The horizontal displacement of the wall (crack) in the superior side
was around 15cm, and in the inferior side was around 5 cm (photo 22d)

4. - Damage Building itself

Photo 23. Crack at the house’s corner. Due to lateral displacement and settlement in
the front side, this house suffered damage in the back side, specifically crack at the bothmainly corner.

Photo 24. Differential settlement of the two stories
building. This kind of damage was observed inseveral houses around the area visited, this is due toliquefaction phenomenon and foundation condition.

5. - Ground Condition

25a)

25b)

25c)

25d)

Photo 25a), 25b), 25c) and 25d). Alteration of surface soil characteristics. Before
the earthquake this kind of soil (fine sand) there was not on the surface, due toliquefaction phenomenon, the uplift of the underground occurred. The kind of sand isfine sand silty (photo 25d), even on the paving stone the sand came up (photo 25c)

Photo 26. Sand boils was observed. Sand boils are diagnostic evidence of elevatedpoor water pressure at depth and an indication that liquefaction has occurred.

Photo 27. Deformation of the surface ground. Difference of level of the ground, dueto settlement occurred.

Conclusion and final comments
Always that occur the earthquake several damages are presented, on the ground byitself and on the civil structure (building, road, basic facilities), this damages depend of
the condition of the affected area (soil condition, characteristic of the structures,underground structures).
In this study trip we had the opportunity of observe several damages at Inode district inItako city, specifically the liquefaction was presented due to soil condition. Was alreadyestimated (according with information obtained from researches and engineer that areworking in recover of the city) the depth of the sand, around 4m.
In general much kind of damages is associated with liquefaction phenomenon, including
rise of poor water pressure, sand boils, and various types of deformation. Suchdeformation of the ground is called ground failure and may be manifested in several
forms or types.
This was a good experience for us, due that we could see the damage directly on thefield, and how solve the problems when the liquefaction phenomenon affects a specificarea, also how is directly related the site condition with the damage occurred.
The liquefaction phenomenon is a complex problem to solve, and now the idea is, how
we can reduce the effect on the structure, when these are located over groundsusceptible to suffer liquefaction.
We can think in specific kind of foundation, like piles, or another special foundation,
however, always we need considerer the monetary cost, so the goal is get structure withhigh performance and good behavior when the earthquake occur, without increase
considerably the cost of the structure.