Volume 1, Number 4, December 2003

19TH US-JAPAN BRIDGE ENGINEERING WORKSHOPThe Task Committee G (Transportation Systems) hosted the 19th US – Japan Bridge EngineeringWorkshop during 27-29 October 2003, at the PWRI Tsukuba Japan. Workshop special themes
were: 1) Advancing Technology in Seismic Engineering and 2) Innovative Technology for
Extending Bridge Service Lives. Sixteen participants from the US and 45 participants from Japanattended the workshop, and 40 papers were presented. After the workshop, technical site visit
around Kyushu and Chugoku regions were held. The workshop was closed with the Resolutions
that the 20th Workshop will be held in the US, autumn
2004.
Contact: Mr. Jiro Fukui, Leader, Foundation Engineering
Research Team, Public Works Research Institute,fukui@pwri.go.jp, 011-81-29-879-6795 (029-879-6795) toobtain a copy of the workshop proceedings.

Technical Visit at Kintai-Kyo Bridge

INTERNATIONAL WORKSHOP ON ADVANCEDSENSORS, STRUCTURAL HEALTH MONITORING, AND SMART STRUCTURESAn International Workshop on Advanced Sensors, Structural Health Monitoring, and Smart
Structures was held at Keio University, Japan on 10-11 November 2003 with the support of theJapan Society for the Promotion of Science, the US National Science Foundation, and Keio
University. Participation in this Workshop integrally supports and advances the mission of thePanel’s Task Committee B on Next Generation Building and Infrastructure Systems. Sixty-nine
experts participated; 20 from the US, 43 from Japan, and other Pan-Pacific countries (6)participated in the Workshop. The Workshop brought together researchers with diverse
backgrounds to discuss the current status of research and development in the U.S. and Japan in
the subject area for civil and mechanical systems. On the second day of the workshop, working
groups were formed to identify critical and strategic research issues that need further
investigation for broad and diverse implementations of innovative sensor and sensing systems incivil and mechanical systems including advanced sensors and actuators; sensor network andsensor system integration; signal processing for diagnostics and prognostics; implementation ofstructural health monitoring system, and smart materials and structural systems. An action plan
was formulated including facilitating mechanisms for promoting and conducting cooperative
research investigations. Participants in the Workshop unanimously adopted a set of resolutions
that included the need to develop a five-year plan for US-Japan cooperation in advanced sensors,structural health monitoring, and smart structures. The plan is proposed to be developed by theend of 2004. The resolutions were delivered to the US National Science Foundation and to
Japan’s Building Research Institute and the National Research Institute for Earth Science andDisaster Prevention. The proceedings will be published by Keio University.
Contact: Dr. Akira Mita, Department of System Design Engineering, Keio University, Tokyo,
mita@sd.keio.ac.jp.

REPORT ON THE 26 SEPTEMBER 2003 TOKACHI-OKI EARHQUAKE, JAPANA strong earthquake (Mw8.0), named the Tokachi-oki Earthquake, occurred at 0450 on 26
September 2003 at Tokachi-oki (southeast offshore of Hokkaido). The maximum peak groundacceleration of 0.99 g (970 gal) was recorded by K-NET and extensive damage was caused tovarious structures including engineered structures.
Rupture Process of the 2003 Tokachi-oki Earthquake Obtained from Strong Motion Data ofK-NET
The Tokachi-oki Earthquake (Mw 8.0), struck Hokkaido in the early morning of 26 September
2003 at 4:50 a.m. local time (JST). Its ground motion was recorded at 655 stations of nationwide
strong motion networks, K-NET and KiK-net. The maximum peak ground motion, 970 gal, wasobserved at station HKD100 and large amplitudes were observed in a wide area of EasternHokkaido.
Data and method
We estimated the rupture process from strong motion data of 13 stations (Figure 1) with multitime linear inversion method. Theoretical waveforms were calculated by the discrete wavenumber
method with a 1-D layered medium. The observed acceleration records were integrated into
velocity and bandpass filtered between 0.02 - 0.2 Hz. We inverted 85 sec of the S-wave portion(from 5sec before to 80 sec after S-wave arrivals).

Figure 1

Estimated slip distribution on the fault plane. Colored circles are thrust typeaftershocks. The star shows the epicenter. Arrows indicate the amplitude anddirection of slip.

Finite fault model
A fault model was assumed as follows,(1) The epicenter determined by JMA (41.7795N, 144.0785E)(2) The focal depth and the strike angle from a CMT solution with F-net records (29 km and 246
degrees)(3) The dip angle and the fault area inferred from the aftershock distributions (20 degrees and140km x 160km).

Results
Figure 1 shows the estimated total slip distribution, which consists of two major slip areas; (a)around epicenter and (b) the north-west part of the fault with the maximum slip of 7.1 m.
Relatively small slip velocity (~ 0.75 m/s) and long slip duration (nearly 13 sec) are obtained atregion (a). This corresponds to the fact that onsets of direct waves were obscure in manyobserved seismograms.
Contributors: *Ryou Honda (ryou@bosai.go.jp), *S. Aoi, *N. Morikawa, **H. Sekiguchi, *T.
Kunugi and *H. Fujiwara (*National Research Institute for Earth Science and Disaster Prevention,**National Institute of Advanced Industrial Science and Technology).
Tsunamis Caused by the Tokachi-oki Earthquake
The Tokachi-oki Earthquake in 2003 generated a series of tsunamis. The main shock occurred at
4:50 (JST) on 26 September. The tsunamis were observed on the Pacific coasts from Hokkaido tothe Tohoku region in Japan. Many researchers including members of PARI conducted tsunami
field survey started at the same day, when the main shock occurred. The highest evidence oftsunami run-up was found at Cape Erimo and it was 4.0m. The tsunami height of 2.5m wasobserved at the tide station in the Tokachi Port at 5:24 (JST) about 30 minutes after the mainshock. After the tsunamis arrived at the coasts in Hokkaido, they propagated along the coasts likeedge waves and a number of tsunami attacked the coasts. At the Kushiro Port, the first tsunami of
1m arrived at 5:06 (JST), the maximum tsunami of 1.2m observed at 9:03 (JST) and a 1mtsunami attacked again at 14:20 (JST). At that time tsunami inundation occurred because thetsunami added to the normal high tide and the resultant sea level became high. At the TokachiRiver, the tsunamis ran up 11km from the river mouth.
Contributor: Takashi Tomita, Head, Storm Surge and Tsunami Division, Marine Environment
and Engineering Department, Port and Airport Research Institute, tomita@pari.go.jp.

Hokkaido
Chiyonoura Fishing Port: 1.9m
Kushiro Port: 1.65 – 1.75m
Otsu Fishing Port:2.65 – 3.40m
Tokachi Port: 2.45 – 2.90m

Figure 2 Tsunami run-up measured by PARI

Photo 1 Evidence of tsunami run-up at
Tokachi Port
Falling Down of Ceiling of Kushiro Airport Terminal Building
The Tokachi-oki Earthquake in 2003 occurred in the early morning on September 26, 2003,
which caused large-scale falling down of departure lobby ceiling of the Kushiro airport terminalbuilding. The Building Research Institute (Building Research Institute) and the National Institutefor Land and Infrastructure Management (National Institute for Land and InfrastructureManagement) surveyed the earthquake damage.
The terminal building (structural steel) was three stories with 19.6 m in total height. Thedeparture lobby was open ceiling and covered by a 9.7 m high ceiling with 36 m in length (northsouth direction) and 18 m in width (east-west direction). The supporting system of the ceiling wasa Japanese traditional one, that is, the 12 mm thick rock wool acoustic board on the 9 mm thickplaster board substrate screwed to the light gage structural steel members was hanged by hanger
rods. The hanger rods were placed every 1.1 m x 0.9 m and every four hanger rods in eachdirection were braced to reduce pendulum displacement.
The three edges (north, south and east) of the ceiling were separated from surrounding structuralelements and only the west edge was rigidly connected to the structure. Due to the pounding of
the ceiling to the west structural frame, a large area of the ceiling fell down. No one was injured
due to the early morning shock.
Contributors: Isao Nishiyama, Chief Researcher, Production Engineering Department, Building
Research Institute, isao@kenken.go.jp and Tadashi Ishihara, Researcher, Building Department,
National Institute for Land and Infrastructure Management, ishihara-t92hd@nilim.go.jp.

Photo 2 Outside view of airport terminalbuilding

Photo 3 Damaged ceiling

Damage to River Dikes
River dikes in Obihiro area including Tokachi river, Urahoro-Tokachi river and Usikubibetsu
river were severely damaged during the earthquake. The total length of the damaged dike adds up
to more than 25 km. Typical layout of the dikes in the area, particularly for the dikes of Tokachi
river, has geometry of 5-10 m wide crest, 4-8 m height and gentle slope angle of 1:5. The
observed damage to the dikes is mostly longitudinal crack and settlement of crests and lateral
spreading of the gentle slopes as shown in Photo 4. The similar damage to the dikes in thisparticular area was observed during the 1993 Kushiro-oki earthquake.
In this area, extremely soft peat soil prevails the ground surface and ground water table are close
to the ground surface. The dikes in this area, which were constructed using sandy soils, havesignificantly settled, causing the base of the dikes penetrated into the foundation soil. The
mechanism and the main cause of the damage to the dikes is presumed to be liquefaction of thedike material blow the ground water table, which is similar to that during the 1993 event.

Contributor: Mitsu Okamura, Senior Research Engineer, Ground Vibration Research Team,
Public Works Research Institute, okamura@pwri.go.jp.

Photo 4 Collapse of slope of Tokachi river dike (right bank, 3.5 km from river mouth)
Dams
Two survey teams were dispatched to Hokkaido between 1st and 3rd October. The objectives ofthat investigation were to check the effects of the Tokachi-oki Earthquake on dams, collect theearthquake data at dam sites and collect other measurement data observed at dam sites before andafter the earthquake. Table 1 shows the dams at which the survey teams visited and the maximum
acceleration recorded at those dams. The inspections by dam owners and our investigation
revealed the following effects on dams; some shallow longitudinal cracks at the crest occurred at
an embankment dam, the amount of seepage flow in the foundation and/or leakage in the dam
body increased temporally at some dams, the turbid seepage flow and/or leakage were observed
just after the earthquake at some dam. The extent of these effects was, however, very small andthere were nothing to be worried about dam safety.
Table 1 Dams investigated and maximum accelerations
Horizontal Maximum Acceleration (gal)**
Base
Crest
Satsunaigawa
G114
1998
69677
Tokachi
R
84.3
1984
43
155
Izarigawa
R
45.5
1980
51
113
Takami
R
120
1983
58
325
Sahoro
G
46.6
1984
82
364
SamaniG
44
1974–
156***Urakawa
G
42.1
1999
103
124
Monbetsu
E
20.8
1971
––
Bisei
GR
47.2
1999
67 (G), 125 (R)
153 (G), 167 (R)
Azuma
R
38.2
1969
––
Mitsuishi
R35
1991
––
Makubetu
E
26.9
During first filling
174
261
Niikappu
R102.8
1974
20276
Iwamatsu
G37.2
1943
72–Kuttari
R
27.5
1987
112196
Horoman No.3
G42.5
1954
––
*
G: Concrete Gravity Dam, R: Rockfill Dam, E: Earthfill Dma, GR: Combined Dam (Concrete Gravity Dam
and Rockfill Dam)** Maximum value in two horizontal directions*** Composed value of two horizontal directions
Dam Name

Type*Height (m)Year of completion

Contributor: Yoshikazu Yamaguchi, Team Leader, Dam Structures Research Team, Public
Works Research Institute, yamaguti@pwri.go.jp.
Highway Bridges
During the Tokachi-oki Earthquake, some significant damages to the highway bridges including
damage to bearings and substructures were developed in the strong motion area. Two types ofdamage are presented here as a representative damage.
Chiyoda Bridge (Photo 5)
Chiyoda bridge was constructed in 1966 and has 15-span simply-supported girder/truss bridgewith total length of 706m. The substructures are wall-type RC columns. The damage wasdeveloped at the mid-height sections of RC columns where some of the longitudinal
reinforcement is terminated. Photo 5 shows the damage of Pier #13 in which the heaviest damage
was found. The cover concrete was spalled-off, and some of the longitudinal reinforcement wasbuckled at the section. The columns was repaired and strengthened by concrete injection and steel
jacketing.
Tokachi River Bridge (Photo 6)
Tokachi river bridge with total length of 926m was completed in 1992. The bridge consists of 3
superstructures with 3-span continuous PC box girders and 3-span PC frame bridge. The
substructures consist of wall-type RC columns and pile foundations. The bridge is located close
to the fault zone where very strong ground motion was observed. The bearings were failed andthe residual displacement of about 70cm in the transverse direction was developed at thecontinuous box girders as shown in Photo 6. Damage to substructures was not found.
The damage patterns observed during the Tokachi-oki earthquake were the usual type including
the damage to bearing, RC columns and expansion joints that were found in the past earthquakes.
However, since the strong ground motion data over 500 to 1000gal acceleration on the groundlevel was observed, further study on the relation between the damage and the strong motion isnecessary.
Contributor: Shigeki Unjoh, Team Leader, Earthquake Engineering Research Team, Public
Works Research Institute, unjoh@pwri.go.jp.

Photo 5 Damage of wall-type reinforcedconcrete columns (Chiyoda Bridge.
Spall-off of cover concrete wasrepaired by concrete injection.)

Photo 6 Damage of bearings and transverse
residual displacement of deck (about70cm) (Tokachi River Bridge)

Damage to Road Embankments
We investigated damage to road embankments from Obihiro City to the coast along the National
Highway Route 38, and we also surveyed the Route 336, which runs along the coast. Theinvestigated area spreads over the Tokachi Plain, and most parts of those highways are low
embankments on soft grounds. The damaged road embankments of the national highways werelarge in number, however the degree of damage was not so conspicuous, comparing to thedamage in the past major earthquakes. The most typical damage was settlement and collapse ofroad shoulder and sidewalk. The cases in which damage extended to roadways were ratherlimited. The principal causes of damage to road embankments may be attributed to soft ground,change in topography or embankment structure and existence of a crossing structure underneath ahighway. No distinct evidence of liquefaction was observed within the scope of reconnaissancesurvey. Typical damage to road embankments is briefly described in the following:
Approach of Toyokoro Bridge, National Highway Route 38
This part of the highway is an approximately 10m high embankment that connects with the dikeof Tokachi River. A longitudinal crack was observed on the slope of embankment, and the roadsurface was settled over approximately 15m long (Photo 7).
Chobushi, National Highway Route 336
This portion of the highway is a half-bank and half-cut. The valley-side of embankment is aswamp, and the groundwater level seemed to be high. The sidewalk was collapsed over more than
100m and the roadway was partially damaged (Photo 8).
Contributor: Keiichi Tamura, Team Leader, Ground Vibration Research Team, Public Works
Research Institute, tamura@pwri.go.jp.

Photo 7 Approach of Toyokoro Bridge,
National Highway Route 38 (Photo byHokkaido Development Bureau)

Photo 8 Chobushi, National Highway Route336

Damage to Port Structures
The major damage of port facilities during the 2003 Tokachi-oki Earthquake is No.4 pier caissontype quay wall (-10m, k=0.2) of Kushiro port moved toward sea 10cm to 20cm and large
settlement (roughly 0.5m) of apron occurred as shown in Figure 3. The reclaimed material iscement treated dredged fine sands (SPT N=10), the PGA at Kushiro port were 575 Gal in EW,
347 Gal in NS and 149 in UD respectively. The key point of the damage mechanism is behavior

of backfill rubbles and cement treated soils during the earthquake as follows, 1) the confiningpressure of backfill rubbles should be suddenly decreased due to movement of the caisson, 2)
then re-arrangement of rubble particles occurred, 3) cement treated fine sands could not follow
the deformation of backfill rubbles, 4) large settlement occurred just behind the caisson body.
During the earthquake, Tomakomai Port was shaken with 70 Gal in EW, 69 Gal in NS and 40 Gal
in UD respectively, long period component of 5-8 second and around 180 seconds duration asshown in Figure 4. The cylindrical oil tank (a diameter of 43m, oil depth of 18m and the natural
period of first mode of sloshing is 7.1 sec) having floating roof burned due to the earthquake.
From the results of back analysis of tank during the earthquake, the maximum uplift of thefloating roof occurred 3m at 48sec in EW and 2.3m at 80sec in NS respectively.
Contributor: Takahiro Sugano, Head, Structural Dynamics Division, Port and Airport ResearchInstitute, sugano@pari.go.jp.
15.20

2.50 4.70

Settlement

20.00
2.0%

CAISSON
LB
H
17.00×14.50×11.60
2.70
-10.0

1.0%

11:1:11.50 1.00 .2

Cement treated fine sands

Rubble6.3

0.90
1 :2-10.10
1:2 1:2 -11.60
2.70(unit:m)

Crack+3.53

0.64

0.50

1.00+3.13
H.W.L +1.50 +1.50
L.W.L ±0.00

0.20
4.30

14.50

1 :2

1.000.70

Figure 3 Cross section of -10m caisson type quay wall at Kushiro port No.4 pierNSEWUD

Figure 4 Strong motion records at Tomakomai port during 2003 Tokachi-oki Earthquake

Damage to Sewer Facilities
Sewer facilities in Obihiro area and Kushiro area were severely damaged during the earthquake.
The amount of damage to sewer facilities is up to 5 billion yen. The observed damage to thesewer facilities is mostly uplift of pipes and manholes and settlement of road surface above thedamaged pipes as shown in Photo 9. The damaged pipes were constructed by the open-cut
method, in which sandy soils were used for backfill. The similar damage to the sewer pipes inKushiro city and Kushiro town was observed during the 1993 Kushiro-oki earthquake and the1994 Hokkaido-Toho-Oki earthquake. The most of the damaged pipes were located in wetland,
where extremely soft peat soil prevails the ground surface and the ground water levels are shallow.
Liquefaction of the backfill soil blow the ground water level was considered to be a major causeof the damage, while amplification of the ground motion at the peat layer was considered to affectthe extent of the liquefaction of backfill soil.
Contributor: Tetsuya Sasaki, Senior Research Engineer, Ground Vibration Research Team,
Public Works Research Institute, t-sasaki@pwri.go.jp.

Photo 9 Ejected manhole and settlement of road surface
Related Web Sites
Building Research Institutehttp://iisee.kenken.go.jp/special/20030926japan.htm
National Research Institute for Earth Science and Disaster Prevention
http://www.k-net.bosai.go.jp/k-net/index_en.shtml
http://www.kik.bosai.go.jp/kik/index_en.shtml