ICUS NEWSLETTER
International Center for Urban Safety Engineering

Institute of Industrial Science
The University of Tokyo

SPECIAL ISSUE
January 2005

International Center for
Urban Safety Engineering

Central Part of Niigata Prefecture, Japan
was Striken by M 6.8 Earthquake on October 23, 2004
By
Kimiro MEGURO
A magnitude 6.8 earthquake, with a focal depth of 13 km, stroke the central part of Niigata
Prefecture, Japan, at 17:56 on October 23, 2004. Due to this earthquake, strong groundmotions up to 1.7 g were recorded. Forty people were killed and 2,800 houses collapsed or wereheavily damaged. Many landslides and liquefied sites were observed. Civil infrastructure suchas highway facilities, bullet train system, and many other lifeline systems were also damaged.
ICUS dispatched reconnaissance teams to the affected sites several times to investigate various
damage due to the earthquake. This is a quick report summarizing these site surveys.
On October 23, 2004, at 17:56, amagnitude 6.8 earthquake, with a
focal depth of 13 km, stroke thecentral part of Niigata Prefecture.
The Japanese Meteorological
Agency (JMA) named this event the
2 0 0 4 M i d - N i i ga t a P r e f e c t u r eEarthquake. Due to this earthquake,strong ground motions with JMA
seismic intensity, I J M A , 7, whichcorresponds to the highest intensity
in this scale, were observed. This is
the first time since the JMA changed
its intensity def inition, from ahuman perception based definition
to an instrumental observation based
one, that this intensity was observed.
Peak ground accelerations up to
1.7g and peak ground velocities up
to 133 kines were observed. These

are much higher than those of theground motion recorded during the
1995 Kobe Earthquake. IJMA 7 wasobserved at Kawaguchi town andOjiya city. Yamakoshi village andOguni town experienced I JMA 6+
while I J M A 6- was obser ved at
Nagaoka city, Tookamachi city,
Tochio city, Koshiji town, Mishimat ow n , a n d H o r i n o u c h i t ow n .

(Urasa-agaoka, Joetsu-Shinkansen, Nagaoka city, 25/10/2004)

The bullet train derailed for the first time since it started operations in 1964.

page 2

Very strong ground motion was observed...
Number and intensity of aftershocks as of December 17, 2004
by the Japan Meteorological Agency

Distribution of JMA Intensities atthe earthquake hit area during themain shock on October 23, 2004,
5:56PM
Hirokami village, Sumon village,
Irihirose village, Kawanishi town,
Nakasato town, Kariwa town, and ave r y w i d e a r e a f r o m To h o k u(Northeast part of Japan) to Kinki(Mid-west part of Japan) registered
IJMA, ranging from 1 to 5+. Becauseof this earthquake, 40 people were
killed and 4,500 were injured.
This earthquake was the firstevent in which the derailment of abullet train was observed since they
entered service in 1964. Fortunately,
no fatal victims were reported. This
service line is not very congested
and at the time of the earthquake
only one of the lanes was being used.
One of the most impor tantcharacteristics of this earthquake ist h e h u g e n u m b e r o f l a rg e
aftershocks. On the same day of themain shock, three aftershocks withmagnitude 6 or more stroke. The
first occurred at 18:03, just sevenminutes after the main shock, andhad a M6.3 and a maximum recorded
IJMA 5+. Eight minutes after, at 18:11,
a M6.0 event with a maximum
recorded IJMA 6+ was felt. At 18:34,
a M6.5, maximum IJMA 6+ stroke thesame region. Beside these three
events, three more with IJMA 6+ werefelt on October 23, 19:45, M5.7,
maximum IJMA 6-, on October 27,
10:40, M6.1, maximum IJMA 6-, andon November 8, 11:15, M5.9, IJMA 5+,
as shown in the table at the top of
this page. This table shows thenumber of aftershocks and thecorresponding maximum recorded

ICUS Newsletter SPECIAL ISSUE

intensities. Because of a large
number of aftershocks, landslides
and structural damage graduallyp r og r e s s e d a n d c o n s e q u e n t ly
affected the life of the people livingin the area.
The statistics of human casualties
and structural damage are
introduced in the table on the next
page. Because of this earthquake,
40 people were killed, 9 of them due
to structural collapse. The othervictims died for other reasons suchas shock, exhaustion, stress, and theeconomy class syndrome. The latter
was caused by the long periods thatpage 3the residents had to sleep in theircars, in uncomfortable positions,because of the insecurity of theirhouses and their fear due to the huge
number of aftershocks. The numberof collapsed, moderately damaged,
and slightly damaged houses were
2,800, 10,600, and 88,500,
respectively.
The ground motion due to the 2004
Mid-Niigata Prefecture Earthquake
was very large. Peak groundaccelerations (PGA) up to 1.7g andpeak ground velocities (PGV) up to
133kines were obser ved. The
response spectra depicted below
shows the earthquake high power inthe high frequency, or short period,
range, from 0 to 1sec. Response
accelerations over 6,000 Gals areobserved. This is much higher thanthe power of the ground motion
during the 1995 Kobe Earthquake
for a similar frequency range.
However, on a longer period range,from 1 to 2 sec, the Kobe groundmotion power was higher. The
frequency content characteristics oft h e M i d - N i i ga t a P r e f e c t u r eEarthquake may partially explain therelatively small structural damage
observed as compared to that during
the Kobe Earthquake. However,other reasons such as the highstructural strength of the dwellings
should also be taken into account.

Due to the severe winter and hugesnow fall that is common in this area,
houses are built with small openings,
to keep them warm, and robust
foundations and structural elements,
to resist the snow weight. Thesef e a t u r e s i n c r e a s e t h e ove r a l l
structural strength. It is not surprise
to observe that most of the collapsed

houses were either old or presented
soft stories in the 1st floor were open
spaces were allocated. On the other
hand, the extremely high power inthe high frequency range may explain
the huge number of rock falls andlandslides, non-tensile material
structures, which are more affectedby this type of excitations.

Casualties, damaged buildings, and fires
caused by the earthquake at different prefectures(as of December 24, 2004 by Fire and Disaster Management Agency)(Kawaguchi, Kawaguchi town, 27/10/2004)

Graveyard at Kawaguchi town where IJMA was 7

Strong ground motion recordedat the K-Net Ojiya station(PGA: 1500.7gal, PGV: 133.4kine, IJMA: 6.73)

Response spectra corresponding to the 2004 Mid
Niigata Prefecture and the 1995 Kobe Earthquakes

ICUS Newsletter SPECIAL ISSUE

page 4Landslides and rock falls blocked roads...
The 2004 Mid-Niigata Prefecture
E a r t h q u a ke o c c u r r e d i n a
mountainous area which was hit byheavy rainfalls and typhoons justprior to the earthquake occurrence.
These previous events saturated andloosen the soil, and therefore whenthe earthquake stroke the mountainslopes where particularly vulnerable.
For this reason, the geotechnicalrelated damage was widespread andmuch more considerable than the
structural damage.

Geotechnical related damage to people and buildings.
(as of November 26, 2004
by Ministry of Land, Infrastructure and Transport)

Route 291 which connects Ojiya to Yamakoshi was blocked. (Yokowatashi, Ojiya city, 26/10/2004)

Route 291 which connects Ojiya to Yamakoshi was blocked. (Kawai, Ojiya city, 9/12/2004)

ICUS Newsletter SPECIAL ISSUE

page 5(Myoken, Nagaoka city, 25/10/2004)

Huge landslide on the riverside of Shinano River
View from the riverside opposite to the landslide(Myoken, Nagaoka city, 25/10/2004)(Myoken, Nagaoka city, 24/10/2004)© JAPAN SPACE IMAGING CORPORATION

Satellite view of the area before (left) and after (right) the earthquake(Myoken, Nagaoka city, 26/10/2004)

View of the landslide from the riverside where it occurred

ICUS Newsletter SPECIAL ISSUE

page 6Landslides also blocked riverbeds
forming natural dams and causing flooding...

(Higashi-Takezawa, Yamakoshi village, 24/10/2004)(Higashi-Takezawa, Yamakoshi village, 29/10/2004)© JAPAN SPACE IMAGING CORPORATION

Satellite image of the area one (left) and six (right) days after the earthquake(Higashi-Takezawa, Yamakoshi village, 24/10/2004) KOKUSAI KOGYO CO., LTD.

Aerial view of the landslide affcted area

ICUS Newsletter SPECIAL ISSUE

page 7

(Tanesuhara, Yamakoshi village, 24/10/2004) KOKUSAI KOGYO CO., LTD.

(Iketani, Yamakoshi village, 24/10/2004) KOKUSAI KOGYO CO., LTD.

Aerial view of the landslide affcted area

ICUS Newsletter SPECIAL ISSUE

page 8(Uragara, Ojiya city, 26/10/2004)

House turned into dam due to a landslide that blocked the river flowing next to it before the earthquake(Uragara, Ojiya city, 26/10/2004)

Uragara, Ojiya city was flooded due to over flowed water from the dam shown in the photo on the top of this page.

ICUS Newsletter SPECIAL ISSUE

page 9Liquefaction induced severe damage...
Numerous manholes uplifted by theincrease in the pore water pressure
associated with liquefaction induced by
the earthquake(Wakaba, Ojiya city, 27/10/2004)(Katada-cho, Nagaoka city, 29/10/2004)

In the left photo, the concrete belt
along the centerline of the road is asnow melting water system. Thissystem is widely used in the affectedarea and together with other lifeline
systems, it was also severely damaged
due to liquefaction.
(Kawaguchi, Kawaguchi town, 27/10/2004)

The photo on the right shows a temporary
snow melting system prepared for winter.
(Kawaguchi, Kawaguchi town, 09/12/2004)

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page 10

Weak houses collapsed...
B e c a u s e o f s eve r e w i n t e r
condition in the affected area, suchas cold temperature and heavy snow
fall, houses are built with small
openings, to keep them warm, androbust foundations and structuralelements, to resist the snow weight.
The roofs are made of light materials
to prevent snow accumulation.
Furthermore, due to the weather
conditions in the area, there is lessdeterioration of wooden structures(Kawaguchi, Kawaguchi town, 27/10/2004)(Kawaguchi, Kawaguchi town, 27/10/2004)(Kawaguchi, Kawaguchi town, 27/10/2004)

ICUS Newsletter SPECIAL ISSUE

page 11...but, new strong houses remained intact.
due to termite attack. These features
increase the overall structural
strength against earthquake motion.
Most of the collapsed houses
were old and had soft first story,
without enough walls, used forparking or shop. Relatively new andtypical houses, constructedconsidering the winter weather
condition in the affected area,
remained intact even at the locations
where very strong ground motion
was recorded.

(Kawaguchi, Kawaguchi town, 07/12/2004)(Kawaguchi, Kawaguchi town, 27/10/2004)(Shimojima, Horinouchi town, 26/10/2004)

ICUS Newsletter SPECIAL ISSUE

page 12

Bullet train derailed and its service
was disrupted...

(Urasa-Nagaoka, Joetsu-Shinkansen,
Kawaguchi town, 29/10/2004)

A bullet train viaduct pillar with little transverse reinforcement
failed in shear.

The 2004 Mid-Niigata
Prefecture Earthquake was the firstevent in which the derailment of abullet train, Shinkansen in Japanese,
was observed since they enteredservice in 1964. Fortunately, thisservice line is not very congested
and at the time of the earthquake
only one of the lanes, the one boundfor Niigata, was being used. No fatal
victims were reported. If two trains
had been r unning in opposite
directions when the earthquake
stroke, most likely the consequences
would have been more severe. The
photos show damage to the pillars of
the bullet train viaduct. At several
columns, concrete cover spalling
was observed at the points where a
portion of the longitudinal rebars
were cut. On others, the few amountof transverse reinforcement caused
column shear failure.
The Urgent Earthquake Detection
and Alar m System, UrEDAS,
system, whose objective is to stoprunning bullet trains before the major
earthquake wave reaches them, wasin operation during this earthquake.
This system is very useful when the
distance between the epicenter andthe running train is long enough so

Bullet train viaduct pillars
exhibited concrete spalling at
the sections where longitudinal
rebars were cut.
(Urasa-Nagaoka, Joetsu-Shinkansen, Kawaguchi town, 26/10/2004)(Urasa-Nagaoka, Joetsu-Shinkansen, Nagaoka city, 25/10/2004)

The bullet train derailed for the first time since it started operations in 1964.

ICUS Newsletter SPECIAL ISSUE

page 13...other train
facilities were also
disrupted.
that the alerting signal arrives before
the earthquake motion. However,when the train is too close to theepicenter, as in this event, the
UrEDAS system cannot accomplish
its objective.
Not only the bullet train but alsol o c a l l i n e s we r e d i s r u p t e d .
Landslides blocked railways,
embankments settled and left
railways hanging, and pillars
constructed according to oldstandards failed.

(Echigo-Kawaguchi-Uchigamaki, Iiyama-line, Kawaguchi town, 29/10/2004)

Pillars constructed according to
old standards failed.

Embankments settled and left
railways hanging.
(Echigo-Kawaguchi-Uchigamaki, Iiyama-line, Kawaguchi town, 29/10/2004)(Kita-Horinouchi-Echigo-Kawaguchi, Joetsu-line, Horinouchi town, 26/10/2004)

Railway facilities were damaged at many locations by landslides.

ICUS Newsletter SPECIAL ISSUE

page 14Highways and roads were damaged...

(Ojiya-ohashi bridge, Route 17, Ojiya city, 26/10/2004)

A bridge pillar suffered concrete spalling at the location where the longitudinal rebars where
discontinued and where there was a drastic change of the pillar cross section.

(Ojiya-Tokamachi, Route 117, Ojiya city, 26/10/2004)

Settlement of the bridge abutment caused damage to the bridge access section.

ICUS Newsletter SPECIAL ISSUE

page 15

(Horinouchi-Echigo-Kawaguchi, Kanetsu Expressway, Horinouchi town, 24/10/2004) KOKUSAI KOGYO CO., LTD.

(Ojiya-Yamakoshi, Route 291, Ojiya city, 26/10/2004)

Geotechnical related damage caused disruptions at several locations
along highways (top) and national roads (bottom).

ICUS Newsletter SPECIAL ISSUE

page 16

Lifelines were disrupted...
Another feature of the MidNiigata Prefecture Earthquake is thelarge number of evacuees if theextent of the structural damage isconsidered. The main reason fort h i s i s t h e l a rg e n u m b e r o f
aftershocks, which caused 100,000
people to flee to evacuation centers.
The graph below shows that after
lifelines were restored, the numberof evacuees dramatically decreased.
The city with the largest number of
evacuees was Nagaoka.
As mentioned in the previous
paragraph, this earthquake evacuees
were people who flee to evacuation
centers due to fear of theaftershocks and lifeline disruption.
After these factors were eliminated,most of them were able to promptly
return to their homes. During theKobe earthquake, evacuees werepeople whose houses collapsed andtherefore had no place to go. As
result, the earthquake indirect
victims were numerous. Thisphenomenon will most likely not be
obser ved for the Mid-Niigata
Prefecture Earthquake.

The Mid-Niigata
Prefecture Earthquake
also put in evidence theimportance of
coordination among
lifeline recovery
activities for efficient
recovery operations.

(Misawa, Nagaoka city, 01/11/2004)
THE JAPAN GAS ASSOCIATION

Gas pipe line was filled with leaked waterfrom damaged or under reparing water supply system

Relation between number of evacuees and recovery
ratio of lifeline system in Nagaoka city

ICUS Newsletter SPECIAL ISSUE(Echigo-Kawaguchi Station, Kawaguchi town, 30/11/2004)
NOMURA RESEARCH INSTITUTE, LTD.

Damage to power supply system

page 17... but life continues in the affected areas

Quick inspection of buildings
was carried out to determine
damage levels. Seals - red,
yellow, and green, in order ofdamage severity - were posted
accordingly.
(Honcho, Ojiya city, 27/10/2004)

A center for collection of reliefmaterial sent to the affected area
(Tamugiyama Branch of Higashii-Kawaguchi
Nursery, Kawaguchi town, 07/12/2004)

A disaster relief operation centerat Nagaoka city hall
(Nagaoka city hall, Nagaoka city, 07/12/2004)

ICUS Newsletter SPECIAL ISSUE

page 18

Life of the victims in the affected areas

Portable kitchen
facilities prepared by
Self Defense Force(Kawaguchi, Kawaguchi town, 07/12/2004)

Tents prepared by
Self Defense Force(Asahi-cho, Ojiya city, 07/12/2004)

Temporary housing
for the people
displaced by theearthquake was set
up before the arrivalof the winter season.
(Tamugiyama, Kawaguchi town, 07/12/2004/)

ICUS Newsletter SPECIAL ISSUE

page 19

Geographic Information System greatly
contributed for damage assessment,
quick recovery and reconstruction activities
In the aftermath of the Mid-Niigata Prefecture
Earthquake, Geographic Information System, GIS, waseffectively used to support relief operations. GIS databases
were fed with information of building damage, landslides,
road disruption, refugee centers, relief operations, etc.
Location, characteristics, photos, etc. were easily accessed
through the INTERNET. Cooperation agreements among
national and local governments, academic institutions andthe private sector were established to provide assistanceon damage assessment evaluation and recovery/
reconstruction efforts.

(http://chuetsu-gis.nagaoka-id.ac.jp/)

GIS database was quickly set to assist the relief operations.

ICUS Newsletter SPECIAL ISSUE

page 20
Editor’s Note
The 2004 Mid-Niigata
Prefecture Earthquake wascharacterized by high seismic
intensities and a large number ofaftershocks. In spite of this, theobserved structural damage wasrelatively minor. This is clearly
showing us that structural strength is
the key issue to reduce overall
earthquake damage. Obviously,
other issues, which have not beenpreviously discussed, such as the
economy class syndrome, wereobserved. However, if the structural
damage would not have been so
minor, these issues would have notbeen highlighted.
Because the stricken area wasmountainous and huge number oflandslides occurred, many areas andits residents were isolated. Under
these circumstances, the use ofhelicopters proved to be essential. In
the future, similar situations will be
faced in mountainous areas andtherefore we should device
procedures to deal with them.
Another lesson learnt from thisearthquake is related to how to
perform recovery activities when asevere winter season is very close to
the earthquake occurrence. In thiscase, there is a very short time period
to perform reconstruction activities
and furthermore, heavy snow loads
acting on already damaged structures
are enough to cause their collapse. In
the case of the Mid-Niigata Prefecture
E a r t h q u a k e , a l l re c ov e r y /reconstruction activities have been
postponed until spring. Up to thattime, how to maintain the remaining
structures and how to prevent moredamage needs to be addressed.
Lifeline recovery, especially the water
snow melting system, which iscurrently stopped, should also begiven careful consideration for future
events. As observed during the Kobe
Earthquake, coordination among theentities in charge of repairing different
lifelines was essential for an efficientand prompt service restoration.
Another point that needs to beaddressed is the issue of housedamage certificates. According to thecurrent system in Japan, the authority
in charge of emitting damage

International Center for Urban Safety Engineering, ICUS
Institute of Industrial Science, The University of Tokyo
4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
Tel: (+81-3)5452-6472, Fax: (+81-3)5452-6476
E-mail:icus@iis.u-tokyo.ac.jp
http://icus.iis.u-tokyo.ac.jp/

International Center for
Urban Safety Engineeringcertificates is different from the onethat provides the f inancial
compensation to the house owner. The
amount of the compensation isdecided according to the damage
certificate. Because two entities are
involved in this process, it is difficult
to conceal their approaches. This may
eventually lead to an unrealistic large
number of highly damaged structures,
which are eligible for huge financial
compensations. Because damage waslimited during the Mid-Niigata
Prefecture Earthquake, this problem
did not cause a huge burden to thegovernment. However, if a larger
scale event strikes Japan, the financial
compensation system may collapse.
The photos shown in this special
issue were taken by members of ICUS
unless otherwise stated. The
institutions that kindly granted
permission for using their materials
are gratefully acknowledged.
Dr. Paola Mayorca, Post Doctoral
fellow, and Mr. Shinya Kondo, Ph.D
candidate of Meguro research groupof ICUS contributed to the
preparation of this special issue.
(K. Meguro)

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