Preliminary Reconnaissance : The 2004 Mid Niigata Prefecture Earthquake
also available in Japanese.
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Notice : This is a preliminary report. Please note that this
might include erroneous information or misunderstanding. Following
report is made based on the opinion of the author, Riki Honda, and it
does not necessarily reflect those of the Disaster Prevention Research
Institute, Kyoto University.
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0.1 th edition : 2004-10-28
0.0 th edition : 2004-10-27
Let us emphasize that our report is preliminary and does not cover all
serious damages. There have been many strong aftershocks and they are
worsening the situation. For further information, refer to the
information provided by newspapers etc, too.
On October 23, 2004, at 5:56pm (8:56 p.m. GMT), a huge earthquake with
a magnitude of 6.8 in JMA Magnitude (Japan Meteorological Agency
Magnitude) hit the Mid Niigata area in Japan. In Ojiya City, Niigata
prefecture, Shindo (JMA seismic intensity scale) hit 6+ (ouf of 7).
The JMA named the earthquake "The Mid Niigata Prefecture Earthquake in
2004." As of the morning of October 27th, thirty-one were killed,
more than 2,200 were injured and more than 100,000 people were in
evacuation, according to the report.
We departed for Niigata 6 hours after the earthquake and started our
preliminary site investigation 12 hours after the earthquake had
occurred. Following is a brief report of our reconnaissance.
Note : figures in [ ] denote pictures listed below each
- Date : October 23rd to 25th. (Reconnaissance was held on 24th.)
- Members :
- SAWADA, Sumio (Associate Professor, DPRI, Kyoto University) : Leader of the team.
- TAKAHASHI, Yoshikazu (Assistant Professor, Dept. of Urban Management, Kyoto University.)
(His report is also available here, but only in Japanese.)
- HONDA, Riki (Assistant Professor, DPRI, Kyoto University.)
- Kashiwaza City and Oguni Town :
We arrived at Kashiwazaki City in the early morning of October 24th,
2004. The area was still suffering from blackout and most traffic
lights were not working. The store facing the Route 8 was in business
but without electricity supply.
On the Route 291, between Kashiwazaki City and Ojiya City, some manholes
rose out of the ground. In the Nanokamachi Town, the slope collapsed
, and road surface subsided inequally, causing gaps as high as
one meter [2105, 2106, 2110]. There were many similar road subsides
in many places in Ojiya City. Landslide occurred on the slope on the
south of the route . Liquefaction induced the sand boiling at
the foot of the slope .
- Ojiya City (near the Ojiya Exit of Kan-etsu Expressway)
The Sakuramachi Bridge, the bridge of Kan-etsu Expressway, striding
over the Route 291, had its girder collide lightly with the top of the
abutment . The liquefaction-induced sand boil left its trace
 at the foot of the pier. Apparently, no damage was observed
with the support .
At the toll gate of Ojiya Exit, which was closed due to the damage of
the Kan-etsu expressway, the road surface had minor damage .
The house in front of the gate suffered severe damage. The first
(ground) floor was totally crushed [2121, 2122] and its rock-made
fence was destroyed . Some other houses and buildings in the
neighborhood were also damaged. For example, a house had its
ceramics-made roofing tiles ("Kawara" in Japanese) severely
Almost all tomb stones fell down [2117, 2118] in the garden of the
stone store located about 100m in the west of the Sakuramachi Bridge.
Different stones fell in different directions and no clear trend was
seen in the falling direction, which suggests that the ground motion
did not exhibit strong directivity (in this site). The store itself
was not severely damaged. It indicates that the ground motion might
have been large in the high frequency component.
- Ojiya City (incl. Motomachi Town, Honmachi Town and Wakaba District)
Several manholes were raised due to the liquefaction of the
surrounding ground [2147, 2149]. (We were hit by quite a strong
aftershock when we were studying these manholes. Horrifying
experience.) The liquefaction caused the tilt of the electric poles
 and traffic lights  in several places. The cut electric
cable put the car in the trouble . Another car was left at an
awkward position because the ground subsided leaving the manhole
In Hon-machi Town, the Futaara-Jinja Shrine had its gates and other
ornaments severely damaged. [2194, 2195]
The route 291 was blocked because of the gap of as high as 1m 
and it prevented us from visiting Kawaguchi City.
- K-Net Ojiya Observation Station
K-net is the strong observation network covering the whole nation of
Japan with high density. For further information, visit their website. The peak
acceleration recorded at the Ojiya observation station  (map) exceeded 1,500 gal and its strong motion
has the JMA seismic intensity of 7, the severest level.
The observation site is in the middle of the flat area. There are a
school ground in the north-west , a small paddy field in the
south-west , and a school gym in the north-east direction.
Judging from the fact that it is next to the paddy field, the ground
might be quite soft, which could have affected the strong motion records.
Near this site, some manholes were raised [2201, 2205]. There was a
car left upside-down , near one of the raised manholes. (There
was a scarce track on the road connecting the car and the manhole. I
guess that the car hit the raised manhole and turned over.)
In the vicinity of this site, some houses seemed to be undamaged
[2206, 2209] and some were damaged [2210, 2203]. The Jigenji temple,
which is also located near the observation site, was damaged [0089,
0090] and most of the tomb stones in the temple garden fell down.
Nagaoka Ojiya City
(neighborhood of the Nagaoka Ojiya Station)
(Corrected. Thanks to Prof. Shimomura, Nagaoka University of Technology.)
In the mall near the
Station, the surface of the road was not severely damaged .
However, many stores suffered various types of damage, including pier
collapse  and fall-off of the wall . Most of the shops
that had no external damage also suffered various damage inside, such
as scattering of the goods, or fall of the shelves. (We did not take
pictures of the inside of the damaged houses or stores, to pay respect
to the feeling of the owners.)
- Shinkansen, or Super Express Train, Derailed near Tokamachi Town.
The Super Express Train (Shinkansen) derailed due to the strong shake
of the earthquake.
There were some damages on the piers located 10 to 100m away in the
north direction from the derailed point [2183, 2185, 2186, 2188, 2189,
2191]. The tag on the pier says their construction started in 1977
and finished in 1979.
Liquefaction occurred at the foot of the piers which were 10 to 20m
away in the north direction from the above-mentioned piers, and the
boiled sand reached 70 to 90cm [2162, 2159, 2160]. The gap between
the pier and the ground indicates the large displacement the pier
experienced [2157, 2158, 2161].
On the top of the wall-type pier, which was just under the derailed
cars, there was a fall-off of concrete pieces.
Although the piers were damaged as described above, I believe that
these were not the reason of the derailing of the train. Their
performance was well acceptable because they survived such a strong
earthquake with relatively small damage.
- Ojidaya Ohashi Bridge
The Ojidaya Ohashi Bridge on the Route 17, striding over the Shinano
(River), had one of its piers damaged, the second from the south-east
end . The concrete fell off on the side facing the north-east
to south-east direction . The X-shaped crack was found on the
south-west side . The gap between lateral bars was about 20cm
- Embankment near the Yoita Bridge
The embankment near the Yoita bridge had several cracks which were 10
to 40cm wide, 1.5 to 2.0m deep [2215, 2217], and several tens of
meters long . Some part of the embankment settled and lost its
Thank you for reading up to here. If you have some comments,
corrections or questions, please make contact to : . Thank you.
The reconnaissance was conducted under the great leadership of
Prof. Sawada, (DPRI, Kyoto Univ.) and with great support of
Prof. Takahashi (Dept. Urban Management Engng., Kyoto Univ.). They
also contributed some pictures shown above.
-- Riki Honda. All rights reserved. 2004.