reconnaissance in chiba after “the 2011 off the pacific coast of tohoku earthquake” mohsin u....
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Reconnaissance in Chiba after “Reconnaissance in Chiba after “The 2011 off the Pacific coast of Tohoku Earthquake”The 2011 off the Pacific coast of Tohoku Earthquake”Mohsin U. Qureshi and Ikuo Towhata Mohsin U. Qureshi and Ikuo Towhata
Department of Civil Engineering, The University of Tokyo, Tokyo, Japan. Department of Civil Engineering, The University of Tokyo, Tokyo, Japan.
1. Introduction1. IntroductionA reconnaissance was made in Chiba (prefecture
lies next to Tokyo in NE) after a massive
earthquake of magnitude 9.0 on 11 March 2011,
14:46 JST, off the Pacific coast of the northeastern
part of the Japanese Archipelago which also raised
a devastating tsunami. Epicenter is located at
38.322°N, 142.369°E, which is 373km NE of
Tokyo. This magnitude places the earthquake as the
fourth largest in the world since 1900 and the
largest in Japan since modern instrumental
recordings began 130 years ago.
2. Tsunami2. Tsunami
5. Concluding remarks5. Concluding remarks
CONTACT: Mohsin Usman Qureshi (Ph. D. Student)Geotechnical Engineering Laboratory, Department of Civil Engineering, The University of Tokyo7-3-1, Hongo, Bunkyo-ku, 113-8656, Tokyo, JAPAN , Email: [email protected]
4. Ground displacement4. Ground displacement
6. References6. References
Tsunami warning
followed the
earthquake whose
height exceed 10m
in northeastern
coasts of Japan.
Chiba was also
highly affected by
the tsunami.
As a consequence of liquefaction, marks of sand
boils, subsidence, uplifting of manholes and ground
cracks were observed. Infact the shaking was not
too strong but its frequency was too high.
Widespread liquefaction in some areas can be
inferred to; 1) located on reclaimed land, 2)
historically rivers were flowing through that area,
3) shallow ground water table. Pictures shown here
were taken on 13th and 14th of March, 2011
A huge disaster left with directions to improve our
efforts in tackling with natural disaster. Survey was
conducted with objectives to collect information
about the type of damage with respect to the
location of area. The authors focused on the
following points;
• Tsunami devastation in coastal areas
• Widespread liquefaction on reclaimed land
• Embankment subsidence along the river
“A Bridge over another Bridge”
Tsunami warning
CHIBA
M9.0
Issued on 11 March 2011
Coastal protection remained safe as compared to roads
Water level
Coastal protections are designed to resist wave action
3. Liquefaction3. Liquefaction
Location map of Chiba
TOKYO
Tokyo Disneyland
M9.0
CHIBA
NARITA AIRPORT
Liquefaction Embankment subsidence Tsunami Damage
0km 105
“Devastation of coastal town”
Force of Tsunami is higher when it flows back to the sea
The “Otori” performed well like the piers of bridge
Scenes at harbor and beach
Ships floated over the docks Partially submerged ship in shallow waters near the beach
April 3-8, 2011 Vienna, AustriaApril 3-8, 2011 Vienna, Austria 東京大学東京大学
• Japan meteorological agency http://www.jma.go.jp/jma/indexe.html• April Issue of ISSMGE Bulletin 2011http://www.issmge.org/web/page.aspx?refid=430
After such an extreme experience of disaster, future research of Geotechnical Engineering has been provoked, few remarks are as follow, however many to come;
• Revision in Ground improvement techniques as a countermeasure against liquefaction.
• Extreme scenario of tsunami should be envisioned for urbanization along the coast.
Sand boils
Thickness at the origin: 15-20cm
Traces of seashell in boiled sand
Unforeseen uplifting of man holes near Disneyland
2m
1m
Few signs of liquefaction near Narita Airport area
0.5m
Sand boils
An interesting example of continuous horizontal
ground displacement was observed on the levees of
Tone River. The beams supporting the side walls of
a drain running parallel to the levee were failed due
to the subsidence of levee as illustrated below. The
hydraulic structures along the river showed no
damage.
Ground Displacement along southern levee of Tone River
1m
Continuous