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M9.0. CHIBA. Issued on 11 March 2011. Continuous. Tsunami warning. 1m. Traces of seashell in boiled sand. M9.0. CHIBA. TOKYO. NARITA AIRPORT. “A Bridge over another Bridge”. Thickness at the origin: 15-20cm. Sand boils. Tokyo Disneyland. 0 km. 5. 10. Water level.
Issued on 11 March 2011
Traces of seashell in boiled sand
“A Bridge over another Bridge”
Thickness at the origin: 15-20cm
Ground Displacement along southern levee of Tone River
Location map of Chiba
Coastal protections are designed to resist wave action
Coastal protection remained safe as compared to roads
Force of Tsunami is higher when it flows back to the sea
Unforeseen uplifting of man holes near Disneyland
The “Otori” performed well like the piers of bridge
“Devastation of coastal town”
Partially submerged ship in shallow waters near the beach
Ships floated over the docks
Few signs of liquefaction near Narita Airport area
Scenes at harbor and beach
Reconnaissance in Chiba after “The 2011 off the Pacific coast of Tohoku Earthquake”
Mohsin U. Qureshi and Ikuo Towhata
Department of Civil Engineering, The University of Tokyo, Tokyo, Japan.
April 3-8, 2011 Vienna, Austria
4. Ground displacement
A 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.
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
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.
5. Concluding remarks
CONTACT: Mohsin Usman Qureshi (Ph. D. Student)
Geotechnical Engineering Laboratory, Department of Civil Engineering, The University of Tokyo
7-3-1, Hongo, Bunkyo-ku, 113-8656, Tokyo, JAPAN , Email: firstname.lastname@example.org