2017 Volume 70 Pages 25-34
The 2011 off the Pacific coast of Tohoku Earthquake occurred on March 11, 2011, and caused enormous damage on Japan. The Tokyo Bay and the Tone River downstream regions were widely damaged by liquefaction. In this research, we carried out a surface wave survey at the Tone River northern coast area in Katori, Chiba, Japan which belongs to the Tone River downstream region, and obtained the S-wave velocity (Vs) structure down to about 30 m below the ground surface. As a result, the subsurface of the survey area is classified into three layers; the sandy surface layer which has relatively high Vs, the low Vs silty layer, and the high Vs sandy basement layer. Using the obtained Vs distribution, we investigated whether 1.5 m below the ground surface of the survey area would liquefy or not when it will be shaken by the same scale earthquake as the 2011 off the Pacific coast of Tohoku Earthquake. As a result, it was presumed that liquefaction would not occur on most of the survey line. Moreover, the estimated domains where liquefaction occurred correlated well with those estimated by geological surveys and also well with marshy area distributions in Meiji Era. These results showed that liquefaction resistance estimation using Vs distribution was useful.
