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| | Abstract | | The Tokyo Bay and Tone River downstream regions were seriously damaged by liquefaction caused by the off the Pacific coast of Tohoku Earthquake occurred on March 11, 2011. Most of the damaged areas by liquefaction have been recovered by repair work. However, since soils have not been improved, it is thought that the groundwater level now is almost same as that before an earthquake disaster. If the groundwater level is the same and this area will be again hit by the large-scale earthquake, the liquefaction damage may happen again. In such a case, the groundwater-level lowering method is sometimes performed for reducing liquefaction damage by lowering the groundwater level by forced drainage. When such a method is performed, the effective method for checking its effect is required. If the physical property change caused by groundwater level change is detectable, the geophysical exploration with non-contact and the non-destructive feature is the optimal for monitoring of the groundwater-level lowering method. Accordingly, this research considered focused on the S-wave velocity change caused by the groundwater-level-lowering-method. |
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