The east Japan great earthquake struck from the northeast of Japan to the whole area of Kanto with a magnitude of 9.0 and maximum seismic intensity of 7 on March 11, 2011. Seismic hazard such as liquefaction has especially affected a number of detached houses. From the results of in-situ investigation, the authors found that the liquefaction damage is apparently concentrated on newly reclaimed land, and closely related to the thickness of weak soil, soil types and groundwater level. In addition, where ground improvement method had been already carried out, damage to buildings, facilities and detached houses located even in the newly reclaimed land were found to be very small. In order to predict and prepare for liquefaction, information of the soil classification and groundwater level as well as soil strength and density are important parameters, and these kinds of information also become necessary for considering the rational countermeasures to liquefaction.
The east Japan great earthquake struck from the northeast Japan to the whole area of Kanto with a magnitude of 9.0 and maximum seismic intensity of 7 (Kurihara city, Miyagi Prefecture) on March 11, 2011. Seismic hazards such as tsunami and liquefaction have especially affected detached houses. At present, in spite of announcement #1113 of the Ministry of Land, Infrastructure, Transportation and Tourism which addresses the possibilities of liquefaction, organized/systematic measure of liquefaction has hardly been accomplished for detached houses. The authors investigated the damage caused by liquefaction in the Urayasu area, Chiba Prefecture, where severe liquefaction damage has occurred.
Extensive damage has occurred in northeast Japan by the east Japan great earthquake, from Aomori to Kanagawa prefectures, especially where the seismic intensity of more than 5+ was observed.