Liquefaction in the Kanto region during the 2011 off the pacific coast of Tohoku earthquake

The present text is a summary of liquefaction events that occurred in the Kanto Region during the 2011 off the Pacific coast of Tohoku Earthquake, excluding those events in the Tokyo Bay area that are discussed elsewhere. Most liquefaction occurred in the abandoned river channels and former lakes that had been recently filled with liquefiable soils. Noteworthy was the damage to private housing lands and river dikes that had not been well treated against liquefaction risk. Many sites experienced repeated liquefaction after former earthquakes in 1923 or 1987, if they existed in those times. In contrast to the recent liquefaction-prone soils, more-aged sands scarcely liquefied because of what is called the “ageing” effect. The present study analyzed cases in Tokyo area to quantitatively assess the temporal development of ageing so that liquefaction risk in more aged soils might be reasonably assessed. In the appendix, remarks are made of the reliability of air-photo survey in quick detection of liquefaction sites.