Estimation of Liquefaction Risk Ratio Based on Liquefaction Point Information in Recent Earthquakes

Abstract

Due to the 2011 off the Pacific coast of Tohoku Earthquake, liquefaction occurred over a wide area and caused enormous damage. After that, a maximum seismic intensity of 7 was observed during the 2016 Kumamoto Earthquake and the 2018 Hokkaido Eastern Iburi Earthquake, and liquefaction occurred over a wide area. In this study, we selected earthquakes that can count liquefaction points using detailed aerial imagery. The selected earthquakes were the 2011 off the Pacific coast of Tohoku Earthquake, the 2016 Kumamoto Earthquake, the 2016 Tottori Prefecture Central Earthquake, the 2018 Osaka Northern Earthquake, and the 2018 Hokkaido Eastern Iburi Earthquake. Based on the information on the liquefaction occurrence points of these earthquakes, the liquefaction occurrence ratio based on the 250 m mesh unit, and the liquefaction area ratio considering the liquefaction area within the 250 m mesh were estimated. Furthermore, we proposed a formula for estimating the liquefaction risk ratio by the product of the liquefaction occurrence ratio and the liquefaction area ratio.