Liquefaction-induced ground subsidence extracted from Digital Surface Models and its application to hazard map of Urayasu city, Japan

抄録

The major problems associated with liquefaction-induced ground subsidence are tilting of houses, buckling of roads, lifelines cut off, etc. For the mitigation and preparedness over the liquefaction-induced damage, a detailed study on prediction of ground subsidence for future earthquake is important. On the 11th of March 2011, the Off the Pacific Coast of Tohoku Earthquake (MW=9) hit Japan and caused severe liquefaction in Urayasu City, Chiba Prefecture. In this study, in order to investigate the relationship between liquefaction potential, PL, and liquefaction-induced subsidence which occurred in the 2011 earthquake, liquefaction assessment is first carried out by using a number of boreholes and relevant soil test data from Urayasu city. Then, the liquefaction-induced road subsidence is extracted from a set of the Digital Surface Models (DSMs) from airborne LiDAR (Light Detection And Ranging) surveys before (2006) and after (2011) the earthquake. The extracted subsidence from the DSMs indicates that the liquefaction-induced road subsidence is larger for the residential roads than that of the main roads, thus the relationship between PL and road subsidence is different for each type of road. Finally, an attempt is made to apply the obtained PL and road subsidence relations to attain a unique hazard map for Urayasu city.