Zoning for liquefaction and damage to port and harbor facilities and others during the 2005 Fukuoka-ken Seiho-oki Earthquake

On March 20, 2005, an earthquake of magnitude 7.0, which was named as the 2005 Fukuoka-ken Seiho-oki Earthquake, occurred in the northwest part of Fukuoka City. During the earthquake, liquefaction occurred mainly in the reclaimed lands of the Hakata Bay area, resulting in structural damage. In this paper, the distribution of the sites where liquefaction occurred and the characteristics of the gradation of sand boils collected at the sites were clarified. Further, the occurrence of liquefaction in the reclaimed land was discussed with reference to some instances, and structural damages, mainly to port and harbor facilities, and a flow failure of sloping ground due to liquefaction were summarized. Furthermore, liquefaction analysis was performed using a program for one-dimensional seismic response analysis and several soil profiles of the reclaimed land and alluvial ground in order to investigate the relationship between the occurrence of liquefaction and the distribution of acceleration; this was estimated from the analyses and the mechanical and physical properties of the soils.