By using the measured data of liquefaction-induced permanent ground displacement due to the 1969 Niigata, the 1971 San-Fernando and the 1983 Nihonkai-Chubu earthquakes, the primary factors governing the magnitude of the ground displacement were quantitatively discussed. It was clarified that the thickness of the liquefied layers and the gradient of the ground surface and/or the liquefied layer were most influential on the displacement magnitude, and an experimental formula was proposed for the estimation of the permanent ground displacement. Also, quantitative correlations of the magnitude of the permanent ground displacement with the degree of damage to structures such as houses and buried pipelines were analysed. Furthermore, permanent ground strain was calculated from the observed displacements, and the correlation with earthquake damage such as ground failure was discussed.