ABSTRACT The critical intensity of earthquake ground motion which separates liquefiable to non-liquefiable conditions is investigated. The peak ground acceleration and velocity are calculated at about 130 liquefied and non-liquefied sites during 19 Japanese earthquakes. These sites are on natural levee, river channel, reclaimed land or drained land, and have high liquefaction susceptibility. In the calculation, the effects of fault rupture and local site condition are considered, to obtain more accurate results than those in previous studies. The results of the calculation indicate that (1) the occurrence of soil liquefaction is better correlated with the peak ground velocity than with the peak ground acceleration, (2) soil liquefaction is likely to occur for the ground with high liquefaction susceptibility, when the peak ground velocity exceeds 15 kines (cm/s), and (3) the degree of soil liquefaction shows no clear correlation with peak ground velocity or acceleration.