The past activity of the Fukui Earthquake fault prior to the 1948 event is unknown because the fault is covered by a thick deposit. We estimated the depth of the basement for a profile across the fault by means of seismic exploration using an air-gun as source apparatus as well as by the delay times determined by two natural earthquakes. The basement in the western side was obtained to be deeper by 50-200m than that in the eastern side. The basement estimated in this work, the results of leveling survey before and after the earthquake, the present topography, and the boundary shape between the alluvium and the diluvium across the fault suggest the recurrence of earthquakes associated with this fault. The mean rate of displacement is estimated to be 0.1-1.0m/1, 000 years.
