長崎県平山地域地すべり地帯の地下水の化学成分について

抄録

Since 1966, the authors have determined the chemical compositions of ground waters in the Hirayama landslide area, which has been known to be a very large scale landslide area, which has been known to be a very large scale landslide area. The landslide at coal-mine zone occurs in the area where the coal-bearing Tertiary formation is widely covered by basaltic flow. The chemical compositions of ground waters reflect the geological feature of the area. High quantities of HCO₃^-, SO₄^2-, Ca²⁺ and Mg²⁺ are supplied to the ground waters in this landslide area through the processes of water-rock interaction. Those concentrations are higher in landslide area than in non-landslide area. The concentrations of chemical constituents of ground waters in the landslide area seem to have increased slightly since 1966. The positive relationships are observed between the concentrations of Ca²⁺, Mg²⁺, HCO₃^- and SO₄^2- in the ground waters. The chemical composition of ground water in landslide area clearly indicates the condition for the chemical weathering of rocks in the area. There seems to exist a certain relationship between the concentrations of major chemical constituents in ground water and the occurrence of landslide.