地殻歪の観測に及ぼす降雨の影響の地下水浸透モデル

抄録

The relation between strain changes and amounts of precipitation has been investigated using data obtained from twenty-one crustal movement observatories in Japan. As a possible mechanism to explain this relation, a hydrological model of ground-water flow in a porous medium is considered.
Observation tunnels, in which extensometers are installed, are generally excavated in rocks containing many cracks or fissures. These rocks near the surface are assumed to be a porous medium. The water level in the medium shows rapid drawdown toward the tunnel because of drainage of ground-water into the tunnel. And the fluid pressure is predominant in the direction perpendicular to the axis of tunnel. Local strains under the action of fluid pressure around the tunnel are calculated with the finite element method.
Based on this model, observational results obtained from extensometers at Ide, Amagase and Iwakura observatories are explained well.