逢坂山地殻変動観測所における潮汐ひずみの地形による影響

抄録

Topographic effects on the earth tidal strains have been estimated quantitatively at the extensometer site. The observed M₂ and O₁ values obtained from four extensometers, installed at Osakayama Crustal Deformation Observatory near Kyoto, have been compared with the predicted ones. Topographic effects have been calculated by means of three dimensional finite element method based on two models. In Model I, the uniform boundary stresses have been applied to the region used in calculation of topographic effects. The amplitude ratios of the observed values to the predicted ones-Body tide corrected by ocean load effects and topographic effects calculated by Model I-are 0.5-0.7 for M₂ and 0.5-0.8 for O₁. The observed phase lags are almost in good agreement with the predicted ones. It is presumed that one of the possibilities to explain the small observed amplitudes is the crustal block structual effects proposed by Latynina (1973). In Model II, the lower boundary stresses as same as Model I and the upper ones decreasing to zero at the surface have been applied to the same region as Model I. The observed values are in good agreement with the predicted ones-Body tide corrected by ocean load effects and topographic and crustal structual effects calculated by Model II. In Model II, the problems of the depth that the boundary stresses become uniform and the block dimension still remain, but it is infered that the crustal block structure affects the earth tidal strains.