In order to observe the ground-strain due to the tide generating force of the earth, it is neccesary to record measurably the linear strains, which are as large as 10-10. For that purpose, it should not only make longer the base line on the ground, but also magnify extremly the relative displacement of the both edge-points of the base line. A new type of high sensitive extensometer of which magnifier is a Zöllner suspension type tiltmeter is devised. In the mechanism of the extensometer, a super-invar rod that the length is constant, is put parallel with the base line, and an edge of the rod is fixed on one edge of the line so that the relative displacement of the unfixed edge of the rod and the other edge of the line may be transformed into the inclination of a support of the Zöllner pendulum. Cosequently, the pendulum of the tiltmeter rotates magniloquently. And also the rotaional angle of the pendulum is enlarged and recorded with an optical lever on a photographic printing paper. The extensometer has a sensitivity in the order that is higher than the formerly using one, and the sensitivity is able to be perfectly controlledat will. As the sensitivity to the linear strain is more than 100 times as large as that of the extensometer as to the ground-tilting, the influence from the tilting may be neglected. Then, the linear strains of the earth's surface in earth tide is observed with this extensometer at Osakayama Observatory, and is obtained the following analyzed values that are sbtructed the influence of ground-tilting, in the prime vertical direction, M
2-component: 0.689 x 10
-8 cos (2t -0.9°), O
1-component: 0.705 x 10
-8 cos ( t-19.1°).And also the records (of the ground-strain) which are observed with new type extensometer are compared with them which are observed with other types'. In these records, the interresting phenomena which are generated within a short hour, are found.
抄録全体を表示