Abstract
Strain type tiltmeter (rotationmeter) which is able to observed the rotational strain respect to the horizontal axis has been devised. These instruments have been set in the directions of N38°E and N52°W in the Osakayama tunnel in 1978. They have stable observational recordings in the sensitivity of around 0.″.0027/mm. And their observations have been performed for long period very well.Their earth tidal components have been analyzed on the observed records for the periods of three months. These sesults show that the amplitude ratios between the components tides have good fit to those of the direct terms of the tide generating potential at the observations in the direction of N52°W (rotational strain respect to N38°E axis), but S2-component is predominant at that in the direction of N38°E (rotational strain respect to N52°W axis). Then, the vertical deflection of the crust is calculated by means of the combinations with the results of the tidal analyses of the horizontal pendulum type tiltmeters and water-tube tiltmeter.
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