THE OBSERVATION OF THE ROTATIONAL STRAIN, AND RELATION TO THAT OF EXTENSIONAL STRAINS IN THE EARTH TIDE

Abstract

Observations by means of a rotationmeter were carried out at Otsu Observatory, and their analysed value for three months is given in this paper. It has been proved that the gradient of the displacements with respect to their orthogonal directions can be obtained by use of the observations of the ground extensions in azimuth of more than three in the earth tide. Then the results of the orthogonal gradient of the tidal horizontal displacement which is observed directly by means of a rotationmeter, which is calculated from the strain elements observed by extensometers, and which is calculated by the elastic theory in the earth tide are compared with each other. There are good agreements between the amplitudes and the phase lags of the calculated values from the observations of the extensometers and that from the elastic theory. And there is an agreement between the amplitude of the observed values of M_2 wave by means of the rotationmeter and those obtained by the extensometers and the elastic theory in the earth tide.