Simultaneous Tilt Observations with Two Different Types of Water-Tube Tiltmeters at the Esashi Earth Tides Station (II)

-Earth Tide Analyses-

Abstract

This paper describes a result of tidal analyses of tilts observed with two kinds of water-tube tiltmeters at the Esashi Earth Tides Station, and discusses the revealed periodic variations on the amplitudes and phase differences of major tidal constituents. Both the amplitudes and phase differences of major tidal constituents (Q₁, O₁, K₁, N₂, M₂ and S₂) obtained from the records of each tiltmeter for the period from April, 1980 to September, 1982 were very close each other, and were also very consistent with those presented in the previous paper. A clear seasonal or annual variation was distinguished not only on the amplitudes but also on the phase differences for several tidal constituents. The most typical pattern was found out on the M2 constituent of the EW component. Almost the same pattern of annual variation on the ocean tides near the Esashi Station, and the coincidence in phases of amplitude changes among the tilts and ocean tide suggested an effect of the ocean load upon the solid earth. An estimation of this effect made by using the Green's function given by Farrell against the Gutenberg-Bullen's Amodel accounted for just half of the observed amplitude variation of about 0.3 mseca/cm.