Abstract
Effects of earth and oceanic tides on the Earth's gravitational constant, hereinafter called gravity for short, are estimated for precise gravity measurements in Izu peninsula. In calculating the oceanic effects, we apply Green's function given by Farrell to hourly tidal records obtained at the nearby tidal stations and to the tidal charts given by Tiron et al. As a result, the oceanic effect ranges from about 5 to 10μgal in the peninsula. This fact may lead to the conclusion that hereafter, the oceanic tidal correction seems to be necessary for precise gravity measurements. The optimal tidal factor of gravity (G-factor) and phase lag used in the earth tidal corrections are estimated as 1.15 with a phase lag of 0.1 hour, although we have usually adopted a G-factor of 1.20 without any phase lag. The difference between gravity values corrected with the usual tidal constants and ones estimated in the present study amounts to about 5μgal.
