中部日本における重力潮汐の観測

抄録

Tidal gravity observations were made with a LaCoste and Romberg (G 34) gravimeter during 80-100 days at four stations in Central Japan ranging from latitude 35°N to 38°N. At the base station (Tokyo) observations were made twice, before and after the period of observations at other three stations, to check the reliability of the obtained tidal para meters. The tidal constants for different two epochs at the Tokyo station agree reasonab ly well. The result of the analysis shows that the tidal factor has a tendency to decrease systematically with a distance from the Pacific coast to Japan Sea coast. However, such a tendency, consistent with the regional distribution of effects of ocean tides, is almost eliminated by ocean tide corrections, by using TIRON et al . and PARKE-HENDERSHOTT models. The fluctuation of the observed phase lags are also reduced to some extent by the ocean tide corrections. The tidal factor obtained at an inland station (Yatsugatake) is 1-3% small relatively to those obtained at the other stations. This result may suggest the possibility of a regional anomaly of tidal factor. The lateral heterogeneity in the crust-mantle or the long-wavelength topography can be considered as a possible cause. Simultaneous tidal observations at many stations in Central Japan are necessary for confirming this regional anomaly.