In this paper, it is intended to find out the methods to derive the vertical earth movements from the result of the tide observations. The mean sea level along the coast of Japan fluctuates considerably under the influences of the meteorological and the oceanographic causes. Therefore, in the first place, we must eliminate the fluctuations of the mean sea level originated from these influences.
In Part I, as the basis for the further studies, the characteristics of the monthly and the annual mean sea level variations, especially their regional distributions, are investi gated, using the tidal data obtained at 58 stations in Japan. The locations of the stations are shown in Fig. 1 and tabulated in Table I.
At first, the monthly mean sea level h, is assumed to consist of h_s, Δh_a and Δh_f, thatis;
h=h_s+Δh_a+Δh_f
where h is the monthly mean sea level corrected with the atmospheric pressure, using the theoretical barometric factor of -10 mm/mb, h_s is the value of linear variation with the constant annual velocity α mm/year, Δh_a is the value of mean annual variation or normal seasonal variation, and δh_a is the value of irregular variation or the departure of monthly mean sea level from the value of regular variation which consists of h_s, and Δh_a. The constants α and Δh_a are determined from the data during 10 years, 1951-1960. The method of separation of these constituents is described in § 2.
The mean annual velocities α's are given in Table II. Only 8 of 58 stations have the mean annual velocities larger than ±10 mm/year, and at 4 of them, Osaka, Nagoya, Toba and Kobe, the existence of the the local subsidence of the ground is known. The mean of the velocities for all stations, except Osaka where the artificial sinking of the ground is conspicuous, is ±1.14±1.24 (m.e.) mm/year.
The observed mean annual variation Δl_α and the pressure-corrected one Δh_α are shown in Table III and IV, and Fig. 6. The harmonic constants of Sa-, Ssa- and Statides are derived from them (cf. Tables V and VI and Fig. 8). The result is almost similar to those obtained by KAWABATA (1950) and MIYAZAxr (1955) as shown in Fig. 9. It is interestingthat the phases of both Ssa- and Sta- tides in the northern part of Japan are almost opposite to those in the southern part of Japan, and this fact coincides qualitatively with that expected from the equilibrium tidal theory. But the amplitudes of the observed tides are much larger than the expected ones.
In §5-7, the irregular variations or the departures of annual mean sea level (ΔH_f) and monthly mean sea level (Δh_f) from the value of regular variation are discussed. Figs. 10 and 13 show ΔH_f and Δh_f at all stations. Examing these figures, we easily recognize that the coast of Japan can be divided into several regions, as shown in Fig. 3, in each of which the mean sea levels at the stations fluctuate similarly, although there also are many variations being traceable throughout the all regions. The departures of mean sea levels from the values of regular variation, averaged in each region, ΔH_f and Δh_f are shown in Tables VIII and XI and Figs. 11 and 14. The fluctuations of the mean sea level in Region III and N are extremely different from those in other regions as known from Fig. 12, and the boundary between Region II and III is located between Choshi and Mera, southeastern coast of the Boso Peninsula, and boundary between Region IV and V is located between Uragami and Kushimoto, near the southern end of the Kui Peninsula. The discontinuity in the mode of sea level fluctuation on the latter is very remarkable as was

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The terdiurnal component tide is chiefly consists of the harmonic function of third order of tide generating potential (W₃) which is dependent on the term of fourth power of the parallax of the moon at the observatory. The relation constants (l' and h') between the earth-tidal displacements and the potential W₃ is determined in the same manner to Love's number h and Shida's number 1. In this paper, the relations among l', h', l and h are computed on the assumption that the earth is an incompressible and homogeneous elastic sphere. The observations of tidal linear-strains are performed in the various directions at Osakayama Observatory and Kishu Mine and the some values of horizontal areal strain are obtained. From these observations, the observed values of h'- 6l' are computed. According to these observations, the values of h'- 6l' are as large as about ten times of the value which is calculated on the assumption that the earth is a homogeneous and incompressible elastic sphere and the mean rigidity is 2 × 10¹²c. g. s.. But the observed phase lags of M₃-tide components of the strain elements agree with the theoretical values of the components in the all observations.

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