The phase boundary for calcite I-II inversion was determined on the P-T plane up to 700°C and 25kb. The change in longitudinal ultrasonic velocity, which shows a remarkable minimum at the inversion point, was measured. The slope of the phase boundary is negative up to about 250°C; this coincides with the results of P.W. Bridgman and C. Wang. Above 300°C, the slope of the boundary turns to positive, and the inversion pressure rapidly rises with increasing temperature. The boundary has a minimum pressure at about 250°C. Since the boundary of calcite I and calcite II will never cross the boundary of calcite I and aragonite, there is no stable region for calcite II.

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A comparative study of S wave spectra has been carried out for earthquakes occurring near the Japanese arc. Data obtained at the Tsukuba Seismological Observatory (TSK) are used. The epicentral distance of these events from TSK ranges from 4 to 18°, and the magnitude mb is mainly between 4.0 and 4.8.
S-wave amplitude in the frequency range of 10 to 20Hz is compared with that in the range of 4 to 8Hz. The relative amplitude ratio is investigated for earthquakes in various seismic regions.
A regional difference in the S phase spectra can be seen in events at depths shallower than about 400km. This difference is probably caused by the inhomogeneity of the upper mantle structure. The spectra of events at depth deeper than 400km do not show any noticeable difference among the regions. High frequency components are lost on the seismograms. It is suggested that the source spectrum is different between the upper and the lower mantles, the boundary being at about 400km depth.

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The results of measurements made with a Tokyo Surface Ship Gravity-meter (a T.S.S.G.) aboard the R/V Hakuho Maru and measurements with a Graf-Askania sea gravimeter aboard the R/V Vityaz when both ships were cruising with the same heading and at the same speed were compared. The average difference between the results of measurements with the two gravity meters for 6 hours comparison was only 1.8 mgal.

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The "residual gravity anomalies" in the Pacific and the surrounding marginal seas are calculated from free-air anomalies and explosion seismic results. The heat flow versus residual anomaly relation in the Pacific basin shows a clear systematic tendency which reflects the variation in thermal expansion of the upper mantle. On the other hand, the rosidual anomalies in the marginal seas, such as the Sea of Japan, are somewhat different from those in the Pacific basin. This situation implies a possibility that the upper mantle beneath the Sea of Japan is originally of high density. Its rather "soft" response to surface waves and gravity may be due to high temperature.
A contour map of the Moho depth around Japan is constructed from corrected Bouguer anomalies. The heat-flow values are used in order to remove the effect of the upper mantle heterogeneity on the observed Bouguer anomalies. The map agrees well with the explosion seismic results.

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A normal force limited in space and time, is applied to the surface(x-axis) of an elastic quarter space, and the propagation of disturbances caused by this external force is studied by the use of the finite difference technique. The feature of wave propagation is shown by the wave profiles on the x and z axes, and also by a number of two dimensional displacement fields in which P and S waves, PS and SS waves, and Rayleigh waves are observed. Velocity and the orbital motion are studied quantitatively in comparison with exact theoretical values.

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Regionalized shear-velocity models of the upper mantle were inferred from phase and group velocities of mantle Love and Rayleigh waves. Im-portant conclusions are: (1) Major shear-velocity differences among the dif-ferent tectonic regions exist at depths less than 300km. (2) Shear velocities in the upper mantle are markedly higher for the shield areas and lower for the tectonic areas than for the oceanic areas. The velocity difference between the shield and tectonic models is approximately 10% at depths less than 100 km, decreasing gradually to 5% at a depth of 200km. (3) The shield data do not require a pronounced low-velocity channel in the upper mantle, as does the oceanic model, but only a slight low-velocity channel if the Sn velocity is 4.6km/sec. (4) The tectonic data do not necessarily require the presence of a high-velocity lid just beneath the M-discontinuity. (5) Unlike the other two regions, the oceanic data clearly require a pronounced low-velocity channel. (6) The dispersion of Love and Rayleigh waves for the tectonic regions can be explained more easily by different shear-velocity structures rather than by a single isotropic-layered structure. The shear velocities inferred from Love waves are higher by 0.2km/sec than those inferred from Rayleigh waves, the velocity differences being concentrated at depths from 150 to 300km. This discrepancy suggests anisotropy or an equivalent laminar-melting structure, or elliptical magma pockets.
The phase-velocity data were taken from Kanamori's paper. The group velocities were recently determined by Hamada for moderate-size earthquakes recorded at LASA (Large Aperture Seismic Array in Montana) and at a deep mine observatory in Ogdensburg New Jersey.

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A travel time curve in the first paper were obtained from the observed data for the focal depths 0, 20, 40, 60 and 80 km. In the present paper, they are adjusted that the contradiction among them may be minimized, using the velocity structure near the surface as parameters. As a first step, the first approximation velocity structure is calculated by the Herglotz-Wiechert's method from the corrected β-approximation travel time curve for 20km focal depth in the first paper. Six combinations of the starting velocity structure and travel time curve are examined. The most probable results are graphically shown by the chain lines in Figs. 20 and 23. The corresponding velocity structures in these figures are not emphasized since they are obtained as parameter. However, various calculations give fairly constant values, nearly 28-33km for the thickness of the crust and 7.35-7.45 km/sec for the P wave velocity at the top of the mantle.

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