The depth of the upper boundary of a layer in the crust, h, and its velocity, V, should have a relation like that obtained by a high pressure measurement of a rock. In this paper the values of h and V obtained by explosion seismological method are compared with V and the pressure P obtained by experiments. The ninety percents of V and h of the layers in which the velocities range from 5.9 to 6.3km/sec are in the domain corresponding to granitic rocks in a V-P diagram.

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Computer techniques are used for the reduction of seismograms consisting of only maxima and minima, possibly with various distortions such as zero line shift and the effect of finite arm length. After the reduction the calculation of Fourier transform is carried out so that the spectrum of the disturbance may be obtained. The method is applied to actual seismograms obtained at two stations with different foundation conditions, and the spectrum intensity is compared.

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Model experiments were carried out for relatively short body waves compared withthe dimension of the model to obtain their travel times, amplitudes and wave forms.A plexiglass disk of radius of 1m with thickness of 2mm is used as a two-dimen-sional model of the earth. The cylinder-shaped source transducer without directionalityis devised so that the amplitudes observed at any point on the surface can be analyzedand compared.
The time duration at the source is about 0.03 with the unit of a/Vs, Where a is theradius of the disk and Vs the shear velocity. The disk was also preferred as themodel by OLIVER et al. (1954) and by KATO and TAKAGI (1956), where time durationswere about 0.3 and 0.04 with the same units, respectively. Theoretical seismogramswere synthesized by SATO and USAMI (1964) and ALTERMAN and ABRAMOVICI (1965)with the time durations of 0.19 and 0.03, respectively.
The seismograms are obtained at the surface with 5° intervals of epicentral dis-tances for four models where distances between the source and the center of the diskare 0.775m, 0.850m, 0.925m and 0.997m.
The rules of phase change for reflected waves such as pP, PP, pPP, PPP, etc.derived theoretically are verified by the model experiments. Diffracted pulses whichappear at shorter epicentral distances than those of cusp points of travel time curvesfor pP, sS and pS are identified. When attenuation due to the lossy medium is takeninto account, observed amplitudes of pP and PP pulses show good agreement withtheoretical values when these pulses are not interfered by other phases.
The present experiments suggest that the possibility of further study when themedium has some velocity gradient with depth and a core is feasible.
Seismograms from real earthquakes are compared with those obtained in the experi-ments. When both focal mechanism and the phase shift rule are taken into account, it is found that wave forms of reflected waves such as pP and PP can be interpreted.This implies that not only P and S waves but also the reflected waves are useful fordetermining the focal mechanism.

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