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Volume 22, Issue 4
Displaying 1-12 of 12 articles from this issue
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Toshiki KAKUTA1970 Volume 22 Issue 4 Pages 261-270
Published: February 28, 1970
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSSeismograms at small epicentral distances, usually, show higher harmonics, which appear as the waves superposed on the lower frequency waves and disappear with the increasing of epicentral distance. The investigations of these harmonics and their travel times make us possible to estimate the source spectrum.
If we count peaks (or troughs) of seismic waves as many as possible, we can define the apparent highest frequency fmas n/τ, where n is the number of peaks (or troughs) in the time interval τ. Using some of the seismograms of the earthquakes occurred off the east coast of Hokkaido, we have the relation logfm=K0-b logtm, where K0 and b are constants and tm is the travel time at the beginning of τ. Since this relation may be concerned with source spectrum, it will be obtained from this in combination with theoretical formulae. It will be a reasonable assumption that fm is equal to the frequency of the sinusoidal wave of which amplitude is the smallest in those composing the seismogram. The obtained source spectrum is S(f)=Gf-p/bexp (Cf(b-1)/b), where G, p and C are constants. p is concerned with geometrical expansion and C may be related to dissipation of waves.View full abstractDownload PDF (896K) -
Hitoshi TAKEUCHI, Shoji SAKATA1970 Volume 22 Issue 4 Pages 271-277
Published: February 28, 1970
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSThe BIOT'S theory of folding of viscous fluid plate and the HASKELL'S theory of viscous rebound can explain typical features of folding of geological structures and the post-glacial uplift in Scandinavia, respectively, quite well. They appear to be independent and to have no relationship. Examining them in more detail, however, will make it clear that they are intimately connected. In fact, we can make a general computer program to study both of the problems. These points will be made clear in the present paper.View full abstractDownload PDF (511K) -
Shoji SAKATA, Hitoshi TAKEUCHI1970 Volume 22 Issue 4 Pages 278-287
Published: February 28, 1970
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSIn this paper we deal with the stationary convection in a horizontal layer of fluid that has a variable viscosity with depth to explain the convection in the earth's mantle. Five models have been proposed and examined by computation. Each of them has a low viscosity layer in its upper part. It is found that, when the low viscosity layer is thin, (1) The critical Rayleigh-number and the aspect ratio of the convection cell are nearly equal to those when the low viscosity layer is not there, (2) Streamlines are concentrated in the low viscosity layer, but not closed and (3) The horizontal velocity is one sign in the upper low viscosity layer, and the other sign in the lower high viscosity region. These results seem to well confirm the existence of a “jet-stream type” convection in the earth's mantle.View full abstractDownload PDF (756K) -
Tables of Partial Derivatives of Love Wave Phase VelocityYûkô OGUCHI, Hitoshi TAKEUCHI1970 Volume 22 Issue 4 Pages 288-303
Published: February 28, 1970
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSPartial derivatives of Love wave phase velocity with respect to changes of physical parameters in the Gutenberg model are tabulated over the period range from 5sec to100sec. Three partial derivatives, ∂c/∂ρ, ∂cl∂ VSH·H and ∂c/∂ VSH·V are shown in these tables.
We can calculate the increment of phase velocity, Δc, by knowing changes of the physical parameters Δρ, Δ VSH·H, Δ VSH·V and making use of the following formula,
Δc=Σ{(∂c/∂, ρ) Δρ+(∂c/∂ VSH·H) ΔVSH·H+(∂c/∂ VSH·V) Δ VSH·V}.View full abstractDownload PDF (32947K) -
Tables of Partial Derivatives of Love Wave Phase VelocityYûkô OGUCHI, Hitoshi TAKEUCHI1970 Volume 22 Issue 4 Pages 304-312
Published: February 28, 1970
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSPredictions of Love wave phase velocity for the transversely isotropic CANSD and J-S-01 models are made by using the tables of partial derivatives in the previous paper III-a.
Departures of the predicted phase velocities from the exact ones are within 0.03km/sec. So, these tables will be usefull for the calculation of Love wave phase velocity for any plausible continental models.
Corrections for the sphericity are considered in view of the linearity between phase velocities of plane and spherical Love waves.View full abstractDownload PDF (697K) -
Tatsuo USAMI, Yoshiko KOTAKE, Yasuo SATÔ1970 Volume 22 Issue 4 Pages 313-317
Published: February 28, 1970
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSTo make clear the features of the spectrum splitting due to the introduction of a soft solid core, the frequency and spectral amplitude of torsional oscillations are calculated for the modes with colatitudinal order number n from 2 to 9, assuming GUTENBERG-BULLEN A′ earth model. The only deviation from the G-B model is the assumption that the distribution of rigidity is constant in the core. The possibillity of estimating the rigidity of the core by the use of spectrum splitting was discussed.View full abstractDownload PDF (477K) -
Toshikatsu YOSHII1970 Volume 22 Issue 4 Pages 318-327
Published: February 28, 1970
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSPL modes in the earthquake seismogram were discussed again. Theoretical dispersion curves for three watercovered crustal models were computed by OLIVER and MAJOR'S and SU and DORMAN'S methods. The transition from the oceanic PL to the continental PL was discussed. Analyzed records are rather “new” and are supported by the high accuracy of time and the suitable instrumental response. Crustal thicknesses were determined from observed group velocities of PL modes. Some discussions on the dispersion of the PL mode which was represented in HUNKINS and KUO'S paper were also given.View full abstractDownload PDF (871K) -
Shokichi NAKANO, Yukio OKANO1970 Volume 22 Issue 4 Pages 328-346
Published: February 28, 1970
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSThe variations of amplitudes are discussed as to longitudinal and transverse waves radiated from explosive sources with cylindrical shape. It is assumed that only the axially symmetrical pressure is distributed on the side-wall and the both bases of cylinder, having such a form as r-nφ(t) where r and n denote the distance from the center and a positive integer, respectively. Several properties are pointed out, common to the cylindrical sources with the above pressures, with respect to the relative increase of S amplitude and the change of minimal versus maximal P amplitudes connected with the variation of the shape of cylinder.View full abstractDownload PDF (1303K) -
H. TAKEUCHI1970 Volume 22 Issue 4 Pages 347
Published: February 28, 1970
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (110K) -
Shiro WATANABE, Kumizi IIDA1970 Volume 22 Issue 4 Pages 348-349
Published: February 28, 1970
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (226K) -
Shiro WATANABE, Harumi AOKI1970 Volume 22 Issue 4 Pages 349-352
Published: February 28, 1970
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (374K) -
Tomeo NAGAMUNE1970 Volume 22 Issue 4 Pages 352-355
Published: February 28, 1970
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (382K)
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