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Volume 22 (1974)
- Issue 4 Pages 395-
- Issue 3 Pages 313-
- Issue 2 Pages 177-
- Issue 1 Pages 1-
Volume 22, Issue 4
Displaying 1-5 of 5 articles from this issue
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Takao MOMOI1974 Volume 22 Issue 4 Pages 395-414
Published: 1974
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSAn exact solution of long wave is numerically obtained for two models of the L-shaped channel with square and rounded bends to discuss the transmission (reflexion) coefficients and the transmitted (reflected) energies to both sides of the bend of the channel. At kd=mπ (k, wave number; d, width of the channel and m, positive integers), the behavior of the wave for the square bend differs definitely from that for the rounded bend. At the above value of kd, standing waves, for the former, appear throughout the entire portion of the channel (no transmissions of the energy take place), while, for the latter, the waves advance zigzag in the leeward channel (most of the incident wave energy is then transmitted to the leeward channel through the bend). In the corner bend, at kd=mπ-ε(ε:a small positive), the one-degree-lower (m-1th) mode is excited by degrading the energy of the mth mode.View full abstractDownload PDF (1987K) -
Teruo YAMASHITA, Ryosuke SATO1974 Volume 22 Issue 4 Pages 415-440
Published: 1974
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSCharacteristics of tsunami waves caused by a fault model are investigated theoretically in detail. Effect of focal parameters on tsunami amplitudes, relation with the static deformation at the source area, sense of initial motion and directivity are discussed.
Main results are summarized as follows: The dip-angle, fault length and focal depth play important roles in the generation of tsunami. As an estimate of the directivity, we define an index α, which is the ratio of the maximum amplitude in the wave train at φ=90°, where φ is measured from a direction along the strike of the fault plane, to that at φ=0°. The index α is strongly affected by the change of the dip-angle and the ratio (fault width)/(fault length). The moving directions of initial motions of tsunami waves at φ=90° and 270° reflect the sense (upheaval or subsidence) of the static deformation but not at φ=0°.View full abstractDownload PDF (2469K) -
Yukio HAGIWARA1974 Volume 22 Issue 4 Pages 441-453
Published: 1974
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSThe present paper is devoted to obtaining Molodenskii's G1 based on the practical data of the Tanzawa Mountain area, southwest of Tokyo. For numerical calculations of the G1 integral, we adopt 20km as a truncation distance. It is seen, as a result, that the G1 distribution has a strong resemblance to short wavelength topographic undulations. Assuming as a rough estimate, the effect of the Molodenskii correction on the deflection of the vertical amounts to about 10sec. This quantity is significant as compared with the astrogeodetically observed deflections.View full abstractDownload PDF (1301K) -
Ryosuke SATO1974 Volume 22 Issue 4 Pages 455-462
Published: 1974
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSStatic surface deformations due to a strike-slip fault which takes place along the dipping boundary between two different media are investigated in a two-dimensional case by using the Mellin transform.
Numerical computations reveal that the smaller the rigidity of the upper layer is, the larger the maximum displacement becomes, and the larger the dip-angle is, the larger the difference becomes between maximum deformations in an obliquely layered medium and those in a uniform medium. When the rigidity of the upper medium is half of that of the lower medium, the maximum surface displacement is about 1.2 times as large as that in a uniform medium. When one intends to obtain focal parameters by comparing observed residual displacements with theoretical values for a uniform medium, one should bear in his mind the difference mentioned above.View full abstractDownload PDF (556K) -
HIGH FREQUENCY SPECTRAL STRUCTURE AND SOURCE PARAMETERS OF ULTRA MICROEARTHQUAKES IN MATSUSHIRO AREAKei TAKANO1974 Volume 22 Issue 4 Pages 463-475
Published: 1974
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSThe microstructure of the ultra microearthquakes in Matsushiro area in 1966 is investigated by spectral analysis of seismic waves, which were recorded on FM magnetic tapes by using instruments of wide dynamic range and flat response in velocity amplitude up to high frequency. The magnitude of earthquakes analyzed is from -1.0 to 1.5.
Spectral curves are presented. The predominant frequencies in velocity spectra are different each other by a factor of 2 or 3 even for the same magnitude. The scaling law between the predominant frequency and the velocity amplitude is given as f-4 on the average. The source dimension and stress drop are estimated by means of a model proposed by Sato and Hirasawa. The source dimension L (radius of the circular crack) varies between 11m and 110m according as the magnitude varies between -1.0 to 1.5. The stress drop is estimated to be between 0.1 and 10 bars. The maximum displacement at the center of crack is about 10-2cm for the earthquake whose magnitude is about 0.View full abstractDownload PDF (913K)
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