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Volume 23 (1975)
- Issue 4 Pages 289-
- Issue 3 Pages 205-
- Issue 2 Pages 113-
- Issue 1 Pages 1-
Volume 23, Issue 2
Displaying 1-6 of 6 articles from this issue
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Ryosuke SATO, Teruo YAMASHITA1975 Volume 23 Issue 2 Pages 113-125
Published: 1975
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSIn the Part I of this paper, static surface displacements due to a strike-slip fault which takes place along a dipping boundary between two different media were investigated by applying the Mellin transform. The problem is extended to the case of a dip-slip fault and surface displacements are compared with those in a uniform semi-infinite medium with the same dislocation.
Main conclusions are summarized as follows: The horizontal displacements are much affected than the vertical displacements by the dipping structure. The displacements on the surface of a soft dipping layer are amplified. For the dip-slip fault with dip-angle of 45°, for example, the maximum horizontal displacement, when the rigidity of the dipping layer is half of that of the lower medium, is about 1.6 times as large as that for the uniform medium. The position which gives the maximum displacement moves toward the dipdirection of the fault as the rigidity contrast increases. When comparing observed data with theoretical values derived under the assumption of uniform semi-infinite medium, one should pay attention to these differences.View full abstractDownload PDF (608K) -
Ichiro YAMASHITA1975 Volume 23 Issue 2 Pages 127-144
Published: 1975
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSThe seismic acceleration recorded at the Parkfield, Cholame No.2 station in California at the time of the Parkfield earthquake of June 28, 1966, is analysed to determine the focal parameters on the dynamical process of faulting.
A direct comparison of the calculated accelerations with the recorded one yields focal parameter estimates of 0.5-0.7sec for the rise time of the source time function, 50-70cm for the average dislocation and 50cm/sec for the particle velocity of the fault motion. The effective stress is determined from the particle velocity to be 25-50bars by the dynamic faulting models recently developed. The wave form of the calculated acceleration shows a good peak-to-peak correspondence with the recorded one, only when the source time function is assumed to be of a ramp type. This suggests that the ramp function is a good approximation for the source time function of this earthquake.
We obtain an amplitude of about 7cm for the perpendicular component of the theoretical ground displacement if the values of 50-70cm for the average dislocation and of 0.5-0.7sec for the rise time as estimated above are used. The value of 30cm for the amplitude of displacement, obtained by previous investigators from numerical integration of the record acceleration, seems to be too large. The integrated displacements may not be good approximations for the true ground displacements.View full abstractDownload PDF (1192K) -
Isao SUZUKI1975 Volume 23 Issue 2 Pages 145-159
Published: 1975
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSThermal expansions of single-crystal periclase and olivine were measured by a dilatometric method in a temperature range from room-leve1 to 1000°C. The calculated thermal expansion coefficients of periclase and olivine are given in a range of temperature from -250 to 1500°C based on the Gruneisen's theory of thermal expansion. This theory involves several harmonic and anharmonic parameters. The parameters determined in this study are well related to acoustic wave velocities, pressure and temperature derivatives of bulk modulus, Gruneisen's parameter, which have been determined by other means. It is shown that the accurate thermal expansion data provide a good estimation of elastic wave velocities and other physical constants, which are important in the study of the equation of state of the deep interior of the earth.View full abstractDownload PDF (1301K) -
Masayuki KIKUCHI1975 Volume 23 Issue 2 Pages 161-172
Published: 1975
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSWe examine dynamic propagation of a screw-type crack in relation to crack-resistance force, i.e., energy dissipation per unit extension. We show that a crack may have any terminal velocity only when the resistance force is proportional to crack length. In this case, the value of (1-υ/β), where v and β are, respectively, crack and shear wave velocities, gives a measure of the irreversible effect associated with the fracturing process. Next, we consider such a resistance force in relation to the deformational properties of material, and show that the linear dependence ofthe resistance force on crack length can be related to elastic-plastic properties. Finally, we try to apply these results to earthquake mechanism studies.View full abstractDownload PDF (846K) -
B. BHATTACHARYA1975 Volume 23 Issue 2 Pages 173-187
Published: 1975
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSThe November 9, 1968, south central Illinois earthquake generated fundamental and higher mode Love and Rayleigh waves, which were recorded widely by stations in North America and Canada. After applying the necessary corrections, the reduced observed Love wave amplitude versus distance data were fitted by a function in which the amplitudes decrease exponentially with epicentral distance, yielding average fundamental mode values for the coefficient of anelastic attenuation γ as a function of period in the period range of 5 to 50 sec. For paths to the west of the Rocky Mountains, γ=1.2×10-3km-1 at a period of 5 sec, decreases to 0.8×10-3km-1 at a period of 7 sec and then remains approximately constant through a period of 12 sec. In the period range 15 to 50 sec, γ=0.4×10-3km-1. For paths to the north and northeast, γ=0.6×10-3km-1 in the period range of 5 to 8 sec and γ=0.19×10-3km-1 at a period of 15 sec remaining nearly constant through a period of 40 sec. A comparison of the theoretical Love wave spectral values with the observed data yielded a focal depth of approximately 20 km and a seismic moment of (2+0.8)×1024 dyne-cm, for the 1968 event. The Love wave radiation pattern is consistent with the focal mechanism solution of STAUDER and NUTTLI (1970).View full abstractDownload PDF (1250K) -
Akira HASEGAWA, Takeshi HASEGAWA, Shuichiro HORI1975 Volume 23 Issue 2 Pages 189-203
Published: 1975
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSPremonitory change in the ratio of compressional and shear wave velocities was observed for the shallow earthquake of magnitude 6.2 which occurred in the southeastern part of Akita Prefecture in northeastern Japan on October 16, 1970. The time duration of the anomalous velocity preceding this earthquake was about two years, the value being in good accordance with the period expected from the relation between earthquake magnitude and precursor time interval based on the dilatancy model. The size of the anomalous region, in this case, was estimated to be about two times as large as the aftershock area.
The temporal variations of the b value in the earthquake frequency-magnitude relation and the seismic activity near the focal region were also investigated. A positive correlation was obtained between the b value and the velocity ratio of compressional and shear waves. A remarkable foreshock activity was observed just after the recovery of seismic wave velocity to the normal value.View full abstractDownload PDF (1260K)
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