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Volume 35 (1987)
- Issue 6 Pages 415-
- Issue 5 Pages 347-
- Issue 4 Pages 255-
- Issue 3 Pages 195-
- Issue 2 Pages 111-
- Issue 1 Pages 1-
Volume 35, Issue 2
Displaying 1-6 of 6 articles from this issue
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PROPAGATION VELOCITY ACROSS A 1, 500-km-LONG, DEEP OCEAN HYDROPHONE ARRAYDaniel Alvin WALKER, Charles Stoddard McCREERY1987 Volume 35 Issue 2 Pages 111-125
Published: 1987
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSPo/So phases from numerous earthquakes along the margin of the Northwestern Pacific Basin were successfully recorded by a 1, 500-km-long ocean bottom hydrophone (OBH) array deployed for two months near Wake Island. Data from ten shallow-focus (<100km) events at 20°(2, 200 km) to 34°(3, 800 km) epicentral distance were used to compute propagation velocities across the array for the onsets of Po and So. The values found are 7.96±0.05 km/s for Po and 4.58±0.06 km/s for So. Travel-time intercepts associated with these velocities are, respectively, -7.21±2.40 s and -12.84±7.61 s. These velocities are significantly lower than those previously reported for the Northwestern Pacific using single station data. Although the low velocities and negative intercepts could simply be the result of bias in the data, they might also be due to the effects of azimuthal anisotropy along travel paths, or to increasing propagation velocity with lithospheric age, or to a different mode of propagation near the source.View full abstractDownload PDF (1497K) -
KANEGAHARA FAULT STRUCTURE NEAR KYOTO, JAPANYoshimasa KOBAYASHI, Masanori HORIKE1987 Volume 35 Issue 2 Pages 127-141
Published: 1987
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSA seismic reflection exploration has been conducted at a site on the western margin of the Kyoto basin. An air gun suspended under water in a river was used as a source device, and a measuring line was spread over 800 m on an embankment of the river. An underground structure model has been determined by comparing the travel times and the amplitudes of main phases in the recorded seismograms with those computed by the ray method. A vertical step of subsurface bedrock is found below the middle of the measuring line due to the presence of a reverse fault with a vertical offset of about 200 m. The inferred model is compatible with existing geological, seismological and gravitational data.View full abstractDownload PDF (1435K) -
Deo Datta SIGH1987 Volume 35 Issue 2 Pages 143-157
Published: 1987
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSSeismicity, focal mechanism and moment tensor are used to estimate the strain deformation for earthquakes occurring in the Himalayan and nearby regions during the last 80 years. The average strain values are found to vary from 0.86×10-8 yr-1 to 9.2×10-8 yr-1 at different places. The average rate of deformation is estimated for the Himalayan and nearby regions. These values are obtained to be maximum for the region of NE India. An east-west extension of 10.3 mm/yr and north-south compression of 11.6 mm/yr are estimated for NE India. Similarly, we estimate 2.8 mm/yr extension and 2.7 mm/yr compression for the Himalaya region; 6.2 mm/yr extension and 5.7 mm/yr compression for Pamir-Hindu Kush and 3.8 mm/yr extension and 2.9 mm/yr compression for Burma region, in north-south and east-west directions, respectively.
Moment tensor values obtained in different parts of Himalaya and nearby regions suggest the east-west extension and north-south compression. Vertical extensions are obtained in the regions of Hindu Kush, Burma, NE India and Himalaya. The tension and compression strain deformation values obtained in these regions support the hypothesis of continental collision of the Indian and Eurasian plates. The large vertical extension value of moment tensor supports the hypothesis of subduction of Pamir-Hindu Kush seismic zone in the western part of the Indian plate and also subduction of the Indian plate beneath the Burmese arc in eastern part.View full abstractDownload PDF (1240K) -
Eiji MOCHIZUKI1987 Volume 35 Issue 2 Pages 159-170
Published: 1987
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSFree oscillations of a homogeneous, anisotropic, elastic, rectangular parallelepiped are studied by means of the group theory. Normal modes are classified and selection rules for excitation are obtained.View full abstractDownload PDF (638K) -
Yasuo IZUTANI, Tomowo HIRASAWA1987 Volume 35 Issue 2 Pages 171-190
Published: 1987
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSA simple method is developed for rapid determination of fault parameters of a large shallow earthquake from the azimuthal dependence in duration of strong ground motion. The fault length and the direction of rupture propagation can be evaluated by this method within a short time after the earthquake origin time. As an example, the fault parameters are determined for the Tokachi-Oki earthquake of May 16, 1968. They are consistent with the main rupture process revealed by other investigators from far-field long-period seismic records, near-field strong motion records and aftershock distribution. Thus, the present method may be applicable to near-field tsunami warning, provided that a sufficient number of digital accelerographs are installed with a good azimuthal coverage.View full abstractDownload PDF (1775K) -
Eiji MOCHIZUKI1987 Volume 35 Issue 2 Pages 191-193
Published: 1987
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSDownload PDF (180K)
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