Journal of Physics of the Earth
Online ISSN : 1884-2305
Print ISSN : 0022-3743
ISSN-L : 0022-3743
Volume 18, Issue 3-4
Displaying 1-4 of 4 articles from this issue
  • Part 2. Results of the Measurements
    Jiro SEGAWA
    1970 Volume 18 Issue 3-4 Pages 203-284
    Published: 1970
    Released on J-STAGE: April 30, 2009
    JOURNAL FREE ACCESS
    Among numerous cruises on which gravity was measured by use of the T.S.S.G. the cruises of the Umitaka-maru of the Tokyo University of Fisheries made in July and August 1966 and from November 1967 to February 1968, the cruises of the Hakuho-maru of the Ocean Research Institute, University of Tokyo made in August 1967, in July and August 1968 and from April to June 1969, and the cruise of the Meiyo of the Hydrographic Office, Maritime Safety Agency of Japan are selected to illustrate actual situations of gravity measurements during each of the cruises. Gravity measurements by use of the Vening Meinesz gravity meter made in 1934 and 1935 by Matsuyama et al. are also taken up and compared with the measurements by use of the T.S.S.G.
    Gravity values obtained by these measurements have been compiled into gravity tables, and maps or profiles of certain tectonically intimate areas have been drawn. The areas selected from tectonical viewpoint are; Japan trench and its vicinity, Suiko sea-mount at the emperor ridge, Brisbane Hill at the coral sea, Shatzky rise (north-west Pacific rise), Bismark plateau, Mariana trench and Solomon trench.
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  • Tomowo HIRASAWA
    1970 Volume 18 Issue 3-4 Pages 285-294
    Published: 1970
    Released on J-STAGE: April 30, 2009
    JOURNAL FREE ACCESS
    A least squares method is derived for the focal mechanism determination from S wave observations (polarization angles) of different quality. Some considerations are made on how to determine a weight appropriate to each observation.
    As one of numerical examples, a least squares solution is obtained for the Southeast Nevada earthquake of August 16, 1966, that occurred near the Nevada Test Site. This S wave solution represented by a pure strike-slip motion satisfies well the observed initial motions of P waves, and the tension axis trends to S 34°E (±4°) nearly on the horizontal plane.
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  • Jun IRIYAMA
    1970 Volume 18 Issue 3-4 Pages 295-311
    Published: 1970
    Released on J-STAGE: April 30, 2009
    JOURNAL FREE ACCESS
    Various possible ways of core formation are tested from the thermal history of the Earth. Calculation shows that the conversion of gravitational to thermal energy from a uniform to the present differentiated Earth is 1.68×1038 ergs. It is concluded that the release of the gravitational energy on core formation dominates the thermal state of the Earth.
    Earth models in which the core has been growing slowly since 4500 My ago or 3000 My ago fail to meet the requirement of a solid mantle. In these models the present surface heat flows are in excess of the observed heat flow.
    Earth models in which the core was substantially complete at 4500 My ago or 3000 My ago within a short period less than 100 My give the observed heat flow.
    The gravitational energies released in reconstruction of the terrestrial planets are also calculated. Calculation gives the gravitational energies of 1.02×1038 ergs, 1.10×1036 ergs, and 1.34×1036 ergs for Venus, Mars, and Mercury respectively. The results show that the energies released by the formation of iron cores of the Earth and Venus play an important role for the internal heating of these planets.
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  • 1970 Volume 18 Issue 3-4 Pages 313
    Published: 1970
    Released on J-STAGE: January 25, 2010
    JOURNAL FREE ACCESS
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