Journal of Physics of the Earth
Online ISSN : 1884-2305
Print ISSN : 0022-3743
ISSN-L : 0022-3743
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Volume 42, Issue 6
Displaying 1-5 of 5 articles from this issue
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  • Surface Waves in Vertically Heterogeneous and Transversely Isotropic Layer Overlying a Homogeneous Isotropic Half-Space and under a Uniform Layer of Liquid
    Ved P. Kaushik, Sushil K. Tomar
    1994 Volume 42 Issue 6 Pages 399-409
    Published: 1994
    Released on J-STAGE: April 30, 2009
    DOIhttps://doi.org/10.4294/jpe1952.42.399
    JOURNAL FREE ACCESS
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    The effect of heterogeneity and anisotropy on the dispersion of Rayleigh-type surface waves in a heterogeneous anisotropic layer of elastic medium overlying a homogeneous elastic solid half-space and lying under a homogeneous liquid layer of uniform depth is discussed. The variation of phase velocity with the wavenumber is obtained numerically for the fundamental mode. The results are compared with the homogeneous case. The results show that the heterogeneity of the layer decreases the phase velocity for small values of wavenumber. The problem of Gogna (1979) has been reduced as a special case.
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  • Raman Spectra of High-Pressure Polymorphs of MgSiO3 at Various Temperatures
    Liu Lin-Gun, Terry P. Mernagh, Tetsuo Irifune
    1994 Volume 42 Issue 6 Pages 411-424
    Published: 1994
    Released on J-STAGE: April 30, 2009
    DOIhttps://doi.org/10.4294/jpe1952.42.411
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    Raman spectra of two of the three known high-pressure polymorphs (the ilmenite and perovskite modifications) of MgSiO3 were investigated in the temperature range 105-875 K at atmospheric pressure. Even with extreme care, MgSiO3-perovskite was found to become amorphous at temperatures greater than about 500 K, but MgSiO3-ilmenite was still crystalline even after the highest temperature run. Negative variations of all Raman modes with temperature were observed for both polymorphs. Except for the most intense Raman mode of MgSiO3-ilmenite, only a linear temperature variation can be established within the experimental uncertainty and temperature range spanned. This is the first report of slopes of the variation (dvi/dT) for both MgSiO3-ilmenite and MgSiO3-perovskite. By utilizing these data and others from the literature, the volume thermal expansivity for MgSiO3-ilmenite was calculated to be (2.8±0.5)×10-5deg-1 and that for MgSiO3-perovskite to be (3.1±0.5)×10-5deg-1 at ambient conditions.
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  • Continuum Theory of Earthquake Fracturing
    Teruo Yamashita, Roman Teisseyre
    1994 Volume 42 Issue 6 Pages 425-437
    Published: 1994
    Released on J-STAGE: April 30, 2009
    DOIhttps://doi.org/10.4294/jpe1952.42.425
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    We theoretically study spatio-temporal evolution of macroscopic stress in an elastic medium permeated by continuously distributed dislocations. We develop a system of equations governing stress evolution, taking account of growth and coalescence of dislocations. As dislocation distribution evolves, we observe the compatible evolution of stresses. Numerical calculations of these equations denote that stress evolution shows both an increase and a decrease inside the medium, which is due to dislocation interactions, for fixed-stress load on the boundary. This kind of approach will be useful to understand the preparatory process of shallow earthquakes from physical laws at the microscopic level.
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  • H2O and Magmatism in Island Arc Mantle Inferred from Seismic Anelasticity and Heat Flow Data
    Hiroki Sato
    1994 Volume 42 Issue 6 Pages 439-453
    Published: 1994
    Released on J-STAGE: January 25, 2010
    DOIhttps://doi.org/10.4294/jpe1952.42.439
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    The presence of hydrous minerals or H2O in the mantle wedge beneath northeastern Japan was investigated by comparing temperatures estimated from seismic Q and heat flow. Applying the laboratory Q results of dry peridotite onto the seismic anelasticity structures, the upper mantle temperatures were estimated. We then compared these temperatures with those obtained from observed heat flow. In the fore-arc region from the aseismic front to the wedge apex, the heat flow temperatures are much lower (-250-660°C lower) than the temperatures estimated from the seismic Q of dry peridotite. This temperature difference indicates the presence of hydrous minerals or free-H2O. On the other hand, no such temperature difference is found beneath the volcanic front to the Japan Sea coast area, indicating that the uppermost mantle wedge of this region is generally dry. Low Q values (Qs≅100) beneath this zone are due to high subsolidus temperatures (-1, 000°C) in the anhydrous mantle, and intermediate Q values (Qs≅550) beneath the aseismic front to the wedge apex are due to hydration of the low-temperature mantle (≤600°C). For island arc magmatism, we suggest that local enrichment of melt as well as H2O occurs beneath volcanoes in the mostly dry mantle.
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  • Source Directivity Revealed by Array Analysis of Short-Period Teleseismic Body Waves: The 1990 Manjil, Iran, Earthquake
    Taku Tada, Kunihiko Shimazaki
    1994 Volume 42 Issue 6 Pages 455-460
    Published: 1994
    Released on J-STAGE: April 30, 2009
    DOIhttps://doi.org/10.4294/jpe1952.42.455
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