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1994 Fiscal Year Final Research Report Summary

Study of Attenuation Mechanism of Seismic Waves in the Crust

Research Project

Project/Area Number 05680355
Research Category

Grant-in-Aid for General Scientific Research (C)

Allocation TypeSingle-year Grants
Research Field Natural disaster science
Research InstitutionTohoku University

Principal Investigator

SATO Haruo  Tohoku University, Science, Associate Professor, 理学部, 助教授 (80225987)

Project Period (FY) 1993 – 1994
KeywordsScattering / Attenuation / Crust / Seismic waves
Research Abstract

There are three major contributions for the quantitative prediction of seismic ground motion : source ; path, and site. Here we focused on the second and the third subjects : scattering and attenuation as a path effect ; site amplification study of hard rocks as a site effect. Based on the filed observation at Ashio, Tochigi prefecture, we have clarified the frequency dependent amplification factors of both P and S waves at hard rocks as granite (Yoshimoto et al., 1993b). Developing the conventional coda normalization method, we first measured the frequency dependence of both P and S wave attenuation in the Kanto area (Yoshimoto et al., 1993a). We have newly developed a mathematical formulation of the energy propagation through scattering and attenuation media based on the energy transport theory (Sato, 1994a, 1994b, 1995b). This formalism adopt any type of no-isotropic scattering, and is useful for the study of high frequency seismogram envelopes. The numerical synthesis based on this formulation well explains the spatially uniform distribution of energy density (1995b). This method is applied to seismograms obtained at Onagawa, Miyagi prefecture. The estimated S wave attenuation factor is proportional to frequency, and the contribution ratio of scattering loss to the total attenuation, the seismic albedo, is small as about 0.25. If we increase the forward scattering, the seismic albedo becomes twice. Based on the analysis of seismogram envelopes, we found that the randomness of the lithosphere is much larger under the west of the volcanic front compared with that under the east in Kanto-Tokai area, Japan (Obara and Sato, 1995a)

  • Research Products

    (11 results)

All Other

All Publications (11 results)

  • [Publications] Yoshimoto,K.et al.: "High-Frequency Site Effect of Hard Rocks at Ashio,Central Japan" Journal of Physics of the Earth. 41. 327-335 (1993)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Sato,H.: "Multiple isotropic scattering model including P-S conversions for the seismogram envelope formation" Geophysical Journal International. 117. 487-494 (1994)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Sato,H.: "Formulation of the multiple non-isotropic scattering process in 2-D space on the basis of energy-transport theory" Geophysical Journal International. 117. 727-732 (1994)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Obara,H. and H.Sato: "Regional differences of random inhomogeneities around the volcanic front in the Kanto-Tokai area,Japan,revealed from the broadening of S wave seismogram envelopes" Journal of Geophysical Research. 100. 2103-2121 (1995)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Sato,H.: "Formulation of the multiple non-isotropic scattering process in 3-D space on the basis of energy-transport theory" Geophysical Journal International. (印刷中). (1995)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Yoshimoto, K., H.Sato, and M.Ohtake: "Frequency dependent attenuation of P and S waves in the Kanto area, Japan, based on the coda normalization method" Geophys.J.Int.114. 165-174 (1993)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Yoshimoto, K., H.Sato, S.Konoshita, and M.Ohtake: "High frequency site effect of hard rocks at Ashio, central Japan" J.Phys.Earth. 41. 327-335 (1993)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Sato, H.: "Multiple isotropic scattering model including P-S conversions for the seismogram envelope formation" Geophys.J.Int.117. 487-494 (1994)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Sato, H.: "Formulation of the multiple non-isotropic scattering process in 2-D space on the basis of energy transport theory" Geophys.J.Int.117. 722-732 (1994)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Obara, K., and H.Sato: "Regional differences of random inhomogeneities around the volcanic front in the Kanto-Tokai area, Japan, revealed from the broadening of S wave seismogram envelopes" J.Geophys.Res.100. 2103-2121 (1995)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Sato, H.: "Formulation of the multiple non-isotropic scattering process in 3-D space on the basis of energy transport theory" Geophys.J.Int.(in press). (1995)

    • Description
      「研究成果報告書概要(欧文)」より

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Published: 1996-04-15  

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