Free oscillations of a fluid sphere in an infinite elastic medium and long-period volcanic earthquakes

• Sakuraba Ataru

  Department of Earth and Planetary Physics, University of Tokyo

• Oikawa Jun

  Earthquake Research Institute, University of Tokyo

• Imanishi Yuichi

  Ocean Research Institute, University of Tokyo

Abstract

A source model of long-period volcanic earthquakes is presented. We consider that a fluid-filled spherical cavity surrounded by an infinite elastic medium is excited into resonance like the Earth's free oscillations. The eigenequation of this system is derived in a general manner, making use of the spherical harmonic and spherical Bessel expansions. The solution is given as a complex number; its real part is the eigenfrequency and the imaginary part represents the attenuation coefficient of the oscillation. The eigenmodes are classified into five groups: (1) the compressional modes in a fluid sphere, (2) the compressional modes in a solid medium, (3) the shear modes in a solid medium, (4) the Stoneley modes, and (5) the torsional modes. We apply them to the long-period volcanic earthquake observed at Asama volcano, Japan. Estimating the characteristic frequencies and attenuation coefficients of the observed vibrations and assuming that the primary component ( f = 1.73 Hz) corresponds to the fundamental translation mode of a fluid sphere as one of the compressional modes in fluid, we conclude that the resonator which is a spherical cavity of diameter 220 m filled with steam of temperature 500°C and pressure 170 atm is favorable.

Journal

• Earth, Planets and Space

  Earth, Planets and Space 54 (2), 91-106, 2002

  Society of Geomagnetism and Earth, Planetary and Space Sciences, The Seismological Society of Japan, The Volcanological Society of Japan , The Geodetic Society of Japan , The Japanese Society for Planetary Sciences

Keywords

• Space and Planetary Science
• Geology

Details

• CRID: 1390001206511640832
• NII Article ID: 10008634283
• NII Article ID: 130003780878
• NII Book ID: AA11211921
• DOI: 10.1186/bf03351710
• ISSN: 18805981
• ISSN: 13438832
• NDL BIB ID: 6084032
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I6084032
• Web Site: https://link.springer.com/content/pdf/10.1186/BF03351710.pdf
• Web Site: https://link.springer.com/article/10.1186/BF03351710/fulltext.html
• Web Site: http://link.springer.com/content/pdf/10.1186/BF03351710
• Text Lang: en
• Data Source:
  • JaLC
  • NDL
  • Crossref
  • CiNii Articles
• Abstract License Flag: Disallowed