Skip to main content
Earth, Planets and Space
Download PDF

Incessant excitation of the Earth’s free oscillations

Earth, Planets and Space volume 50, pages 3–8 (1998)Cite this article

Abstract

We, for the first time, report the evidence of incessant excitation of the Earth’s free oscillations, mainly the fundamental spheroidal modes in a frequency range from 0.3 to 5 mHz, based on the three year record of a superconducting gravimeter at Syowa Station, East Antarctica. The frequency-time spectrogram of this record is striped by more than 30 lines at nGal level parallel to the time axis, mostly corresponding to the fundamental spheroidal modes. This spectrogram is characterized by relatively efficient excitation of gravest fundamental modes, enhancement of signal intensities in the austral winter and amplification of signal in the frequency band from 3 to 4 mHz. Assuming that earthquakes are only the sources for the free oscillations, we calculate the synthetic spectrograms, which have not shown such a series of parallel lines as observed. The result of this synthetic test and characteristics of the observed spectrogram suggest that the mode signals we found are not of earthquake origin. We tentatively suggest atmospheric or oceanic origin for this newly discovered phenomenon of the solid Earth.

References

  • Agnew, D. C., J. Berger, W. E. Farrell, J. F. Gilbert, G. Masters, and D. Miller, Project IDA: A decade in review, EOS, 67(16), 203–212, 1986.

    Article  Google Scholar 

  • Benioff, H., J. C. Harrison, L. LaCoste, W. H. Munk, and L. B. Slichter, Searching for the Earth’s free oscillations, J. Geophys. Res., 64, 1334–1337, 1959.

    Article  Google Scholar 

  • Benioff, H., F. Press, and S. Smith, Excitation of the free oscillations of the earth by earthquakes, J. Geophys. Res., 66, 605–619, 1961.

    Article  Google Scholar 

  • Beroza, G. and T. Jordan, Searching for slow and silent earthquakes using free oscillations, J. Geophys. Res., 95, 2485–2510, 1990.

    Article  Google Scholar 

  • Buland, R., J. Berger, and F. Gilbert, Observations from the IDA network of attenuation and splitting during a recent earthquake, Nature, 277, 358–362, 1979.

    Article  Google Scholar 

  • Dziewonski, A. M. and D. L. Anderson, Preliminary reference Earth model (PREM), Phys. Earth Planet. Inter., 25, 297–356, 1981.

    Article  Google Scholar 

  • Dziewonski, A. M., G. Ekström, and M. P. Salganik, Centroid-moment tensor solutions for October–December 1994, Phys. Earth Planet. Inter., 91, 187–201, 1995.

    Article  Google Scholar 

  • Gilbert, F. and A. M. Dziewonski, An application of normal mode theory to the retrieval of structural parameters and source mechanisms from seismic spectra, Phil. Trans. R. Soc. London. A, 278, 187–269, 1975.

    Article  Google Scholar 

  • Kanamori, H. and J. Mori, Harmonic excitation of mantle Rayleigh waves by the 1991 eruption of Mount Pinatubo, Philippines, Geophys. Res. Lett., 19, 721–724, 1992.

    Article  Google Scholar 

  • Kanao, M. and T. Sato, Observation of tidal gravity and free oscillation of the earth with a LaCoste & Romberg gravity meter at Syowa Station, East Antarctica, Proc. 12th Int. Symp. Earth Tides, Beijing, edited by H. T. Hsu, pp. 571–580, 1995.

  • Kobayashi, N., Oscillation of solid planets excited by atmospheric motions (abstract in Japanese), Fall meeting of the Jpn. Soc. Planet. Sci., 84, 1996.

  • Park, J., C. R. Lindberg, and D. J. Thomson, Multiple-taper spectral analysis of terrestrial free oscillations: part I, Geophys. J. R. Astron. Soc., 91, 755–794, 1987.

    Article  Google Scholar 

  • Sato, T., K. Shibuya, Y. Tamura, M. Kanao, M. Ooe, K. Okano, Y. Fukuda, N. Seama, K. Nawa, K. Kaminuma, Y. Ida, M. Kumazawa, and T. Yuku-take, One year observation with a superconducting gravimeter at Syowa Station, Antarctica, J. Geod. Soc. Jpn., 41, 75–89, 1995.

    Google Scholar 

  • Sato, T., K. Shibuya, K. Nawa, K. Matsumoto, and Y. Tamura, On the diurnal and semidiurnal tidal factors at Syowa Station, Antarctica, J. Geod. Soc. Jpn., 42, 145–153, 1996.

    Google Scholar 

  • Tamura, Y., A harmonic development of the tide-generating potential, Marées Terrestres Bulletin d’Informations, 99, 6813–6855, 1987.

    Google Scholar 

  • Tamura, Y., Y. Aoyama, and K. Nawa, Gravimetric tidal factors at Syowa Station obtained from three-year observations with a superconducting gravimeter, Proc. NIPR Symp. Antarct. Geosci., 10, 1–10, 1997.

    Google Scholar 

  • Watada, S., Near-source acoustic coupling between the atmosphere and the solid earth during volcanic eruptions, Ph.D. dissertation, Caltech, 1995.

  • Widmer, R. and W. Zürn, Bichromatic excitation of long-period Rayleigh and air waves by the Mount Pinatubo and El Chichon volcanic eruptions, Geophys. Res. Lett., 19, 765–768, 1992.

    Article  Google Scholar 

Download references

Author information

Affiliations

  1. Department of Earth and Planetary Sciences, Nagoya University, Furo, Chikusa-ku, Nagoya, 464-8602, Japan

    Kazunari Nawa & Naoki Suda

  2. Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032, Japan

    Yoshio Fukao

  3. National Astronomical Observatory, Mizusawa, 2-12 Hoshigaoka, Mizusawa, Iwate, 023-0861, Japan

    Tadahiro Sato

  4. The Graduate University for Advanced Studies, 2-12 Hoshigaoka, Mizusawa, Iwate, 023-0861, Japan

    Yuichi Aoyama

  5. National Institute of Polar Research, 1-9-10 Kaga, Itabashi-ku, Tokyo, 173-0003, Japan

    Kazuo Shibuya

Authors
  1. Kazunari Nawa
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Naoki Suda
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Yoshio Fukao
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Tadahiro Sato
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Yuichi Aoyama
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Kazuo Shibuya
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Kazunari Nawa.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Nawa, K., Suda, N., Fukao, Y. et al. Incessant excitation of the Earth’s free oscillations. Earth Planet Sp 50, 3–8 (1998). https://doi.org/10.1186/BF03352080

Download citation

  • Received:

  • Revised:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1186/BF03352080

Keywords

  • Free Oscillation
  • Synthetic Seismogram
  • nGal Level
  • Superconducting Gravimeter
  • Syowa Station