Incessant excitation of the Earth's free oscillations

• Nawa Kazunari

  Department of Earth and Planetary Sciences, Nagoya University

• Suda Naoki

  Department of Earth and Planetary Sciences, Nagoya University

• Fukao Yoshio

  Earthquake Research Institute, University of Tokyo

• Sato Tadahiro

  National Astronomical Observatory

• Aoyama Yuichi

  The Graduate University for Advanced Studies

• Shibuya Kazuo

  National Institute of Polar Research

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.

Journal

• Earth, Planets and Space

  Earth, Planets and Space 50 (1), 3-8, 1998

  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: 1390282681485617536
• NII Article ID: 10002205455
• NII Article ID: 130003955856
• NII Book ID: AA11211921
• DOI: 10.1186/bf03352080
• ISSN: 18805981
• ISSN: 13438832
• ISSN: http://id.crossref.org/issn/13438832
• Web Site: https://link.springer.com/content/pdf/10.1186/BF03352080.pdf
• Web Site: https://link.springer.com/article/10.1186/BF03352080/fulltext.html
• Web Site: http://link.springer.com/content/pdf/10.1186/BF03352080
• Text Lang: en
• Data Source:
  • JaLC
  • Crossref
  • CiNii Articles
• Abstract License Flag: Disallowed