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No. 118: Jul-Aug 1998

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The Song Of The Earth

After a major earthquake, the entire earth quivers like a sphere of jelly suspended in space. Already a slightly oblate sphere, the planet becomes successively a bit more oblate, then a bit more prolate, as illustrated. The amplitudes of these deformations are small, just a centimeter or so after big quakes. The tone or frequency of the quivers is just a few millihertz, which translates to periods ranging from 3-54 minutes. We doubt that the telestomping elephants mentioned under BIOLOGY can detect these quiverings.

That the earth does indeed "ring" is old news. Geophysicist A.E.H. Love mentioned the possibility in 1911. It is also recognized that large earthquakes can set the earth to ringing ("quivering" is better). What is news is the discovery by N. Suda et al that our planet rings even when no major quakes are occurring, and no one yet knows why. Suda et al write:

"The observed "background" free oscillations represent some unknown dynamic process of Earth."

Suda and his colleagues detected these oscillations using a superconducting gravimeter, which they installed in a seismically-quiet place: Antarctica.

The favorite explanation for the background oscillations is turbulence in the earth's atmosphere. Ocean tides and currents are also on the list as potential "bell-ringers." [El Ninos were not mentioned!]

(Suda, Naoki, et al; "Earth's Background Free Oscillations," Science, 279: 2089, 1998. Also: Kanamori, Hiroo; "Shaking without Quaking," Science, 279:2063, 1998.)

Earth vibrations: song of the Earth

From Science Frontiers #118, JUL-AUG 1998. 1998-2000 William R. Corliss

Science Frontiers Sourcebook Project Reviewed in:

Quotes

  • "A sourcebook of unexplained phenomena is therefore a valuable addition to a collection of scientific literature. William R. Corliss has provided this in the past with his source books of scientific anomalies in several subjects, and now he has provided it for astronomy. He has done an excellent job of collecting and editing a large amount of material, taken in part from scientific journals and in part from scientific reporting in the popular or semi-scientific press." -- "The Mysterious Universe: A Handbook of Astronomical Anomalies", reviwed by Thomas Gold, Cornell University, in Icarus, vol.41, 1980

  • "An interesting, systematic presentation of unusual weather [..] This book is recommended for a general audience" --"Corliss, William R., Tornados, Dark Days, Anomalous Precipitation, and Related Weather Phenomena, Sourcebook Project, 1983.", revieweed in Choice, September 1983
  • "..the science is necessarily somewhat speculative, but Corliss's symthesis is based on reputable sources." -- "Corliss, William R. (Compiler). Lightning, Auroras, Nocturnal Lights, and Related Luminous Phenomena" reviwed by Joseph M. Moran, Univ. of Wisconsin in Science Books and Films, Sep/Oct 1983

  • "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 (1987), p. 24., 02/1987