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No. 29: Sep-Oct 1993

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Astronomy And Earthquakes

"Large earthquakes in southern California with epicenters between 33 and 36N have statistically significant 12 hourly, lunar fortnightly and 18.6-yr periodicities. Smaller earthquakes in the same region do not display these periodicities. A search for tidal effects associated with these periodicities shows that large earthquakes have significant correlations with the times and orientations of daily/semi-daily tidal stresses while the lunar fortnightly terms are associated with the ocean tides along the Southern Californian coast."

(Kilston, S., and Knopoff, L; "Lunar-Solar Periodicities of Large Earthquakes in Southern California," Nature, 304:21, 1983.)

Comment. The literature contains many similar correlations for quakes of various sizes, for various restricted geographical areas, and for various depths. Many of these studies are summarized in our Catalog volume Earthquakes, Tides, Unidentified Sounds. For more information on this book, visit: here.

Tidal strain over a fortnight around an earthquake
One tidal strain component (normalized) plotted for 20 days before and after the earthquake of June 25, 1925, showing the large fortnightly modulation of the diurnal tide. Curiously (perhaps anomalously) the quake occurred during a period of minimum strain.

From Science Frontiers #29, SEP-OCT 1983. 1983-2000 William R. Corliss

Science Frontiers Sourcebook Project Reviewed in:


  • "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