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Cascadia Earthquake

A map of the Cascadia Earthquake

The Cascadia Earthquake was a magnitude 8.7 — 9.2 megathrust earthquake of the Juan de Fuca Plate in the Pacific ocean, from mid-Vancouver Island of southwest Canada off British Columbia to northern California, off what is now the Pacific Northwest of the United States.

It took place at about 9:00 in the evening of January 26, 1700, While no one who lived there at the time kept written records, the earthquake's occurrence is known from Japanese records of a tsunami that could not be tied to any other earthquake. The natives have oral traditions. The most important initial clue came from studies of tree rings (dendrochronology) which showed a large number of fallen trees whose last year of growth was 16991700; with this information, the Japanese tsunami records were then used to determine the exact date.

It may be linked to the Bonneville slide.

Other megathrust earthquakes are the slightly more powerful 1964 American Good Friday Earthquake measured at magnitude 9.2, the 1960 Great Chilean Earthquake measured at 9.5, and the 2004 Indian Ocean earthquake at 9.0.

See also New Madrid Earthquake, which measured 8.0 or higher (the Richter Scale had not been invented yet).

Wikipedia links

External links and references

  • USGS on the Cascadia earthquake http://earthquake.usgs.gov/regional/pacnw/paleo/greateq/index.html
  • Repository of information on the Cascadia earthquake http://www.pnsn.org/HIST_CAT/histcat.html
  • Japanese tsunami descriptions http://www.agu.org/pubs/crossref/2003/2003JB002521.shtml
  • Science Daily on the Cascadia Earthquake & Japanese evidence http://www.sciencedaily.com/releases/2003/10/031031062553.htm
  • Canadian source with a nice map http://www.pep.bc.ca/cascadia_1700/cascadia_1700.html
  • earthquake.usgs.gov/ on possible tie to the Bonneville Slide http://earthquake.usgs.gov/regional/pacnw/paleo/greateq/20020515.html


Last updated: 02-10-2005 16:33:08
Last updated: 05-03-2005 02:30:17