Earthquake of Cascadia of 1700

The earthquake of the Cascades of 1700 (in English the 1700 Cascadia Earthquake ) is a supposed earthquake of a magnitude between 8,7 and 9,2 which occurred in the zone of subduction of the Cascades in 1700 in the north-eastern Pacific. This earthquake implied the Plaque Juan de Fuca which is inserted under the North-American Plaque in the Pacific Ocean, since the medium of the Vancouver Island off the south-western coast of Canada as a Colombia-British until the north of the California, along the north-western coast of the Pacific. The length of the rupture was approximately 1000 kilometers with an average slip of 20 meters.

The earthquake of the Cascades caused a Tsunami which struck the coasts of Japan and the coasts of the North-West of North America and can also be related to the Bonneville slide , the landslide which closed the valley Columbia.

Evidence of the earthquake

The elements supporting the assumption of the earthquake into 1700 were gathered in the book of 2005, The Orphan Tsunami off 1700 , by the Géologue Brian Atwater.

It suggests that the earthquake occurred in the 9 hour old neighborhoods of the evening the January 26th 1700. Although it is not did not exist any document written at this period in the area, the date and specific time could be given in the Japanese writings of the time which announces an important tsunami on the Eastern coasts of Japan, tsunami which is not dependant has any earthquake in this area of the sphere. The principal evidence connecting this tsunami describes in Japan and an earthquake in the north-western Pacific comes from the studies made on the rings of the tree trunks, the Dendrochronologie, which show that the giant thujas of Califonie (called red cedars in the area) of the low North-American coastal forests, i.e. in the zone covered by the tide caused by the earthquake, had their last ring of growth in 1699, the last season of growth of the front shafts the tsunami. A Oral tradition of the Amerindian inhabitants of the area also exists, evoking such a catastrophe, but without specifying the date of it.

Future threats

The geological data reveal that the " mégas tremors of terre" (those which have a magnitude of 8 or more) occur in the zone of Cascadia subduction approximately every 500 years on average, often accompanied by Tsunami S. There exist indices that at least 13 events of this type one took place, with intervals varying from 300 to 900 years, with a 590 years average. It is estimated that the preceding earthquakes intervened in 1310 before JC, 810 before JC and 170 after JC.

When the zone of subduction yields with an earthquake of magnitude 9, that sends a powerful tsunami towards the coast. The jolts last 4 minutes or more, involving landslides. Then the tsunami strikes the coastal area, destroying the structures which are there. That is probably more the violent one earthquake who can strike the continental United States.

As that was seen at the time of the Earthquake of December 26th, 2004, the principal damage comes from the tsunamis generated in the zone of subduction. However in the case of future an earthquake of the zone Cascadia, the majority of the damage would come rather from the earthquake him even because of the density of the urban areas of the sector of which Seattle, Portland, Vancouver, Victoria and Tacoma and with vulnerable constructions like the brick buildings or those great height. The coast of the Cascades is equipped with various escape way and alarm systems to the tsunamis.

Other zones of subduction know such earthquakes all the 100– 200 years; the length of the interval here results from a slower displacement of the tectonic plate.

This rate of convergence between the Plate Juan de Fuca and the North-American Plaque is of 40 mm/an.

Similar earthquakes of subduction

Other earthquake of subduction similar already occurred of which the slightly more powerful earthquake of the Good Friday of 1964 in Alaska with a magnitude of 9,2 the great earthquake of Chile of 1960 with a magnitude of 9,5, earthquakes of Kamchatka a magnitude of 9 and finally the earthquake of the Indian Ocean of December 2004 to 9,2.

See too

List of seismic catastrophes

Source

External bonds and references

national English

Canada Resources: evaluation off Cascadia subduction zone hazards
USGS one the Cascadia earthquake
Repository off information one the Cascadia earthquake
Japanese tsunami descriptions
Science Daily one the Cascadia Earthquake & Japanese obviousness
Canadian with source has possible Nice map
earthquake.usgs.gov/one tie to the Bonneville Slide
300th year article
Lessons from surviving has tsunami
The Orphan Tsunami off 1700
Seattle scenario description

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