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Topic: Cascadia Earthquake

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In the News (Fri 26 Apr 19)

  Cascadia subduction zone - Wikipedia, the free encyclopedia
The width of the Cascadia subduction zone fault varies along its length, depending on the temperature of the subducted oceanic plate, which heats up as it is pushed deeper beneath the continent.
The movement was the equivalent of a 6.7 magnitude earthquake.
The last known great earthquake in the northwest was in January of 1700, the Cascadia Earthquake.
en.wikipedia.org /wiki/Cascadia_subduction_zone   (444 words)

 Cascadia earthquake - Wikipedia, the free encyclopedia
The 1700 Cascadia Earthquake was a magnitude 8.7 – 9.2 megathrust earthquake in 1700.
The earthquake involved 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 known as the Pacific Northwest of the United States.
In the case of a future Cascadia Earthquake, however, most of the damage would probably be from the earthquake itself due to the immense numbers of urban areas inluding three major cities and large quantity of vulnerable structures like brick buildings and highrises in the Cascadia region.
en.wikipedia.org /wiki/Cascadia_Earthquake   (527 words)

 Earthquake - Voyager, the free encyclopedia   (Site not responding. Last check: 2007-10-22)
Earthquakes also occur in volcanic regions and as the result of a number of anthropogenic sources, such as reservoir induced seismicity, mining and the removal or injection of fluids into the crust.
Deep focus earthquakes, at depths of 100's km, are possibly generated as subducted lithospheric material catastrophically undergoes a phase transition since at the pressures and temperatures present at such depth elastic strain cannot be supported.
Earthquakes have also been known to be caused by the removal of natural gas from subsurface deposits, for instance in the northern Netherlands.
www.voyager.in /Earthquake   (2040 words)

 Geodynamics - Giant earthquakes beneath Canada's West coast
Although the regional earthquake activity is quite high in some areas (magnitude 7 events occurred in 1918, 1946, 1949 and 1965), no earthquakes of any size have been detected on the subduction thrust fault itself (Figure 4).
The deformation through the earthquake cycle includes a viscous component that gives a time dependence to the deformation pattern and rate (e.g., Wang et al., 1994), but to a first approximation the response is elastic and at a steady rate between earthquakes.
Earthquakes are common in the continental crust of the northern Cascadia coastal region at depths less than 35 km, which corresponds to a maximum temperature of about 350°C. "Wadati-Benioff " earthquakes occur to a greater depth within the downgoing oceanic plate (to about 750°C).However, no earthquakes have been detected on the subduction thrust fault.
gsc.nrcan.gc.ca /geodyn/mega_e.php   (5978 words)

The epicenter, the focal depth and preliminary tensor analysis indicate that the mechanism for this earthquake was due to tensional (normal) faulting which occurred along the subducting Benioff seismic zone of the Juan de Fuca tectonic plate.
Thus, major earthquakes in the region are possible and have the potential of generating destructive tsunamis which could affect the entire coastal area from British Columbia to northern California, as well as Puget Sound.
It is difficult to estimate the recurrence interval of tsunamis since larger earthquakes on the Cascadia Megathrust are infrequent.
www.drgeorgepc.com /Earthquake2001USSeattle.html   (1786 words)

 Great Cascadia Earthquake Penrose Conference-Conveners
Further understanding of the great earthquake potential of the Cascadia subduction zone is required for seismic hazard characterization, engineering design, emergency planning and response, and other mitigation efforts in a region with a population of nearly 10 million people.
Evidence for past Cascadia earthquakes was examined and discussed during a canoe trip along the Niawiakum River in southwestern Washington and at a nearby park where lake, tidal marsh, and deep-sea cores collected during previous paleoseismological investigations were displayed.
Great Cascadia earthquakes generate tsunamis, the most recent of which was probably at least 10 m high on the Pacific coast of Washington, Oregon, and northern California, and up to 5 m high in Japan.
earthquake.usgs.gov /regional/pacnw/paleo/greateq/conf.html   (1637 words)

 Cascadia Earthquakes
Cascadia seismicity clearly is related to oblique convergence of oceanic (Juan de Fuca and Gorda) lthospheric plates with North America, resulting in components of both normal convergence and margin-parallel (roughly N-S) compression.
Earthquakes associated with relatively shallow (crustal) deformation, often on strike-slip faults in the upper plate.
A recent notable earthquake (M 3.7; 1 Jan 1997) of this type was related to dextral strike-slip motion on a fault near Yakima WA.
www.ruf.rice.edu /~leeman/CascadiaEQs.html   (1434 words)

 Giant Megathrust Earthquakes
While megathrust earthquakes have not been observed in the short (~150 year) written history of the west coast of Canada, there is compelling evidence that they have occurred in prehistorical times.
The landward extent of the rupture is an important factor for the shaking hazard at the inland cities of Victoria and Vancouver.
The potential for the next megathrust earthquake for Cascadia is also being studied by monitoring the deformation of the crust using very precise satellite technology (GPS), repeat levelling, changes in gravity, and long term tide gauge measurements.
earthquakescanada.nrcan.gc.ca /zones/cascadia/mega_e.php   (423 words)

 Cascadia Region
Cascadia's western boundary, in a geologic sense, lies approximately 50 to 70 miles off the Pacific coast, where two tectonic plates, the North America and Juan de Fuca plates, meet and collide at the breathtaking velocity of 1.5 inches per year.
Over the past decade, geologists have gathered ample evidence indicating that subduction along Cascadia's western boundary is accompanied by large (magnitude 8 or greater) earthquakes that occur along the contact zone between the two plates.
The "Earthquake" in "Cascadia Region Earthquake Workgroup" refers primarily to these subduction earthquakes, because it is this kind of earthquake that can have effects over a substantial part of Cascadia.
www.crew.org /about/cascadia.html   (390 words)

 LiveScience.com - Tsunami-Generating Earthquake Near U.S. Possibly Imminent
The Cascadia subduction zone, a 680-mile fault that runs 50 miles off the coast of the Pacific Northwest -- from Cape Mendocino in California to Vancouver Island in southern British Columbia -- has experienced a cluster of four massive earthquakes during the past 1,600 years.
At the Cascadia subduction zone, an oceanic tectonic plate called the Juan de Fuca is pulled and driven (subducted) beneath the continental North American plate, setting up conditions for undersea "megathrust" earthquakes.
Earthquakes at subduction zones (rather than at other types of faults such as thrust faults) produce the highest energy tsunamis, especially when they occur in deep water.
www.livescience.com /forcesofnature/050103_cascadia_tsunami.html   (973 words)

 Great Cascadia Earthquake Penrose Conference
The earthquake (or earthquakes) was caused by the sudden slip of the Pacific plate beneath the North America plate along the Cascadia subduction zone, a 1000-km(600-mi)-long fault that marks the landward-dipping boundary between the two tectonic plates off the coast of western North America.
A large tsunami that was generated by sudden movements of the ocean floor during the earthquake(s) deposited the layers when it inundated the coasts bordering the fault zone.
Because written records from other coasts that experience great earthquakes, such as western South America, suggest that no earthquake large enough to produce this type of tsunami in Japan occurred during this period, the Japanese researchers concluded that the tsunami was probably produced at the Cascadia subduction zone.
earthquake.usgs.gov /regional/pacnw/paleo/greateq/index.html   (1094 words)

 Cascadia Subduction Zone - SeattleWiki
The Cascadia Subduction Zone is a giant fault running off the coast of the Pacific Northwest.
The Cascadia Subduction Zone is in close enough range to Seattle to cause serious damage to the city.
In an earthquake, fill turns to liquid and structures on it can't be supported,so they collapse as their foundations sink into the ground.
seattlewiki.org /wiki/Cascadia_Subduction_Zone   (372 words)

 The Republic of Cascadia: Earthquake 2001
While Federalist controlled agencies such as the USGS are claiming that the Nisqually Earthquake was caused by a release of pent up energy from the Juan de Fuca plate subducting under the North American plate, Cascadian geoscientists remain skeptical.
However, it is an open secret in the military community that HAARP is really a program that aims to build a weapon of mass destruction that can trigger earthquakes, tsunamis, extreme weather events, and other seemingly natural disasters.
Had it not been for the foresight and technical know-how of Cascadian earthquake preparedness programs, the ballroom that they were in could have been a death trap, thereby wiping out a large chunk of the Cascadian technological brain trust.
www.zapatopi.net /cascadia/quake.html   (438 words)

 LiveScience.com - Orphan Tsunami Gets a Frightening Parent
Normally, tsunamis are preceded by earthquakes: the deadly Indian Ocean tsunami that devastated Southeast Asia last December, for example, was foreshadowed by a magnitude-9.3 undersea temblor.
Cascadia is located in the northwestern United States and is bounded on the east by the Cascades—the mountain range that includes the volcanic Mount St. Helens—and on the west by the Pacific Ocean.
It is now known that the Cascadia subduction zone is active and that the Juan de Fuca Plate is sliding under the North American Plate at an average rate of about 13 feet (4 meters) per century.
www.livescience.com /forcesofnature/051220_orphan_tsunami.html   (1141 words)

 Geodynamics - Cascadia Subduction Zone
In the period between the mega-earthquakes, the Juan de Fuca plate continues trying (unsuccessfully) to slide beneath the North American plate with the consequence that the rocks all along the edges of the plates are compressed or squeezed and uplifted.
Subduction-thrust earthquakes or mega-earthquakes are known to be one stage of a subduction-thrust Earthquake Cycle.
At the time of the next great earthquake it is expected that the accumulated compression will be totally released and that the outer coast of southern Vancouver Island will move up to 5 metres to the south-west.
gsc.nrcan.gc.ca /geodyn/cascadia_e.php   (736 words)

 ScienceDaily: Japanese Shipwreck Adds To Evidence Of Great Cascadia Earthquake In 1700
To judge the 1700 earthquake's size, its estimated magnitude can be compared with those of the 20th century's largest quakes the 1952 Kamchatka earthquake at magnitude 9.0, the 1960 Chilean earthquake at 9.5 and the 1964 Alaskan earthquake at 9.2.
Earthquake 'Pulses' Could Predict Tsunami Impact (December 5, 2005) -- The magnitude 9.2 earthquake that triggered a devastating tsunami in the Indian Ocean in December of 2004 originated just off the coast of northern Sumatra, but an "energy pulse" -- an area where...
Earthquake -- An earthquake is a sudden and sometimes catastrophic movement of a part of the Earth's surface.
www.sciencedaily.com /releases/2003/10/031031062553.htm   (2189 words)

 The M9 Cascadia Megathrust Earthquake of January 26, 1700
The undersea Cascadia thrust fault ruptured along a 1000 km length, from mid Vancouver Island to northern California in a great earthquake, producing tremendous shaking and a huge tsunami that swept across the Pacific.
The Cascadia fault is the boundary between two of the Earth's tectonic plates: the smaller offshore Juan de Fuca plate that is sliding under the much larger North American plate.
The earthquake also left unmistakeable signatures in the geological record as the outer coastal regions subsided and drowned coastal marshlands and forests that were subsequently covered with younger sediments.
earthquakescanada.nrcan.gc.ca /historic_eq/15-19th/1700/1700_e.php   (498 words)

 'Clusters' of earthquakes yield an ominous scenario
Alternatively, the current cluster of earthquakes may have one or more events left in it — some clusters within the past 10,000 years have had clusters of up to five events — and within a cluster, the average time interval between earthquakes is 300 years.
Since the last major Cascadia earthquake occurred in the year 1700, the next event may well be imminent.
That earthquake happened as the Indian plate moved towards the northeast beneath Asia, just like the Juan de Fuca plate is in the Pacific Northwest before it disappears beneath the North American plate.
www.eurekalert.org /pub_releases/2004-12/osu-oe122904.php   (942 words)

 Earthquake hazards - Oregon at Risk
Scientists also know the last Cascadia earthquake like the one just described was probably a magnitude 9 on January 26, 1700 and that these types of earthquakes have occurred many times in the Pacific Northwest in the last few thousand years.
Whatever size of earthquake your community can reasonably expect, the same preparation steps can be taken to prevent damage and protect lives.
Most earthquakes in Oregon are small in size, but many can produce significant damage at a local level.
www.oregongeology.com /sub/earthquakes/oratrisk.htm   (519 words)

 Seismo-Watch Notable Earthquake of the Week, The Great Cascadia M9+ Earthquake, January 26, 1700
The team examined records of great earthquakes and tsunamis throughout the Pacific region and concluded the waves must have originated from a powerful earthquake along the Cascadia subduction zone, a megathrust fault located off the Northern California, Oregon and Washington coast.
Cascadia earthquake is enormous and is being intensely studied.
Subsequent geologic investigations have shown that earthquakes of similar strength have occurred at irregular time in the past 6,000 years.
www.seismo-watch.com /EQSERVICES/NotableEQ/Jan/0126.Cascadia.html   (231 words)

 GSC Pacific - Sidney: Pacific Geoscience Centre
Using computer models, it is estimated that the earthquake in January 1700, that caused the tsunami in Japan, must have had a magnitude of 9.0.
This Cascadia earthquake of 1700 was the largest earthquake in Canada, as such, it needs to be studied.
This paper confirms that the January 1700 earthquake was large enough to have ruptured the entire length of the plate boundary of the Pacific Coast (from northern Vancouver Island to northern California) resulting in strong ground shaking and a significant tsunami.
www.pgc.nrcan.gc.ca /press/index_e.php   (441 words)

 Cascadia Seismic Hazard Studies - USGS WCMG   (Site not responding. Last check: 2007-10-22)
Computer simulations were made of tsunamis generated by potential earthquakes along known faults offshore of Washington and Oregon.
The relationship between the parameters that define earthquake rupture and local tsunamis is complex.
For tsunamis that have traveled far from the origin of the earthquake, the magnitude of the earthquake is a good measure of the size of the tsunami.
walrus.wr.usgs.gov /cascadia   (685 words)

 Protecting our Ports and Harbors Bibliography
Evidence for large earthquakes at the Cascadia subduction zone.
Archeological Evidence for Village Abandonment Associated with the Late Holocene Earthquakes at the Northern Cascadia Subduction Zone.
Fore-arc Migration in Cascadia and its Neotectonic Significance.
www.csc.noaa.gov /products/tsunamis/htm/cascadia/papers.htm   (409 words)

 1700 Japan tsunami linked to massive North American quake
The earthquake apparently ruptured the full length of an enormous fault, known as the Cascadia subduction zone, which extends more than 1,000 kilometers [600 miles] along the Pacific coast from southern British Columbia to northern California.
A giant Cascadia earthquake would also warp large areas of seafloor, thereby setting off a train of ocean waves -- a tsunami -- that could prove destructive even on the far side of the Pacific Ocean.
Few scientists took that threat in the Cascadia region seriously until 1996, when Japanese researchers, in a letter to the journal Nature, stunned their North American colleagues by linking a tsunami in Japan to geologic reports of an earthquake and tsunami at the Cascadia subduction zone.
www.eurekalert.org /pub_releases/2003-11/agu-1jt112003.php   (878 words)

 Earthquake Catalogs: Multidisciplinary Center for Earthquake Engineering Research (MCEER)   (Site not responding. Last check: 2007-10-22)
An attempt to enumerate, summarize, and evaluate available information for earthquakes in the Pacific Northwest Cascadia Region; and to indicate what other materials might be improve understanding of each event.
The Cascadia Catalog is available via ftp and based on a Microsoft ACCESS 2.0 compilation of a dozen existing catalogs, plus newspaper articles, weather observers' reports, diary entries, and other information about earthquakes in Washington, Oregon, and British Columbia between 1793-1929.
This search engine is produced by the US National Earthquake Information Center (NEIC) and provides access to historical and current databases which cover earthquakes worldwide form 2150 B.C. to the present, and magnitude from 0.9 to 9.9.
mceer.buffalo.edu /links/eqcatalogs.asp   (533 words)

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