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Topic: Cascadia subduction zone

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	Subduction - Wikipedia, the free encyclopedia
		Subduction zones are associated with the deepest earthquakes on the planet.
		Subduction zones are also notorious for producing devastating earthquakes because of the intense geological activity.
		Subduction Zone Biology: Because subduction zones are the coldest parts of the Earth's interior and life cannot exist at temperatures >150°C, subduction zones are almost certainly associated with the deepest (highest pressure) biosphere.
	en.wikipedia.org /wiki/Subduction_zone (1162 words)

	Cascadia subduction zone - Wikipedia, the free encyclopedia
		The Cascadia subduction zone is a very long sloping fault that stretches from mid-Vancouver Island to northern California.
		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.
		Thermal and deformation studies indicate that the locked zone is fully locked for 60 kilometers downdip from the deformation front.
	en.wikipedia.org /wiki/Cascadia_subduction_zone (418 words)

	NationMaster.com - Encyclopedia: Subduction zone (Site not responding. Last check: 2007-11-06)
		Subduction zones exist where an oceanic plate collides with a continental plate and sinks below the latter plate into the asthenosphere.
		When oceanic plate collides with continental plate, the oceanic plate is subducted, creating regions such as the Cascadia subduction zone of northwestern North America.
		Subduction zones are also notorious for producing earthquakes because of the intense geological activity.
	www.nationmaster.com /encyclopedia/Subduction-zone (208 words)

	Geologic Setting of Mount Shasta
		The Cascadia subduction zone is a shallowly-dipping fault that separates the Gorda, Juan de Fuca, and Explorer plates from the overriding North American plate (Figure 4).
		Only the upper part of the subduction zone is marked by seismic and volcanic activity, however, because this is where the downgoing oceanic plates are rigid and water-rich.
		In addition to producing earthquakes and tsunamis, however, the subduction zone is also the source of the magmas that sustain volcanism in the Cascades.
	www.siskiyous.edu /shasta/geo/set.htm (1069 words)

	Earthquake Information for Port Orford, Oregon
		CSZ earthquakes are believed to occur every 200 to 600 years.
		The Cascadia subduction zone is the convergent boundary between the large North America plate and the small Juan de Fuca and Gorda plates to the west.
		Subduction earthquakes such as those that occur off the Oregon coast are particularly effective in generating tsunamis.
	www.portorford.org /community/earthquake.html (209 words)

	Cascadia Megathrust Earthquakes
		The width of the Cascadia Subduction Zone fault varies along its length, depending on the temperature of the subducted oceanic slab, which heats up as it is pushed deeper beneath the continent.
		Great Subduction Zone earthquakes are the largest earthquakes in the world, and can exceed magnitude 9.0.
		Earthquake size is porportional to fault area, and the Cascadia Subduction Zone is a very long sloping fault that stretches from mid-Vancouver Island to Northern California.
	www.pnsn.org /HAZARDS/CASCADIA/cascadia_zone.html (303 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.
		The Cascadia subduction zone occurs where the relatively thin Juan de Fuca plate moves eastward and under the westward-moving North American Plate.
	www.livescience.com /forcesofnature/050103_cascadia_tsunami.html (961 words)

	Cascadia Earthquake: Facts and details from Encyclopedia Topic (Site not responding. Last check: 2007-11-06)
		The juan de fuca plate is a tectonic plate subducting under the northerly portion of the western side of the north american plate....
		Other subduction zones usually have such earthquakes every 100–200 years; the longer interval here may indicate unusually large stress buildup and subsequent unusually large earthquake slip.
		Cascadia is the ecological and climateclimatic region of north america bounded by the cascade range and the pacific ocean....
	www.absoluteastronomy.com /encyclopedia/c/ca/cascadia_earthquake.htm (1583 words)

	CCALMR TSUNAMI!
		CSZ earthquakes are rare events: the last has occurred about 300 years ago, and they are believed to occur every 200 to 600 years.
		The length of the crosshatched area is the approximate length of the postulated fault rupture for a magnitude 8.8 earthquake on the Cascadia subduction zone.
		An extensive subsidence zone is visible off the coast of Oregon and Washington, leading to subsidence at the shoreline that does not match coseismic subsidence inferred from studies by Curt Peterson of buried wetland soils.
	www.ccalmr.ogi.edu /tsunami (849 words)

	Pacific coast's tsunami threat
		The newest studies on the Cascadia Subduction Zone off the coast of the Pacific Northwest have identified a "clustering" of great earthquakes of the type that would cause a major tsunami.
		The studies show the quake zone has already experienced four major quakes in the past 1,600 years, which could mean the cluster is over and has entered a quiet period.
		The other is the Cascadia zone, a 600-mile long fault zone that runs from Cape Mendocino in California to Vancouver Island in southern British Columbia.
	www.his-forever.com /pacific_coasts_tsunami_threat.htm (923 words)

	Sinking coastlines may precede large subduction zone quakes
		If coastal subsidence is common before subduction zone quakes, areas such as those ringing the Pacific Rim could be on the lookout for subsidence as a warning of possible future megathrust quakes like the Dec. 26 9.0 Sumatra-Andaman Islands earthquake, the researchers say.
		Subduction zones are areas where one of the Earth's tectonic plates slips under another, raising mountain ranges along the margin sprinkled with volcanoes.
		Whether suitable coastal marshes can be found near all subduction zones is a big question, however, and not all subduction zones may act the same.
	www.eurekalert.org /pub_releases/2005-01/uoc--scm012005.php (1263 words)

	Strain Accumulation Along the Cascadia Subduction Zone
		Geodetic measurements of present-day deformation show that the Cascadia subduction zone (CSZ) (Figure 24.1) is accumulating strain, and geologic evidence of abrupt episodic coastal subsidence in the past suggests that this strain is periodically released in large earthquakes [Clague, 1997].
		The contraction rates are highest in networks close to the CSZ deformation front, such as in northern California, and decrease with distance from it, becoming indistinguishable from zero at the most distant network near Hanford (Figure 24.3).
		The observed horizontal strain rates indicate that strain is accumulating everywhere along the CSZ from Cape Mendocino to the Strait of Juan de Fuca.
	www.seismo.berkeley.edu /seismo/annual_report/ar99_00/node28.html (1430 words)

	The Eureka Reporter... Real News by Real People (Site not responding. Last check: 2007-11-06)
		The Cascadia subduction zone is the area where the Juan de Fuca and Gorda plates are moving beneath the North American plate, Cashman said.
		Kelsey said the Cascadia subduction zone earthquakes and their subsequent tsunamis appear to have occurred in clusters — several magnitude 9 earthquakes during a few hundred years followed by a gap of roughly 1,000 years.
		Kelsey said that he thought that the magnitude-9 earthquake 300 years ago was probably the beginning of the next cluster of big Cascadia subduction zone quakes that he said is more likely to occur in the next few decades to hundreds of years.
	www.eurekareporter.com /Stories/fp-01270511.htm (665 words)

	Subduction Zone Processes
		Fluids expelled from subducted or accreted sediments transport chemical constituents both within the sediment section, thereby assisting in diagenesis and hydrocarbon concentration, and to the seafloor, supplying nutrients to chemosynthetic animal communities.
		While the three-dimensional architecture of subduction zones and their accretionary prisms has been well-characterized in some locations around the world, our understanding of the time dependence of the processes affecting them is poor for the simple technological reason that time-series observations at long time scales are difficult to obtain at sea.
		Curves for several fault geometries are given; parameters are fault dip, and widths of the locked zone and a transition zone where inter-seismic slip varies from zero to the full plate rate (derived from Hyndman and Wang, 1995; curves from model of Thatcher and Rundle, 1984).
	www.neptune.washington.edu /pub/white_paper/scidriv3.html (2063 words)

	Cascadia Subduction Zone Earthquake Scenario Project
		Cascadia Subduction Zone Earthquakes: A magnitude 9.0 earthquake scenario
		A Cascadia Subduction Zone earthquake scenario will illustrate private sector dependencies on the continued functioning of public sector infrastructure, such as transportation networks, to carry out their own response and recovery actions.
		The Cascadia Subduction Zone is the major fault zone that extends offshore parallel to the Pacific coast from central Vancouver Island, Canada south to northwestern California.
	www.crew.org /about/scenario.html (678 words)

	'Clusters' of earthquakes yield an ominous scenario
		CORVALLIS, Ore. — The newest studies on the Cascadia Subduction Zone off the coast of the Pacific Northwest have identified a "clustering" of great earthquakes of the type that would cause a major tsunami, yielding a historical record with two distinct implications - one that's good, the other not.
		Since the last major Cascadia earthquake occurred in the year 1700, the next event may well be imminent.
		The Asian event happened where the India plate was being subducted beneath the Burma microplate, and it ruptured — for the first time since 1833 - along a 600-mile front that is just about the same length as the Cascadia Subduction Zone.
	www.eurekalert.org /pub_releases/2004-12/osu-oe122904.php (942 words)

	ScienceDaily: 'Clusters' Of Earthquakes Yield An Ominous Scenario
		CORVALLIS, Ore. -- The newest studies on the Cascadia Subduction Zone off the coast of the Pacific Northwest have identified a "clustering" of great earthquakes of the type that would cause a major tsunami, yielding a historical record with two distinct implications - one that's good, the other not.
		The Asian event happened where the India plate was being subducted beneath the Burma microplate, and it ruptured -- for the first time since 1833 - along a 600-mile front that is just about the same length as the Cascadia Subduction Zone.
		Sediment Could Be A Major Factor In Biggest Subduction Zone Earthquakes (February 1, 2006) -- New research indicates sediment buildup in tectonic plate deformations could play a major role in determining the severity of subduction zone...
	www.sciencedaily.com /releases/2005/01/050111161713.htm (2242 words)

	Cascadia Subduction Zone (Site not responding. Last check: 2007-11-06)
		In 1989, we piggybacked on an multichannel seismic reflection survey offshore to conduct an onshore/offshore experiment to image a transect across the margin from the subduction zone deformation front to the Willamette Valley (funded by NSF).
		In 1993 and 1994, with colleagues from USGS and from Stanford, Lehigh, and Rice Universities) we moved to northern California to image the southern Cascadia subduction zone and northern San Andreas Fault (funded by NSF and USGS).
		Trehu, A.M., G. Lin, E. Maxwell, C. Goldfinger, A seismic reflection profile across the Cascadia subduction zone offshore central Oregon: new constraints on the deep crustal structure and on the distribution of methane in the accretionary prism, Jour.
	quakes.oce.orst.edu /Trehu/Ships (251 words)

	CascadiaSubduction-Sci-52501
		In contrast, the Cascadia event occurred on the downward extension of the locked earthquake-generating fault, where aseismic slip or distributed ductile shearing (7) was expected to occur at a uniform speed.
		The Cascadia subduction zone last experienced a great earthquake in 1700 (10) and so may be only about halfway through its ~600-year earthquake cycle.
		For the Cascadia episode, the ratio of fault slip to fault area was quite small, about two orders of magnitude less than that typical for earthquake slip.
	ajdubre.tripod.com /Physics/CascadiaSubduction-Sci-52501.html (1094 words)

	subduction
		Because subduction zones are the coldest parts of the Earth's interior and life cannot exist at temperatures >150°C, subduction zones are almost certainly associated with the deepest (highest...
		Subduction Zones : When two oceanic plates collide, the younger of the two plates, because it is less dense...
		Subduction Subduction zones exist where an oceanic plate collides with a continental plate and sinks, below the latter plate, into the asthenosphere.
	www.logicjungle.com /find-subduction.html (244 words)

	12-30-04 "CLUSTERS" OF EARTHQUAKES HAVE AN OMINOUS SCENARIO
		CORVALLIS, Ore. - The newest studies on the Cascadia Subduction Zone off the coast of the Pacific Northwest have identified a "clustering" of great earthquakes of the type that would cause a major tsunami, yielding a historical record with two distinct implications - one that's good, the other not.
		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.
		The Asian event happened where the India plate was being subducted beneath the Burma microplate, and it ruptured - for the first time since 1833 - along a 600-mile front that is just about the same length as the Cascadia Subduction Zone.
	www.oregonstate.edu /dept/ncs/newsarch/2004/Dec04/clusters.htm (957 words)

	Geological Society of America - Penrose Conference - 2000
		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.
		In addition, the transition zone, which separates the locked zone from the zone of continuous sliding to the east, is also poorly constrained.
	www.geosociety.org /penrose/00pcrpt2.htm (1656 words)

	LiveScience.com - Orphan Tsunami Gets a Frightening Parent
		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.
		The tsunami showed that the risk of a major earthquake striking the Cascadia region not only existed but that it had manifested itself at least once in the recent past, Atwater said.
	www.livescience.com /forcesofnature/051220_orphan_tsunami.html (1140 words)

	ScienceDaily: Deepsea Cores Offer New Clues To Earthquake Cycles
		This Cascadia subduction zone, long thought to be strangely dormant, presented an enigma to earthquake scientists.
		Subduction zones are areas where two plates of the earth's crust meet, with one plate bending and sliding down under the other.
		In another typical scenario, the two plates of a subduction zone may periodically slip violently, causing some of the greatest earthquakes in the earth's crust.
	www.sciencedaily.com /releases/2001/12/011205065937.htm (2137 words)

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