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Structure of the Cascadia subduction zone. The Cascadia subduction zone is a 1,000 km (620 mi) long dipping fault that stretches from Northern Vancouver Island to Cape Mendocino in northern California. It separates the Juan de Fuca and North America plates. New Juan de Fuca plate is created offshore along the Juan de Fuca Ridge.
The name "Cascadia" was first applied to the whole geologic region by Bates McKee in his 1972 geology textbook Cascadia; the geologic evolution of the Pacific Northwest. Later the name was adopted by David McCloskey, a Seattle University sociology professor, to describe it as a bioregion. McCloskey describes Cascadia as "a land of falling waters."
Evolution of the Pacific Northwest Good text on the geology of Cascadia. One link on Northwest geology; Reducing Earthquake Losses Throughout the United States: Averting Surprises in the Pacific Northwest (USGS) USGS site on earthquakes; On the eruption of Mt. Meager Archived 2007-04-17 at the Wayback Machine
The boundary between the two is known as the megathrust, or the Cascadia subduction zone, fault. “That plate-boundary fault is normally locked, and stresses build up, and then when it lets go ...
Geology of the Cascade Range-related plate tectonics. See also: Geology of the Pacific Northwest and Cascade Volcanic Arc The Cascade Range is made up of a band of thousands of very small, short-lived volcanoes that have built a platform of lava and volcanic debris.
The 1700 Cascadia earthquake occurred along the Cascadia subduction zone on January 26, 1700, with an estimated moment magnitude of 8.7–9.2. The megathrust earthquake involved the Juan de Fuca plate from mid-Vancouver Island, south along the Pacific Northwest coast as far as northern California. The plate slipped an average of 20 meters (66 ...
In Cascadia, these events are marked by about two weeks of 1 to 10 Hz seismic trembling and non-earthquake ("aseismic") slip on the plate boundary equivalent to a magnitude 7 earthquake. (Tremor is a weak seismological signal only detectable by very sensitive seismometers.)
Atwater has spent much of his career studying the likelihood of large earthquakes and tsunamis in the Pacific Northwest region of North America. In 2005, he published a book with others, "The Orphan Tsunami of 1700," that summarizes the evidence for an 8.7–9.2 M w megathrust earthquake in the Pacific Northwest on 26 January 1700, known as the 1700 Cascadia earthquake.