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The Cascadia subduction zone is a 960 km (600 mi) fault at a convergent plate boundary, about 100–200 km (70–100 mi) off the Pacific coast, that stretches from northern Vancouver Island in Canada to Northern California in the United States.
Scientists pieced together an understanding of the last such Cascadia quake, in 1700, in part via Japanese records of an unusual orphan tsunami that was not preceded by shaking there.
The most important clue linking the tsunami in Japan and the earthquake in the Pacific Northwest comes from studies of tree rings (dendrochronology), which show that several "ghost forests" of red cedar trees in Oregon and Washington, killed by lowering of coastal forests into the tidal zone by the earthquake, have outermost growth rings that formed in 1699, the last growing season before the ...
Scientists now know the 700-mile fault called the Cascadia Subduction Zone, 100 miles off the coast of Northern California stretching north to Vancouver Island, could trigger a 9.0 magnitude ...
Scientists say that the Cascadia subduction zone off the coast of the Pacific Northwest has the potential to spark a magnitude-9.0+ earthquake, plus a subsequent tsunami. That scenario last ...
The Pacific Northwest is seismically active. The Juan de Fuca Plate is capable of producing megathrust earthquakes of moment magnitude 9: the last such earthquake was the 1700 Cascadia earthquake, which produced a tsunami in Japan, [5] and may have temporarily blocked the Columbia River with the Bonneville Slide. [6]
On Jan. 26, 1700, an earthquake on the Cascadia fault caused the forest to lurch downward by more than 3 feet. Soon after, a tsunami perhaps 100 feet high barreled through at 20 or 30 mph.
Area of the Cascadia subduction zone and the modern Cascade Volcanic Arc. Because of the very large fault area, the Cascadia subduction zone can produce large earthquakes of magnitude 7.0 or greater. The interface between the Juan de Fuca and North American plates remains locked for periods of roughly 500 years.