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Originally posted by dreams n chains
Anyone have recordings of these sounds from out west? The ones the news reports are about? Or did I miss them somewhere?
Feb. 2, 2009 -- A bizarre form of earthquake, which happens over the course of two to three weeks but makes barely a rumble, are lending important clues to the Cascadia subduction zone in the Pacific northwest, one of the most dangerous fault zones on Earth.
For the last decade, slow-slip earthquakes have been measured in fault zones all over the world, baffling scientists. Though the 'quakes' release as much energy as a normal earthquake between magnitude 6.0 and 6.5, they produce almost no shaking.
But researchers have measured separate, small tremors at around the same time as the silent quakes. And in a new study in the journal Science, a team of seismologists show the two events are really one in the same.
The 1700 Cascadia Subduction Zone Earthquake - A Tsunami strikes Japan
An earthquake of magnitude 9 rocked the Pacific Northwest on January 26, 1700 around 9:00 PM. A series of independent discoveries over the past two decades have narrowed the window of occurrence of this "great quake" to a precise time. Preliminary evidence consistant with this date came from carbon dating, tree ring studies, and soil deposits. Although these lines of evidence enabled scientists to verify that a great subduction zone earthquake struck the Pacific Northwest within one or two decades of 1700, the exact date date remained unknown.
Kenji Satake, a researcher from the Geological Survey of Japan, along with a team of scientists from the University of Tokyo found Japanese records to tsunami occurrences along the country's eastern coastline between January 27 and 28, 1700. Careful analysis of these historic tsunami records indicated that several coastal villages were damaged.
SEATTLE - You can't feel it, but at this moment, parts of Washington and British Columbia are having an earthquake. It is a slow-moving trembler that can't be felt and won't cause any injuries or damage. Still, by the end of the event, which already has lasted more than two weeks, it is likely to have released about as much energy as equivalent to a 6.7 quake similar to that the Nisqually earthquake did in February 2001.
The movement is occurring deep beneath the Strait of Juan de Fuca and parts of Vancouver Island in the area where the Juan de Fuca tectonic plate slides beneath, or subducts, the North American plate. The event began on Feb. 26 and could continue for another two or three weeks.
And scientists are now learning that these quakes may not be all that rare.
For years, a Canadian scientist fretted about tiny tremors that registered on seismographs - when they registered at all - only as background noise.
But about six months ago, Garry Rogers decided that the little high-frequency tremors signaled the slow, so-called "silent earthquakes" deep below the surface of the Earth - quakes that over a period of weeks can release as much energy as damaging surface temblors.
"People have been ignoring them for years," Rogers said of the tremors in a telephone interview Friday from the Pacific Geoscience Center in Victoria, British Columbia.
He and colleagues plan to outline the connection between the tremors and the silent quakes next month at the Seismological Society of America's annual meeting in Puerto Rico.
Now "we know that as soon as we see these tremors, that it's started," he said.
Rogers "has been worrying about this for years now," said a colleague, geophysicist Tony Qamar at the University of Washington's Seismology Lab in Seattle. "In the early days, some people tried to tell him it's not anything to worry about."
Rogers said the tremors "look very much like wind noise," but when he looked outside while they were registering, trees were still and there clearly was no wind.
After studying the data - and realizing that the tremors coincided with Global Positioning System readings that indicated silent quakes or "slip events" - he waited. Researchers at Central Washington University in Ellensburg had determined that the deep quakes occur every 12 to 14 months, so action was expected this spring.
evidence indicates that great earthquakes may have occurred at least seven times in the last 3,500 years, suggesting a return time of 300 to 600 years. There is also evidence of accompanying tsunamis with every earthquake
Recent findings concluded the Cascadia subduction zone was more hazardous than previously suggested. The feared next major earthquake has some geologists predicting a 10 to 14% probability that the Cascadia Subduction will rupture in the next 50 years, producing an event of magnitude 9 or higher