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By JEFF BARNARD
GRANTS PASS, Ore. - Scientists listening to underwater microphones have detected an unusual swarm of earthquakes off central Oregon, something that often happens before a volcanic eruption — except there are no volcanoes in the area.
There have been more than 600 quakes over the past 10 days in a basin 150 miles southwest of Newport. The biggest was magnitude 5.4, and two others were more than magnitude 5.0, OSU reported.
Originally posted by verylowfrequency
reply to post by OzWeatherman
I see. So, you saying by having many like this it negates having one big more destructive one. That makes sense, thanks.
Originally posted by pynner
But to make the statement that these quakes are good cause they release energy and avoid the big one... sorry, that's not accurate at all.
For more details on this topic, see Mount Mazama.
Volcanic activity in the area is fed by subduction off the coast of Oregon as the Juan de Fuca Plate slips below the North American Plate (see plate tectonics). Heat and compression generated by this movement has created a mountain chain topped by a series of volcanoes, which together are called the Cascade Range. The large volcanoes in the range are called the High Cascades. However, there are many other volcanoes in the range as well, most of which are much smaller.
Scientists listening to underwater microphones have detected an unusual swarm of earthquakes off central Oregon, something that often happens before a volcanic eruption — except there are no volcanoes in the area.
Scientists don't know exactly what the earthquakes mean, but they could be the result of molten rock rumbling away from the recognized earthquake faults off Oregon, said Robert Dziak, a geophysicist for the National Oceanic and Atmospheric Administration and Oregon State University
On the hydrophones, the quakes sound like low thunder and are unlike anything scientists have heard in 17 years of listening, Dziak said. Some of the quakes have also been detected by earthquake instruments on land.
Microseismic records from five broadband IRIS stations located at distances of 1000-2000 km from the earthquake source are studied. Unordinary programs are used to extract hidden periodicities, determine signal coherence at different stations, and reveal asymmetry in wave amplitudes. The records obtained at a few stations 60 h before the Sumatra earthquake include periodic oscillations in the range of periods from 20 to 60 min that arose after the McQuary earthquake and continued for about 24 h. Synchronization of waves recorded at all stations commenced 53 h before the Sumatra earthquake and continued up to the time of the earthquake, with the predominant period gradually increasing from a few minutes to tens of minutes.
Between 9:00 PM and 10:00 PM, local time, on January 26th 1700, a great earthquake shook the Pacific Northwest. This quake, with magnitude estimated at 9.0, rocked the region with strong shaking for several long minutes minutes while coastal Washington plummeted as much as 1.5 meters relative to coastal waters.
How is it possible to know that any event on the Cascadia Subduction ever occurred, let alone to place it within one hour of its occurrence 300 years ago? Let the evidence speak for itself and discover an ancient earthquake in the Pacific Northwest.