600 quakes in past ten days
Unusual earthquake swarm detected off Oregon:
80 percent of all the planet's earthquakes occur along the rim of the Pacific Ocean, called the "Ring of Fire."
Our quakes are different from the quakes in California which are "strike-slip" quakes caused by the Pacific tectonic plate moving north and rubbing against the North American tectonic plate. Southern California is actually moving north and LA and SF will be adjacent to each other eventually - like millions of years from now.
Strike-slip fault.
The quakes in the Pacific Northwest happen because the San Juan de Fuca plate is sliding under the North American plate. This fault is called a subduction fault. The Cascadia Subduction Zone stretches from northern California to Washington.
Subduction zone.
Subduction quakes are the ones most likely to cause tsunamis and there are tsunami warning signs and sirens all along the Oregon coast.
HT Chas' Compilation.
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.We have small to medium size quakes under the ocean here regularly but they are too far away (100 to 150 miles out to sea) to be felt on land.
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.
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.
The hydrophones are left over from a network the Navy used to listen for submarines during the Cold War. They routinely detect passing ships, earthquakes on the ocean bottom and whales calling to one another.
Scientists hope to send out an OSU research ship to take water samples, looking for evidence that sediment has been stirred up and chemicals that would indicate magma is moving up through the Juan de Fuca Plate, Dziak said.
80 percent of all the planet's earthquakes occur along the rim of the Pacific Ocean, called the "Ring of Fire."
Our quakes are different from the quakes in California which are "strike-slip" quakes caused by the Pacific tectonic plate moving north and rubbing against the North American tectonic plate. Southern California is actually moving north and LA and SF will be adjacent to each other eventually - like millions of years from now.
Strike-slip fault.
The quakes in the Pacific Northwest happen because the San Juan de Fuca plate is sliding under the North American plate. This fault is called a subduction fault. The Cascadia Subduction Zone stretches from northern California to Washington.
Subduction zone.
Subduction quakes are the ones most likely to cause tsunamis and there are tsunami warning signs and sirens all along the Oregon coast.
HT Chas' Compilation.
Labels: earthquakes. tsunamis
posted by Joubert at 11:46 AM
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