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Scientists eye threat of Pacific Northwest megaquake
Scientists used a supercomputer-driven "virtual earthquake" to explore likely ground shaking in a magnitude 9.0 megathrust earthquake in the Pacific Northwest. Peak ground velocities are displayed in yellow and red. The legend represents speed in meters per second (m/s) with red equaling 2.3 m/s. Although the largest ground motions occur offshore near the fault and decrease eastward, sedimentary basins lying beneath some cities amplify the shaking in Seattle, Tacoma, Olympia, and Vancouver, increasing the risk of damage. (Credit: Kim Olsen, SDSU)
EWA BEACH (HawaiiNewsNow) – Scientists say there are parallels between recent earthquakes and ground movement in the Pacific Northwest and what happened in Japan before last year’s devastating quake and tsunami.
The research was discussed over the weekend at the annual meeting of the American Association for the Advancement of Science. Scientists at the Pacific Tsunami Warning Center in Ewa Beach are well aware of the new research.
The disaster in Japan occurred because of stress from the Pacific tectonic plate sliding below Japan. The plates locked together, slowly pushing Japan westward, and then released, resulting in the magnitude 9.0 earthquake and tsunami that killed thousands. Japan moved about ten to 15 feet eastward in the quake.
Scientists said the same thing is now in the works off the coast of British Columbia, Washington and Oregon, as the Juan de Fuca plate moves beneath the Pacific Northwest.
“The Pacific Northwest is being deformed because the plates are locked together, and the shoreline is sinking and the rest of the thing is being bent. We can see that,” said Dr. Gerard Fryer, a geophysicist with the warning center. “It’s just like Japan, only a mirror image.”
According to Fryer, the last big earthquake in the Pacific Northwest happened in January 1700. Like the Japan quake, it also was a magnitude 9.0, and sent a destructive Pacific wide tsunami that reached Japan.
While there has been more ground movement in the northwest, there’s still the question of Read more…
Surprise Underwater Volcanic Eruption Discovered
The chain is all that is visible of an ocean-bottom hydrophone, an instrument that detects earthquakes, buried in about six feet of new lava produced by a recent eruption at the Axial Seamount. Credit: Bill Chadwick, Oregon State University, © Woods Hole Oceanographic Institution.An undersea volcano has erupted off the coast of Oregon, spewing forth a layer of lava more than 12 feet (4 meters) thick in some places, and opening up deep vents that belch forth a cloudy stew of hot water and microbes from deep inside the Earth.
Scientists uncovered evidence of the early April eruption on a routine expedition in late July to the Axial Seamount, an underwater volcano that Read more…
Scientists Study Future Megathrust Earthquake In Pacific Northwest
The Olympic Peninsula in Washington State, USA, and British Columbia, Canada, could be among the hardest hit locations in the event of a future megathrust earthquake along the Pacific coast.
A new study led by Simon Fraser University earth scientist Andy Calvert and published in Nature Geoscience this week indicates the depth of the fault between the two tectonic plates forming the Earth’s surface in the Pacific Northwest is seven kilometres deeper than previously proposed.
Calvert speculates it may mean part of the fault’s locked zone — where a megathrust earthquake can occur — could be beneath the Olympic Peninsula.
Calvert’s team studied a 200-kilometre section of a fault formed by the subduction of the oceanic Juan de Fuca plate under the Read more…
Case Study: Tsunami in Seaside, Oregon
Oregon Coast’s Vulnerability
Recent research suggests that a Cascadia Subduction Zone earthquake could create tsunami waves that impact over 1,000-km of coastline in the U.S. and Canada. Source: USGSThe northwestern coast of Oregon is susceptible to both local and far-field tsunamis. The Cascadia Subduction Zone, where the eastward moving Juan de Fuca plate meets the westward moving North American Plate, is just off the Pacific Northwest coast of the United States and Canada. It is a 750-kilometer long fault zone. This area is very active tectonically, and therefore has the potential to produce large earthquakes and possibly, subsequent tsunamis. This subduction zone is thought to have last ruptured in 1700.
Additionally, far-field earthquakes throughout the Pacific are also capable of spawning tsunamis that could eventually reach the Oregon coast. Historical records show that since 1812, about 28 tsunamis with wave heights greater than one meter have reached the U.S. west coast. The March 1964 “Good Friday” earthquake created the most devastating of these tsunamis. The epicenter of this earthquake was near Anchorage, Alaska. The tsunami that followed this earthquake reached coasts all along the western U.S. within six hours. Cannon Beach, a small coastal community in northwestern Oregon was inundated during Read more…
4.3-magnitude earthquake near Mount St. Helens is biggest in 30 years
By Stuart Tomlinson, The Oregonian
Fault line, won’t you be my Valentine?
The second largest earthquake since Mount St. Helens erupted — a magnitude 4.3 shaker — rocked a fault line six miles north of the volcano Monday morning. People felt it as far away as Astoria, Lake Oswego, Hood River and even Bremerton, Wash., near Seattle.
The last one, as it happens, was 30 years ago also on Valentine’s Day, a magnitude 5.5 temblor.
That 1981 earthquake appeared to be the result of the earth’s crust readjusting after magma oozed up through the fault and blew the mountain’s Read more…
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