12/08/2022

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Over 40 earthquakes in 24 hours strike waters off US northwest

PORTLAND Oregon: A swarm of more than 40 earthquakes, ranging from a magnitude 3.5 to 5.8, has rattled the coast of Oregon, catching the attention of millions of residents in the region.

Beginning early last week, the series of quakes were all clustered between 200 to 250 miles west of the coastal town of Newport, OR.

In an interview with CNN, Harold Tobin, Director of the Pacific Northwest Seismic Network at the University of Washington, said, “If you had asked me yesterday where on Earth would be most likely to produce a bunch of magnitude 5.0-plus quakes in a single day, this would have been high on my list.”

The fault line responsible for the quakes is the Blanco Fracture Zone, which, according to Oregon State University, is more active than the infamous San Andreas Fault in California.

This week’s quakes included at least nine tremors reaching a magnitude 5.0 to 5.8, with most occurring at depths of only 10 kilometers, though none caused a tsunami alert, said the U.S. National Tsunami Warning Center.

The region is among the most earthquake-prone areas in North America, but the Blanco Fracture Zone, among the most seismically active in North America, rarely causes destructive quakes.

The fault is some 275 miles west of the Oregon coastline.

“Blanco Fracture zone quakes are strike-slip, or lateral motions of the crustal blocks on either side, rather than up-down displacement, so it is very unlikely for them to pose a tsunami threat, even if a bigger quake happened, like a magnitude 7.0 for example,” Tobin told CNN.

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There have been more than 133 quakes of magnitude 5 or greater on the Blanco Fracture Zone since 1980, and have never been followed by an earthquake on land, said seismologist Dr. Lucy Jones.

Though this week’s quakes have raised the concerns that the so-called “big one” could be coming soon, Tobin stressed this is not necessarily the case.

“Although we have had a remarkable number of magnitude 5.5-plus quakes in a short period of time, it is not inherently alarming, but rather seismologically interesting,” he added.

Earlier this year, a similar swarm of quakes, though not equal to this week’s magnitudes, occurred near the Salton Sea in Southern California.