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Wave of small-to-moderate earthquakes strike off Oregon coast; no tsunami threat, NWS says

More than 50 earthquakes, including 14 above magnitude 5.0, have struck since Tuesday morning, about 200-250 miles west of Newport.

NEWPORT, Ore. — More than 50 small-to-moderate earthquakes struck far off the Oregon coast since Tuesday morning, but there is no threat of a tsunami, the National Weather Service (NWS) said. The quakes hit roughly 200 to 250 miles off the coast of Newport. More than a dozen of the earthquakes have been magnitude 5.0 or higher.

The Pacific Northwest Seismic Network tweeted that this area — the Blanco Fracture Zone — is one of the most seismically active near North America, and the high activity is not a cause for concern.

The United States Geological Service (USGS) earthquake map shows all earthquakes 2.5 magnitude and higher over the past 24 hours. During that time frame, the map shows more than 50 earthquakes in that area, with more than a dozen registering 5.0 magnitude or higher.

Earthquakes are relatively common off the coast of Oregon, a reminder of the state's close proximity to moving fault lines. The Juan de Fuca plate off the coast is building up pressure and subsiding under the North American plate and has not produced a major earthquake in more than 300 years. Scientists predict a 37% chance of a 7.1 magnitude earthquake or higher in the Cascadia Subduction Zone in the next 50 years, likely to trigger a major tsunami and potentially devastate many parts of the Northwest. 

ShakeAlert, an early earthquake warning system, launched in Oregon earlier this year. The system is made up of a network of sensors that shares information about the magnitude, location and expected shaking from earthquakes on the West Coast. 

One of the state's leading earthquake scientists said there is no need to be alarmed.

Chris Goldfinger is a marine and earthquake geologist at Oregon State University. He said swarms similar to this happen almost every month in this area. 

"They're completely normal events," he said. "They're sort of like two conveyor belts going side by side and there has there's a fault between them."

The obvious question: Are these smaller quakes precursors to a much larger and much more destructive Cascadia Subduction Zone earthquake?

"They're not," said Goldfinger. "They're not doing anything to load that subduction zone itself and they're not precursors of anything, so people can relax."

Goldfinger said there's about 10-15% chance of a really big earthquake happening in the next 50 years.

If that sounds low, consider this:

"We're sitting at about the same probability of an earthquake in the next 50 years that Northeast Japan was in 2011," said Goldfinger. 

Goldfinger said while people shouldn't be overly concerned about this swarm, they should consider it a wake-up call and to prepare for a large earthquake.

"This is a great time to remind folks that thinking about putting together a 'go bag' or a kit for earthquakes or thinking about doing more extensive things," he said.

People should think about securing their water heaters or retrofitting their homes.

"Oregon's made a lot of progress," he said. "But we've got really a long, long way to go."