A total of seven earthquakes shook about 300 miles off the Oregon Coast in the past 24 hours. The first struck just after midnight Monday. The largest was a 5.9 magnitude earthquake.
The latest earthquakes occurred Monday night at 7:50 and 8:11. They registered at magnitudes 3.9 and 4.2, respectively.
The series of quakes aren't directly on the Cascadia Subduction Zone, but are related. As U.S. Geological Survey scientist Harley Benz explained Monday, rather than being in an area where one tectonic plate is being pushed under another, the series of quakes is happening in an area where the two plates slide next to each other.
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"You’ll probably see a few more and then it’ll die off after time," Benz said. "That’s pretty typical. There is a small probability of having an earthquake of a similar size."
The tremors shook about 6 miles under the ocean floor, which USGS has said is relatively shallow. No tsunamis were triggered and no damage has been reported.
While there is no immediate danger from the earthquake swarm, Jay Wilson — chairman of the Oregon Seismic Safety Policy Advisory Commission — says they can serve as a "teachable moment" about preparedness.
"What these quakes demonstrate is the continual push of the Juan de Fuca plate under the N. American Plate and thus directly loading the Cascadia Subduction Zone fault with pressure – for the past 315 years," Wilson said in an email. "Each (earthquake) is another notch on the ratchet adding stress to the locked (Cascadia Subduction Zone) fault."
Four earthquake-related bills are awaiting approval in the Ways and Means Committee in Salem. The proposed legislation would create an earthquake resilience officer, direct state agencies to better plan for earthquakes, and establish a task force to look into housing and health care after a large quake.
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