Swarm of more than 50 earthquakes rumbles off Oregon coast


Quakes happened along the less worrisome Blanco Fault Zone

PORTLAND, Ore. (KOIN) – A series of more than 50 earthquakes off the Oregon coast were recorded Tuesday and Wednesday, but they are not expected to trigger a much larger quake.

The earthquakes ranged in strength, with many between a 4.0 and 5.8 magnitude. The U.S. Geological Survey recorded over 50 in a 24-hour period.

All the earthquakes were recorded about 6 miles below the surface. No injuries or damage was reported by the USGS.

There was no tsunami threat following the earthquakes. Portland State University geology professor Scott Burns said you typically need an 8.0-magnitude quake or above to see a tsunami threat.

“We had 10 earthquakes of significant size. That’s quite a bit,” said Burns. “(They were) off the coast, in deep water, so the damage is minimal.”

The quakes happened in the Blanco Fault Zone, a common place for earthquake swarms, KOIN’s chief meteorologist Natasha Stenbock said. A more serious occurrence would have been if they had been in the Cascadia Subduction Zone.

A 2019 article in Scientific American said a “Blanco Fault Zone earthquake is fun, not fearsome.”

In part, the article states: “The BFZ is a nice transform fault zone that’s a bit like the San Andreas, only underwater and much less dangerous to humans. It forms the boundary between the Juan de Fuca and Pacific plates, and is around 200 kilometers west of the Cascadia subduction zone, where the Juan de Fuca dives under the North American plate. This may not seem like a great distance on a global scale, but it’s pretty darned far when it comes to separation between fault zones.”

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