The Blanco Transform Fault Zone (BTFZ) off Oregon’s coast, one of North America’s most active fault lines, generated 50 earthquakes in the last 24 hours.
The quake swarm hit 200-250 miles west of Newport, Oregon, and ranged between magnitude 3.5 to 5.8. The area’s seismic activity has generated a lot of buzz on social media, of worried people believing the next big one could be nearing.
There has been a ‘swarm’ of earthquakes off the Oregon coast this evening; the strongest reaching 5.8!
Such swarms are common. Thankfully, they mostly occur far from shore along strike-slip faults.
This means there is NO tsunami risk because little water is displaced! pic.twitter.com/8reA3m3rL0
— NWS Eureka (@NWSEureka) December 8, 2021
“If you had asked me yesterday where on Earth would be most likely to produce a bunch of magnitude 5.0+ quakes in a single day, this would have been high on my list,” Harold Tobin, Director of the Pacific Northwest Seismic Network at the University of Washington, told CNN.
BTFZ is a strike-slip boundary which means tectonic plates slide along one another. The most dangerous are the subduction zones, where one plate dives underneath another.
“Blanco Fracture zone quakes are strike-slip (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 said.
Social media users were concerned that the quake swarm was from the Cascadia Subduction Zone closer to shore.
Whew! Coast of Oregon has been on the move a LOT the last 24 hours. 45 quakes M3 to M 5.8. That’s not counting the additional quakes listed for coast of CA and WA. Where the Pacific plate and Juan de Fuca plate are pulling apart at. Keeping an eye on cascadia subduction zone. pic.twitter.com/zgCMUT6R3o
— WhooIamNot (@WhooIAmNot) December 8, 2021
There’s a bit of a vigorous earthquake swarm along the Blanco Transform Fault. This is NOT involving the Cascadia Subduction Zone but this tectonic movement will ultimately contribute to further loading of that plate boundary as stress transfers eastward. #BlancoTransformFault. pic.twitter.com/iKsKJCqPmT
— CaliforniaDisasters (@CalDisasters) December 8, 2021
Fortunately this swarm is not part of the Cascadia subduction zone. https://t.co/qIAiuWRjzy
— J.F. Riordan (@AudacityofGoats) December 8, 2021
Swarm of 5+ magnitude earthquakes off the coast of Oregon.
Keep an eye on the Cascadia subduction zone.
— Rabon Vincent Jr. (@jr_rabon) December 8, 2021
Meanwhile, the Oregon Office of Emergency has warned if a powerful 9.0+ magnitude earthquake originates from the Cascadia Subduction Zone, it could unleash a “tsunami of up to 100 feet in height that will impact the coastal area.”
The state agency adds, “Currently, scientists are predicting that there is about a 37 percent chance that a megathrust earthquake of 7.1+ magnitude in this fault zone will occur in the next 50 years.”
The Cascadia Subduction Zone has had seven major earthquakes. The last one was in the 1700s.
Professor of Marine Geology Dr. Chris Goldfinger at Oregon State University has focused research on the Cascadia Subduction Zone. He warned at a 2016 TED Conference, an earthquake for the area is “overdue.”
So when Pacific Northwest residents hear about quake swarms off the coast, they get concerned because a monster tsunami could be headed their way. They also have to worry about supervolcano fears in Yellowstone National Park.