Resilience Natural Disasters

Wave of 40 earthquakes in 24 hours rocks northwest

Story at a glance

  • The earthquakes occurred along Oregon’s coast within an area called the Blanco Fracture Zone.
  • Experts say the Blanco Fracture Zone is one of the most active earthquake areas near North America.
  • The Pacific Northwest Seismic Network said there have been 49 earthquakes above magnitude 4.5 in the area in the last five years alone.

Oregon experienced a series of more than 50 earthquakes all ranging in magnitude this week, but experts say the seismic activity is nothing to be alarmed about.  

 

The National Weather Service announced on Tuesday that there had been a “swarm” of earthquakes off the Oregon coast with the strongest one hitting 5.8 magnitude. However, the agency said the earthquakes were considered common in that area and little water was displaced, meaning there was no risk of tsunami.

Local media reported a series of earthquakes began Tuesday afternoon about 200 to 250 miles off the coast of Newport, Ore. Two earthquakes with magnitudes 5.3 and 5.5 occurred around 1:30 p.m. and 2 p.m. on Tuesday, with two more magnitude 5.0 and 5.8 quakes hitting several hours later. Another 5.8 quake came along just before 5:30 p.m., and multiple smaller aftershocks continued into Tuesday evening. 

According to the Pacific Northwest Seismic Network (PNSN), the series of earthquakes occurred on the Blanco Fracture Zone, which has a long history of being the most active earthquake area near North America. The group said there have been 49 earthquakes above magnitude 4.5 in the area in the last five years alone.


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Oregon is a unique state, being so close to moving fault lines, specifically the Cascadia Subduction Zone, which is a 600-mile fault line that runs from northern California up to Canada. According to the Oregon state government, about 70 to 100 miles of the fault runs off the Pacific coast shoreline, which has had 41 earthquakes in the last 10,000 years. The last earthquake that occurred in this fault line was on Jan. 26, 1700.

Oregon is located in the middle of the Cascadia Subduction Zone, which means the state has the potential for a 9.0+ magnitude earthquake and a resulting tsunami of up to 100 feet high.

However, experts and local authorities are not particularly concerned about Oregon’s risk for serious earthquakes, with scientists predicting there’s about a 37 percent chance that a megathrust earthquake of 7.1+ magnitude would occur in the next 50 years. 

“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,” Harold Tobin, director of PNSN at the University of Washington, told CNN.

Oregon is preparing though, using ShakeAlert, a service created by the United States Geological Survey (USGS) to give people a few seconds heads up that an earthquake is happening and that shaking is imminent. The ShakeAlert system is made up of a network of sensors that share information about the magnitude, location and expected shaking from earthquakes along the West Coast. The program serves not just Oregon, but California and Washington state.


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