A cluster of earthquakes was recorded early Wednesday off the Oregon coastline about 300 miles west of Newport but caused no damage, according to the U.S. Geological Survey.
The agency recorded nine earthquakes within five hours, with three occurring only minutes apart. The first earthquake was recorded at 2:54 a.m. and was 3.8-magnitude. By 7:01 a.m., eight more had hit.
The largest earthquake in the series happened at 4:56 a.m. and registered a magnitude of 5.6, data shows.
There were no tsunami threats reported, said Joan Gomberg, a U.S. Geological Survey seismologist in Seattle.
“It’s nothing alarming, and these are relatively small, particularly given their distance offshore,” Gomberg said. “To create a tsunami you need the seafloor to go up or down, and in this case, the seafloor is going sideways.”
According to Gomberg, the earthquakes occurred along the Blanco Fracture Zone, a fault between two tectonic plates that runs about 300 miles northwest of the Oregon coast and tends to generate a lot of small earthquakes.
Gomberg said the Blanco Fracture Zone shouldn’t be confused with the Cascadia Subduction Zone, a fault that runs for 600 miles along the West Coast, from northern California to British Columbia, and is capable of producing potentially devastating earthquakes of up to magnitude 9.0. The Cascadia Subduction Zone is about 200 miles closer to the Oregon coast than the Blanco Fracture Zone.
In subduction zones where two tectonic plates collide, forcing one plate under another, the movement of the plates can create mountains and volcanoes and lead to major earthquakes and tsunamis. Tectonic plates in fracture zones, however, move side to side and parallel with each other, leading to much smaller earthquakes on average, Gomberg said.
“This is way far off the subduction zone, and a fracture zone is a completely different structure,” Gomberg said. “This is not really extraordinary activity by any means.”
— Catalina Gaitán
