The second-largest earthquake near Mount St. Helens since 1981 shook the area early Wednesday, prompting a series of 15 aftershocks that were felt more than 100 miles away.
It was 12:36 a.m. when the first, and largest, temblor struck. It registered as a magnitude 3.9 at a depth of six miles, according to the Pacific Northwest Seismic Network.
The aftershocks started moments later and ranged from magnitude 0.6 to 2.7. All were south-southeast of Morton.
More than 100 people reported feeling a slight shaking from Portland to Puget Sound.
No injuries or damage were reported.
In the last month, PNSN said there have been 82 earthquakes within 10 kilometers of Mount St. Helens.
“Earthquakes are common in this area with about 1 to 5 occuring per month, although this is the largest recorded event,” U.S. Geological Survey Volcanoes wrote in a Facebook post.
The last swarm was in October 2010, with the strongest earthquake being a magnitude 2.
Officials said there is no sign the quakes are related to volcanic activity.
The strongest earthquake near Mount St. Helens was a magnitude 4.2 at Johnson Ridge Observatory on Feb. 14, 2011.
Stacia Glenn: 253-597-8653