6.2 Magnitude earthquake felt in Adak

There were approximately 10 “felt reports” from Adak as of 11 a.m. this morning, following a 6.2 magnitude earthquake 50 miles from the community on Wednesday night. (Courtesy USGS)

A strong earthquake struck about 50 miles from Adak around 9 p.m. last night, registering a magnitude of 6.2.

Ken MacPherson, a seismologist for the Alaska Earthquake Center, said this was a “crustal earthquake,” meaning it was relatively shallow, at a depth of about 10 km. 

“To give you an idea of how large that is, you get only about 100 magnitude 6 earthquakes on the globe annually,” said MacPherson. “So that’s a fairly significant earthquake.”

MacPherson said Adak residents felt the shallow earthquake, which followed a series of smaller quakes in the same area. There were approximately 10 “felt reports” from Adak as of 11 a.m. this morning. He also said there have been dozens of aftershocks.

“And some of them are in the magnitude four range,” said MacPherson. “We could see up to a magnitude five. A general rule of thumb is that the largest aftershock will be about one whole magnitude less than the main shock.”

MacPherson said the earthquake is nothing out of the ordinary in the seismically-active Aleutian Islands. He said there was no tsunami threat.

The quake struck near Takawangha and Tanaga volcanoes, and while there’s no clear evidence it’s volcanic in origin, the Alaska Volcano Observatory (AVO) said scientists are monitoring for signs of volcanic unrest.

The current volcano alert level for Takawangha Volcano is “normal” and the aviation color code is “green.”