Southeast experienced a late-night shake with a magnitude 5.9 earthquake near Sitka

By Jasz Garrett

A map from the U.S. Geological Survey showing the spread of the earthquake.

Juneau, Alaska (KINY) – Residents around Southeast Alaska may have felt some shaking last night as a 5.9 magnitude earthquake happened 43 miles from Sitka which sent lesser shockwaves across the region.

The quake, which had a depth of 12 miles, was recorded at 10:46 p.m. Thursday by the U.S. Geological Survey. By the time it was felt in Sitka, the strength dropped to 3.5 and by Juneau and Ketchikan it dropped to a magnitude of 2.5.

There is no tsunami warning, according to the National Tsunami Warning Center.

Alaska Earthquake Center’s Communication Manager Elisabeth Nadin gave more details on this event.

“It’s been reported as felt by almost 600 people in the area. Although they reported it as light to weak shaking, it’s significant that many people reported it as felt,” she said. “It is the biggest earthquake in Alaska so far this year, it’s also the biggest in that region in about a decade.”

She said on average, about 100 people fill out a “Did You Feel It” report.

Residents of Sitka reported light shaking, while residents of Juneau reported weak shaking.

The earthquake was on the Queen Charlotte fault, which in Southeast Alaska, forms the boundary between the Pacific plate and the North American plate. It’s a strike-slip fault, meaning the Pacific plate is moving northward and the North American plate is moving southward. It’s only lateral or horizontal motion, which is why it doesn’t trigger any kind of tectonic tsunami.

More earthquakes than usual (called aftershocks) will continue to occur near the mainshock. The mainshock is the largest earthquake in a sequence (a series of earthquakes related to each other).

Nadin said there is a 66% chance there could be a magnitude 3 and above earthquake following this event. In the next month, there’s about an 80% chance of magnitude 3 and above aftershocks.

“Magnitude 3 is kind of our cut-off for feeling shaking, so I would say it’s almost guaranteed that people will feel light aftershocks in the next week,” she said.

Aftershock rates will decrease over time but may remain elevated over the following year or longer.

If you feel shaking, remember to “Drop, Cover, and Hold On”.