Jan. 11 earthquake south of Sitka registers 5.9 magnitude

An earthquake jolted some Sitka residents awake Thursday night, Jan. 11, but no damage was reported and no tsunami occurred.

The Alaska Earthquake Center at Fairbanks said the magnitude 5.9 earthquake occurred at 10:46 p.m. on the seafloor 50 miles south of Sitka. It was felt across Southeast, including Wrangell.

Assistant Sitka Fire Chief David Johnson said the department received a half dozen or so calls about the momentary shaking that people experienced throughout town.

Elisabeth Nadin, communications manager of the earthquake center, said the quake was typical of those on the faults that run along the seabed west of Southeast Alaska.

“It was strike-slip motion, lateral motion — no up and down — which is the type of motion that happens right there on the Queen Charlotte-Fairweather faults,” Nadin said. “That fault separates the Pacific plate to the west, from the North American plate to the east.”

The risk of a tsunami from such a quake is low, but not zero, she noted, due to the nature of the tectonic plates in the area.

“There’s always the chance that a large enough earthquake could trigger landslides that would displace enough material into the ocean that you have vertical motion of water,” the geologist said. “On a strike-slip fault, with just lateral shifting, you’re not going to displace large volumes of water upward that then have to fall downward. And that’s what a tsunami is, effectively.”

 

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