Two strong quakes rattle homes, stores

 


Two vigorous earthquakes centered about 60 miles northwest of Haines rumbled the Chilkat Valley early Monday, tossing items off shelves and causing one woman to break her foot.

The quakes came at 4:30 a.m. and 6:18 a.m., measuring 6.2 and 6.3 on the Richter scale, respectively.

Howser’s IGA store manager Kevin Shove said a few bottles of body wash fell off the store’s shelves. The earthquake woke him up at home but nothing was damaged, Shove said.

“The cats freaked out,” Shove said. “My cat just laid on the floor and belly crawled.”

Chris Thorgesen said two sewing baskets, one upstairs and another downstairs, fell off his shelves at home.

A sock monkey plummeted off a shelf at The Babbling Book.

The disarray wasn’t benign for Carrie Kinison, who lives at 38.5 Mile Haines Highway.

The first quake woke her up.

“I was getting out of bed and there’s this platform about six inches off the floor and I was trying to step off it and the earthquake threw me forward and my foot just swiveled on the edge of the platform and broke,” Kinison said. “It was throwing us around pretty good. Glass fell off the shelves and bottles fell off. It was quite a shaker.”


Kinison will be on crutches the next six weeks while her foot heals.

Both quakes originated in a remote area between the U.S. and Yukon Territory border along the Denali fault line in Canada.

The arc-shaped fault extends from Baranof Island northwest to near Healy before bending south toward Bethel.

According to Rob Witter, a research geologist with the U.S. Geological Survey in Anchorage, the fault is one of many on the North American plate where blocks of crust all move relative to one another. The block on the east side of the fault moves southeast at a rate of less than an eighth of an inch per year. The western block moves at one-third of an inch per year.

When two blocks move at different rates, the area is more prone to earthquakes, Witter said. Seismic data suggests the two quakes didn’t occur exactly on the fault line.

“Lots of faults haven’t been mapped,” Witter said. “The earth’s crust is composed of a whole network of faults. The most visible faults create valleys and scars in the landscape and those are the easiest to map. It’s possible that the earthquakes that occurred happened on faults we haven’t completely mapped or we didn’t know about. They’re in an area that’s tectonically active.”


More than 100 aftershocks had occurred by Tuesday and Witter said they will likely continue for days after the main event. “Aftershocks are the rest of the earth adjusting to the changes and strains released during the first earthquake.”

The second quake occurred six miles below the earth, a relatively shallow depth when compared to global earthquakes. The 1964 Good Friday earthquake that devastated several regions of Alaska was twice that depth, Witter said. That 9.2 magnitude quake occurred in a subduction zone, where one plate slides under another. The rumble from shallow earthquakes are typically more violent because the waves travel through less crust.

People across Alaska and Canada felt the temblors. Some Petersburg residents felt the quake. According to the CBC, sections of Whitehorse lost power and building damage was reported.

“It radiates out from the focus, the origin point of the earthquake,” Witter said. “It radiates out in every direction as a sphere, like an exploding bubble.”

Witter said if the earthquakes had occurred closer to more densely populated areas, damage could have been more extensive.

“There are many areas around the world where a 6.3 caused quite a bit of damage,” Witter said.

This week’s quakes may have been the most severe ones to shake Haines in about 30 years. In November 1987, a 5.3 magnitude earthquake hit 10 miles southeast of Haines. A second, 6.9 quake struck two days later 90 miles southwest of Yakutat and triggered a tsunami alert. Five hours later, a 5.1 shook 30 miles east of Haines.


“The takeaway is a reminder that we need to be prepared for earthquakes because we live in earthquake country,” Witter said.

 
 

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