Earthquake Swarm on Alaska’s North Slope


OK, the ground up there isn’t jumping so much it knocks down polar bears–this is just a laid-back local resident.

But a magnitude 6.4 quake is unusual on Alaska’s Arctic Ocean coast, and no one really knows what caused the Sunday event.

They call this region the North “Slope,” not the North “Trench,” because it’s not a subduction zone like the Aleutian Islands, where megathrust quakes are possible. There’s a lot of petroleum down there, and at the surface it is a national wildlife refuge. Apparently there is no drilling ongoing at the epicenter site, near an Inuit village called Kaktovic.

The Sunday quake was part of an ongoing swarm. There were a few events in the magnitude-6 range, with the 6.4 being the largest ever recorded up there. The rest are M3 or lower, and it’s still quite active up there along the Arctic Ocean today.



Nothing dire seems imminent, but it is unusual and worth noting. There hasn’t been much in the news, just this Arctic Today article (you’ll have to give them an email address to read it – sorry, but there are no alternative news sources) and this Alaska Earthquake Center post, which links to their continuously updated data pages. They’re really excited about it because they happened to have a dense array of seismometry equipment in place and now have a lot of data about the region’s geology, which isn’t well understood yet.


August 17, 2018: Here’s how last Sunday’s event looked as it travelled through that seismometer array that happens to be set up across Alaska at present.


August 22, 2018: Nothing much new in the news, though reportedly the petroleum people in the region did a flurry of inspections and found no equipment problems after the August 12th quake. The general epicenter area is still having lots of very low-level activity per today’s “latest earthquakes” USGS website (am guessing it’s the regional stress field adjusting to whatever rock formations “broke” down there).


September 18, 2018: An M5.1 in the general region of Kaktovik today. However, per the Alaska Earthquake Center event page, this may be related more to the Brooks Range than to the bigger August event on the North Slope.

Alaska’s geology is very complicated, even far from the Aleutian subduction zone.


Featured image: Alaska Region US Fish & Wildlife Service


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