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On a Sunday morning (August 12, 2018) at 6:58 Alaska time, a magnitude 6.4 earthquake occurred 52 miles southwest of Kaktovik. It was, by a wide margin, the largest earthquake ever recorded north of the Brooks Range in Alaska. This earthquake started a vigorous aftershock sequence, including a magnitude 6.0 earthquake at 1:15pm—the second largest ever recorded north of the Brooks Range.

The epicenter was in the remote Sadlerochit Mountains, about 25 miles south of the Beaufort Sea coast.

Below is thirty minutes of ground motion data from seismic stations across Alaska. The red star is the epicenter, and the dots are stations. The animation includes two aftershocks, a M4.9 at 7:14am and a M4.7 at 07:18.

Last Modified: May 20, 2020