During the month of December 2024, the Alaska Earthquake Center reported 3189 earthquakes within the state with magnitudes ranging from 0.6 and 6.3 and depths between 0 and 210 km. The largest of these were two magnitude 6.3 earthquakes that occurred on the same day as part of a significant earthquake swarm south of Adak. The first one occurred on December 8 at 10:57:07 AKST (December 8, 19:57:07 UTC), 66 miles S of Bobrof Island, and the second occurred on December 8 at 15:15:30 AKST (December 9,  00:15:30 UTC), 68 miles S of Adak. There was one more earthquake in this swarm above a magnitude 6, which was a magnitude 6.1 that occurred on December 8 at 15:38:52 AKST (December 9, 00:38:52 UTC), 76 miles S of Bobrof Island. 

In total, this earthquake swarm included over 300 earthquakes recorded between December 8 and December 16. The events ranged in magnitude from 1.6 to 6.3, also including 15 events of magnitude 5.0-5.9,  19 events of magnitude 4.0-4.9, and 68 events of magnitude 3.0-3.9. Depths ranged from 1 to 59 km, but a large majority were in the 5-30 km depth range. For more information about this sequence, please see the article “Earthquake Swarm Emerges Southwest of Adak Island.”

Overall in the month of December, there were 53 earthquakes of magnitude 4.0 or above, all occurring along the subduction zone with the exception of two events that occurred just across the border in the northern Yukon Territory, CA. 

We also reported seismic sources other than regional tectonic earthquakes. Of these, 19 were suspected mine blasts (M=1.2-2.2) in Interior Alaska. There were also 46 icequakes (M=1.2-2.1), mostly located in the Prince William Sound and Yakutat areas. 

We detected 56 volcanic earthquakes, mostly located at Mt. Spurr and the Katmai Volcanic Group. Mt. Spurr was particularly active this month, with 42 volcanic events recorded ranging in magnitude from 0.6 to 3.2 and ranging in depth from 1 to 16 km. 

Eight events were reported as felt in December. The largest number of DYFI (Did You Feel It) responses, 353, came from the magnitude 4.5 earthquake that occurred on December 19 at 19:03:22 AKST, 19 miles SE of Redoubt Volcano. This event was felt throughout the Cook Inlet region.