Monthly Seismicity Report For September 1, 2021 to September 30, 2021

During the month of September 2021, the Alaska Earthquake Center reported 4633 earthquakes within the state. The largest earthquake was magnitude 6.1 that occurred on September 24th at 03:52:28 AKST (September 24, 11:52:28 UTC), 51 miles S of Mt. Gareloi, in Andreanof Islands. It was a subduction zone interface event. 13 earthquakes of magnitude between 4.0 and 6.1 were located in the Alaska Peninsula and along the Aleutian Arc. The largest earthquake in mainland Alaska was a magnitude 4.9 that occurred on September 13th, at 9:56 PM AKDT (September 14th, at 5:56 UTC), 8 miles east of Salcha, followed by ~140 aftershocks. Also there were two earthquakes of magnitude 4.0 and 4.2 at Yakutat, on September 5th and September 6th,  followed by ~ 700 aftershocks. We continued recording 2020 M7.8 Simeonof and 2021 M8.2 Chignik aftershocks. In September, there were  about 300 records. Also 30 earthquakes  occurred at Kaktovik (NE  Brooks Range) and 17 in offshore Kodiak. Glacial icequakes were recorded in the Prince William Sound, Icy Bay, and Mt Ogden. 14 earthquakes were reported as felt: about 1100 felt reports were sent for the Salcha earthquake.

Notable Events in Descending Order of Magnitude

Magnitude 6.1, 51 miles S of Mt. Gareloi, September 24 03:52:28 AKST
Magnitude 5.6, 112 miles SE of Chignik, September 16 09:51:56 AKST
Magnitude 5.5, 48 miles S of Mt. Gareloi, September 23 23:02:29 AKST
Magnitude 5.1, 89 miles SE of Westdahl Peak, September 9 11:23:25 AKST
Magnitude 5.1, 124 miles SE of Chignik, September 16 15:05:08 AKST
Magnitude 4.9, 7 miles S of Pump Station #8, September 13 21:56:37 AKST
Magnitude 4.4, 67 miles SE of Sand Point, September 2 00:08:36 AKST
Magnitude 4.3, 90 miles SE of Westdahl Peak, September 12 09:03:12 AKST
Magnitude 4.3, 30 miles SE of Nikolski, September 23 14:41:09 AKST
Magnitude 4.2, 74 miles SE of Westdahl Peak, September 2 19:55:48 AKST

This report was compiled by N.Kozyreva

The data in this report are preliminary and subject to revision. The earthquake parameters have been determined by the AEC, with supplemental data provided by the USGS National Earthquake Information Center. The data are released on the condition that none of the cooperating agencies may be held liable for any damaged resulting from its authroized or unauthorized use.

For more information on earthquakes and seismology, contact the AEC at (907)-474-7320.