During the month of September 2023, the Alaska Earthquake Center reported 3626 earthquakes within the state and neighboring regions, with magnitudes ranging between 0.3 and 5.5 and depths between 0 and 240 km. The largest earthquake was magnitude 5.5 that occurred on September 20 at 17:13:58 AKDT (September 21, 01:13:58 UTC), 31 miles S of Sand Point. There were 13 other earthquakes with magnitudes 4.0-4.8. All earthquakes of magnitude greater than 4.0 occurred along the subduction zone, except  the M4.8  49 miles SE of St George island in Bering Sea in the depth of 3 miles.

We reported 138 seismic sources that were something other than regional tectonic earthquakes. Of these, 35 were suspected quarry blasts (magnitudes M=0.7-2.6), all of which were located in the vicinity of either Fort Knox or Usibelli mines in Interior Alaska, 67 ice quakes (magnitudes M=0.8-2.8), primarily located in the Prince William Sound, Icy Bay, and Yakutat Bay areas, as well as at Wright Glacier. We characterized 94 quakes as seismic events associated with volcanic activity (M=0.7-2.6).  Seismic activity  remained MOSTLY at the volcanoes in the Katmai group. We also located 8 suspected landslides (two of which were confirmed) of magnitude 1-3 in Denali area and SE of Alaska (Valerie Glacier).

10 earthquakes were reported as being felt in September, and the magnitude 3.9 event at Salcha, on September 23d,  received 89 DYFI reports. 



Magnitude 5.5, 31 miles S of Sand Point, September 20 17:13:59 AKDT
Magnitude 5.0, 38 miles S of Adak, September 12 15:17:35 AKDT
Magnitude 5.0, 31 miles S of Sand Point, September 22 01:04:41 AKDT
Magnitude 5.0, 15 miles E of Amukta Pass, September 24 07:01:39 AKDT
Magnitude 4.9, 73 miles S of Sand Point, September 10 05:03:56 AKDT
Magnitude 4.9, 48 miles SE of Westdahl Peak, September 12 13:48:57 AKDT
Magnitude 4.8, 24 miles SW of Segula Peak, September 9 10:06:00 AKDT
Magnitude 4.8, 49 miles E of St. George, September 27 01:51:06 AKDT
Magnitude 4.7, 120 miles SE of Chignik, September 11 21:23:16 AKDT
Magnitude 4.7, 31 miles S of Sand Point, September 26 18:14:27 AKDT

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 authorized or unauthorized use.

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