Alaska earthquakes

M3.9 earthquake 177 km SSW of Adak, Alaska

A magnitude 3.9 earthquake struck 177 km SSW of Adak, Alaska on Mon, Sep 27, 2021, 1:03 PM HADT (22:03 UTC), 10 km (6 mi) below the surface.

A larger quake followed: M5.0 128 km WSW of Adak, Alaska. This one was a foreshock.

Map

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The earthquake

Magnitude: 3.9 (mb), minor
Local time: Mon, Sep 27, 2021, 1:03 PM HADT
UTC: 2021-09-27 22:03:21 UTC
Depth: 10.0 km (6.2 mi), shallow
Epicenter: 50.525° N, 177.980° W
Region: Alaska
Tsunami flag: No
Status: Reviewed by a seismologist

Did you feel it?

No one has reported feeling this quake to the USGS.

How well it is located

Reviewed by a seismologist.

Location uncertainty: About 3.6 km horizontally, 2.0 km in depth
Magnitude uncertainty: ±0.08
Depth from: Operator assigned
Station coverage gap: 244°, poorly surrounded by stations
Stations used: 72

Nearby

Within 100 km, magnitude 1.5 and up: 54 in the 60 days after this one and 27 in the 30 days before it.

After

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us6000fxmr (also filed as ak021cew7xma). Read Thu, Sep 24, 2026, 9:06 AM UTC.