Alaska earthquakes

M3.9 earthquake 139 km WSW of Adak, Alaska

A magnitude 3.9 earthquake struck 139 km WSW of Adak, Alaska on Tue, Feb 16, 2021, 6:58 AM HAST (16:58 UTC), 35 km (22 mi) below the surface.

A larger quake followed: M5.6 209 km WSW of Adak, Alaska. This one was a foreshock.

Map

Where this earthquake was located, with the others nearby. Select one for its page.

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The earthquake

Magnitude: 3.9 (mb), minor
Local time: Tue, Feb 16, 2021, 6:58 AM HAST
UTC: 2021-02-16 16:58:45 UTC
Depth: 35.0 km (21.7 mi), shallow
Epicenter: 51.202° N, 178.329° 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 5.0 km horizontally, 2.0 km in depth
Magnitude uncertainty: ±0.08
Depth from: Operator assigned
Station coverage gap: 182°, poorly surrounded by stations
Stations used: 76

Nearby

Within 100 km, magnitude 1.5 and up: 140 in the 60 days after this one and 61 in the 30 days before it.

After

The first 60 of 140.

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us6000di50 (also filed as ak0212604s5b). Read Thu, Sep 24, 2026, 12:17 PM UTC.