Alaska earthquakes

M3.7 earthquake 66 km SSE of Adak, Alaska

A magnitude 3.7 earthquake struck 66 km SSE of Adak, Alaska on Tue, Jul 20, 2021, 11:04 PM HADT (08:04 UTC), 37 km (23 mi) below the surface.

A larger quake followed: M4.5 161 km S of Adak, Alaska. This one was a foreshock.

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The earthquake

Magnitude: 3.7 (mb), minor
Local time: Tue, Jul 20, 2021, 11:04 PM HADT
UTC: 2021-07-21 08:04:40 UTC
Depth: 37.5 km (23.3 mi), shallow
Epicenter: 51.290° N, 176.398° 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 7.8 km horizontally, 12.6 km in depth
Magnitude uncertainty: ±0.12
Depth from: From location
Station coverage gap: 217°, poorly surrounded by stations
Stations used: 33

Nearby

Within 100 km, magnitude 1.5 and up: at least 199 in the 60 days after this one and 76 in the 30 days before it.

After

The first 60 of at least 199.

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us6000ezi1 (also filed as ak0219a7cimg). Read Thu, Sep 24, 2026, 1:43 PM UTC.