Alaska earthquakes

M3.7 earthquake 157 km SW of Nikolski, Alaska

A magnitude 3.7 earthquake struck 157 km SW of Nikolski, Alaska on Fri, Aug 20, 2021, 1:28 AM HADT (10:28 UTC), 25 km (15 mi) below the surface.

A larger quake followed: M3.9 191 km ESE of Atka, Alaska. This one was a foreshock.

Map

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The earthquake

Magnitude: 3.7 (mb), minor
Local time: Fri, Aug 20, 2021, 1:28 AM HADT
UTC: 2021-08-20 10:28:08 UTC
Depth: 24.5 km (15.2 mi), shallow
Epicenter: 52.068° N, 170.686° 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 5.5 km horizontally, 7.2 km in depth
Magnitude uncertainty: ±0.12
Depth from: From location
Station coverage gap: 181°, poorly surrounded by stations
Stations used: 57

Nearby

Within 100 km, magnitude 1.5 and up: 24 in the 60 days after this one and 28 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 us6000f8rf (also filed as ak021anusvbx). Read Thu, Sep 24, 2026, 12:36 AM UTC.