Alaska earthquakes

M4.0 earthquake 74 km S of Adak, Alaska

A magnitude 4.0 earthquake struck 74 km S of Adak, Alaska on Sat, Jul 24, 2021, 4:30 AM HADT (13:30 UTC), 35 km (22 mi) below the surface.

A larger quake followed: M4.5 161 km S 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: 4.0 (mb), light
Local time: Sat, Jul 24, 2021, 4:30 AM HADT
UTC: 2021-07-24 13:30:06 UTC
Depth: 35.0 km (21.7 mi), shallow
Epicenter: 51.217° N, 176.432° 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 7.3 km horizontally, 2.0 km in depth
Magnitude uncertainty: ±0.10
Depth from: Operator assigned
Station coverage gap: 227°, poorly surrounded by stations
Stations used: 15

Nearby

Within 100 km, magnitude 1.5 and up: 186 in the 60 days after this one and 83 in the 30 days before it.

After

The first 60 of 186.

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us6000eynl (also filed as ak0219f937xi). Read Thu, Sep 24, 2026, 1:37 PM UTC.