Alaska earthquakes

M3.9 earthquake 220 km WSW of Adak, Alaska

A magnitude 3.9 earthquake struck 220 km WSW of Adak, Alaska on Sat, Jul 31, 2021, 12:52 PM HADT (21:52 UTC), 35 km (22 mi) below the surface.

A larger quake followed: M6.1 187 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.

Open the live map with earthquakes

The earthquake

Magnitude: 3.9 (mb), minor
Local time: Sat, Jul 31, 2021, 12:52 PM HADT
UTC: 2021-07-31 21:52:20 UTC
Depth: 35.0 km (21.7 mi), shallow
Epicenter: 50.997° N, 179.471° 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: 216°, poorly surrounded by stations
Stations used: 73

Nearby

Within 100 km, magnitude 1.5 and up: 153 in the 60 days after this one and 67 in the 30 days before it.

After

The first 60 of 153.

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us6000f12y (also filed as ak0219qyqv6u). Read Fri, Sep 25, 2026, 5:04 PM UTC.