Alaska earthquakes

M3.3 earthquake 40 km SSE of Adak, Alaska

A magnitude 3.3 earthquake struck 40 km SSE of Adak, Alaska on Thu, Dec 21, 2017, 5:43 PM HAST (03:43 UTC), 38 km (24 mi) below the surface.

A larger quake followed: M5.2 22 km SSW 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: 3.3 (ML, local (Richter)), minor
Magnitude from: USGS National Earthquake Information Center
Local time: Thu, Dec 21, 2017, 5:43 PM HAST
UTC: 2017-12-22 03:43:54 UTC
Depth: 38.0 km (23.6 mi), shallow
Epicenter: 51.544° N, 176.395° W
Region: Alaska
Tsunami flag: No
Status: Reviewed by a seismologist

Magnitude estimates

Different scales measure different things and differ by a few tenths. The USGS marks one as preferred, and it is the one this page uses.

Mag.	Scale	Computed by	Notes
3.3	ML, local (Richter)	USGS National Earthquake Information Center	Preferred · Reviewed
3.3	ML, local (Richter)	Alaska Earthquake Center	Preliminary

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 4.5 km horizontally, 45.0 km in depth
Depth from: From location
Station coverage gap: 216°, poorly surrounded by stations
Stations used: 25

Nearby

Within 100 km, magnitude 1.5 and up: 176 in the 60 days after this one and 65 in the 30 days before it.

After

The first 60 of 176.

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us1000bxbh (also filed as ak017gctd6jh, ak17637038). Read Thu, Oct 1, 2026, 11:42 PM UTC.