Alaska earthquakes

M3.9 earthquake 128 km W of Adak, Alaska

A magnitude 3.9 earthquake struck 128 km W of Adak, Alaska on Tue, Jun 20, 2017, 10:50 PM HADT (07:50 UTC), 132 km (82 mi) below the surface.

A larger quake followed: M4.8 138 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.

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The earthquake

Magnitude: 3.9 (mb, body-wave), minor
Magnitude from: USGS National Earthquake Information Center
Local time: Tue, Jun 20, 2017, 10:50 PM HADT
UTC: 2017-06-21 07:50:34 UTC
Depth: 132.2 km (82.1 mi), intermediate-depth
Epicenter: 52.013° N, 178.494° 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
3.9	mb, body-wave	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.1 · 26 stations
3.5	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 10.3 km horizontally, 8.8 km in depth
Magnitude uncertainty: ±0.10
Depth from: From location
Station coverage gap: 107°
Stations used: 64

Nearby

Within 100 km, magnitude 1.5 and up: at least 201 in the 60 days after this one and at least 200 in the 30 days before it.

After

The first 60 of at least 201.

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us20009q1p (also filed as ak16210334, ak0177wkwioz). Read Sat, Oct 3, 2026, 1:18 AM UTC.