Alaska earthquakes

M4.0 earthquake 73 km SW of Nikolski, Alaska

A magnitude 4.0 earthquake struck 73 km SW of Nikolski, Alaska on Mon, Feb 20, 2017, 7:09 PM AKST (04:09 UTC), 50 km (31 mi) below the surface.

A larger quake followed: M5.1 132 km SW of Nikolski, Alaska. This one was a foreshock.

Unalaska forecast More in Alaska

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, body-wave), light
Magnitude from: USGS National Earthquake Information Center
Local time: Mon, Feb 20, 2017, 7:09 PM AKST
UTC: 2017-02-21 04:09:00 UTC
Depth: 49.9 km (31.0 mi), shallow
Epicenter: 52.489° N, 169.649° 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
4.0	mb, body-wave	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.08 · 42 stations
4.0	mb, body-wave	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 5.7 km horizontally, 7.1 km in depth
Magnitude uncertainty: ±0.08
Depth from: From location
Station coverage gap: 176°
Stations used: 76

Nearest places

Distance and direction from each place to the epicenter, with its forecast.

Unalaska, AlaskaPopulation 4,491. Forecast258 kmSW

Nearby

Within 100 km, magnitude 1.5 and up: 63 in the 60 days after this one and 14 in the 30 days before it.

After

The first 60 of 63.

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us20008mpy (also filed as ak15419621, ak0172e2dm9m). Read Sun, Oct 4, 2026, 12:44 PM UTC.