Alaska earthquakes

M4.0 earthquake 54 km ESE of Nikolski, Alaska

A magnitude 4.0 earthquake struck 54 km ESE of Nikolski, Alaska on Tue, Dec 21, 2021, 7:59 AM AKST (16:59 UTC), 35 km (22 mi) below the surface.

A larger quake followed: M6.8 100 km SE 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.

Open the live map with earthquakes

The earthquake

Magnitude: 4.0 (mb), light
Local time: Tue, Dec 21, 2021, 7:59 AM AKST
UTC: 2021-12-21 16:59:50 UTC
Depth: 35.0 km (21.7 mi), shallow
Epicenter: 52.701° N, 168.159° W
Region: Alaska
Felt reports: 1
Strongest shaking: I, not felt shaking
Tsunami flag: No
Status: Reviewed by a seismologist

Shaking

The USGS ShakeMap: shaking estimated from seismic stations and the quake’s size, on the Modified Mercalli intensity scale.

Strongest estimated: I, not felt shaking
Peak ground acceleration: 0.1% of gravity
Peak ground velocity: -3.8 cm/s
Map: Automatic

USGS ShakeMap: estimated shaking intensity around the epicenter — Estimated shaking intensity. Map: USGS ShakeMap.

Did you feel it?

1 person reported to the USGS what they felt.

How well it is located

Reviewed by a seismologist.

Location uncertainty: About 5.0 km horizontally, 2.0 km in depth
Magnitude uncertainty: ±0.09
Depth from: Operator assigned
Station coverage gap: 141°
Stations used: 69

Nearest places

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

Unalaska, AlaskaPopulation 4,491. Forecast169 kmSW

Nearby

Within 100 km, magnitude 1.5 and up: at least 199 in the 60 days after this one and 28 in the 30 days before it.

After

The first 60 of at least 199.

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us6000ge7s (also filed as ak021gbdwkmi). Read Mon, Sep 28, 2026, 11:43 AM UTC.