Alaska earthquakes

M4.0 earthquake 110 km SSW of Unalaska, Alaska

A magnitude 4.0 earthquake struck 110 km SSW of Unalaska, Alaska on Sun, May 21, 2023, 2:24 AM AKDT (10:24 UTC), 40 km (25 mi) below the surface.

A larger quake followed: M4.3 49 km ESE 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), light
Local time: Sun, May 21, 2023, 2:24 AM AKDT
UTC: 2023-05-21 10:24:11 UTC
Depth: 39.8 km (24.7 mi), shallow
Epicenter: 52.904° N, 166.892° W
Region: Alaska
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: 0.0% of gravity
Peak ground velocity: -4.3 cm/s
Map: Automatic

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

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 6.2 km horizontally, 8.2 km in depth
Magnitude uncertainty: ±0.08
Depth from: From location
Station coverage gap: 170°
Stations used: 69

Nearest places

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

Unalaska, AlaskaPopulation 4,491. Forecast110 kmSSW

Nearby

Within 100 km, magnitude 1.5 and up: 132 in the 60 days after this one and 93 in the 30 days before it.

After

The first 60 of 132.

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us6000kdl5 (also filed as ak0236hcvfbk). Read Wed, Sep 30, 2026, 9:12 AM UTC.