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.

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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
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.

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 todayAlaska earthquakesLive 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.