Alaska earthquakes

M5.5 earthquake 260 km W of Adak, Alaska

A magnitude 5.5 earthquake struck 260 km W of Adak, Alaska on Thu, Feb 29, 2024, 3:50 AM GMT+12 (15:50 UTC), 120 km (75 mi) below the surface.

A larger quake followed: M5.8 Rat Islands, Aleutian Islands, 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: 5.5 (Mww, W-phase moment), moderate
Magnitude from: USGS National Earthquake Information Center
Local time: Thu, Feb 29, 2024, 3:50 AM GMT+12
UTC: 2024-02-28 15:50:21 UTC
Depth: 120.0 km (74.5 mi), intermediate-depth
Epicenter: 52.002° N, 179.583° E
Region: Alaska
Strongest shaking: IV, light shaking
PAGER alert: Green
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
5.5	Mww, W-phase moment	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.043 · 51 stations
5.5	Mww, W-phase moment	Alaska Earthquake Center	Preliminary
5.5	Mwb, body-wave moment	USGS National Earthquake Information Center	Moment tensor · Reviewed
5.5	Mww, W-phase moment	USGS, automatic first solution	First automatic solution · Preliminary

Shaking

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

Strongest estimated: IV, light shaking
Peak ground acceleration: 1.2% of gravity
Peak ground velocity: 0.7 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.

Estimated impact

The USGS PAGER system estimates deaths and economic losses from the shaking and the population and buildings exposed to it.

Alert level: Green: little or no damage or loss of life expected

Deaths: estimated chance of each range
Range	Chance
Under 1	69%
1 to 10	29%
10 to 100	2%
100 to 1,000	Under 1%
1,000 to 10,000	Under 1%
10,000 to 100,000	Under 1%
100,000 to 10,000,000	Under 1%

Economic losses: estimated chance of each range
Range, million USD	Chance
Under 1	65%
1 to 10	30%
10 to 100	4%
100 to 1,000	Under 1%
1,000 to 10,000	Under 1%
10,000 to 100,000	Under 1%
100,000 to 10,000,000	Under 1%

Fault motion and ground failure

How the rock slipped, from the moment tensor, and the USGS estimate of landslides and liquefaction.

Faulting: Strike-slip
Moment magnitude: 5.5 Mww
Nodal plane 1: Strike 91°, dip 65°, rake 176°
Nodal plane 2: Strike 183°, dip 86°, rake 25°

How well it is located

Reviewed by a seismologist.

Location uncertainty: About 6.3 km horizontally, 4.1 km in depth
Magnitude uncertainty: ±0.04
Depth from: From location
Station coverage gap: 27°
Stations used: 144

Nearby

Within 100 km, magnitude 2.5 and up: 60 in the 60 days after this one and 27 in the 30 days before it.

After

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us6000mflq (also filed as usauto6000mflq, ak0242ptxqql). Read Thu, Oct 1, 2026, 1:16 PM UTC.