Alaska earthquakes

M5.0 earthquake 128 km WSW of Adak, Alaska

A magnitude 5.0 earthquake struck 128 km WSW of Adak, Alaska on Wed, Nov 17, 2021, 11:50 PM HAST (09:50 UTC), 48 km (30 mi) below the surface.

A larger quake followed: M5.1 Andreanof 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: 5.0 (mww), moderate
Local time: Wed, Nov 17, 2021, 11:50 PM HAST
UTC: 2021-11-18 09:50:37 UTC
Depth: 47.7 km (29.6 mi), shallow
Epicenter: 51.373° N, 178.309° W
Region: Alaska
Felt reports: 1
Strongest shaking: IV, light 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: IV, light shaking
Peak ground acceleration: 3.8% of gravity
Peak ground velocity: 0.3 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; the strongest reported shaking was II, weak shaking.

Fault motion and ground failure

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

Faulting: Reverse (thrust)
Moment magnitude: 4.9 Mwr
Nodal plane 1: Strike 61°, dip 72°, rake 74°
Nodal plane 2: Strike 284°, dip 24°, rake 130°

How well it is located

Reviewed by a seismologist.

Location uncertainty: About 5.7 km horizontally, 4.5 km in depth
Magnitude uncertainty: ±0.09
Depth from: From location
Station coverage gap: 81°
Stations used: 176

Nearby

Within 100 km, magnitude 2.0 and up: 72 in the 60 days after this one and 24 in the 30 days before it.

After

The first 60 of 72.

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us7000fv2c (also filed as ak021esopfx2, iscgem621414838). Read Thu, Sep 24, 2026, 3:36 PM UTC.