Alaska earthquakes

M5.6 earthquake 181 km SE of Chignik, Alaska

A magnitude 5.6 earthquake struck 181 km SE of Chignik, Alaska on Thu, Sep 16, 2021, 9:51 AM AKDT (17:51 UTC), 37 km (23 mi) below the surface.

Sand Point 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: 5.6 (mww), moderate
Local time: Thu, Sep 16, 2021, 9:51 AM AKDT
UTC: 2021-09-16 17:51:55 UTC
Depth: 36.8 km (22.9 mi), shallow
Epicenter: 55.071° N, 156.499° W
Region: Alaska
Felt reports: 2
Strongest shaking: III, weak shaking
PAGER alert: Green
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: III, weak shaking
Peak ground acceleration: 0.3% of gravity
Peak ground velocity: -0.5 cm/s
Map: Automatic

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

Did you feel it?

2 people reported to the USGS what they felt; the strongest reported shaking was II, weak shaking.

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: Reverse (thrust)
Moment magnitude: 5.6 Mww
Nodal plane 1: Strike 256°, dip 9°, rake 112°
Nodal plane 2: Strike 54°, dip 81°, rake 86°
Landslide alert: Green
Liquefaction alert: Green

How well it is located

Reviewed by a seismologist.

Stations used: 178

Nearest places

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

Sand Point, AlaskaPopulation 1,064. Forecast256 kmE

Nearby

Within 100 km, magnitude 2.5 and up: 39 in the 60 days after this one and 63 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 ak021bwmmasc (also filed as usauto7000fbv4, us7000fbv4, iscgem621080781). Read Wed, Sep 23, 2026, 3:54 AM UTC.