Alaska earthquakes

M4.7 earthquake 67 km ESE of Atka, Alaska

A magnitude 4.7 earthquake struck 67 km ESE of Atka, Alaska on Fri, Aug 20, 2021, 3:20 AM HADT (12:20 UTC), 79 km (49 mi) below the surface.

A larger quake followed: M4.9 81 km S of Atka, 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: 4.7 (mb), light
Local time: Fri, Aug 20, 2021, 3:20 AM HADT
UTC: 2021-08-20 12:20:19 UTC
Depth: 79.5 km (49.4 mi), intermediate-depth
Epicenter: 51.980° N, 173.278° W
Region: Alaska
Strongest shaking: III, weak 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: III, weak shaking
Peak ground acceleration: 0.8% of gravity
Peak ground velocity: -1.3 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 6.9 km horizontally, 5.9 km in depth
Magnitude uncertainty: ±0.07
Depth from: From location
Station coverage gap: 40°
Stations used: 151

Nearby

Within 100 km, magnitude 1.7 and up: 57 in the 60 days after this one and 53 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 us6000f8s7 (also filed as ak021anvy1qc). Read Thu, Sep 24, 2026, 7:15 AM UTC.