Alaska earthquakes

M3.9 earthquake 42 km ENE of Pedro Bay, Alaska

A magnitude 3.9 earthquake struck 42 km ENE of Pedro Bay, Alaska on Sat, Aug 14, 2021, 2:35 AM AKDT (10:35 UTC), 149 km (92 mi) below the surface.

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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: 3.9 (ML, local (Richter)), minor
Magnitude from: Alaska Earthquake Center
Local time: Sat, Aug 14, 2021, 2:35 AM AKDT
UTC: 2021-08-14 10:35:15 UTC
Depth: 148.6 km (92.3 mi), intermediate-depth
Epicenter: 59.977° N, 153.456° W
Region: Alaska
Felt reports: 1
Strongest shaking: II, weak shaking
PAGER alert: Green
Tsunami flag: Yes: a large quake in an oceanic region
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
3.9	ML, local (Richter)	Alaska Earthquake Center	Preferred · Preliminary
3.9	mb, body-wave	USGS National Earthquake Information Center	Reviewed · ±0.195 · 8 stations
4.0	ML, local (Richter)	NOAA National Tsunami Warning Center	Reviewed · 22 stations

Tsunami

The USGS flags a quake this large in an oceanic region. The flag does not mean a tsunami happened; the tsunami warning centers decide that, and their messages are below when they issued any.

Current tsunami warnings: tsunami.gov. Warnings in force in the US also appear on our alerts pages.

Shaking

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

Strongest estimated: II, weak shaking
Peak ground acceleration: 0.1% of gravity
Peak ground velocity: -3.4 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.

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%

How well it is located

Reviewed by a seismologist.

Stations used: 260

Nearest places

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

Nearby

Within 100 km, magnitude 1.5 and up: at least 199 in the 60 days after this one and at least 200 in the 30 days before it.

After

The first 60 of at least 199.

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event ak021adxmavp (also filed as at00qxts2q, us6000f647). Read Mon, Oct 5, 2026, 7:15 AM UTC.