Alaska earthquakes

M4.9 earthquake 9 km NW of Harding-Birch Lakes, Alaska

A magnitude 4.9 earthquake struck 9 km NW of Harding-Birch Lakes, Alaska on Mon, Sep 13, 2021, 9:56 PM AKDT (05:56 UTC), 4 km (2 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: 4.9 (ML, local (Richter)), light
Magnitude from: Alaska Earthquake Center
Local time: Mon, Sep 13, 2021, 9:56 PM AKDT
UTC: 2021-09-14 05:56:36 UTC
Depth: 3.9 km (2.4 mi), shallow
Epicenter: 64.437° N, 146.737° W
Region: Alaska
Felt reports: 1,086
Strongest shaking: VI, strong 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
4.9	ML, local (Richter)	Alaska Earthquake Center	Preferred · Preliminary
4.7	Mww, W-phase moment	USGS National Earthquake Information Center	Reviewed · ±0.034 · 82 stations
4.6	Mwr, regional moment	USGS National Earthquake Information Center	Moment tensor · Reviewed

What happened

The USGS’s account of the effects of this earthquake.

This event was felt in North Pole, Fairbanks, and Delta Junction.

From the USGS event page for ak021bt4ffvw. U.S. Geological Survey text and figures are in the public domain.

Shaking

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

Strongest estimated: VI, strong shaking
Peak ground acceleration: 24.1% of gravity
Peak ground velocity: 1.6 cm/s
Map: Automatic

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

Did you feel it?

1,086 people reported to the USGS what they felt; the strongest reported shaking was V, moderate 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	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%

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: 4.7 Mww
Nodal plane 1: Strike 243°, dip 79°, rake 11°
Nodal plane 2: Strike 151°, dip 80°, rake 169°

How well it is located

Reviewed by a seismologist.

Stations used: 114

Nearest places

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

Nearby

Within 100 km, magnitude 1.9 and up: 27 in the 60 days after this one and 2 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 ak021bt4ffvw (also filed as us7000fayl). Read Thu, Oct 1, 2026, 5:05 AM UTC.