Alaska earthquakes

M4.1 earthquake 18 km ESE of Elmendorf Air Force Base, Alaska

A magnitude 4.1 earthquake struck 18 km ESE of Elmendorf Air Force Base, Alaska on Thu, Oct 15, 2020, 8:05 AM AKDT (16:05 UTC), 35 km (22 mi) below the surface.

A larger quake followed: M5.1 2 km E of Big Lake, Alaska. This one was a foreshock.

Elmendorf Air Force Base 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: 4.1 (ML, local (Richter)), light
Magnitude from: Alaska Earthquake Center
Local time: Thu, Oct 15, 2020, 8:05 AM AKDT
UTC: 2020-10-15 16:05:15 UTC
Depth: 34.7 km (21.6 mi), shallow
Epicenter: 61.173° N, 149.324° W
Region: Alaska
Felt reports: 460
Strongest shaking: IV, light 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
4.1	ML, local (Richter)	Alaska Earthquake Center	Preferred · Preliminary
4.2	Mwr, regional moment	USGS National Earthquake Information Center	Reviewed · ±0.028 · 121 stations
4.3	ML, local (Richter)	NOAA National Tsunami Warning Center	Reviewed · 18 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: IV, light shaking
Peak ground acceleration: 312.0% of gravity
Peak ground velocity: 1.0 cm/s
Map: Automatic

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

Did you feel it?

460 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	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: Oblique normal
Moment magnitude: 4.2 Mwr
Nodal plane 1: Strike 290°, dip 25°, rake -132°
Nodal plane 2: Strike 155°, dip 72°, rake -73°

How well it is located

Reviewed by a seismologist.

Stations used: 292

Nearest places

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

Nearby

Within 100 km, magnitude 1.5 and up: 189 in the 60 days after this one and 95 in the 30 days before it.

After

The first 60 of 189.

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event ak020da7vc4e (also filed as us6000c8js, at00qi93cr). Read Thu, Oct 1, 2026, 6:21 AM UTC.