Alaska earthquakes

M3.5 earthquake 103 km W of Adak, Alaska

A magnitude 3.5 earthquake struck 103 km W of Adak, Alaska on Fri, Sep 11, 2020, 9:58 AM HADT (18:58 UTC), 17 km (10 mi) below the surface.

A larger quake followed: M4.8 135 km WSW of Adak, 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: 3.5 (ML, local (Richter)), minor
Magnitude from: USGS National Earthquake Information Center
Local time: Fri, Sep 11, 2020, 9:58 AM HADT
UTC: 2020-09-11 18:58:16 UTC
Depth: 16.8 km (10.4 mi), shallow
Epicenter: 51.834° N, 178.136° W
Region: Alaska
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
3.5	ML, local (Richter)	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.105 · 12 stations
3.0	ML, local (Richter)	Alaska Earthquake Center	Preliminary
3.11	ML, local (Richter)	AV	Final · ±0.330058578865384 · 26 stations

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 1.8 km horizontally, 1.8 km in depth
Magnitude uncertainty: ±0.10
Depth from: From location
Station coverage gap: 118°
Stations used: 50

Nearby

Within 100 km, magnitude 1.5 and up: 125 in the 60 days after this one and 96 in the 30 days before it.

After

The first 60 of 125.

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us7000bm1j (also filed as av91123456, ak020bq13rn3). Read Mon, Oct 5, 2026, 3:13 AM UTC.