Alaska earthquakes

M4.1 earthquake 248 km WSW of Adak, Alaska

A magnitude 4.1 earthquake struck 248 km WSW of Adak, Alaska on Tue, Aug 21, 2018, 1:31 AM GMT+12 (13:31 UTC), 70 km (43 mi) below the surface.

A larger quake followed: M4.2 Andreanof Islands, Aleutian Islands, 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: 4.1 (mb, body-wave), light
Magnitude from: USGS National Earthquake Information Center
Local time: Tue, Aug 21, 2018, 1:31 AM GMT+12
UTC: 2018-08-20 13:31:31 UTC
Depth: 69.8 km (43.4 mi), shallow
Epicenter: 51.188° N, 179.964° E
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
4.1	mb, body-wave	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.059 · 79 stations
4.1	mb, body-wave	Alaska Earthquake Center	Preliminary

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 6.0 km horizontally, 6.5 km in depth
Magnitude uncertainty: ±0.06
Depth from: From location
Station coverage gap: 118°
Stations used: 144

Nearby

Within 100 km, magnitude 1.5 and up: 76 in the 60 days after this one and 63 in the 30 days before it.

After

The first 60 of 76.

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us1000gdwu (also filed as ak018anwlv3x, ak20123641). Read Fri, Oct 2, 2026, 6:30 AM UTC.