Alaska earthquakes

M3.9 earthquake 38 km SSW of Adak, Alaska

A magnitude 3.9 earthquake struck 38 km SSW of Adak, Alaska on Mon, Mar 12, 2018, 1:38 PM HADT (22:38 UTC), 34 km (21 mi) below the surface.

A larger quake followed: M4.2 81 km SW of Adak, Alaska. This one was a foreshock.

Map

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The earthquake

Magnitude: 3.9 (mb, body-wave), minor
Magnitude from: USGS National Earthquake Information Center
Local time: Mon, Mar 12, 2018, 1:38 PM HADT
UTC: 2018-03-12 22:38:46 UTC
Depth: 34.3 km (21.3 mi), shallow
Epicenter: 51.558° N, 176.865° 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
3.9	mb, body-wave	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.101 · 26 stations
3.4	ML, local (Richter)	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 4.5 km horizontally, 9.3 km in depth
Magnitude uncertainty: ±0.10
Depth from: From location
Station coverage gap: 200°, poorly surrounded by stations
Stations used: 64

Nearby

Within 100 km, magnitude 1.5 and up: 103 in the 60 days after this one and 57 in the 30 days before it.

After

The first 60 of 103.

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us1000d3jg (also filed as ak18693007, ak01839shf3k). Read Fri, Oct 2, 2026, 11:52 AM UTC.