Alaska earthquakes

M3.4 earthquake 101 km S of Unalaska, Alaska

A magnitude 3.4 earthquake struck 101 km S of Unalaska, Alaska on Tue, Mar 20, 2018, 12:01 AM AKDT (08:01 UTC), 30 km (19 mi) below the surface.

A larger quake followed: M4.4 89 km E of Nikolski, Alaska. This one was a foreshock.

Unalaska 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: 3.4 (ML, local (Richter)), minor
Magnitude from: USGS National Earthquake Information Center
Local time: Tue, Mar 20, 2018, 12:01 AM AKDT
UTC: 2018-03-20 08:01:10 UTC
Depth: 30.1 km (18.7 mi), shallow
Epicenter: 52.974° N, 166.747° 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
3.4	ML, local (Richter)	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.128 · 8 stations
3.0	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 5.6 km horizontally, 14.0 km in depth
Magnitude uncertainty: ±0.13
Depth from: From location
Station coverage gap: 209°, poorly surrounded by stations
Stations used: 35

Nearest places

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

Unalaska, AlaskaPopulation 4,491. Forecast101 kmS

Nearby

Within 100 km, magnitude 1.5 and up: 83 in the 60 days after this one and 44 in the 30 days before it.

After

The first 60 of 83.

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us1000dahz (also filed as ak18714718, ak0183ms84hk). Read Thu, Oct 1, 2026, 10:19 AM UTC.