Alaska earthquakes

M4.8 earthquake 127 km SW of Adak, Alaska

A magnitude 4.8 earthquake struck 127 km SW of Adak, Alaska on Wed, Jan 1, 2020, 5:05 AM HAST (15:05 UTC), 38 km (24 mi) below the surface.

A larger quake followed: M6.2 84 km W 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: 4.8 (Mww, W-phase moment), light
Magnitude from: USGS National Earthquake Information Center
Local time: Wed, Jan 1, 2020, 5:05 AM HAST
UTC: 2020-01-01 15:05:57 UTC
Depth: 38.0 km (23.6 mi), shallow
Epicenter: 51.202° N, 178.130° W
Region: Alaska
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
4.8	Mww, W-phase moment	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.117 · 7 stations
4.96	Mw, moment	ISC-GEM global catalog	Final · ±0.1
4.8	ML, local (Richter)	Alaska Earthquake Center	Preliminary
5.0	ML, local (Richter)	NOAA National Tsunami Warning Center	Reviewed · 8 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.

Did you feel it?

No one has reported feeling this quake to the USGS.

Fault motion and ground failure

How the rock slipped, from the moment tensor, and the USGS estimate of landslides and liquefaction.

Faulting: Reverse (thrust)
Moment magnitude: 4.8 Mww
Nodal plane 1: Strike 257°, dip 33°, rake 102°
Nodal plane 2: Strike 63°, dip 58°, rake 82°

How well it is located

Reviewed by a seismologist.

Location uncertainty: About 4.6 km horizontally, 4.5 km in depth
Magnitude uncertainty: ±0.12
Depth from: From location
Station coverage gap: 61°
Stations used: 194

Nearby

Within 100 km, magnitude 1.8 and up: at least 200 in the 60 days after this one and 47 in the 30 days before it.

After

The first 60 of at least 200.

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us70006t5u (also filed as at00q3folw, ak0201wi1ij, iscgem617050353). Read Thu, Oct 1, 2026, 10:57 PM UTC.