Alaska earthquakes

M4.9 earthquake 91 km SSE of Adak, Alaska

A magnitude 4.9 earthquake struck 91 km SSE of Adak, Alaska on Thu, Mar 20, 2025, 1:21 AM HADT (10:21 UTC), 34 km (21 mi) below the surface.

A larger quake followed: M6.2 88 km SSE 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: 4.9 (Mww, W-phase moment), light
Magnitude from: USGS National Earthquake Information Center
Local time: Thu, Mar 20, 2025, 1:21 AM HADT
UTC: 2025-03-20 10:21:04 UTC
Depth: 33.6 km (20.9 mi), shallow
Epicenter: 51.107° N, 176.174° W
Region: Alaska
Strongest shaking: III, weak shaking
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
4.9	Mww, W-phase moment	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.073 · 18 stations
5.0	mb, body-wave	Alaska Earthquake Center	Preliminary
5.0	Mww, W-phase moment	USGS, automatic first solution	First automatic solution · Preliminary

Shaking

The USGS ShakeMap: shaking estimated from seismic stations and the quake’s size, on the Modified Mercalli intensity scale.

Strongest estimated: III, weak shaking
Peak ground acceleration: 0.8% of gravity
Peak ground velocity: 0.5 cm/s
Map: Automatic

USGS ShakeMap: estimated shaking intensity around the epicenter — Estimated shaking intensity. Map: USGS ShakeMap.

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: 4.9 Mww
Nodal plane 1: Strike 267°, dip 24°, rake 108°
Nodal plane 2: Strike 67°, dip 67°, rake 82°

How well it is located

Reviewed by a seismologist.

Location uncertainty: About 4.3 km horizontally, 5.0 km in depth
Magnitude uncertainty: ±0.07
Depth from: From location
Station coverage gap: 127°
Stations used: 113

Nearby

Within 100 km, magnitude 1.9 and up: at least 199 in the 60 days after this one and 109 in the 30 days before it.

After

The first 60 of at least 199.

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us6000pzzb (also filed as usauto6000pzzb, ak0253mtj9bl). Read Fri, Oct 2, 2026, 2:11 AM UTC.