Alaska earthquakes

M5.0 earthquake 209 km WSW of Adak, Alaska

A magnitude 5.0 earthquake struck 209 km WSW of Adak, Alaska on Sat, Apr 18, 2026, 4:15 AM HADT (13:15 UTC), 38 km (23 mi) below the surface.

A larger quake followed: M6.1 Rat 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: 5.0 (Mww, W-phase moment), moderate
Magnitude from: USGS National Earthquake Information Center
Local time: Sat, Apr 18, 2026, 4:15 AM HADT
UTC: 2026-04-18 13:15:09 UTC
Depth: 37.7 km (23.4 mi), shallow
Epicenter: 51.456° N, 179.584° W
Region: Alaska
Strongest shaking: V, moderate 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
5.0	Mww, W-phase moment	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.059 · 28 stations
5.2	ML, local (Richter)	Alaska Earthquake Center	Preliminary · ±0.1 · 42 stations
4.9	Mwr, regional moment	USGS National Earthquake Information Center	Moment tensor · Reviewed
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: V, moderate shaking
Peak ground acceleration: 11.5% of gravity
Peak ground velocity: 4.3 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.

Aftershock forecast

The chance of at least one aftershock this large or larger, from the USGS operational aftershock forecast, issued Sat, Sep 26, 2026, 1:15 PM UTC. The USGS updates it as the sequence unfolds.

Within	M3+	M4+	M5+	M6+	M7+
1 day	Under 1%	Under 1%	Under 1%	Under 1%	Under 1%
1 week	3%	Under 1%	Under 1%	Under 1%	Under 1%
1 month	10%	1%	Under 1%	Under 1%	Under 1%
1 year	47%	8%	Under 1%	Under 1%	Under 1%

In the coming week the USGS expects about 0 aftershocks of magnitude 3 or more, and most likely between 0 and 1.

Fault motion and ground failure

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

Faulting: Oblique normal
Moment magnitude: 4.9 Mwr
Nodal plane 1: Strike 221°, dip 82°, rake -38°
Nodal plane 2: Strike 317°, dip 52°, rake -170°

How well it is located

Reviewed by a seismologist.

Location uncertainty: About 12.0 km horizontally, 8.4 km in depth
Magnitude uncertainty: ±0.06
Depth from: From location
Station coverage gap: 79°
Stations used: 175

Nearby

Within 100 km, magnitude 2.0 and up: 119 in the 60 days after this one and 45 in the 30 days before it.

After

The first 60 of 119.

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us6000sr43 (also filed as usauto6000sr43, aka2026hplbjb). Read Thu, Oct 1, 2026, 3:12 PM UTC.