Alaska earthquakes

M5.5 earthquake 126 km WSW of Adak, Alaska

A magnitude 5.5 earthquake struck 126 km WSW of Adak, Alaska on Tue, Apr 23, 1996, 11:03 AM HADT (20:03 UTC), 29 km (18 mi) below the surface.

A larger quake followed: M7.9 77 km WSW 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: 5.5 (Mwc, centroid moment), moderate
Magnitude from: USGS National Earthquake Information Center
Local time: Tue, Apr 23, 1996, 11:03 AM HADT
UTC: 1996-04-23 20:03:25 UTC
Depth: 29.3 km (18.2 mi), shallow
Epicenter: 51.485° N, 178.360° 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
5.5	Mwc, centroid moment	USGS National Earthquake Information Center	Preferred · Reviewed
5.49	Mw, moment	ISC-GEM global catalog	Final · ±0.1
5.5	Mwc, centroid moment	Global CMT project	Preliminary
5.5	Mw, moment	Alaska Earthquake Center	Preliminary

What happened

The USGS’s account of the effects of this earthquake.

Felt on Adak.

From the USGS event page for usp0007ghg. U.S. Geological Survey text and figures are in the public domain.

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: Oblique reverse
Nodal plane 1: Strike 274°, dip 24°, rake 128°
Nodal plane 2: Strike 53°, dip 72°, rake 75°

How well it is located

Reviewed by a seismologist.

Depth from: CONSTRAINED_BY_DEPTH_PHASES

Nearby

Within 100 km, magnitude 2.5 and up: 133 in the 60 days after this one and 2 in the 30 days before it.

After

The first 60 of 133.

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event usp0007ghg (also filed as gcmtb042396c, gcmt19960423200325, ak99658v6xgi, iscgem960456). Read Mon, Oct 5, 2026, 4:25 AM UTC.