Alaska earthquakes

M5.6 earthquake 84 km S of Atka, Alaska

A magnitude 5.6 earthquake struck 84 km S of Atka, Alaska on Sat, Mar 12, 2016, 3:23 AM HAST (13:23 UTC), 13 km (8 mi) below the surface.

A larger quake followed: M6.3 72 km SSE of Atka, 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: 5.6 (Mww, W-phase moment), moderate
Magnitude from: USGS National Earthquake Information Center
Local time: Sat, Mar 12, 2016, 3:23 AM HAST
UTC: 2016-03-12 13:23:38 UTC
Depth: 12.7 km (7.9 mi), shallow
Epicenter: 51.450° N, 173.972° W
Region: Alaska
Strongest shaking: IV, light shaking
PAGER alert: Green
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
5.6	Mww, W-phase moment	USGS National Earthquake Information Center	Preferred · Reviewed
5.65	Mw, moment	ISC-GEM global catalog	Final · ±0.1
5.7	Mw, moment	Alaska Earthquake Center	Preliminary
5.5	Mi	NOAA National Tsunami Warning Center	Reviewed · 3 stations
5.4	Mwb, body-wave moment	USGS National Earthquake Information Center	Moment tensor · Reviewed

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.

Shaking

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

Strongest estimated: IV, light shaking
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.

Estimated impact

The USGS PAGER system estimates deaths and economic losses from the shaking and the population and buildings exposed to it.

Alert level: Green: little or no damage or loss of life expected

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: 5.6 Mww
Nodal plane 1: Strike 68°, dip 73°, rake 89°
Nodal plane 2: Strike 250°, dip 17°, rake 92°

How well it is located

Reviewed by a seismologist.

Location uncertainty: About 5.2 km horizontally, 3.1 km in depth
Depth from: From location
Station coverage gap: 54°
Stations used: 282

Nearby

Within 100 km, magnitude 2.6 and up: 122 in the 60 days after this one and 13 in the 30 days before it.

After

The first 60 of 122.

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us10004x0f (also filed as ak12969021, at00o3xh7g, gcmt20160312132339, ak0163bakmzo, iscgem608482484). Read Mon, Oct 5, 2026, 8:35 AM UTC.