Alaska earthquakes

M5.1 earthquake 68 km SSE of Adak, Alaska

A magnitude 5.1 earthquake struck 68 km SSE of Adak, Alaska on Tue, Apr 4, 2017, 1:49 AM HADT (10:49 UTC), 27 km (17 mi) below the surface.

A larger quake followed: M5.9 95 km SSW 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: 5.1 (Mww, W-phase moment), moderate
Magnitude from: USGS National Earthquake Information Center
Local time: Tue, Apr 4, 2017, 1:49 AM HADT
UTC: 2017-04-04 10:49:06 UTC
Depth: 26.6 km (16.5 mi), shallow
Epicenter: 51.267° N, 176.435° W
Region: Alaska
Strongest shaking: III, weak shaking
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
5.1	Mww, W-phase moment	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.073 · 18 stations
5.18	Mw, moment	ISC-GEM global catalog	Final · ±0.1
5.2	Mw, moment	Alaska Earthquake Center	Preliminary
5.2	ML, local (Richter)	NOAA National Tsunami Warning Center	Reviewed · 8 stations
5.0	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: III, weak 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.

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: 5.1 Mww
Nodal plane 1: Strike 271°, dip 24°, rake 108°
Nodal plane 2: Strike 72°, dip 68°, rake 82°

How well it is located

Reviewed by a seismologist.

Location uncertainty: About 6.7 km horizontally, 3.6 km in depth
Magnitude uncertainty: ±0.07
Depth from: From location
Station coverage gap: 63°
Stations used: 419

Nearby

Within 100 km, magnitude 2.1 and up: at least 199 in the 60 days after this one and 23 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 us10008e99 (also filed as ak15677323, at00onvspu, ak0174bmrh3x, iscgem610478108). Read Sat, Oct 3, 2026, 12:59 AM UTC.