Alaska earthquakes

M5.2 earthquake 22 km SSW of Adak, Alaska

A magnitude 5.2 earthquake struck 22 km SSW of Adak, Alaska on Thu, Feb 15, 2018, 2:00 PM HAST (00:00 UTC), 51 km (32 mi) below the surface.

Map

Where this earthquake was located, with the others nearby. Select one for its page.

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The earthquake

Magnitude: 5.2 (Mww, W-phase moment), moderate
Magnitude from: USGS National Earthquake Information Center
Local time: Thu, Feb 15, 2018, 2:00 PM HAST
UTC: 2018-02-16 00:00:15 UTC
Depth: 50.8 km (31.6 mi), shallow
Epicenter: 51.690° N, 176.778° W
Region: Alaska
Felt reports: 1
Strongest shaking: IV, light 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
5.2	Mww, W-phase moment	USGS National Earthquake Information Center	Preferred · Reviewed · ±0.05 · 39 stations
5.22	Mw, moment	ISC-GEM global catalog	Final · ±0.1
5.2	Mw, moment	Alaska Earthquake Center	Preliminary
5.0	ML, local (Richter)	NOAA National Tsunami Warning Center	Reviewed · 5 stations

What happened

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

Felt strongly on Adak.

From the USGS event page for us2000d2yz. U.S. Geological Survey text and figures are in the public domain.

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?

1 person reported to the USGS what they felt; the strongest reported shaking was III, weak shaking.

Fault motion and ground failure

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

Faulting: Oblique reverse
Moment magnitude: 5.2 Mww
Nodal plane 1: Strike 278°, dip 39°, rake 120°
Nodal plane 2: Strike 61°, dip 57°, rake 68°

How well it is located

Reviewed by a seismologist.

Location uncertainty: About 6.1 km horizontally, 3.9 km in depth
Magnitude uncertainty: ±0.05
Depth from: From location
Station coverage gap: 84°
Stations used: 217

Nearby

Within 100 km, magnitude 2.2 and up: 59 in the 60 days after this one and 46 in the 30 days before it.

After

Before

Earthquakes today Alaska earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event us2000d2yz (also filed as ak18437406, ak01825q9cac, at00p47uof, iscgem611689076). Read Fri, Oct 2, 2026, 12:40 AM UTC.