Alaska earthquakes

M5.6 earthquake 22 km W of Atka, Alaska

A magnitude 5.6 earthquake struck 22 km W of Atka, Alaska on Thu, May 15, 1986, 12:34 AM HADT (09:34 UTC), 33 km (21 mi) below the surface.

A larger quake followed: M6.5 25 km NW of Atka, Alaska. This one was a foreshock.

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The earthquake

Magnitude: 5.6 (Mw, moment), moderate
Magnitude from: USGS National Earthquake Information Center
Local time: Thu, May 15, 1986, 12:34 AM HADT
UTC: 1986-05-15 09:34:05 UTC
Depth: 33.0 km (20.5 mi), shallow
Epicenter: 52.217° N, 174.527° 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
5.6	Mw, moment	USGS National Earthquake Information Center	Preferred · Reviewed
5.6	Mw, moment	ISC-GEM global catalog	Final · ±0.1
5.6	Mwc, centroid moment	Global CMT project	Preliminary

What happened

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

CENTROID, MOMENT TENSOR (HRV) Data Used: GDSN L.P.B.: 13S, 28C Centroid Location: Origin Time 09:34: 6.5 0.5 Lat 52.41N 0.08 Lon 174.74W 0.11 Dep 26.9 8.1 Half-duration 2.4 Moment Tensor; Scale 10**24 D-CM Mrr=-0.29 0.13 Mtt=1.50 0.15 Mff=-1.21 0.13 Mrt=0.65 0.45 Mrf=1.73 0.34 Mtf=-2.21 0.18 Principal Axes: (T) Val=2.77 Plg=7 Azm=212 (N) Val=0.73 Plg=59 Azm=313 (P) Val=-3.50 Plg=30 Azm=118 Best Double Couple:Mo=3.1*10**24 NP1:Strike=259 Dip=64 Slip=-163 NP2:Strike=161 Dip=74 Slip=-27

From the USGS event page for usp0002u1f. 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.

How well it is located

Reviewed by a seismologist.

Depth from: OPERATOR_ASSIGNED

Nearby

Within 100 km, magnitude 2.6 and up: 46 in the 60 days after this one and 98 in the 30 days before it.

After

Before

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Sources

From the USGS Earthquake Hazards Program and its partner networks, event usp0002u1f (also filed as gcmtb051586b, gcmt19860515093405, iscgem495720). Read Thu, Oct 1, 2026, 5:48 AM UTC.