M5.5 earthquake 228 km W of Adak, Alaska
A magnitude 5.5 earthquake struck 228 km W of Adak, Alaska on Fri, Dec 31, 1971, 8:51 AM GMT-11 (19:51 UTC), 104 km (64 mi) below the surface.
A larger quake followed: M5.8 Rat Islands, Aleutian Islands, Alaska. This one was a foreshock.
Map
Where this earthquake was located, with the others nearby. Select one for its page.
The earthquake
- Magnitude
- 5.5 (mw), moderate
- Local time
- UTC
- 1971-12-31 19:51:19 UTC
- Depth
- 103.5 km (64.3 mi), intermediate-depth
- Epicenter
- 51.673° N, 179.925° W
- Region
- Alaska
- Tsunami flag
- No
- Status
- Reviewed by a seismologist
Did you feel it?
No one has reported feeling this quake to the USGS.
How well it is located
Reviewed by a seismologist.
- Magnitude uncertainty
- ±0.41
- Depth from
- From location
Nearby
Within 100 km, magnitude 2.5 and up: 1 in the 60 days after this one and 0 in the 30 days before it.
After
Earthquakes todayAlaska earthquakesLive radar here
Sources
From the USGS Earthquake Hazards Program and its partner networks, event iscgem778206. Read Tue, Sep 22, 2026, 9:36 AM UTC.