M5.5 earthquake 90 km SSW of Adak, Alaska
A magnitude 5.5 earthquake struck 90 km SSW of Adak, Alaska on Thu, Feb 11, 1971, 1:55 AM GMT-11 (12:55 UTC), 35 km (22 mi) below the surface.
A larger quake followed: M5.8 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.
The earthquake
- Magnitude
- 5.5 (mw), moderate
- Local time
- UTC
- 1971-02-11 12:55:53 UTC
- Depth
- 35.0 km (21.7 mi), shallow
- Epicenter
- 51.120° N, 177.114° 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
- ±0.20
- Depth from
- From location
Nearby
Within 100 km, magnitude 2.5 and up: 1 in the 60 days after this one and 5 in the 30 days before it.
After
Before
- 5.5103 km SSW of Adak, Alaska · 20316 days ago · 35 km deep · 14 km away
- 5.682 km SSW of Adak, Alaska · 20316 days ago · 25 km deep · 11 km away
- 5.986 km SSW of Adak, Alaska · 20316 days ago · 25 km deep · 3 km away
- 6.961 km SSW of Adak, Alaska · 20316 days ago · 30 km deep · 31 km away
- 6.492 km WSW of Adak, Alaska · 20329 days ago · 40 km deep · 59 km away
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Sources
From the USGS Earthquake Hazards Program and its partner networks, event iscgem787288 (also filed as ushis3147). Read Tue, Sep 22, 2026, 8:04 AM UTC.