Aleutian Megathrust
Alaska, USA · subduction interface · 2431.4 km of mapped active fault in 41 traces
background as of 7 November 2026.
consistent with baseline
| Window | the last 30.0 days |
|---|---|
| Earthquakes counted | 0 at M4.5 or above |
| Expected in that window | 0.25 |
What this system normally does
From 1995 to 2025 the catalogue holds 93 earthquakes of M4.5 or larger attributable to this system: about 3.10 a year. That figure is what "elevated" on this page is measured against.
The fault itself
| Mapped length | 2431.4 km |
|---|---|
| Traces | 41 |
| Tectonic setting | subduction interface |
| Slip types | Subduction_Thrust |
| Depth attributed to it | down to 700.0 km |
| Extent | 50.48 to 58.35 latitude, -180.00 to -146.76 longitude |
Recorded history
NOAA's hazard records hold 10 significant earthquakes and 6 tsunamis attributed to this system since 1900.
The deadliest was the 1 April 1946 magnitude 8.6 earthquake (Alaska: Unimak Island), which killed 168 people.
The strongest earthquake on record here was magnitude 8.7, on 4 February 1965 (Alaska: Aleutian Islands: Rat Islands).
The most recent entry is the 29 July 2021 magnitude 8.2 earthquake (Alaska Peninsula).
Across the entries that record a death toll, 170 people died.
| Date | What | Where | Toll |
|---|---|---|---|
| 1 April 1946 | tsunami (waves to 42 m) | Unimak Island, Ak | 168 dead, $26 million damage |
| 1 April 1946 | magnitude 8.6 earthquake | Alaska: Unimak Island | 168 dead, $26 million damage |
| 9 March 1957 | tsunami (waves to 32 m) | Andreanof Islands, Ak | 2 dead, damage $5 to 25 million |
| 9 March 1957 | magnitude 8.6 earthquake | Alaska | 2 dead, damage $5 to 25 million |
| 4 February 1965 | magnitude 8.7 earthquake | Alaska: Aleutian Islands: Rat Islands | damage under $1 million |
| 9 October 1900 | magnitude 8.3 earthquake | Alaska: Kodiak Island | damage under $1 million |
| 29 July 2021 | magnitude 8.2 earthquake | Alaska Peninsula | - |
| 7 May 1986 | magnitude 8.0 earthquake | Alaska: Aleutian Islands: Adak | damage $1 to 5 million |
| 14 February 1905 | magnitude 7.9 earthquake | Alaska: Andreanof Islands | - |
| 7 March 1929 | magnitude 7.8 earthquake | Alaska: Aleutian Islands: Fox Islands | - |
| 1 January 1902 | magnitude 7.8 earthquake | Alaska: Aleutian Islands: Fox Islands | - |
| 31 December 1901 | magnitude 7.8 earthquake | Alaska: Aleutian Islands: Fox Islands | damage under $1 million |
| 4 February 1965 | tsunami (waves to 10.7 m) | Rat Islands, Aleutian Islands, Ak | damage under $1 million |
| 7 March 1929 | tsunami (waves to 1 m) | Fox Islands, Aleutian Islands, Ak | damage under $1 million |
| 7 May 1986 | tsunami (waves to 0.9 m) | Andreanof Islands, Ak | damage $1 to 5 million |
| 29 July 2021 | tsunami (waves to 0.4 m) | Kodiak Island, Ak | - |
A dash means NOAA recorded no number, not that nobody died. Older entries are fewer because fewer were written down, not because less happened.
Recorded history: NOAA NCEI hazard databases, public domain, retrieved 2026-10-22.
Who to listen to if you live here
Ready Alaska is the agency that tells people on this system what to do. https://ready.alaska.gov/ (in English)
Other systems in Alaska, USA
Where these numbers come from
Fault geometry, length and segment counts: GEM Global Active Faults Database (GEM GAF-DB), GEM Foundation, https://github.com/GEMScienceTools/gem-global-active-faults Licence: CC-BY-SA-4.0. Figures derived from it here are offered under the same licence. Earthquake counts, magnitudes and depths: United States Geological Survey, public domain. The activity judgement is ours, computed from those two inputs, and is not a statement by either agency.