Reviewed by USGSAlaska4y ago
M2.9 earthquake 43 km SE of Akutan, Alaska
Saturday, December 18, 2021, 10:35:09 UTC · 53.825°N, 165.359°W
A magnitude 2.9 earthquake struck 43 km SE of Akutan, Alaska on Saturday, December 18, 2021, 10:35:09 UTC, at a depth of 62.2 km (shallow).
- Magnitude
- 2.9
- Minor · ml
- Depth
- 62 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- —
- No ShakeMap
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 50 km aftershock search area
In context
How big was it, and why here?
Energy released
338 kg of TNT
That is about 1/44,601 of the Hiroshima bomb. A magnitude 5.0 releases about 1,413 times more energy.
Tectonic setting
120 km
from the nearest mapped plate boundary, between the North American and Pacific plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.
Depth: shallow
62 km
Shallow earthquakes (under 70 km) produce the strongest surface shaking for their size, so they are the ones most likely to cause damage near the epicenter.
Did You Feel It?
Where it was felt
No “Did You Feel It?” reports have been published for this event yet. If you felt it, you can add your report on the USGS website.
I felt it — report to USGS ↗USGS PAGER estimate
Who was exposed to shaking
USGS publishes PAGER impact estimates for significant earthquakes, usually within an hour. No PAGER estimate is available for this event.
After the main event
Aftershocks within 50 km
USGS lists 4 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M3.7 on January 3, 2022. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 555 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.6The 1946 Unimak Island, Alaska EarthquakeApril 1, 1946 · 171 km E of this epicenter
- 7.881 km E of Nikolski, AlaskaJuly 2, 1965 · 177 km SW of this epicenter
- 7.190 km SE of King Cove, AlaskaMay 14, 1948 · 286 km E of this epicenter
- 7.139 km S of Akutan, AlaskaMarch 22, 1957 · 28 km W of this epicenter
- 7.135 km SW of Nikolski, AlaskaMarch 11, 1957 · 284 km SW of this epicenter
- 7.071 km SE of King Cove, AlaskaMay 30, 1991 · 258 km E of this epicenter
- 7.0203 km SSE of Unalaska, AlaskaAugust 22, 1940 · 186 km S of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 10 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 168 recorded deaths. The most severe:
- 1946M8.6
Unimak Island
1 Apr 1946 · 171 km away · intensity VI
168 deaths$26 million damagetsunami
- 1965M6.5
Aleutian Islands: Fox Islands
2 Jul 1965 · 170 km away
Limited damage (under $1M)tsunami
- 1917M7.9
Alaska Peninsula
31 May 1917 · 267 km away · intensity V
- 1902M7.8
Aleutian Islands: Fox Islands
1 Jan 1902 · 213 km away
- 1948M7.5
Alaska Peninsula
14 May 1948 · 294 km away
- 1957M7.5
Aleutian Islands: Fox Islands
22 Mar 1957 · 131 km away · intensity V
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.