Reviewed by USGS4y ago
M4.1 earthquake south of Alaska
Monday, December 6, 2021, 22:20:49 UTC · 55.685°N, 155.964°W
A magnitude 4.1 earthquake struck south of Alaska on Monday, December 6, 2021, 22:20:49 UTC, at a depth of 28.4 km (shallow). The USGS PAGER alert is green: low likelihood of casualties and damage.
- Magnitude
- 4.1
- Light · ml
- Depth
- 28 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- III
- Weak (ShakeMap)
- PAGER alert
- Green
- Impact estimate
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
21 tons of TNT
That is about 1/707 of the Hiroshima bomb. A magnitude 5.0 releases about 22 times more energy.
Tectonic setting
107 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
28 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 populated area was estimated to feel noticeable shaking.
After the main event
Aftershocks within 50 km
USGS has not published any M2.5+ earthquake within 50 km in the 30 days after this event.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 412 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.21938 Semidi Islands, Alaska EarthquakeNovember 10, 1938 · 151 km W of this epicenter
- 8.22021 Chignik, Alaska EarthquakeJuly 29, 2021 · 126 km W of this epicenter
- 7.82020 Perryville, Alaska EarthquakeJuly 22, 2020 · 180 km W of this epicenter
- 7.62020 Sand Point, Alaska EarthquakeOctober 19, 2020 · 262 km SW of this epicenter
- 7.454 km SE of Sand Point, AlaskaMay 31, 1917 · 259 km W of this epicenter
- 7.14 km ENE of Karluk, AlaskaNovember 7, 1912 · 233 km NE of this epicenter
- 7.0113 km ESE of Chignik, AlaskaMay 4, 1923 · 53 km W of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 13 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1900M8.3
Kodiak Island
9 Oct 1900 · 219 km away · intensity VIII
Limited damage (under $1M)
- 1788M8.0
Unga Island
21 Jul 1788 · 234 km away · intensity VII
Limited damage (under $1M)tsunami
- 2020M7.8
Alaska
22 Jul 2020 · 180 km away · intensity VII
Limited damage (under $1M)tsunami
- 1970M6.0
Andreanof Islands
11 Mar 1970 · 238 km away · intensity V
Limited damage (under $1M)tsunami
- 1792
Kodiak Island
1792 · 285 km away · intensity VII
Limited damage (under $1M)tsunami
- 1938M8.2
Alaska
10 Nov 1938 · 153 km away · intensity VI
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.