Reviewed by USGSAlaska4y ago
M2.5 earthquake 80 km E of Chignik, Alaska
Saturday, December 11, 2021, 15:11:52 UTC · 56.399°N, 157.113°W
A magnitude 2.5 earthquake struck 80 km E of Chignik, Alaska on Saturday, December 11, 2021, 15:11:52 UTC, at a depth of 89.2 km (intermediate).
- Magnitude
- 2.5
- Minor · ml
- Depth
- 89 km
- Intermediate
- 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
85 kg of TNT
That is about 1/177,558 of the Hiroshima bomb. A magnitude 5.0 releases about 5,623 times more energy.
Tectonic setting
212 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: intermediate
89 km
Intermediate-depth earthquakes usually break inside a plate that is sinking into the mantle. Shaking spreads over a wide area but is gentler at the epicenter than a shallow quake of the same size.
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 2 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M3.5 on December 27, 2021. 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 415 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 SW of this epicenter
- 8.22021 Chignik, Alaska EarthquakeJuly 29, 2021 · 125 km SW of this epicenter
- 7.82020 Perryville, Alaska EarthquakeJuly 22, 2020 · 174 km SW of this epicenter
- 7.62020 Sand Point, Alaska EarthquakeOctober 19, 2020 · 255 km SW of this epicenter
- 7.454 km SE of Sand Point, AlaskaMay 31, 1917 · 233 km SW of this epicenter
- 7.14 km ENE of Karluk, AlaskaNovember 7, 1912 · 212 km NE of this epicenter
- 7.0113 km ESE of Chignik, AlaskaMay 4, 1923 · 66 km S 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 · 234 km away · intensity VIII
Limited damage (under $1M)
- 1788M8.0
Unga Island
21 Jul 1788 · 260 km away · intensity VII
Limited damage (under $1M)tsunami
- 2020M7.8
Alaska
22 Jul 2020 · 174 km away · intensity VII
Limited damage (under $1M)tsunami
- 1970M6.0
Andreanof Islands
11 Mar 1970 · 230 km away · intensity V
Limited damage (under $1M)tsunami
- 1938M8.2
Alaska
10 Nov 1938 · 129 km away · intensity VI
tsunami
- 2021M8.2
Alaska Peninsula
29 Jul 2021 · 128 km away · intensity VIII
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.