Reviewed by USGSAlaska4y ago
M2.7 earthquake 26 km WNW of False Pass, Alaska
Friday, December 17, 2021, 08:47:52 UTC · 54.986°N, 163.764°W
A magnitude 2.7 earthquake struck 26 km WNW of False Pass, Alaska on Friday, December 17, 2021, 08:47:52 UTC, at a depth of 172.2 km (intermediate).
- Magnitude
- 2.7
- Minor · ml
- Depth
- 172 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
169 kg of TNT
That is about 1/88,990 of the Hiroshima bomb. A magnitude 5.0 releases about 2,818 times more energy.
Tectonic setting
198 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
172 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 4 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M3.4 on December 31, 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 384 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 · 177 km S of this epicenter
- 7.62020 Sand Point, Alaska EarthquakeOctober 19, 2020 · 269 km E of this epicenter
- 7.454 km SE of Sand Point, AlaskaMay 31, 1917 · 248 km E of this epicenter
- 7.190 km SE of King Cove, AlaskaMay 14, 1948 · 172 km E of this epicenter
- 7.139 km S of Akutan, AlaskaMarch 22, 1957 · 187 km SW of this epicenter
- 7.071 km SE of King Cove, AlaskaMay 30, 1991 · 146 km E of this epicenter
- 6.917 km S of Sand Point, AlaskaMay 13, 1993 · 211 km E of this epicenter
- 6.967 km SW of Unalaska, AlaskaFebruary 27, 1987 · 284 km SW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 8 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 · 177 km away · intensity VI
168 deaths$26 million damagetsunami
- 1788M8.0
Alaska Peninsula
6 Aug 1788 · 176 km away
tsunami
- 2020M7.6
Alaska
19 Oct 2020 · 269 km away · intensity IX
tsunami
- 1948M7.5
Alaska Peninsula
14 May 1948 · 185 km away
- 1957M7.5
Aleutian Islands: Fox Islands
22 Mar 1957 · 92 km away · intensity V
- 1820
East Aleutian Islands
1 Mar 1820 · 77 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.