Reviewed by USGSAlaska14y ago
M3.1 earthquake 76 km ESE of Atka, Alaska
Sunday, March 11, 2012, 20:21:46 UTC · 51.834°N, 173.256°W
A magnitude 3.1 earthquake struck 76 km ESE of Atka, Alaska on Sunday, March 11, 2012, 20:21:46 UTC, at a depth of 10.0 km (shallow).
- Magnitude
- 3.1
- Minor · ml
- Depth
- 10 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
674 kg of TNT
That is about 1/22,353 of the Hiroshima bomb. A magnitude 5.0 releases about 708 times more energy.
Tectonic setting
94 km
from the nearest mapped plate boundary, between the North American and Pacific plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
10 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 3 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M4.2 on March 11, 2012. 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 829 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.61957 Atka, Alaska EarthquakeMarch 9, 1957 · 168 km W of this epicenter
- 8.01986 Atka, Alaska EarthquakeMay 7, 1986 · 110 km W of this epicenter
- 7.8234 km SSW of Nikolski, AlaskaMarch 7, 1929 · 262 km E of this epicenter
- 7.65 km WNW of Adak, AlaskaFebruary 14, 1905 · 237 km W of this epicenter
- 7.4133 km WNW of Nikolski, AlaskaApril 18, 1916 · 250 km NE of this epicenter
- 7.346 km SSW of Adak, AlaskaJune 10, 1996 · 251 km W of this epicenter
- 7.3Fox Islands, Aleutian Islands, AlaskaJune 24, 2011 · 100 km E of this epicenter
- 7.175 km S of Adak, AlaskaMarch 14, 1957 · 251 km W of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 12 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 2 recorded deaths. The most severe:
- 1957M8.6
Alaska
9 Mar 1957 · 168 km away
2 deathsSevere damage ($5–24M)tsunami
- 1986M8.0
Aleutian Islands: Adak
7 May 1986 · 110 km away · intensity VI
Moderate damage ($1–5M)tsunami
- 1901M7.8
Aleutian Islands: Fox Islands
31 Dec 1901 · 160 km away
Limited damage (under $1M)tsunami
- 1907M7.8
Aleutian Islands
2 Sep 1907 · 254 km away
- 1929M7.8
Aleutian Islands: Fox Islands
7 Mar 1929 · 244 km away · intensity V
tsunami
- 1916M7.5
Aleutian Islands: Fox Islands
18 Apr 1916 · 274 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.