Reviewed by USGSAlaska14y ago
M2.9 earthquake 7 km SE of Atka, Alaska
Thursday, December 29, 2011, 01:41:56 UTC · 52.146°N, 174.135°W
A magnitude 2.9 earthquake struck 7 km SE of Atka, Alaska on Thursday, December 29, 2011, 01:41:56 UTC, at a depth of 166.6 km (intermediate).
- Magnitude
- 2.9
- Minor · m
- Depth
- 167 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
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
137 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
167 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 3 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M2.9 on January 13, 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 877 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 · 125 km SW of this epicenter
- 8.01986 Atka, Alaska EarthquakeMay 7, 1986 · 82 km SW of this epicenter
- 7.977 km WSW of Adak, AlaskaJune 10, 1996 · 249 km W of this epicenter
- 7.65 km WNW of Adak, AlaskaFebruary 14, 1905 · 178 km W of this epicenter
- 7.4133 km WNW of Nikolski, AlaskaApril 18, 1916 · 274 km NE of this epicenter
- 7.388 km WSW of Adak, AlaskaJuly 7, 1929 · 259 km W of this epicenter
- 7.346 km SSW of Adak, AlaskaJune 10, 1996 · 201 km W of this epicenter
- 7.3Fox Islands, Aleutian Islands, AlaskaJune 24, 2011 · 157 km E 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 2 recorded deaths. The most severe:
- 1957M8.6
Alaska
9 Mar 1957 · 125 km away
2 deathsSevere damage ($5–24M)tsunami
- 1986M8.0
Aleutian Islands: Adak
7 May 1986 · 82 km away · intensity VI
Moderate damage ($1–5M)tsunami
- 1901M7.8
Aleutian Islands: Fox Islands
31 Dec 1901 · 228 km away
Limited damage (under $1M)tsunami
- 1996M7.9
Andreanof Islands
10 Jun 1996 · 249 km away · intensity VI
tsunami
- 1996M7.3
Andreanof Islands
10 Jun 1996 · 201 km away
tsunami
- 2011M7.3
Aleutian Islands: Fox Islands
24 Jun 2011 · 157 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.