Reviewed by USGSAlaska15y ago
M2.9 earthquake 154 km SW of Nikolski, Alaska
Tuesday, August 23, 2011, 10:25:36 UTC · 51.939°N, 170.436°W
A magnitude 2.9 earthquake struck 154 km SW of Nikolski, Alaska on Tuesday, August 23, 2011, 10:25:36 UTC, at a depth of 16.5 km (shallow).
- Magnitude
- 2.9
- Minor · ml
- Depth
- 17 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
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
58 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
17 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 2 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M3.7 on September 15, 2011. 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 694 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.8234 km SSW of Nikolski, AlaskaMarch 7, 1929 · 123 km S of this epicenter
- 7.881 km E of Nikolski, AlaskaJuly 2, 1965 · 223 km NE of this epicenter
- 7.4133 km WNW of Nikolski, AlaskaApril 18, 1916 · 168 km N of this epicenter
- 7.3Fox Islands, Aleutian Islands, AlaskaJune 24, 2011 · 97 km W of this epicenter
- 7.135 km SW of Nikolski, AlaskaMarch 11, 1957 · 119 km NE of this epicenter
- 6.980 km SW of Nikolski, AlaskaMarch 9, 1957 · 76 km NE 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. The most severe:
- 1901M7.8
Aleutian Islands: Fox Islands
31 Dec 1901 · 68 km away
Limited damage (under $1M)tsunami
- 1965M6.5
Aleutian Islands: Fox Islands
2 Jul 1965 · 230 km away
Limited damage (under $1M)tsunami
- 1902M7.8
Aleutian Islands: Fox Islands
1 Jan 1902 · 207 km away
- 1907M7.8
Aleutian Islands
2 Sep 1907 · 87 km away
- 1929M7.8
Aleutian Islands: Fox Islands
7 Mar 1929 · 109 km away · intensity V
tsunami
- 1916M7.5
Aleutian Islands: Fox Islands
18 Apr 1916 · 154 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.