Reviewed by USGSAlaska15y ago
M4.7 earthquake 41 km NNE of Atka, Alaska
Monday, September 26, 2011, 20:08:44 UTC · 52.542°N, 173.983°W
A magnitude 4.7 earthquake struck 41 km NNE of Atka, Alaska on Monday, September 26, 2011, 20:08:44 UTC, at a depth of 219.9 km (intermediate). It is the strongest earthquake within 300 km since an M5.6 on September 19, 2011.
- Magnitude
- 4.7
- Light · mb
- Depth
- 220 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 earthquake
In context
How big was it, and why here?
Energy released
169 tons of TNT
That is about 1/89 of the Hiroshima bomb. A magnitude 5.0 releases about 3 times more energy.
Tectonic setting
179 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
220 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 has not published any M2.5+ earthquake within 50 km in the 30 days after this event.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 781 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 · 162 km SW of this epicenter
- 8.01986 Atka, Alaska EarthquakeMay 7, 1986 · 126 km SW of this epicenter
- 7.977 km WSW of Adak, AlaskaJune 10, 1996 · 272 km W of this epicenter
- 7.65 km WNW of Adak, AlaskaFebruary 14, 1905 · 199 km W of this epicenter
- 7.4133 km WNW of Nikolski, AlaskaApril 18, 1916 · 243 km NE of this epicenter
- 7.388 km WSW of Adak, AlaskaJuly 7, 1929 · 283 km SW of this epicenter
- 7.346 km SSW of Adak, AlaskaJune 10, 1996 · 229 km SW of this epicenter
- 7.3Fox Islands, Aleutian Islands, AlaskaJune 24, 2011 · 156 km E 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 · 162 km away
2 deathsSevere damage ($5–24M)tsunami
- 1986M8.0
Aleutian Islands: Adak
7 May 1986 · 126 km away · intensity VI
Moderate damage ($1–5M)tsunami
- 1901M7.8
Aleutian Islands: Fox Islands
31 Dec 1901 · 236 km away
Limited damage (under $1M)tsunami
- 1996M7.9
Andreanof Islands
10 Jun 1996 · 272 km away · intensity VI
tsunami
- 1907M7.8
Aleutian Islands
2 Sep 1907 · 287 km away
- 1916M7.5
Aleutian Islands: Fox Islands
18 Apr 1916 · 280 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.