Reviewed by USGSAlaska15y ago
M2.5 earthquake 43 km E of Atka, Alaska
Tuesday, September 13, 2011, 23:41:43 UTC · 52.182°N, 173.564°W
A magnitude 2.5 earthquake struck 43 km E of Atka, Alaska on Tuesday, September 13, 2011, 23:41:43 UTC, at a depth of 23.7 km (shallow).
- Magnitude
- 2.5
- Minor · ml
- Depth
- 24 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
85 kg of TNT
That is about 1/177,558 of the Hiroshima bomb. A magnitude 5.0 releases about 5,623 times more energy.
Tectonic setting
136 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: shallow
24 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 4 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M4.7 on September 26, 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 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 · 161 km SW of this epicenter
- 8.01986 Atka, Alaska EarthquakeMay 7, 1986 · 111 km SW of this epicenter
- 7.977 km WSW of Adak, AlaskaJune 10, 1996 · 288 km W of this epicenter
- 7.8234 km SSW of Nikolski, AlaskaMarch 7, 1929 · 297 km SE of this epicenter
- 7.65 km WNW of Adak, AlaskaFebruary 14, 1905 · 217 km W of this epicenter
- 7.4133 km WNW of Nikolski, AlaskaApril 18, 1916 · 240 km NE of this epicenter
- 7.388 km WSW of Adak, AlaskaJuly 7, 1929 · 298 km W of this epicenter
- 7.346 km SSW of Adak, AlaskaJune 10, 1996 · 239 km W of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 13 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 · 161 km away
2 deathsSevere damage ($5–24M)tsunami
- 1986M8.0
Aleutian Islands: Adak
7 May 1986 · 111 km away · intensity VI
Moderate damage ($1–5M)tsunami
- 1901M7.8
Aleutian Islands: Fox Islands
31 Dec 1901 · 193 km away
Limited damage (under $1M)tsunami
- 1996M7.9
Andreanof Islands
10 Jun 1996 · 288 km away · intensity VI
tsunami
- 1907M7.8
Aleutian Islands
2 Sep 1907 · 264 km away
- 1929M7.8
Aleutian Islands: Fox Islands
7 Mar 1929 · 279 km away · intensity V
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.