Reviewed by USGSAlaska22y ago
M3.1 earthquake 56 km SW of Atka, Alaska
Sunday, September 12, 2004, 19:28:19 UTC · 51.782°N, 174.678°W
A magnitude 3.1 earthquake struck 56 km SW of Atka, Alaska on Sunday, September 12, 2004, 19:28:19 UTC, at a depth of 2.7 km (shallow).
- Magnitude
- 3.1
- Minor · ml
- Depth
- 3 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
102 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
3 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 M3.2 on September 28, 2004. 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 816 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 · 73 km SW of this epicenter
- 8.01986 Atka, Alaska EarthquakeMay 7, 1986 · 30 km S of this epicenter
- 7.977 km WSW of Adak, AlaskaJune 10, 1996 · 205 km W of this epicenter
- 7.65 km WNW of Adak, AlaskaFebruary 14, 1905 · 140 km W of this epicenter
- 7.388 km WSW of Adak, AlaskaJuly 7, 1929 · 214 km W of this epicenter
- 7.346 km SSW of Adak, AlaskaJune 10, 1996 · 153 km W of this epicenter
- 7.2162 km WSW of Adak, AlaskaMarch 16, 1957 · 292 km W of this epicenter
- 7.175 km S of Adak, AlaskaMarch 14, 1957 · 156 km SW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 9 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 · 73 km away
2 deathsSevere damage ($5–24M)tsunami
- 1986M8.0
Aleutian Islands: Adak
7 May 1986 · 30 km away · intensity VI
Moderate damage ($1–5M)tsunami
- 1901M7.8
Aleutian Islands: Fox Islands
31 Dec 1901 · 255 km away
Limited damage (under $1M)tsunami
- 1905M7.9
Andreanof Islands
14 Feb 1905 · 294 km away
- 1996M7.9
Andreanof Islands
10 Jun 1996 · 205 km away · intensity VI
tsunami
- 1996M7.3
Andreanof Islands
10 Jun 1996 · 153 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.