Reviewed by USGSAlaska22y ago
M4.0 earthquake 284 km WSW of Adak, Alaska
Saturday, December 4, 2004, 01:44:13 UTC · 50.844°N, 179.629°E
A magnitude 4.0 earthquake struck 284 km WSW of Adak, Alaska on Saturday, December 4, 2004, 01:44:13 UTC, at a depth of 21.7 km (shallow).
- Magnitude
- 4.0
- Light · mb
- Depth
- 22 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
15 tons of TNT
That is about 1/998 of the Hiroshima bomb. A magnitude 5.0 releases about 32 times more energy.
Tectonic setting
36 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
22 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 1 M2.5+ earthquake within 50 km in the following 30 days; the largest was M2.8 on December 19, 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 771 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.71965 Western Aleutian Islands (Hawadax/Rat Islands) EarthquakeFebruary 4, 1965 · 78 km NW of this epicenter
- 8.31906 Western Aleutian Islands (Hawadax/Rat Islands) EarthquakeAugust 17, 1906 · 151 km NW of this epicenter
- 7.977 km WSW of Adak, AlaskaJune 10, 1996 · 207 km NE of this epicenter
- 7.8Rat Islands, Aleutian Islands, AlaskaNovember 17, 2003 · 76 km NW of this epicenter
- 7.6Rat Islands, Aleutian Islands, AlaskaMarch 30, 1965 · 138 km SW of this epicenter
- 7.65 km WNW of Adak, AlaskaFebruary 14, 1905 · 280 km NE of this epicenter
- 7.4265 km WSW of Adak, AlaskaFebruary 4, 1965 · 66 km N of this epicenter
- 7.388 km WSW of Adak, AlaskaJuly 7, 1929 · 196 km E of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 11 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1965M8.7
Aleutian Islands: Rat Islands
4 Feb 1965 · 78 km away · intensity VI
Under $1 million damagetsunami
- 1906M8.3
Aleutian Islands: Rat Islands
17 Aug 1906 · 151 km away
- 1905M7.9
Andreanof Islands
14 Feb 1905 · 129 km away
- 1996M7.9
Andreanof Islands
10 Jun 1996 · 207 km away · intensity VI
tsunami
- 2003M7.8
Aleutian Islands: Rat Islands
17 Nov 2003 · 76 km away
tsunami
- 1916M7.7
Aleutian Islands
6 Feb 1916 · 273 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.