Reviewed by USGSAlaska22y ago
M2.8 earthquake 248 km W of Adak, Alaska
Monday, February 2, 2004, 23:40:21 UTC · 51.658°N, 179.779°E
A magnitude 2.8 earthquake struck 248 km W of Adak, Alaska on Monday, February 2, 2004, 23:40:21 UTC, at a depth of 70.0 km (intermediate).
- Magnitude
- 2.8
- Minor · ml
- Depth
- 70 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 earthquakeDashed circle: 50 km aftershock search area
In context
How big was it, and why here?
Energy released
239 kg of TNT
That is about 1/63,000 of the Hiroshima bomb. A magnitude 5.0 releases about 1,995 times more energy.
Tectonic setting
126 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
70 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 lists 3 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M3.1 on February 26, 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 823 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 · 87 km SW of this epicenter
- 8.31906 Western Aleutian Islands (Hawadax/Rat Islands) EarthquakeAugust 17, 1906 · 112 km W of this epicenter
- 7.977 km WSW of Adak, AlaskaJune 10, 1996 · 179 km E of this epicenter
- 7.8Rat Islands, Aleutian Islands, AlaskaNovember 17, 2003 · 97 km SW of this epicenter
- 7.6Rat Islands, Aleutian Islands, AlaskaMarch 30, 1965 · 202 km SW of this epicenter
- 7.65 km WNW of Adak, AlaskaFebruary 14, 1905 · 243 km E of this epicenter
- 7.4265 km WSW of Adak, AlaskaFebruary 4, 1965 · 28 km SW of this epicenter
- 7.388 km WSW of Adak, AlaskaJuly 7, 1929 · 172 km E of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 10 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 · 87 km away · intensity VI
Under $1 million damagetsunami
- 1906M8.3
Aleutian Islands: Rat Islands
17 Aug 1906 · 112 km away
- 1905M7.9
Andreanof Islands
14 Feb 1905 · 156 km away
- 1996M7.9
Andreanof Islands
10 Jun 1996 · 179 km away · intensity VI
tsunami
- 2003M7.8
Aleutian Islands: Rat Islands
17 Nov 2003 · 97 km away
tsunami
- 1965M7.6
Aleutian Islands: Rat Islands
30 Mar 1965 · 197 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.