M2.6 earthquake 249 km W of Adak, Alaska

Friday, April 23, 2004, 04:09:32 UTC · 51.597°N, 179.777°E

A magnitude 2.6 earthquake struck 249 km W of Adak, Alaska on Friday, April 23, 2004, 04:09:32 UTC, at a depth of 94.4 km (intermediate).

Magnitude: 2.6; Minor · ml
Depth: 94 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

120 kg of TNT

That is about 1/125,702 of the Hiroshima bomb. A magnitude 5.0 releases about 3,981 times more energy.

Tectonic setting

120 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

94 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 8 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M4.4 on May 17, 2004. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 824 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

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 · 83 km away · intensity VI
Under $1 million damagetsunami
1906M8.3
Aleutian Islands: Rat Islands
17 Aug 1906 · 114 km away
1905M7.9
Andreanof Islands
14 Feb 1905 · 151 km away
1996M7.9
Andreanof Islands
10 Jun 1996 · 179 km away · intensity VI
tsunami
2003M7.8
Aleutian Islands: Rat Islands
17 Nov 2003 · 93 km away
tsunami
1965M7.6
Aleutian Islands: Rat Islands
30 Mar 1965 · 192 km away
tsunami

NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.

Nearby trackers