M2.8 earthquake 65 km SW of Adak, Alaska

Thursday, December 23, 2004, 01:43:09 UTC · 51.421°N, 177.240°W

A magnitude 2.8 earthquake struck 65 km SW of Adak, Alaska on Thursday, December 23, 2004, 01:43:09 UTC, at a depth of 23.9 km (shallow).

Magnitude: 2.8; 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

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

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

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 10 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M2.8 on January 15, 2005. 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 960 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 11 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 · 112 km away
2 deathsSevere damage ($5–24M)tsunami
1986M8.0
Aleutian Islands: Adak
7 May 1986 · 171 km away · intensity VI
Moderate damage ($1–5M)tsunami
1965M8.7
Aleutian Islands: Rat Islands
4 Feb 1965 · 282 km away · intensity VI
Under $1 million damagetsunami
1905M7.9
Andreanof Islands
14 Feb 1905 · 119 km away
1996M7.9
Andreanof Islands
10 Jun 1996 · 31 km away · intensity VI
tsunami
2003M7.8
Aleutian Islands: Rat Islands
17 Nov 2003 · 287 km away
tsunami

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

Nearby trackers