M6.6 earthquake 146 km ESE of Akutan, Alaska

Monday, April 1, 1946, 18:57:40 UTC · 53.540°N, 163.784°W

A magnitude 6.6 earthquake struck 146 km ESE of Akutan, Alaska on Monday, April 1, 1946, 18:57:40 UTC, at a depth of 25.0 km (shallow). It is the strongest earthquake within 300 km since an M8.6 on April 1, 1946.

Magnitude: 6.6; Strong · mw
Depth: 25 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: 100 km aftershock search area

In context

How big was it, and why here?

Energy released

112 kilotons of TNT

That is about 7 times the Hiroshima bomb. It released about 234 times the energy of a magnitude 5.0.

Tectonic setting

52 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

25 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 100 km

USGS lists 5 M2.5+ earthquakes within 100 km in the following 30 days; the largest was M6.2 on April 2, 1946. 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 38 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 6 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 168 recorded deaths. The most severe:

1946M8.6
Unimak Island
1 Apr 1946 · 63 km away · intensity VI
168 deaths$26 million damagetsunami
1788M8.0
Alaska Peninsula
6 Aug 1788 · 243 km away
tsunami
1902M7.8
Aleutian Islands: Fox Islands
1 Jan 1902 · 279 km away
1820
East Aleutian Islands
1 Mar 1820 · 123 km away
tsunami
1868
Alaska Peninsula
15 May 1868 · 243 km away
tsunami
1878
East Aleutian Islands
29 Aug 1878 · 173 km away
tsunami

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

Nearby trackers