M6.4 earthquake 133 km SW of Adak, Alaska

Tuesday, March 12, 1957, 07:39:20 UTC · 51.191°N, 178.214°W

A magnitude 6.4 earthquake struck 133 km SW of Adak, Alaska on Tuesday, March 12, 1957, 07:39:20 UTC, at a depth of 10.0 km (shallow). It is the strongest earthquake within 300 km since an M6.5 on March 11, 1957.

Magnitude: 6.4; Strong · mw
Depth: 10 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

69 kilotons of TNT

That is about 5 times the Hiroshima bomb. It released about 145 times the energy of a magnitude 5.0.

Tectonic setting

78 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

10 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 7 M2.5+ earthquakes within 100 km in the following 30 days; the largest was M7.2 on March 16, 1957. 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 123 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 5 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 · 183 km away
2 deathsSevere damage ($5–24M)tsunami
1906M8.3
Aleutian Islands: Rat Islands
17 Aug 1906 · 260 km away
1905M7.9
Andreanof Islands
14 Feb 1905 · 56 km away
1940M7.4
Aleutian Islands: Rat Islands
14 Jul 1940 · 263 km away
1946
East Aleutian Islands
1 Nov 1946 · 260 km away
tsunami

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

Nearby trackers