QuakeScout
Magnitude5.6

Reviewed by USGSAlaska62y ago

M5.6 earthquake 171 km ESE of Attu Station, Alaska

Monday, March 29, 1965, 14:32:43 UTC · 52.042°N, 175.340°E

A magnitude 5.6 earthquake struck 171 km ESE of Attu Station, Alaska on Monday, March 29, 1965, 14:32:43 UTC, at a depth of 38.7 km (shallow). It is the strongest earthquake within 300 km since an M6.3 on March 3, 1965.

Magnitude
5.6
Moderate · mw
Depth
39 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: 75 km aftershock search area

In context

How big was it, and why here?

Energy released

4 kilotons of TNT

That is about 1/4 of the Hiroshima bomb. It released about 9 times the energy of a magnitude 5.0.

Tectonic setting

92 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

39 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 75 km

USGS lists 2 M2.5+ earthquakes within 75 km in the following 30 days; the largest was M5.8 on April 4, 1965. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

M3M4M5M61h6h1d3d7d14d30dMainshock M5.6
Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.
  1. 5.5237 km ESE of Attu Station, Alaska62y ago · 66 km SE of this epicenter
  2. 5.8176 km SE of Attu Station, Alaska62y ago · 21 km S of this epicenter

Regional history

Past M5+ earthquakes within 300 km

USGS lists 131 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 8.71965 Western Aleutian Islands (Hawadax/Rat Islands) EarthquakeFebruary 4, 1965 · 249 km E of this epicenter
  2. 8.31906 Western Aleutian Islands (Hawadax/Rat Islands) EarthquakeAugust 17, 1906 · 196 km E of this epicenter
  3. 7.993 km NW of Attu Station, AlaskaDecember 17, 1929 · 262 km NW of this epicenter
  4. 7.4151 km S of Attu Station, AlaskaSeptember 2, 1907 · 184 km W of this epicenter
  5. 7.2238 km SSE of Attu Station, AlaskaSeptember 8, 1939 · 119 km S of this epicenter
  6. 7.0Rat Islands, Aleutian Islands, AlaskaFebruary 6, 1916 · 292 km SE of this epicenter
  7. 7.024 km E of Attu Station, AlaskaApril 16, 1940 · 151 km NW of this epicenter
  8. 7.080 km SSE of Attu Station, AlaskaApril 16, 1940 · 109 km W of this epicenter

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 7 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:

  1. 1965M8.7

    Aleutian Islands: Rat Islands

    4 Feb 1965 · 249 km away · intensity VI

    Under $1 million damagetsunami

  2. 1906M8.3

    Aleutian Islands: Rat Islands

    17 Aug 1906 · 196 km away

  3. 1909M7.8

    Aleutian Islands

    10 Apr 1909 · 24 km away

  4. 1929M7.8

    Aleutian Islands: Near Islands

    17 Dec 1929 · 266 km away

  5. 1898M7.6

    Aleutian Islands: Near Islands

    29 Jun 1898 · 229 km away

  6. 1965M7.6

    Aleutian Islands: Rat Islands

    30 Mar 1965 · 263 km away

    tsunami

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

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