Reviewed by USGSAlaska62y ago
M5.5 earthquake 175 km ESE of Attu Station, Alaska
Saturday, March 6, 1965, 13:41:19 UTC · 52.013°N, 175.383°E
A magnitude 5.5 earthquake struck 175 km ESE of Attu Station, Alaska on Saturday, March 6, 1965, 13:41:19 UTC, at a depth of 36.3 km (shallow). It is the strongest earthquake within 300 km since an M5.6 on March 5, 1965.
- Magnitude
- 5.5
- Moderate · mw
- Depth
- 36 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
3 kilotons of TNT
That is about 1/5 of the Hiroshima bomb. It released about 6 times the energy of a magnitude 5.0.
Tectonic setting
90 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
36 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.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 130 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.71965 Western Aleutian Islands (Hawadax/Rat Islands) EarthquakeFebruary 4, 1965 · 245 km E of this epicenter
- 8.31906 Western Aleutian Islands (Hawadax/Rat Islands) EarthquakeAugust 17, 1906 · 193 km E of this epicenter
- 7.993 km NW of Attu Station, AlaskaDecember 17, 1929 · 266 km NW of this epicenter
- 7.4265 km WSW of Adak, AlaskaFebruary 4, 1965 · 297 km E of this epicenter
- 7.4151 km S of Attu Station, AlaskaSeptember 2, 1907 · 186 km W of this epicenter
- 7.2238 km SSE of Attu Station, AlaskaSeptember 8, 1939 · 117 km S of this epicenter
- 7.0Rat Islands, Aleutian Islands, AlaskaFebruary 6, 1916 · 288 km SE of this epicenter
- 7.024 km E of Attu Station, AlaskaApril 16, 1940 · 155 km NW 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:
- 1965M8.7
Aleutian Islands: Rat Islands
4 Feb 1965 · 245 km away · intensity VI
Under $1 million damagetsunami
- 1906M8.3
Aleutian Islands: Rat Islands
17 Aug 1906 · 193 km away
- 1909M7.8
Aleutian Islands
10 Apr 1909 · 26 km away
- 1929M7.8
Aleutian Islands: Near Islands
17 Dec 1929 · 270 km away
- 1898M7.6
Aleutian Islands: Near Islands
29 Jun 1898 · 232 km away
- 1965M7.6
Aleutian Islands: Rat Islands
30 Mar 1965 · 259 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.