Reviewed by USGSAlaska52y ago
M4.6 earthquake 179 km SE of Attu Station, Alaska
Wednesday, February 19, 1975, 07:28:58 UTC · 51.724°N, 175.078°E
A magnitude 4.6 earthquake struck 179 km SE of Attu Station, Alaska on Wednesday, February 19, 1975, 07:28:58 UTC, at a depth of 55.0 km (shallow). It is the strongest earthquake within 300 km since an M5.4 on February 9, 1975.
- Magnitude
- 4.6
- Light · mb
- Depth
- 55 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
120 tons of TNT
That is about 1/126 of the Hiroshima bomb. A magnitude 5.0 releases about 4 times more energy.
Tectonic setting
53 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
55 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 1 M2.5+ earthquake within 50 km in the following 30 days; the largest was M4.2 on February 21, 1975. 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 218 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 · 257 km E of this epicenter
- 8.31906 Western Aleutian Islands (Hawadax/Rat Islands) EarthquakeAugust 17, 1906 · 214 km E of this epicenter
- 7.993 km NW of Attu Station, AlaskaDecember 17, 1929 · 272 km NW of this epicenter
- 7.6Rat Islands, Aleutian Islands, AlaskaMarch 30, 1965 · 253 km SE of this epicenter
- 7.636 km NE of Attu Station, AlaskaFebruary 2, 1975 · 188 km NW of this epicenter
- 7.4151 km S of Attu Station, AlaskaSeptember 2, 1907 · 158 km W of this epicenter
- 7.2238 km SSE of Attu Station, AlaskaSeptember 8, 1939 · 81 km S of this epicenter
- 7.0Rat Islands, Aleutian Islands, AlaskaFebruary 6, 1916 · 294 km E of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 9 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1975M7.6
Aleutian Islands: Near Islands
2 Feb 1975 · 188 km away · intensity IX
Moderate damage ($1–5M)
- 1965M8.7
Aleutian Islands: Rat Islands
4 Feb 1965 · 257 km away · intensity VI
Under $1 million damagetsunami
- 1906M8.3
Aleutian Islands: Rat Islands
17 Aug 1906 · 214 km away
- 1909M7.8
Aleutian Islands
10 Apr 1909 · 31 km away
- 1929M7.8
Aleutian Islands: Near Islands
17 Dec 1929 · 259 km away
- 1898M7.6
Aleutian Islands: Near Islands
29 Jun 1898 · 214 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.