Reviewed by USGSAlaska52y ago
M4.9 earthquake 27 km ENE of Attu Station, Alaska
Sunday, February 2, 1975, 15:53:06 UTC · 52.938°N, 173.562°E
A magnitude 4.9 earthquake struck 27 km ENE of Attu Station, Alaska on Sunday, February 2, 1975, 15:53:06 UTC, at a depth of 31.0 km (shallow). It is the strongest earthquake within 300 km since an M7.6 on February 2, 1975.
- Magnitude
- 4.9
- Light · mb
- Depth
- 31 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
338 tons of TNT
That is about 1/45 of the Hiroshima bomb. A magnitude 5.0 releases about 1 times more energy.
Tectonic setting
142 km
from the nearest mapped plate boundary, between the North American and Pacific plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.
Depth: shallow
31 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 M4.8 on February 4, 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 194 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.993 km NW of Attu Station, AlaskaDecember 17, 1929 · 106 km NW of this epicenter
- 7.636 km NE of Attu Station, AlaskaFebruary 2, 1975 · 20 km N of this epicenter
- 7.4151 km S of Attu Station, AlaskaSeptember 2, 1907 · 167 km S of this epicenter
- 7.2238 km SSE of Attu Station, AlaskaSeptember 8, 1939 · 236 km SE of this epicenter
- 7.024 km E of Attu Station, AlaskaApril 16, 1940 · 10 km S of this epicenter
- 7.080 km SSE of Attu Station, AlaskaApril 16, 1940 · 81 km S of this epicenter
- 7.0167 km WSW of Attu Station, AlaskaApril 10, 1909 · 194 km W of this epicenter
- 7.0171 km WNW of Attu Station, AlaskaJanuary 5, 1953 · 189 km NW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 4 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 · 20 km away · intensity IX
Moderate damage ($1–5M)
- 1909M7.8
Aleutian Islands
10 Apr 1909 · 143 km away
- 1929M7.8
Aleutian Islands: Near Islands
17 Dec 1929 · 147 km away
- 1898M7.6
Aleutian Islands: Near Islands
29 Jun 1898 · 149 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.