Reviewed by USGSAlaska52y ago
M7.6 earthquake 36 km NE of Attu Station, Alaska
Sunday, February 2, 1975, 08:43:39 UTC · 53.113°N, 173.497°E
A magnitude 7.6 earthquake struck 36 km NE of Attu Station, Alaska on Sunday, February 2, 1975, 08:43:39 UTC, at a depth of 10.0 km (shallow). It is the strongest earthquake within 300 km since an M7.9 on December 17, 1929.
- Magnitude
- 7.6
- Major · ms
- Depth
- 10 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- VI
- Strong (ShakeMap)
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 200 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
3.8 megatons of TNT
That is about 252 times the Hiroshima bomb. It released about 7,943 times the energy of a magnitude 5.0.
Tectonic setting
157 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
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 200 km
USGS lists 5 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M5.4 on February 9, 1975. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
- 4.6179 km SE of Attu Station, Alaska52y ago · 188 km SE of this epicenter
- 5.487 km E of Attu Station, Alaska52y ago · 74 km SE of this epicenter
- 4.487 km SE of Attu Station, Alaska52y ago · 94 km SE of this epicenter
- 4.832 km NNE of Attu Station, Alaska52y ago · 7 km W of this epicenter
- 4.927 km ENE of Attu Station, Alaska52y ago · 20 km S of this epicenter
Regional history
Past M5+ earthquakes within 300 km
USGS lists 192 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 · 93 km NW of this epicenter
- 7.4151 km S of Attu Station, AlaskaSeptember 2, 1907 · 185 km S of this epicenter
- 7.2238 km SSE of Attu Station, AlaskaSeptember 8, 1939 · 255 km SE of this epicenter
- 7.024 km E of Attu Station, AlaskaApril 16, 1940 · 30 km S of this epicenter
- 7.080 km SSE of Attu Station, AlaskaApril 16, 1940 · 101 km S of this epicenter
- 7.0167 km WSW of Attu Station, AlaskaApril 10, 1909 · 199 km SW of this epicenter
- 7.0171 km WNW of Attu Station, AlaskaJanuary 5, 1953 · 177 km W of this epicenter
- 6.8129 km SSE of Attu Station, AlaskaNovember 13, 1911 · 154 km S 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 · 0 km away · intensity IX
Moderate damage ($1–5M)
- 1909M7.8
Aleutian Islands
10 Apr 1909 · 160 km away
- 1929M7.8
Aleutian Islands: Near Islands
17 Dec 1929 · 151 km away
- 1898M7.6
Aleutian Islands: Near Islands
29 Jun 1898 · 160 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.