Reviewed by USGSAlaska70y ago
M6.6 earthquake 152 km WSW of Adak, Alaska
Wednesday, March 13, 1957, 15:42:11 UTC · 51.425°N, 178.721°W
A magnitude 6.6 earthquake struck 152 km WSW of Adak, Alaska on Wednesday, March 13, 1957, 15:42:11 UTC, at a depth of 25.0 km (shallow). It is the strongest earthquake within 300 km since an M7.1 on March 12, 1957.
- Magnitude
- 6.6
- Strong · mw
- Depth
- 25 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: 100 km aftershock search area
In context
How big was it, and why here?
Energy released
104 kilotons of TNT
That is about 7 times the Hiroshima bomb. It released about 219 times the energy of a magnitude 5.0.
Tectonic setting
103 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
25 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 100 km
USGS lists 5 M2.5+ earthquakes within 100 km in the following 30 days; the largest was M7.2 on March 16, 1957. 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 124 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.61957 Atka, Alaska EarthquakeMarch 9, 1957 · 215 km E of this epicenter
- 8.31906 Western Aleutian Islands (Hawadax/Rat Islands) EarthquakeAugust 17, 1906 · 219 km W of this epicenter
- 7.65 km WNW of Adak, AlaskaFebruary 14, 1905 · 149 km E of this epicenter
- 7.388 km WSW of Adak, AlaskaJuly 7, 1929 · 68 km E of this epicenter
- 7.2238 km WSW of Adak, AlaskaMarch 22, 1905 · 85 km W of this epicenter
- 7.160 km SW of Adak, AlaskaMarch 12, 1957 · 103 km E of this epicenter
- 7.0Rat Islands, Aleutian Islands, AlaskaFebruary 6, 1916 · 172 km SW of this epicenter
- 7.0101 km S of Adak, AlaskaSeptember 9, 1910 · 172 km E of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 5 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 2 recorded deaths. The most severe:
- 1957M8.6
Alaska
9 Mar 1957 · 215 km away
2 deathsSevere damage ($5–24M)tsunami
- 1906M8.3
Aleutian Islands: Rat Islands
17 Aug 1906 · 219 km away
- 1905M7.9
Andreanof Islands
14 Feb 1905 · 78 km away
- 1940M7.4
Aleutian Islands: Rat Islands
14 Jul 1940 · 222 km away
- 1946
East Aleutian Islands
1 Nov 1946 · 292 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.