Reviewed by USGSAlaska70y ago
M6.5 earthquake 173 km WSW of Adak, Alaska
Monday, March 11, 1957, 15:36:01 UTC · 51.297°N, 178.952°W
A magnitude 6.5 earthquake struck 173 km WSW of Adak, Alaska on Monday, March 11, 1957, 15:36:01 UTC, at a depth of 35.0 km (shallow). It is the strongest earthquake within 300 km since an M7.0 on March 11, 1957.
- Magnitude
- 6.5
- Strong · mw
- Depth
- 35 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
79 kilotons of TNT
That is about 5 times the Hiroshima bomb. It released about 166 times the energy of a magnitude 5.0.
Tectonic setting
88 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
35 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 6 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.
- 5.9Andreanof Islands, Aleutian Islands, Alaska70y ago · 37 km SE of this epicenter
- 5.8125 km WSW of Adak, Alaska70y ago · 50 km NE of this epicenter
- 6.0Andreanof Islands, Aleutian Islands, Alaska70y ago · 33 km W of this epicenter
- 7.2162 km WSW of Adak, Alaska70y ago · 15 km NE of this epicenter
- 6.6152 km WSW of Adak, Alaska70y ago · 21 km NE of this epicenter
- 6.4133 km SW of Adak, Alaska70y ago · 53 km E of this epicenter
Regional history
Past M5+ earthquakes within 300 km
USGS lists 120 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 · 232 km E of this epicenter
- 8.31906 Western Aleutian Islands (Hawadax/Rat Islands) EarthquakeAugust 17, 1906 · 208 km W of this epicenter
- 7.65 km WNW of Adak, AlaskaFebruary 14, 1905 · 169 km NE of this epicenter
- 7.388 km WSW of Adak, AlaskaJuly 7, 1929 · 86 km E of this epicenter
- 7.2238 km WSW of Adak, AlaskaMarch 22, 1905 · 65 km W of this epicenter
- 7.0Rat Islands, Aleutian Islands, AlaskaFebruary 6, 1916 · 152 km W of this epicenter
- 7.0101 km S of Adak, AlaskaSeptember 9, 1910 · 185 km E of this epicenter
- 7.0114 km WSW of Adak, AlaskaJuly 5, 1929 · 58 km E 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, which together caused about 2 recorded deaths. The most severe:
- 1957M8.6
Alaska
9 Mar 1957 · 232 km away
2 deathsSevere damage ($5–24M)tsunami
- 1906M8.3
Aleutian Islands: Rat Islands
17 Aug 1906 · 208 km away
- 1905M7.9
Andreanof Islands
14 Feb 1905 · 69 km away
- 1940M7.4
Aleutian Islands: Rat Islands
14 Jul 1940 · 211 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.