Reviewed by USGSAlaska70y ago
M6.9 earthquake 80 km SW of Nikolski, Alaska
Saturday, March 9, 1957, 20:39:22 UTC · 52.351°N, 169.547°W
A magnitude 6.9 earthquake struck 80 km SW of Nikolski, Alaska on Saturday, March 9, 1957, 20:39:22 UTC, at a depth of 25.0 km (shallow). It is the strongest earthquake within 300 km since an M7.0 on August 22, 1940.
- Magnitude
- 6.9
- 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
388 kilotons of TNT
That is about 26 times the Hiroshima bomb. It released about 813 times the energy of a magnitude 5.0.
Tectonic setting
78 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
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 4 M2.5+ earthquakes within 100 km in the following 30 days; the largest was M7.1 on March 11, 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 74 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.8234 km SSW of Nikolski, AlaskaMarch 7, 1929 · 162 km S of this epicenter
- 7.4133 km WNW of Nikolski, AlaskaApril 18, 1916 · 143 km NW of this epicenter
- 7.0203 km SSE of Unalaska, AlaskaAugust 22, 1940 · 276 km E of this epicenter
- 6.9182 km SSE of Atka, AlaskaJanuary 27, 1906 · 282 km SW of this epicenter
- 6.977 km SSW of Nikolski, AlaskaJanuary 23, 1935 · 8 km E of this epicenter
- 6.8167 km W of Nikolski, AlaskaFebruary 21, 1957 · 137 km NW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 8 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1901M7.8
Aleutian Islands: Fox Islands
31 Dec 1901 · 142 km away
Limited damage (under $1M)tsunami
- 1917M7.9
Alaska Peninsula
31 May 1917 · 273 km away · intensity V
- 1902M7.8
Aleutian Islands: Fox Islands
1 Jan 1902 · 139 km away
- 1907M7.8
Aleutian Islands
2 Sep 1907 · 29 km away
- 1929M7.8
Aleutian Islands: Fox Islands
7 Mar 1929 · 153 km away · intensity V
tsunami
- 1916M7.5
Aleutian Islands: Fox Islands
18 Apr 1916 · 110 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.