Reviewed by USGSAlaska70y ago
M7.1 earthquake 39 km S of Akutan, Alaska
Friday, March 22, 1957, 14:21:15 UTC · 53.778°N, 165.771°W
A magnitude 7.1 earthquake struck 39 km S of Akutan, Alaska on Friday, March 22, 1957, 14:21:15 UTC, at a depth of 46.6 km (shallow). It is the strongest earthquake within 300 km since an M8.6 on April 1, 1946.
- Magnitude
- 7.1
- Major · mw
- Depth
- 47 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
607 kilotons of TNT
That is about 40 times the Hiroshima bomb. It released about 1,274 times the energy of a magnitude 5.0.
Tectonic setting
126 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
47 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 2 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M6.8 on March 29, 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 81 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.6The 1946 Unimak Island, Alaska EarthquakeApril 1, 1946 · 196 km E of this epicenter
- 7.135 km SW of Nikolski, AlaskaMarch 11, 1957 · 258 km SW of this epicenter
- 7.0203 km SSE of Unalaska, AlaskaAugust 22, 1940 · 181 km S of this epicenter
- 6.980 km SW of Nikolski, AlaskaMarch 9, 1957 · 298 km SW of this epicenter
- 6.977 km SSW of Nikolski, AlaskaJanuary 23, 1935 · 292 km SW of this epicenter
- 6.881 km ENE of Nikolski, AlaskaJanuary 13, 1955 · 146 km SW of this epicenter
- 6.846 km SSW of Nikolski, AlaskaJuly 22, 1933 · 266 km SW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 9 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 168 recorded deaths. The most severe:
- 1946M8.6
Unimak Island
1 Apr 1946 · 196 km away · intensity VI
168 deaths$26 million damagetsunami
- 1917M7.9
Alaska Peninsula
31 May 1917 · 245 km away · intensity V
- 1902M7.8
Aleutian Islands: Fox Islands
1 Jan 1902 · 192 km away
- 1907M7.8
Aleutian Islands
2 Sep 1907 · 295 km away
- 1916M7.5
Aleutian Islands: Fox Islands
18 Apr 1916 · 284 km away
- 1957M7.5
Aleutian Islands: Fox Islands
22 Mar 1957 · 141 km away · intensity V
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.