PreliminaryAlaska Earthquake70y ago
M8.6 earthquake 1957 Atka, Alaska Earthquake
Saturday, March 9, 1957, 14:22:33 UTC · 51.499°N, 175.626°W
A magnitude 8.6 earthquake struck 1957 Atka, Alaska Earthquake on Saturday, March 9, 1957, 14:22:33 UTC, at a depth of 25.0 km (shallow). No earthquake of this size or larger appears within 300 km in the USGS catalog since 1900.
- Magnitude
- 8.6
- Great · mw
- Depth
- 25 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- VII
- Very strong (ShakeMap)
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 400 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
120 megatons of TNT
That is about 7,955 times the Hiroshima bomb. It released about 251,189 times the energy of a magnitude 5.0.
Tectonic setting
82 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 400 km
USGS lists 32 M2.5+ earthquakes within 400 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.
- 6.3143 km E of Atka, Alaska70y ago · 247 km E of this epicenter
- 5.8150 km SSE of Atka, Alaska70y ago · 184 km E of this epicenter
- 5.8165 km SSE of Atka, Alaska70y ago · 185 km E of this epicenter
- 5.8161 km SSE of Atka, Alaska70y ago · 186 km E of this epicenter
- 5.8174 km SSE of Atka, Alaska70y ago · 194 km SE of this epicenter
- 5.8125 km WSW of Adak, Alaska70y ago · 192 km W of this epicenter
- 5.8220 km ESE of Atka, Alaska70y ago · 301 km E of this epicenter
- 6.899 km SW of Atka, Alaska70y ago · 34 km E of this epicenter
Regional history
Past M5+ earthquakes within 300 km
USGS lists 109 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.65 km WNW of Adak, AlaskaFebruary 14, 1905 · 86 km NW of this epicenter
- 7.388 km WSW of Adak, AlaskaJuly 7, 1929 · 147 km W of this epicenter
- 7.2238 km WSW of Adak, AlaskaMarch 22, 1905 · 297 km W of this epicenter
- 7.0101 km S of Adak, AlaskaSeptember 9, 1910 · 77 km SW of this epicenter
- 7.0114 km WSW of Adak, AlaskaJuly 5, 1929 · 175 km W of this epicenter
- 6.9182 km SSE of Atka, AlaskaJanuary 27, 1906 · 212 km E of this epicenter
- 6.9100 km ESE of Adak, AlaskaOctober 13, 1926 · 23 km E of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 3 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 · 0 km away
2 deathsSevere damage ($5–24M)tsunami
- 1905M7.9
Andreanof Islands
14 Feb 1905 · 221 km away
- 1946
East Aleutian Islands
1 Nov 1946 · 78 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.