Reviewed by USGSAlaska70y ago
M6.8 earthquake 99 km SW of Atka, Alaska
Tuesday, March 19, 1957, 12:50:59 UTC · 51.518°N, 175.135°W
A magnitude 6.8 earthquake struck 99 km SW of Atka, Alaska on Tuesday, March 19, 1957, 12:50:59 UTC, at a depth of 15.0 km (shallow). It is the strongest earthquake within 300 km since an M7.2 on March 16, 1957.
- Magnitude
- 6.8
- Strong · mw
- Depth
- 15 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 earthquake
In context
How big was it, and why here?
Energy released
223 kilotons of TNT
That is about 15 times the Hiroshima bomb. It released about 468 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
15 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 has not published any M2.5+ earthquake within 100 km in the 30 days after this event.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 123 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 · 34 km W of this epicenter
- 7.65 km WNW of Adak, AlaskaFebruary 14, 1905 · 116 km W of this epicenter
- 7.388 km WSW of Adak, AlaskaJuly 7, 1929 · 181 km W of this epicenter
- 7.2162 km WSW of Adak, AlaskaMarch 16, 1957 · 259 km W of this epicenter
- 7.175 km S of Adak, AlaskaMarch 14, 1957 · 117 km W of this epicenter
- 7.160 km SW of Adak, AlaskaMarch 12, 1957 · 146 km W of this epicenter
- 7.0101 km S of Adak, AlaskaSeptember 9, 1910 · 104 km SW 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 · 34 km away
2 deathsSevere damage ($5–24M)tsunami
- 1901M7.8
Aleutian Islands: Fox Islands
31 Dec 1901 · 285 km away
Limited damage (under $1M)tsunami
- 1905M7.9
Andreanof Islands
14 Feb 1905 · 254 km away
- 1946
East Aleutian Islands
1 Nov 1946 · 44 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.