Reviewed by USGSAlaska94y ago
M6.8 earthquake 46 km SSW of Nikolski, Alaska
Saturday, July 22, 1933, 20:55:19 UTC · 52.590°N, 169.234°W
A magnitude 6.8 earthquake struck 46 km SSW of Nikolski, Alaska on Saturday, July 22, 1933, 20:55:19 UTC, at a depth of 30.0 km (shallow). It is the strongest earthquake within 300 km since an M7.8 on March 7, 1929.
- Magnitude
- 6.8
- Strong · mw
- Depth
- 30 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
215 kilotons of TNT
That is about 14 times the Hiroshima bomb. It released about 452 times the energy of a magnitude 5.0.
Tectonic setting
93 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
30 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 30 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 · 191 km S of this epicenter
- 7.4133 km WNW of Nikolski, AlaskaApril 18, 1916 · 135 km NW of this epicenter
- 6.7103 km SE of Nikolski, AlaskaFebruary 20, 1916 · 111 km E of this epicenter
- 6.6135 km SW of Nikolski, AlaskaDecember 23, 1906 · 89 km SW of this epicenter
- 6.596 km SSE of Nikolski, AlaskaSeptember 8, 1909 · 79 km SE of this epicenter
- 6.5173 km ENE of Atka, AlaskaDecember 6, 1930 · 191 km W 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 · 176 km away
Limited damage (under $1M)tsunami
- 1917M7.9
Alaska Peninsula
31 May 1917 · 245 km away · intensity V
- 1902M7.8
Aleutian Islands: Fox Islands
1 Jan 1902 · 119 km away
- 1907M7.8
Aleutian Islands
2 Sep 1907 · 34 km away
- 1929M7.8
Aleutian Islands: Fox Islands
7 Mar 1929 · 184 km away · intensity V
tsunami
- 1916M7.5
Aleutian Islands: Fox Islands
18 Apr 1916 · 94 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.