Reviewed by USGSAlaska89y ago
M6.6 earthquake 104 km SSE of Perryville, Alaska
Friday, November 11, 1938, 00:57:48 UTC · 55.018°N, 158.640°W
A magnitude 6.6 earthquake struck 104 km SSE of Perryville, Alaska on Friday, November 11, 1938, 00:57:48 UTC, at a depth of 35.0 km (shallow). It is the strongest earthquake within 300 km since an M8.2 on November 10, 1938.
- Magnitude
- 6.6
- Strong · mw
- Depth
- 35 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
104 kilotons of TNT
That is about 7 times the Hiroshima bomb. It released about 219 times the energy of a magnitude 5.0.
Tectonic setting
109 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
35 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 1 M2.5+ earthquake within 100 km in the following 30 days; the largest was M6.9 on November 17, 1938. 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 30 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.21938 Semidi Islands, Alaska EarthquakeNovember 10, 1938 · 34 km NE of this epicenter
- 7.454 km SE of Sand Point, AlaskaMay 31, 1917 · 79 km W of this epicenter
- 7.0113 km ESE of Chignik, AlaskaMay 4, 1923 · 149 km NE of this epicenter
- 6.873 km SW of Sand Point, AlaskaJuly 2, 1922 · 166 km W of this epicenter
- 6.768 km SSE of King Cove, AlaskaApril 29, 1937 · 210 km W of this epicenter
- 6.6128 km SE of Chignik, AlaskaJuly 28, 1934 · 139 km NE of this epicenter
- 6.6291 km S of Sand Point, AlaskaMay 13, 1910 · 261 km S of this epicenter
- 6.672 km SE of Sand Point, AlaskaOctober 16, 1932 · 62 km W 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. The most severe:
- 1938M8.2
Alaska
10 Nov 1938 · 54 km away · intensity VI
tsunami
- 1788M8.0
Alaska Peninsula
6 Aug 1788 · 150 km away
tsunami
- 1868
Alaska Peninsula
15 May 1868 · 150 km away
tsunami
- 1880
Alaska Peninsula
29 Sep 1880 · 211 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.