Reviewed by USGSAlaska110y ago
M6.2 earthquake 173 km SSE of Akhiok, Alaska
Friday, December 21, 1917, 20:52:15 UTC · 55.631°N, 152.659°W
A magnitude 6.2 earthquake struck 173 km SSE of Akhiok, Alaska on Friday, December 21, 1917, 20:52:15 UTC, at a depth of 15.0 km (shallow). It is the strongest earthquake within 300 km since an M6.6 on December 21, 1917.
- Magnitude
- 6.2
- 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 earthquakeDashed circle: 100 km aftershock search area
In context
How big was it, and why here?
Energy released
26 kilotons of TNT
That is about 2 times the Hiroshima bomb. It released about 55 times the energy of a magnitude 5.0.
Tectonic setting
19 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 lists 1 M2.5+ earthquake within 100 km in the following 30 days; the largest was M6.4 on December 28, 1917. 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 5 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.9Kodiak Island region, AlaskaOctober 9, 1900 · 221 km NE of this epicenter
- 7.14 km ENE of Karluk, AlaskaNovember 7, 1912 · 242 km NW of this epicenter
- 6.688 km SSE of Old Harbor, AlaskaDecember 21, 1917 · 92 km N of this epicenter
- 6.1132 km E of Chignik, AlaskaSeptember 13, 1911 · 234 km W of this epicenter
- 6.113 km S of Akhiok, AlaskaDecember 5, 1912 · 162 km NW 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:
- 1900M8.3
Kodiak Island
9 Oct 1900 · 170 km away · intensity VIII
Limited damage (under $1M)
- 1788M8.0
Unga Island
21 Jul 1788 · 154 km away · intensity VII
Limited damage (under $1M)tsunami
- 1792
Kodiak Island
1792 · 158 km away · intensity VII
Limited damage (under $1M)tsunami
- 1906M7.6
Aleutian Islands
23 Dec 1906 · 156 km away
- 1912M7.5
Alaska Peninsula
7 Nov 1912 · 252 km away · intensity V
- 1854
Gulf Of Alaska
27 Jan 1854 · 158 km away · intensity V
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.