Reviewed by USGSAlaska110y ago
M6.4 earthquake 103 km SSE of Akhiok, Alaska
Friday, December 28, 1917, 21:14:35 UTC · 56.165°N, 153.245°W
A magnitude 6.4 earthquake struck 103 km SSE of Akhiok, Alaska on Friday, December 28, 1917, 21:14:35 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
- 6.4
- 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
62 kilotons of TNT
That is about 4 times the Hiroshima bomb. It released about 130 times the energy of a magnitude 5.0.
Tectonic setting
50 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 54 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 · 194 km NE of this epicenter
- 7.14 km ENE of Karluk, AlaskaNovember 7, 1912 · 173 km NW of this epicenter
- 6.8Event 48 Novarupta-Mount Katmai area, Alaska PeninsulaJune 10, 1912 · 262 km NW of this epicenter
- 6.688 km SSE of Old Harbor, AlaskaDecember 21, 1917 · 40 km NE 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 · 104 km away · intensity VIII
Limited damage (under $1M)
- 1788M8.0
Unga Island
21 Jul 1788 · 94 km away · intensity VII
Limited damage (under $1M)tsunami
- 1792
Kodiak Island
1792 · 120 km away · intensity VII
Limited damage (under $1M)tsunami
- 1906M7.6
Aleutian Islands
23 Dec 1906 · 86 km away
- 1912M7.5
Alaska Peninsula
7 Nov 1912 · 183 km away · intensity V
- 1854
Gulf Of Alaska
27 Jan 1854 · 120 km away · intensity V
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.