Reviewed by USGSAlaska63y ago
M6.9 earthquake 171 km SW of Akhiok, Alaska
Thursday, February 6, 1964, 13:07:27 UTC · 55.722°N, 155.847°W
A magnitude 6.9 earthquake struck 171 km SW of Akhiok, Alaska on Thursday, February 6, 1964, 13:07:27 UTC, at a depth of 25.7 km (shallow). It is the strongest earthquake within 300 km since an M6.9 on February 13, 1951.
- Magnitude
- 6.9
- Strong · mw
- Depth
- 26 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
338 kilotons of TNT
That is about 22 times the Hiroshima bomb. It released about 708 times the energy of a magnitude 5.0.
Tectonic setting
106 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
26 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 M5.9 on February 6, 1964. 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 108 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 · 159 km W of this epicenter
- 7.454 km SE of Sand Point, AlaskaMay 31, 1917 · 268 km W of this epicenter
- 7.14 km ENE of Karluk, AlaskaNovember 7, 1912 · 226 km NE of this epicenter
- 7.0113 km ESE of Chignik, AlaskaMay 4, 1923 · 59 km W of this epicenter
- 6.9105 km ESE of Perryville, AlaskaNovember 17, 1938 · 123 km W of this epicenter
- 6.9143 km ESE of Chignik, AlaskaFebruary 13, 1951 · 29 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:
- 1900M8.3
Kodiak Island
9 Oct 1900 · 211 km away · intensity VIII
Limited damage (under $1M)
- 1788M8.0
Unga Island
21 Jul 1788 · 226 km away · intensity VII
Limited damage (under $1M)tsunami
- 1792
Kodiak Island
1792 · 276 km away · intensity VII
Limited damage (under $1M)tsunami
- 1938M8.2
Alaska
10 Nov 1938 · 161 km away · intensity VI
tsunami
- 1906M7.6
Aleutian Islands
23 Dec 1906 · 174 km away
- 1912M7.5
Alaska Peninsula
7 Nov 1912 · 204 km away · intensity V
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.