Reviewed by USGSAlaska110y ago
M6.4 earthquake 101 km SSW of Sand Point, Alaska
Wednesday, July 25, 1917, 03:19:15 UTC · 54.488°N, 161.079°W
A magnitude 6.4 earthquake struck 101 km SSW of Sand Point, Alaska on Wednesday, July 25, 1917, 03:19:15 UTC, at a depth of 35.0 km (shallow). It is the strongest earthquake within 300 km since an M7.4 on May 31, 1917.
- Magnitude
- 6.4
- 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
60 kilotons of TNT
That is about 4 times the Hiroshima bomb. It released about 126 times the energy of a magnitude 5.0.
Tectonic setting
96 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
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 M6.0 on July 25, 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 7 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.454 km SE of Sand Point, AlaskaMay 31, 1917 · 95 km NE of this epicenter
- 6.6291 km S of Sand Point, AlaskaMay 13, 1910 · 211 km SE of this epicenter
- 6.5Bristol Bay, AlaskaAugust 22, 1907 · 279 km N of this epicenter
- 6.3298 km SSE of Sand Point, AlaskaJune 4, 1917 · 241 km SE of this epicenter
- 6.054 km E of Sand Point, AlaskaOctober 3, 1916 · 129 km NE of this epicenter
- 5.9113 km SE of Sand Point, AlaskaJune 7, 1917 · 119 km E of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 3 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1788M8.0
Alaska Peninsula
6 Aug 1788 · 57 km away
tsunami
- 1820
East Aleutian Islands
1 Mar 1820 · 231 km away
tsunami
- 1868
Alaska Peninsula
15 May 1868 · 57 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.