Reviewed by USGSAlaska6d ago
M4.6 earthquake 102 km WSW of Nikolski, Alaska
Sunday, September 20, 2026, 13:55:47 UTC · 52.750°N, 170.347°W
A magnitude 4.6 earthquake struck 102 km WSW of Nikolski, Alaska on Sunday, September 20, 2026, 13:55:47 UTC, at a depth of 87.3 km (intermediate). It is the strongest earthquake within 300 km since an M6.5 on September 17, 2026.
- Magnitude
- 4.6
- Light · mb
- Depth
- 87 km
- Intermediate
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- II
- Weak (ShakeMap)
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 50 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
120 tons of TNT
That is about 1/126 of the Hiroshima bomb. A magnitude 5.0 releases about 4 times more energy.
Tectonic setting
139 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: intermediate
87 km
Intermediate-depth earthquakes usually break inside a plate that is sinking into the mantle. Shaking spreads over a wide area but is gentler at the epicenter than a shallow quake of the same size.
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 50 km
USGS lists 1 M2.5+ earthquake within 50 km since this event; the largest was M3.1 on September 20, 2026. 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 805 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.8234 km SSW of Nikolski, AlaskaMarch 7, 1929 · 209 km S of this epicenter
- 7.881 km E of Nikolski, AlaskaJuly 2, 1965 · 183 km E of this epicenter
- 7.4133 km WNW of Nikolski, AlaskaApril 18, 1916 · 80 km N of this epicenter
- 7.3Fox Islands, Aleutian Islands, AlaskaJune 24, 2011 · 128 km SW of this epicenter
- 7.135 km SW of Nikolski, AlaskaMarch 11, 1957 · 78 km E of this epicenter
- 6.980 km SW of Nikolski, AlaskaMarch 9, 1957 · 70 km SE of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 14 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1901M7.8
Aleutian Islands: Fox Islands
31 Dec 1901 · 152 km away
Limited damage (under $1M)tsunami
- 1965M6.5
Aleutian Islands: Fox Islands
2 Jul 1965 · 190 km away
Limited damage (under $1M)tsunami
- 1917M7.9
Alaska Peninsula
31 May 1917 · 241 km away · intensity V
- 1902M7.8
Aleutian Islands: Fox Islands
1 Jan 1902 · 196 km away
- 1907M7.8
Aleutian Islands
2 Sep 1907 · 45 km away
- 1929M7.8
Aleutian Islands: Fox Islands
7 Mar 1929 · 196 km away · intensity V
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.