Reviewed by USGSAlaska7d ago
M4.0 earthquake 85 km SSW of Nikolski, Alaska
Saturday, September 19, 2026, 12:44:03 UTC · 52.251°N, 169.427°W
A magnitude 4.0 earthquake struck 85 km SSW of Nikolski, Alaska on Saturday, September 19, 2026, 12:44:03 UTC, at a depth of 40.5 km (shallow).
- Magnitude
- 4.0
- Light · mb
- Depth
- 41 km
- Shallow
- 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
15 tons of TNT
That is about 1/998 of the Hiroshima bomb. A magnitude 5.0 releases about 32 times more energy.
Tectonic setting
64 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
41 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 50 km
USGS lists 4 M2.5+ earthquakes within 50 km since this event; the largest was M3.2 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 764 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 · 152 km S of this epicenter
- 7.881 km E of Nikolski, AlaskaJuly 2, 1965 · 146 km NE of this epicenter
- 7.4133 km WNW of Nikolski, AlaskaApril 18, 1916 · 156 km NW of this epicenter
- 7.3Fox Islands, Aleutian Islands, AlaskaJune 24, 2011 · 166 km W of this epicenter
- 7.139 km S of Akutan, AlaskaMarch 22, 1957 · 298 km NE of this epicenter
- 7.135 km SW of Nikolski, AlaskaMarch 11, 1957 · 51 km N of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 13 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 · 141 km away
Limited damage (under $1M)tsunami
- 1965M6.5
Aleutian Islands: Fox Islands
2 Jul 1965 · 153 km away
Limited damage (under $1M)tsunami
- 1917M7.9
Alaska Peninsula
31 May 1917 · 283 km away · intensity V
- 1902M7.8
Aleutian Islands: Fox Islands
1 Jan 1902 · 132 km away
- 1907M7.8
Aleutian Islands
2 Sep 1907 · 43 km away
- 1929M7.8
Aleutian Islands: Fox Islands
7 Mar 1929 · 145 km away · intensity V
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.