Earthquake · reviewed by a seismologist
M 4.0ml
Rat Islands, Aleutian Islands, Alaska
Yes. A magnitude 4.0 earthquake was recorded in the Rat Islands, Aleutian Islands, Alaska at 09:52 UTC on 2026-10-17, 87 km deep. No felt reports to USGS yet.
- When
- Magnitude
- M 4.0 (ml)
- Depth
- 87 km below the surface
- Felt
- no reports yet
- Measured shaking
- intensity II (ShakeMap)
- Nearest
- Aleutians West Census Area, 80 km ENE
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 6 hours ago
This was a light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon.
At this magnitude and depth, people at rest would likely notice it out to about 42 km (26 mi) from the epicentre. Estimated from magnitude, depth and distance with the intensity equation USGS Did You Feel It? uses; felt reports, where there are any, are the measurement.
How big was it?
This earthquake released about 15 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.0 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 11,000× the energy of this one
- Mineral, Virginia 2011 M 5.8 500× the energy of this one
- Magna, Utah 2020 M 5.7 350× the energy of this one
- This earthquake M 4.0 about 15 tons of TNT
- Around the size people start to feel M 3.0 this one released 32× more
Energy from the Gutenberg–Richter relation (log10E = 1.5M + 4.8), rounded to two figures; bar length is magnitude, which is already a logarithm of energy. Magnitudes of past earthquakes from the USGS catalogue.
For this area
Tied for the largest within 50 km (31 mi) since 2016, with M 4.0 on 2026-10-07.
Before 2016, the USGS record lists 65 earthquakes of M5 or more within 50 km; the five largest:
- 8.7 1965 Western Aleutian Islands (Hawadax/Rat Islands) Earthquake · 43 km SSE of this epicentre
- 8.3 1906 Western Aleutian Islands (Hawadax/Rat Islands) Earthquake · 37 km NW of this epicentre
- 7.9 Rat Islands, Aleutian Islands, Alaska · 27 km NNE of this epicentre
- 6.8 Rat Islands, Aleutian Islands, Alaska · 46 km S of this epicentre
- 6.5 Rat Islands, Aleutian Islands, Alaska · 36 km SE of this epicentre
Since 2016: the QuakeIndex catalogue (US, M1.5+), built from the USGS FDSN event service. Before 2016: USGS ComCat, M5+ from 1900. Distances are between epicentres. This is the record, not a forecast.
Where
Epicentre 51.6260, 178.5780. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Aleutians West Census Area, AK | 80 km (50 mi) | ENE | earthquakes near Aleutians West Census Area |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
No further earthquakes have been recorded within 50 km since this one.
Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of . QuakeIndex does not forecast aftershocks. When USGS issues an operational aftershock forecast it appears on the USGS event page.
On USGS
- The official USGS event page — the source of record for every value above
- Did you feel it? Report it to USGS — reports go to USGS, not to us
- ShakeMap for this event, when USGS has produced one
QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.