Earthquake · reviewed by a seismologist
M 4.0ml
Central Alaska
Yes. A magnitude 4.0 earthquake was recorded in Central Alaska, at 5:00 pm AKDT on 27 October 2023 (01:00 UTC), 138 km deep. 8 people have reported feeling it to USGS.
- When
- Magnitude
- M 4.0 (ml)
- Depth
- 138 km below the surface
- Felt
- 8 reports · strongest reported intensity II
- Measured shaking
- intensity II (ShakeMap)
- Nearest
- Denali Borough, 22 km N
- Nearest mapped fault
- Denali fault, 18 km from its surface trace — near is not the same as on
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 1045 days 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 it was probably too small to be felt, even directly above it. 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
The largest earthquake within 50 km since 2016 was M 4.4 on 2023-05-09 — about 4 times the energy of this one.
Before 2016, the USGS record lists 16 earthquakes of M5 or more within 50 km; the five largest:
- 7.2 Mount McKinley (Denali) area, Alaska · 23 km SW of this epicentre
- 6.4 Mount McKinley (Denali) area, Alaska · 21 km WSW of this epicentre
- 5.8 52 km WSW of Ferry, Alaska · 40 km N of this epicentre
- 5.7 66 km ESE of Denali National Park, Alaska · 39 km SW of this epicentre
- 5.5 53 km ESE of Denali National Park, Alaska · 31 km WSW 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 63.4853, -150.0999. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Denali Borough, AK | 22 km (14 mi) | N | earthquakes near Denali Borough |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
55 earthquakes have been recorded within 50 km since this one.
- 1.5 32 km WNW of Cantwell, Alaska
- 1.5 42 km W of Denali Park, Alaska
- 1.5 61 km WNW of Cantwell, Alaska
- 1.6 76 km ESE of Denali National Park, Alaska
- 1.6 50 km SW of Cantwell, Alaska
- 1.9 41 km WSW of Denali Park, Alaska
- 1.5 59 km W of Cantwell, Alaska
- 1.8 30 km W of Cantwell, Alaska
- 1.9 71 km N of Petersville, Alaska
- 1.7 60 km W of Cantwell, Alaska
- 2.1 48 km WSW of Denali Park, Alaska
- 2.6 39 km WSW of Denali Park, Alaska
- 1.5 62 km WSW of Cantwell, Alaska
- 1.5 70 km ESE of Denali National Park, Alaska
- 1.7 70 km N of Petersville, Alaska
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.