Earthquake · reviewed by a seismologist
M 0.4md
40 km SSE of Mammoth, Wyoming
Yes. A magnitude 0.4 earthquake was recorded 40 km SSE of Mammoth, Wyoming, at 3:23 pm MDT on 18 October 2026 (21:23 UTC), 7.4 km deep.
- When
- Magnitude
- M 0.4 (md)
- Depth
- 7.4 km below the surface
- Felt
- no reports yet
- Nearest
- Park County, 69 km ESE
- Nearest mapped fault
- Eagle Bay fault, 16 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 23 hours ago
Earthquake alerts for West Yellowstone, MT
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Alerts are on for .
Not a warning. An alert comes after USGS publishes a quake, usually minutes after the shaking. For early warning use ShakeAlert, through your phone's Wireless Emergency Alerts or the MyShake app.
This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.
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 0.11 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 1.4 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 140,000,000× the energy of this one
- Magna, Utah 2020 M 5.7 99,000,000× the energy of this one
- Around the size people start to feel M 3.0 8,800× the energy of this one
- This earthquake M 0.4 about 0.11 lb of TNT
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 4.2 on 2022-05-11 — about 600,000 times the energy of this one.
Before 2016, the USGS record lists 12 earthquakes of M5 or more within 50 km; the five largest:
- 6.5 14 km N of Madison Junction, Wyoming · 38 km WNW of this epicentre
- 6.3 22 km SW of Mammoth, Wyoming · 38 km WNW of this epicentre
- 6.0 21 km E of West Yellowstone, Montana · 33 km W of this epicentre
- 5.9 26 km SSE of Mammoth, Wyoming · 17 km WNW of this epicentre
- 5.7 13 km SSW of Mammoth, Wyoming · 34 km NW 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 44.6670, -110.4248. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Park County, WY | 69 km (43 mi) | ESE | earthquakes near Park County |
| Teton County, WY | 69 km (43 mi) | S | earthquakes near Teton County |
| Park County, MT | 89 km (55 mi) | N | earthquakes near Park County |
| Fremont County, ID | 98 km (61 mi) | WSW | earthquakes near Fremont County |
| Gallatin County, MT | 111 km (69 mi) | NNW | earthquakes near Gallatin County |
| Teton County, ID | 119 km (74 mi) | SSW | earthquakes near Teton County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
8 earthquakes have been recorded within 50 km since this one.
- 0.7 51 km SE of Mammoth, Wyoming
- 1.1 35 km ESE of West Yellowstone, Montana
- 0.8 33 km ESE of West Yellowstone, Montana
- 1.0 30 km ESE of West Yellowstone, Montana
- 0.8 29 km ESE of West Yellowstone, Montana
- 0.6 29 km ESE of West Yellowstone, Montana
- 0.6 29 km ESE of West Yellowstone, Montana
- 1.9 35 km S of Silver Gate, Montana
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.