QuakeIndex

Earthquake · reviewed by a seismologist

M 1.8ml

18 km N of Ennis, Montana

· 5.0 km deep · released about 15 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Madison County 25 kmGallatin County 45 kmJefferson County 72 kmSilver Bow County 83 kmBroadwater County 92 kmPark County 94 kmBeaverhead County 100 km
Distance rings around the epicentre, with the nearest towns at their true direction and later quakes as coloured dots. Not a shaking map — see the USGS ShakeMap for that.
When
Magnitude
M 1.8 (ml)
Depth
5.0 km below the surface
Felt
1 report · strongest reported intensity III
Nearest
Madison County, 25 km SSW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 975 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage. 1 person has reported feeling it to USGS.

How big was it?

This earthquake released about 15 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.8 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 1,000,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 710,000× the energy of this one
  3. Around the size people start to feel M 3.0 63× the energy of this one
  4. This earthquake M 1.8 about 15 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.

Where

Epicentre 45.5186, -111.7406. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Madison County, MT 25 km (16 mi) NNE of here earthquakes near Madison County
Gallatin County, MT 45 km (28 mi) W of here earthquakes near Gallatin County
Jefferson County, MT 72 km (45 mi) SSE of here earthquakes near Jefferson County
Silver Bow County, MT 83 km (51 mi) ESE of here earthquakes near Silver Bow County
Broadwater County, MT 92 km (57 mi) SSW of here earthquakes near Broadwater County
Park County, MT 94 km (59 mi) W of here earthquakes near Park County

Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.

Aftershocks so far

46 earthquakes have been recorded within 50 km since this one.

  1. 2.4 17 km ESE of Harrison, Montana
  2. 1.6 6 km NE of Three Forks, Montana
  3. 1.6 2 km E of Churchill, Montana
  4. 2.1 13 km SSE of Pony, Montana
  5. 1.9 21 km S of Ennis, Montana
  6. 1.6 28 km SE of Virginia City, Montana
  7. 1.8 6 km NE of Three Forks, Montana
  8. 2.0 11 km S of Ennis, Montana
  9. 1.5 28 km S of Ennis, Montana
  10. 2.3 3 km NNW of Pony, Montana
  11. 2.0 2 km NNW of Pony, Montana
  12. 2.4 8 km SSE of Pony, Montana
  13. 1.6 4 km ESE of Twin Bridges, Montana
  14. 1.5 28 km SE of Virginia City, Montana
  15. 1.5 28 km S of Ennis, 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.

For this area

The largest earthquake within 50 km in our catalogue was M 4.0 on 2016-09-03 — it released about 2,200 times the energy of this one.

From the QuakeIndex catalogue, built from the USGS FDSN event service.

On USGS

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.