QuakeIndex

Earthquake · reviewed by a seismologist

M 2.1ml

4 km NNW of Alder, Montana

· 4.5 km deep · released about 51 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Madison County 17 kmBeaverhead County 65 kmSilver Bow County 72 kmGallatin County 77 kmJefferson County 85 kmDeer Lodge County 113 kmBroadwater County 118 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 2.1 (ml)
Depth
4.5 km below the surface
Felt
no reports yet
Nearest
Madison County, 17 km ESE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1969 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

How big was it?

This earthquake released about 51 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.1 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 300,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 210,000× the energy of this one
  3. Around the size people start to feel M 3.0 19× the energy of this one
  4. This earthquake M 2.1 about 51 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 45.3640, -112.1273. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Madison County, MT 17 km (11 mi) WNW of here earthquakes near Madison County
Beaverhead County, MT 65 km (40 mi) ENE of here earthquakes near Beaverhead County
Silver Bow County, MT 72 km (45 mi) SE of here earthquakes near Silver Bow County
Gallatin County, MT 77 km (48 mi) WSW of here earthquakes near Gallatin County
Jefferson County, MT 85 km (53 mi) S of here earthquakes near Jefferson County
Deer Lodge County, MT 113 km (70 mi) SE of here earthquakes near Deer Lodge County

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

Aftershocks so far

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

  1. 3.0 18 km NNE of Ennis, Montana
  2. 1.9 23 km SSE of Dillon, Montana
  3. 2.5 13 km NNW of Ennis, Montana
  4. 1.9 17 km N of Dillon, Montana
  5. 1.9 12 km NNW of Ennis, Montana
  6. 2.3 34 km S of Virginia City, Montana
  7. 1.9 8 km ESE of Sheridan, Montana
  8. 1.8 14 km N of Dillon, Montana
  9. 1.7 19 km NNE of Ennis, Montana
  10. 3.3 17 km NNE of Ennis, Montana
  11. 2.9 20 km SSE of Harrison, Montana
  12. 1.7 17 km S of Pony, Montana
  13. 1.6 11 km NNE of Ennis, Montana
  14. 2.1 32 km S of Virginia City, Montana
  15. 2.2 20 km W of Pony, 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 660 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.