QuakeIndex

Earthquake · reviewed by a seismologist

M 1.6ml

Earthquake near Dillon, MT

No earthquake was likely felt in Dillon in the 24 hours to 4:22 am MST (11:22 UTC). The last one was M 2.0, 14 km (9 mi) N, at 2:45 pm MDT on 7 May 2026, estimated intensity II (weak) in town. Every earthquake near Dillon

This page: a magnitude 1.6 earthquake was recorded 39 km (24 mi) southwest of Dillon, MT, at 4:09 am MST on 15 December 2021 (11:09 UTC), 6.0 km deep.

USGS: Idaho-Montana border region

4:09 am MST, Dec 15, 2021 · · 6.0 km deep · released about 6.4 lb of TNT

Every earthquake near Dillon Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Beaverhead County 19 kmLemhi County 69 kmClark County 93 kmMadison County 94 kmSilver Bow County 105 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
4:09 am MST on 15 December 2021 ()
Where
39 km (24 mi) southwest of Dillon, MT · earthquakes near Dillon
Magnitude
M 1.6 (ml)
Depth
6.0 km below the surface
Felt
no reports yet
Nearest
Beaverhead County, 19 km NNE
Nearest mapped fault
Red Rock fault, 13 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 1793 days ago

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

At this magnitude and depth, people at rest would likely notice it out to about 9 km (6 mi) from the epicentre. In Dillon, 39 km away, the estimate is intensity I (not felt). 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 6.4 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.5 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 2,400,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 1,700,000× the energy of this one
  3. Around the size people start to feel M 3.0 150× the energy of this one
  4. This earthquake M 1.6 about 6.4 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 44.9807, -113.0127. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Beaverhead County, MT 19 km (12 mi) NNE earthquakes near Beaverhead County
Lemhi County, ID 69 km (43 mi) W earthquakes near Lemhi County
Clark County, ID 93 km (58 mi) SE earthquakes near Clark County
Madison County, MT 94 km (59 mi) ENE earthquakes near Madison County
Silver Bow County, MT 105 km (66 mi) NNE earthquakes near Silver Bow County
Custer County, ID 126 km (78 mi) SW earthquakes near Custer County

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

Aftershocks so far

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

  1. 1.7 14 km NW of Lima, Montana
  2. 1.9 23 km SSE of Dillon, Montana
  3. 2.0 28 km WSW of Dillon, Montana
  4. 1.6 26 km NW of Lima, Montana
  5. 2.0 30 km W of Lima, Montana
  6. 2.0 33 km NNW of Lima, Montana
  7. 1.6 22 km WSW of Lima, Montana
  8. 2.4 21 km WSW of Lima, Montana
  9. 2.0 40 km SW of Dillon, Montana
  10. 1.8 39 km SW of Dillon, Montana
  11. 1.9 39 km SW of Dillon, Montana
  12. 1.6 39 km SW of Dillon, Montana
  13. 2.4 41 km SW of Dillon, Montana
  14. 2.4 40 km NNE of Leadore, Idaho
  15. 2.6 41 km NE of Leadore, Idaho

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

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