QuakeIndex

Earthquake · reviewed by a seismologist

M 2.1ml

22 km NNE of Helena Valley Northeast, Montana

· 4.0 km deep · released about 40 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Lewis and Clark County 50 kmCascade County 60 kmBroadwater County 66 kmMeagher County 76 kmPowell County 85 kmJefferson County 86 kmTeton County 110 kmJudith Basin County 116 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
4.0 km below the surface
Felt
no reports yet
Nearest
Lewis and Clark County, 50 km WNW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 579 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 40 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 5.8 380,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 270,000× the energy of this one
  3. Around the size people start to feel M 3.0 24× the energy of this one
  4. This earthquake M 2.1 about 40 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 46.8818, -111.8188. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Lewis and Clark County, MT 50 km (31 mi) ESE of here earthquakes near Lewis and Clark County
Cascade County, MT 60 km (37 mi) SW of here earthquakes near Cascade County
Broadwater County, MT 66 km (41 mi) NNW of here earthquakes near Broadwater County
Meagher County, MT 76 km (47 mi) WNW of here earthquakes near Meagher County
Powell County, MT 85 km (53 mi) E of here earthquakes near Powell County
Jefferson County, MT 86 km (54 mi) NNE of here earthquakes near Jefferson County

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

Aftershocks so far

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

  1. 1.5 16 km NE of Helena Valley Northwest, Montana
  2. 1.6 14 km SSE of Craig, Montana
  3. 2.4 21 km SSE of Craig, Montana
  4. 1.5 1 km SSE of South Hills, Montana
  5. 1.7 0 km NNW of South Hills, Montana
  6. 1.7 8 km S of Marysville, Montana
  7. 2.0 32 km ENE of Helena Valley Northeast, Montana
  8. 2.0 20 km NNE of Helena Valley Northeast, Montana
  9. 1.5 31 km ENE of Helena Valley Northeast, Montana
  10. 1.9 1 km SSE of South Hills, Montana
  11. 2.4 2 km ESE of Clancy, Montana
  12. 1.7 14 km NNW of Winston, Montana
  13. 1.5 3 km SE of Helena Valley West Central, Montana
  14. 1.6 6 km SE of Craig, Montana
  15. 2.3 10 km SSE of Marysville, 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

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