QuakeIndex

Earthquake · reviewed by a seismologist

M 2.1ml

4 km W of East Helena, Montana

· 4.8 km deep · released about 43 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Broadwater County 47 kmJefferson County 53 kmLewis and Clark County 67 kmPowell County 78 kmMeagher County 80 kmCascade County 93 kmSilver Bow County 94 kmDeer Lodge County 106 kmGranite County 114 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
4.8 km below the surface
Felt
2 reports · strongest reported intensity III
Nearest
Broadwater County, 47 km SE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2951 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage. 2 people have reported feeling it to USGS.

How big was it?

This earthquake released about 43 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 5.8 350,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 250,000× the energy of this one
  3. Around the size people start to feel M 3.0 22× the energy of this one
  4. This earthquake M 2.1 about 43 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 46.5951, -111.9687. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Broadwater County, MT 47 km (29 mi) NW of here earthquakes near Broadwater County
Jefferson County, MT 53 km (33 mi) N of here earthquakes near Jefferson County
Lewis and Clark County, MT 67 km (41 mi) SSE of here earthquakes near Lewis and Clark County
Powell County, MT 78 km (49 mi) ESE of here earthquakes near Powell County
Meagher County, MT 80 km (50 mi) W of here earthquakes near Meagher County
Cascade County, MT 93 km (58 mi) SSW of here earthquakes near Cascade County

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

Aftershocks so far

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

  1. 1.6 18 km NW of Marysville, Montana
  2. 1.8 15 km SSE of Craig, Montana
  3. 2.3 Western Montana
  4. 1.7 6 km SSW of The Silos, Montana
  5. 1.8 1 km ENE of South Hills, Montana
  6. 1.6 6 km SSW of The Silos, Montana
  7. 1.6 26 km ENE of Helena Valley Northeast, Montana
  8. 1.5 27 km NE of Winston, Montana
  9. 1.6 12 km WNW of Marysville, Montana
  10. 2.0 7 km SSW of Marysville, Montana
  11. 1.7 7 km SSW of Marysville, Montana
  12. 1.7 6 km W of Townsend, Montana
  13. 1.6 6 km SSW of The Silos, Montana
  14. 1.6 14 km S of Craig, Montana
  15. 1.6 19 km NNE 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.