QuakeIndex

Earthquake · reviewed by a seismologist

M 1.6ml

25 km SSW of Heart Butte, Montana

· 6.2 km deep · released about 6.8 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Pondera County 61 kmTeton County 63 kmGlacier County 68 kmFlathead County 80 kmLake County 94 kmToole County 113 kmLewis and Clark 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 1.6 (ml)
Depth
6.2 km below the surface
Felt
no reports yet
Nearest
Pondera County, 61 km ENE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 3096 days ago

A magnitude 1.6 earthquake was recorded 25 km SSW of Heart Butte, Montana at 11:44 UTC on 2018-04-12. This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

How big was it?

This earthquake released about 6.8 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.6 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 2,200,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 1,600,000× the energy of this one
  3. Around the size people start to feel M 3.0 140× the energy of this one
  4. This earthquake M 1.6 about 6.8 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.

For this area

No earthquake of M4 or more has been recorded within 50 km since our catalogue begins in 2016.

Before 2016, the USGS record since 1900 lists no earthquake of M5 or more within 50 km.

Since 2016: the QuakeIndex catalogue (US, M1.5+), built from the USGS FDSN event service. Before 2016: USGS ComCat, M5+ from 1900. Distances are between epicentres. This is the record, not a forecast.

Where

Epicentre 48.0925, -113.0208. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Pondera County, MT 61 km (38 mi) ENE earthquakes near Pondera County
Teton County, MT 63 km (39 mi) ESE earthquakes near Teton County
Glacier County, MT 68 km (42 mi) N earthquakes near Glacier County
Flathead County, MT 80 km (50 mi) WNW earthquakes near Flathead County
Lake County, MT 94 km (58 mi) WSW earthquakes near Lake County
Toole County, MT 113 km (70 mi) ENE earthquakes near Toole County

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

Aftershocks so far

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

  1. 2.1 27 km E of Swan Lake, Montana
  2. 2.5 24 km E of Swan Lake, Montana
  3. 2.4 27 km E of Swan Lake, Montana
  4. 1.6 18 km SW of Bynum, Montana
  5. 1.6 19 km SSE of East Glacier Park Village, Montana
  6. 2.0 19 km SW of Heart Butte, Montana
  7. 2.2 47 km WNW of Augusta, Montana
  8. 1.8 22 km SW of Heart Butte, Montana
  9. 1.9 17 km NNW of Dupuyer, Montana
  10. 1.9 32 km ESE of Swan Lake, Montana
  11. 2.5 19 km W of Heart Butte, Montana
  12. 2.8 40 km ENE of Condon, 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.