QuakeIndex

Earthquake · reviewed by a seismologist

M 3.9mwr

21 km N of Spencer, Idaho

· 11 km deep · released about 11 tons of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Clark County 32 kmFremont County 69 kmBeaverhead County 83 kmJefferson County 85 kmMadison County 89 kmMadison County 96 kmTeton County 119 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 3.9 (mwr)
Depth
11 km below the surface
Felt
no reports yet
Measured shaking
intensity IV (ShakeMap)
Nearest
Clark County, 32 km SSW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 300 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.

How big was it?

This earthquake released about 11 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.9 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 16,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 710× the energy of this one
  3. Magna, Utah 2020 M 5.7 500× the energy of this one
  4. This earthquake M 3.9 about 11 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 22× more

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 44.5566, -112.2187. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Clark County, ID 32 km (20 mi) NNE of here earthquakes near Clark County
Fremont County, ID 69 km (43 mi) WNW of here earthquakes near Fremont County
Beaverhead County, MT 83 km (52 mi) SE of here earthquakes near Beaverhead County
Jefferson County, ID 85 km (53 mi) N of here earthquakes near Jefferson County
Madison County, MT 89 km (55 mi) SSW of here earthquakes near Madison County
Madison County, ID 96 km (60 mi) NNW of here earthquakes near Madison County

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

Aftershocks so far

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

  1. 1.7 2 km SW of Lima, Montana
  2. 2.3 49 km NNE of Spencer, Idaho
  3. 1.8 20 km NE of Spencer, Idaho
  4. 2.8 19 km NE of Lima, Montana
  5. 1.8 26 km S of Lima, Montana
  6. 1.8 44 km NE of Spencer, Idaho
  7. 1.7 32 km S of Lima, Montana
  8. 2.6 24 km N of Spencer, Idaho
  9. 1.6 22 km N of Spencer, Idaho
  10. 1.8 47 km NE of Spencer, Idaho
  11. 2.1 2 km SSE of Lima, Montana
  12. 2.4 23 km N of Spencer, Idaho
  13. 1.6 23 km N of Spencer, Idaho
  14. 2.4 22 km N of Spencer, Idaho
  15. 2.4 23 km N of Spencer, 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.

For this area

The largest earthquake within 50 km in our catalogue was M 4.6 on 2019-04-09 — it released about 11 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.