QuakeIndex

Earthquake · reviewed by a seismologist

M 4.0mwr

18 km NW of Stanley, Idaho

Yes. A magnitude 4.0 earthquake was recorded 18 km NW of Stanley, Idaho, at 8:23 pm MDT on 31 March 2020 (02:23 UTC), 14 km deep. 20 people have reported feeling it to USGS.

· 14 km deep · released about 15 tons of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Boise County 61 kmCuster County 69 kmValley County 71 kmCamas County 95 kmGem County 106 kmElmore County 107 kmLemhi 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
Idaho today
every earthquake in Idaho in the last 24 hours
Magnitude
M 4.0 (mwr)
Depth
14 km below the surface
Felt
20 reports · strongest reported intensity V
Measured shaking
intensity IV (ShakeMap)
USGS impact alert
green
Nearest
Boise County, 61 km SW
Nearest mapped fault
Sawtooth fault, 4 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 2335 days ago

This was a light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon.

At this magnitude and depth, people at rest would likely notice it out to about 96 km (60 mi) from the epicentre. 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 15 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.0 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 11,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 500× the energy of this one
  3. Magna, Utah 2020 M 5.7 350× the energy of this one
  4. This earthquake M 4.0 about 15 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 32× 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.

For this area

The largest earthquake within 50 km since 2016 was M 6.5 on 2020-03-31 — about 5,600 times the energy of this one.

Before 2016, the USGS record lists 2 earthquakes of M5 or more within 50 km:

  1. 6.1 37 km N of Stanley, Idaho · 31 km NE of this epicentre
  2. 6.0 44 km NNW of Stanley, Idaho · 32 km N of this epicentre

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 44.3232, -115.1185. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Boise County, ID 61 km (38 mi) SW earthquakes near Boise County
Custer County, ID 69 km (43 mi) E earthquakes near Custer County
Valley County, ID 71 km (44 mi) NNW earthquakes near Valley County
Camas County, ID 95 km (59 mi) SSE earthquakes near Camas County
Gem County, ID 106 km (66 mi) WSW earthquakes near Gem County
Elmore County, ID 107 km (67 mi) SSW earthquakes near Elmore 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. 3.2 26 km WNW of Stanley, Idaho
  2. 2.5 20 km NW of Stanley, Idaho
  3. 2.7 13 km WNW of Stanley, Idaho
  4. 3.0 36 km NW of Stanley, Idaho
  5. 3.0 25 km WNW of Stanley, Idaho
  6. 2.9 16 km NW of Stanley, Idaho
  7. 2.8 28 km NW of Stanley, Idaho
  8. 3.0 25 km WNW of Stanley, Idaho
  9. 2.9 16 km NW of Stanley, Idaho
  10. 2.8 25 km NW of Stanley, Idaho
  11. 2.5 26 km NW of Stanley, Idaho
  12. 2.7 15 km WNW of Stanley, Idaho
  13. 3.6 20 km WNW of Stanley, Idaho
  14. 2.8 25 km NW of Stanley, Idaho
  15. 3.0 26 km NW of Stanley, 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.