QuakeIndex

Earthquake · reviewed by a seismologist

M 3.8mwr

Earthquake near Challis, ID

No earthquake was likely felt in Challis in the 24 hours to 2:43 pm MST (21:43 UTC). The last one was M 2.0, 9 km (6 mi) SSW, at 1:32 am MDT on 17 August 2026, estimated intensity II (weak) in town. Every earthquake near Challis

This page: a magnitude 3.8 earthquake was recorded 48 km (30 mi) west-southwest of Challis, ID, at 10:41 pm MDT on 19 September 2021 (04:41 UTC), 15 km deep. 14 people have reported feeling it to USGS.

USGS: 18 km NE of Stanley, Idaho

10:41 pm MDT, Sep 19, 2021 · · 15 km deep · released about 7.6 tons of TNT

Every earthquake near Challis Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Custer County 44 kmBoise County 84 kmValley County 86 kmCamas County 95 kmLemhi County 96 kmElmore 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
10:41 pm MDT on 19 September 2021 ()
Where
48 km (30 mi) west-southwest of Challis, ID · earthquakes near Challis
Idaho today
every earthquake in Idaho in the last 24 hours
Magnitude
M 3.8 (mwr)
Depth
15 km below the surface
Felt
14 reports · strongest reported intensity IV
Measured shaking
intensity III (ShakeMap)
Nearest
Custer County, 44 km ESE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1804 days ago

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

At this magnitude and depth, people at rest would likely notice it out to about 81 km (50 mi) from the epicentre. In Challis, 48 km away, the estimate is intensity II (weak). 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.

Likely felt in: Challis 48 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 7.6 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.8 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 22,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 1,000× the energy of this one
  3. Magna, Utah 2020 M 5.7 710× the energy of this one
  4. This earthquake M 3.8 about 7.6 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 16× 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 11,000 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 · 24 km NNW of this epicentre
  2. 6.0 44 km NNW of Stanley, Idaho · 36 km NW 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 44.3531, -114.7974. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Custer County, ID 44 km (28 mi) ESE earthquakes near Custer County
Boise County, ID 84 km (52 mi) WSW earthquakes near Boise County
Valley County, ID 86 km (53 mi) NW earthquakes near Valley County
Camas County, ID 95 km (59 mi) S earthquakes near Camas County
Lemhi County, ID 96 km (60 mi) NE earthquakes near Lemhi County
Elmore County, ID 119 km (74 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. 2.2 33 km NW of Stanley, Idaho
  2. 2.3 11 km NW of Stanley, Idaho
  3. 2.3 7 km NW of Stanley, Idaho
  4. 3.0 11 km NW of Stanley, Idaho
  5. 2.5 8 km NW of Stanley, Idaho
  6. 2.6 14 km NW of Stanley, Idaho
  7. 2.4 42 km NNW of Stanley, Idaho
  8. 2.2 18 km NNE of Stanley, Idaho
  9. 2.0 17 km NNE of Stanley, Idaho
  10. 2.1 6 km NW of Stanley, Idaho
  11. 1.7 7 km NW of Stanley, Idaho
  12. 2.3 6 km NW of Stanley, Idaho
  13. 1.7 19 km NE of Stanley, Idaho
  14. 2.1 9 km NNE of Stanley, Idaho
  15. 2.8 11 km NNW 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.