QuakeIndex

Earthquake · reviewed by a seismologist

M 2.7ml

Earthquake near Challis, ID

No earthquake was likely felt in Challis in the 24 hours to 10:12 pm MST (05:12 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 2.7 earthquake was recorded 49 km (30 mi) southwest of Challis, ID, at 11:29 am MST on 28 November 2020 (18:29 UTC), 18 km deep. 2 people have reported feeling it to USGS.

USGS: 19 km E of Stanley, Idaho

11:29 am MST, Nov 28, 2020 · · 18 km deep · released about 340 lb of TNT

Every earthquake near Challis Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Custer County 35 kmCamas County 79 kmBoise County 86 kmLemhi County 102 kmValley County 103 kmBlaine County 108 kmElmore County 111 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
11:29 am MST on 28 November 2020 ()
Where
49 km (30 mi) southwest of Challis, ID · earthquakes near Challis
Idaho today
every earthquake in Idaho in the last 24 hours
Magnitude
M 2.7 (ml)
Depth
18 km below the surface
Felt
2 reports · strongest reported intensity IV
Nearest
Custer County, 35 km E
Nearest mapped fault
Sawtooth fault, 24 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 2104 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 18 km (11 mi) from the epicentre. In Challis, 49 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.

How big was it?

This earthquake released about 340 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.7 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 45,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 32,000× the energy of this one
  3. Around the size people start to feel M 3.0 2.8× the energy of this one
  4. This earthquake M 2.7 about 340 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

The largest earthquake within 50 km since 2016 was M 6.5 on 2020-03-31 — about 500,000 times the energy of this one.

Before 2016, the USGS record lists 4 earthquakes of M5 or more within 50 km:

  1. 6.1 37 km N of Stanley, Idaho · 42 km NNW of this epicentre
  2. 5.5 22 km E of Clayton, Idaho · 46 km E of this epicentre
  3. 5.4 23 km E of Clayton, Idaho · 47 km E of this epicentre
  4. 5.1 9 km SE of Challis, Idaho · 49 km ENE 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 44.2129, -114.6888. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Custer County, ID 35 km (22 mi) E earthquakes near Custer County
Camas County, ID 79 km (49 mi) S earthquakes near Camas County
Boise County, ID 86 km (53 mi) WSW earthquakes near Boise County
Lemhi County, ID 102 km (63 mi) NE earthquakes near Lemhi County
Valley County, ID 103 km (64 mi) NW earthquakes near Valley County
Blaine County, ID 108 km (67 mi) SSE earthquakes near Blaine County

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

Aftershocks so far

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

  1. 1.9 southern Idaho
  2. 2.8 22 km NW of Stanley, Idaho
  3. 2.7 18 km NNW of Stanley, Idaho
  4. 2.4 15 km NNW of Stanley, Idaho
  5. 1.9 30 km NW of Stanley, Idaho
  6. 2.4 35 km NNW of Stanley, Idaho
  7. 2.3 21 km WNW of Stanley, Idaho
  8. 1.9 12 km S of Stanley, Idaho
  9. 2.0 31 km NW of Stanley, Idaho
  10. 2.2 32 km NW of Stanley, Idaho
  11. 2.0 31 km NW of Stanley, Idaho
  12. 2.8 southern Idaho
  13. 2.1 18 km WNW of Stanley, Idaho
  14. 2.3 31 km NW of Stanley, Idaho
  15. 1.9 16 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.