QuakeIndex

Earthquake · reviewed by a seismologist

M 1.8ml

42 km NE of Spencer, Idaho

Yes. A magnitude 1.8 earthquake was recorded 42 km NE of Spencer, Idaho, at 8:10 pm MST on 18 February 2020 (03:10 UTC), 11 km deep.

· 11 km deep · released about 14 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Clark County 57 kmFremont County 61 kmMadison County 72 kmBeaverhead County 94 kmMadison County 101 kmJefferson County 104 kmGallatin County 109 kmTeton County 116 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 1.8 (ml)
Depth
11 km below the surface
Felt
no reports yet
Nearest
Clark County, 57 km SW
Nearest mapped fault
Centennial fault, 8 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 2457 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

At this magnitude and depth, people at rest would likely notice it out to about 7 km (4 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 14 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.8 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 1,100,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 790,000× the energy of this one
  3. Around the size people start to feel M 3.0 70× the energy of this one
  4. This earthquake M 1.8 about 14 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 4.3 on 2016-06-13 — about 7,200 times the energy of this one.

Before 2016, the USGS record lists 5 earthquakes of M5 or more within 50 km:

  1. 6.1 30 km SSW of Big Sky, Montana · 48 km NNE of this epicentre
  2. 5.2 32 km WNW of Hebgen Lake Estates, Montana · 33 km NE of this epicentre
  3. 5.2 26 km WNW of Hebgen Lake Estates, Montana · 36 km ENE of this epicentre
  4. 5.0 31 km W of Hebgen Lake Estates, Montana · 28 km ENE of this epicentre
  5. 5.0 39 km W of Hebgen Lake Estates, Montana · 17 km E 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 44.6805, -111.8863. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Clark County, ID 57 km (35 mi) SW earthquakes near Clark County
Fremont County, ID 61 km (38 mi) SSE earthquakes near Fremont County
Madison County, MT 72 km (45 mi) N earthquakes near Madison County
Beaverhead County, MT 94 km (58 mi) WNW earthquakes near Beaverhead County
Madison County, ID 101 km (63 mi) S earthquakes near Madison County
Jefferson County, ID 104 km (65 mi) SSW earthquakes near Jefferson County

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

Aftershocks so far

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

  1. 2.4 25 km N of Spencer, Idaho
  2. 1.5 38 km SSW of Virginia City, Montana
  3. 2.2 35 km NNE of Spencer, Idaho
  4. 2.1 28 km SSE of Virginia City, Montana
  5. 1.7 43 km W of Hebgen Lake Estates, Montana
  6. 1.8 28 km SSE of Virginia City, Montana
  7. 1.6 28 km S of Ennis, Montana
  8. 1.8 28 km SSE of Virginia City, Montana
  9. 2.7 30 km W of Hebgen Lake Estates, Montana
  10. 1.5 38 km WNW of Hebgen Lake Estates, Montana
  11. 2.3 41 km NW of Island Park, Idaho
  12. 2.0 36 km NNE of Spencer, Idaho
  13. 1.8 27 km SE of Virginia City, Montana
  14. 2.0 29 km SSE of Virginia City, Montana
  15. 2.4 27 km WNW of Hebgen Lake Estates, 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.