QuakeIndex

Earthquake · reviewed by a seismologist

M 1.9ml

Earthquake near Three Forks, MT

No earthquake was likely felt in Three Forks in the 24 hours to 8:24 am MST (15:24 UTC). The last one was M 1.6, 7 km (5 mi) NE, at 4:03 pm MDT on 11 August 2026, estimated intensity II (weak) in town. Every earthquake near Three Forks

This page: a magnitude 1.9 earthquake was recorded 8 km (5 mi) south of Three Forks, MT, at 8:26 am MST on 19 February 2021 (15:26 UTC), 4.6 km deep.

USGS: 6 km E of Willow Creek, Montana

42 km (26 mi) WNW of Bozeman, MT

8:26 am MST, Feb 19, 2021 · · 4.6 km deep · released about 22 lb of TNT

Every earthquake near Three Forks Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Gallatin County 46 kmJefferson County 51 kmBroadwater County 56 kmMadison County 62 kmSilver Bow County 85 kmPark County 89 kmMeagher County 98 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
8:26 am MST on 19 February 2021 ()
Where
8 km (5 mi) south of Three Forks, MT · earthquakes near Three Forks
Montana today
every earthquake in Montana in the last 24 hours
Magnitude
M 1.9 (ml)
Depth
4.6 km below the surface
Felt
no reports yet
Nearest
Gallatin County, 46 km SE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2090 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 14 km (9 mi) from the epicentre. In Three Forks, 8 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: Three Forks 8 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 22 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.9 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 680,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 480,000× the energy of this one
  3. Around the size people start to feel M 3.0 43× the energy of this one
  4. This earthquake M 1.9 about 22 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 4.2 on 2019-08-16 — about 2,700 times the energy of this one.

Before 2016, the USGS record lists 6 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.6 The 1925 Clarkston Valley, Montana Earthquake · 29 km N of this epicentre
  2. 6.4 Clarkston Valley, Montana (Aftershock) · 29 km N of this epicentre
  3. 5.5 Clarkston Valley, Montana (Aftershock) · 29 km N of this epicentre
  4. 5.5 Clarkston Valley, Montana (Aftershock) · 29 km N of this epicentre
  5. 5.5 Clarkston Valley, Montana (Aftershock) · 29 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 45.8248, -111.5615. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Gallatin County, MT 46 km (29 mi) SE earthquakes near Gallatin County
Jefferson County, MT 51 km (32 mi) NW earthquakes near Jefferson County
Broadwater County, MT 56 km (35 mi) N earthquakes near Broadwater County
Madison County, MT 62 km (38 mi) SSW earthquakes near Madison County
Silver Bow County, MT 85 km (53 mi) W earthquakes near Silver Bow County
Park County, MT 89 km (56 mi) ESE earthquakes near Park County

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

Aftershocks so far

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

  1. 1.6 11 km NNE of Ennis, Montana
  2. 1.7 3 km NNE of Logan, Montana
  3. 1.5 5 km SW of Manhattan, Montana
  4. 2.1 2 km WSW of Logan, Montana
  5. 1.8 5 km NW of Logan, Montana
  6. 1.7 1 km ENE of Churchill, Montana
  7. 2.0 4 km W of Three Forks, Montana
  8. 1.9 7 km NNE of Manhattan, Montana
  9. 1.5 8 km S of Harrison, Montana
  10. 3.1 6 km NNW of Three Forks, Montana
  11. 2.3 Western Montana
  12. 2.3 3 km NW of Three Forks, Montana
  13. 2.1 3 km NNW of Three Forks, Montana
  14. 2.0 3 km NNW of Three Forks, Montana
  15. 1.6 3 km S of Logan, 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.