QuakeIndex

Earthquake · reviewed by a seismologist

M 1.6ml

Earthquake near Bozeman, MT

No earthquake was likely felt in Bozeman in the 24 hours to 8:32 am MST (15:32 UTC). The last one was M 3.0, 17 km (10 mi) NW, at 7:42 am MDT on 1 June 2024, estimated intensity II (weak) in town; 20 felt reports to USGS. Every earthquake near Bozeman

This page: a magnitude 1.6 earthquake was recorded 50 km (31 mi) northwest of Bozeman, MT, at 7:40 am MDT on 20 September 2021 (13:40 UTC), 8.2 km deep.

USGS: 3 km WNW of Ponderosa Pines, Montana

49 km (30 mi) NW of Bozeman, MT

7:40 am MDT, Sep 20, 2021 · · 8.2 km deep · released about 7.8 lb of TNT

10 km30 km60 km120 km N Broadwater County 33 kmJefferson County 50 kmGallatin County 61 kmMeagher County 71 kmMadison County 88 kmPark County 94 kmSilver Bow County 97 kmSweet Grass County 117 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
7:40 am MDT on 20 September 2021 ()
Where
50 km (31 mi) northwest of Bozeman, MT · earthquakes near Bozeman
Montana today
every earthquake in Montana in the last 24 hours
Magnitude
M 1.6 (ml)
Depth
8.2 km below the surface
Felt
no reports yet
Nearest
Broadwater County, 33 km N
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1875 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 8 km (5 mi) from the epicentre. In Bozeman, 50 km away, the estimate is intensity I (not felt). 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.

Earthquakes near other towns within 30 km: Three Forks, Manhattan.

How big was it?

This earthquake released about 7.8 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.6 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 1,900,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 1,400,000× the energy of this one
  3. Around the size people start to feel M 3.0 120× the energy of this one
  4. This earthquake M 1.6 about 7.8 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 7,700 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 · 8 km WNW of this epicentre
  2. 6.4 Clarkston Valley, Montana (Aftershock) · 8 km WNW of this epicentre
  3. 5.5 Clarkston Valley, Montana (Aftershock) · 8 km WNW of this epicentre
  4. 5.5 Clarkston Valley, Montana (Aftershock) · 8 km WNW of this epicentre
  5. 5.5 Clarkston Valley, Montana (Aftershock) · 8 km WNW 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 46.0410, -111.4160. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Broadwater County, MT 33 km (20 mi) N earthquakes near Broadwater County
Jefferson County, MT 50 km (31 mi) W earthquakes near Jefferson County
Gallatin County, MT 61 km (38 mi) SSE earthquakes near Gallatin County
Meagher County, MT 71 km (44 mi) NNE earthquakes near Meagher County
Madison County, MT 88 km (55 mi) SSW earthquakes near Madison County
Park County, MT 94 km (58 mi) SE earthquakes near Park 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. 1.6 3 km WSW of Ponderosa Pines, Montana
  2. 1.6 8 km W of Townsend, Montana
  3. 1.7 6 km WSW of Townsend, Montana
  4. 1.6 14 km ESE of Harrison, Montana
  5. 1.5 10 km WNW of Four Corners, Montana
  6. 1.6 5 km SE of Three Forks, Montana
  7. 1.6 5 km WSW of Logan, Montana
  8. 2.0 4 km NNW of Logan, Montana
  9. 2.4 12 km E of Elkhorn, Montana
  10. 1.6 5 km W of Three Forks, Montana
  11. 1.5 5 km W of Townsend, Montana
  12. 1.5 18 km SSW of Radersburg, Montana
  13. 1.6 Western Montana
  14. 1.6 7 km WSW of Townsend, Montana
  15. 1.6 8 km WSW of Townsend, 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.