QuakeIndex

Earthquake · reviewed by a seismologist

M 1.6ml

Earthquake near Boulder, MT

No earthquake was likely felt in Boulder in the 24 hours to 12:51 pm MST (19:51 UTC). The last one was M 3.0, 33 km (21 mi) SSW, at 9:32 pm MDT on 26 April 2026, estimated intensity II (weak) in town; 42 felt reports to USGS. Every earthquake near Boulder

This page: a magnitude 1.6 earthquake was recorded 20 km (12 mi) east-southeast of Boulder, MT, at 1:14 pm MDT on 3 July 2021 (19:14 UTC), 6.0 km deep.

USGS: 14 km SSE of Elkhorn, Montana

1:14 pm MDT, Jul 3, 2021 · · 6.0 km deep · released about 6.6 lb of TNT

Every earthquake near Boulder Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Jefferson County 13 kmBroadwater County 37 kmSilver Bow County 65 kmMeagher County 89 kmGallatin County 90 kmMadison County 92 kmDeer Lodge County 96 kmPowell County 111 kmLewis and Clark County 114 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
1:14 pm MDT on 3 July 2021 ()
Where
20 km (12 mi) east-southeast of Boulder, MT · earthquakes near Boulder
Montana today
every earthquake in Montana in the last 24 hours
Magnitude
M 1.6 (ml)
Depth
6.0 km below the surface
Felt
no reports yet
Nearest
Jefferson County, 13 km WSW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1955 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 9 km (6 mi) from the epicentre. In Boulder, 20 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 6.6 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 2,300,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 1,600,000× the energy of this one
  3. Around the size people start to feel M 3.0 140× the energy of this one
  4. This earthquake M 1.6 about 6.6 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

No earthquake of M4 or more has been recorded within 50 km since our catalogue begins in 2016.

Before 2016, the USGS record lists 7 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.6 The 1925 Clarkston Valley, Montana Earthquake · 31 km ESE of this epicentre
  2. 6.4 Clarkston Valley, Montana (Aftershock) · 31 km ESE of this epicentre
  3. 5.9 The 1935 Helena, Montana Earthquakes (Largest Aftershock) · 44 km N of this epicentre
  4. 5.5 Clarkston Valley, Montana (Aftershock) · 31 km ESE of this epicentre
  5. 5.5 Clarkston Valley, Montana (Aftershock) · 31 km ESE 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 46.1487, -111.8972. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Jefferson County, MT 13 km (8 mi) WSW earthquakes near Jefferson County
Broadwater County, MT 37 km (23 mi) ENE earthquakes near Broadwater County
Silver Bow County, MT 65 km (41 mi) WSW earthquakes near Silver Bow County
Meagher County, MT 89 km (55 mi) ENE earthquakes near Meagher County
Gallatin County, MT 90 km (56 mi) SE earthquakes near Gallatin County
Madison County, MT 92 km (57 mi) S earthquakes near Madison County

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

Aftershocks so far

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

  1. 1.7 5 km W of Ponderosa Pines, Montana
  2. 2.3 3 km WSW of Ponderosa Pines, Montana
  3. 2.1 3 km SW of Ponderosa Pines, Montana
  4. 2.0 11 km WSW of Radersburg, Montana
  5. 2.4 3 km WSW of Ponderosa Pines, Montana
  6. 1.7 Western Montana
  7. 2.1 3 km NW of Elkhorn, Montana
  8. 1.6 4 km WNW of Elkhorn, Montana
  9. 1.7 3 km NNE of Logan, Montana
  10. 2.1 2 km WSW of Logan, Montana
  11. 1.8 5 km NW of Logan, Montana
  12. 2.2 11 km NE of Townsend, Montana
  13. 1.6 2 km E of South Hills, Montana
  14. 1.7 9 km WSW of Townsend, Montana
  15. 2.0 4 km W of Three Forks, 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.