QuakeIndex

Earthquake · reviewed by a seismologist

M 1.6ml

Earthquake near Big Sky, MT

No earthquake was likely felt in Big Sky in the 24 hours to 9:58 am MST (16:58 UTC). The last one was M 3.7, 68 km (42 mi) SE, at 7:22 am MDT on 28 October 2025, estimated intensity II (weak) in town; 11 felt reports to USGS. Every earthquake near Big Sky

This page: a magnitude 1.6 earthquake was recorded 28 km (17 mi) west-southwest of Big Sky, MT, at 10:41 pm MDT on 12 July 2023 (04:41 UTC), 5.0 km deep.

USGS: 13 km S of Ennis, Montana

10:41 pm MDT, Jul 12, 2023 · · 5.0 km deep · released about 9 lb of TNT

Every earthquake near Big Sky Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Madison County 19 kmGallatin County 54 kmBeaverhead County 93 kmPark County 96 kmJefferson County 103 kmSilver Bow County 104 kmFremont County 114 kmClark 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
10:41 pm MDT on 12 July 2023 ()
Where
28 km (17 mi) west-southwest of Big Sky, MT · earthquakes near Big Sky
Montana today
every earthquake in Montana in the last 24 hours
Magnitude
M 1.6 (ml)
Depth
5.0 km below the surface
Felt
no reports yet
Nearest
Madison County, 19 km NW
Nearest mapped fault
Madison fault, 9 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 1217 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 11 km (7 mi) from the epicentre. In Big Sky, 28 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 9 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 1,700,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 1,200,000× the energy of this one
  3. Around the size people start to feel M 3.0 110× the energy of this one
  4. This earthquake M 1.6 about 9 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 4 earthquakes of M5 or more within 50 km:

  1. 6.1 30 km SSW of Big Sky, Montana · 24 km SSE of this epicentre
  2. 5.2 32 km WNW of Hebgen Lake Estates, Montana · 41 km SSE of this epicentre
  3. 5.2 26 km WNW of Hebgen Lake Estates, Montana · 46 km SSE of this epicentre
  4. 5.0 31 km W of Hebgen Lake Estates, Montana · 47 km SSE 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 45.2298, -111.7155. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Madison County, MT 19 km (12 mi) NW earthquakes near Madison County
Gallatin County, MT 54 km (33 mi) NE earthquakes near Gallatin County
Beaverhead County, MT 93 km (58 mi) W earthquakes near Beaverhead County
Park County, MT 96 km (60 mi) ENE earthquakes near Park County
Jefferson County, MT 103 km (64 mi) NNW earthquakes near Jefferson County
Silver Bow County, MT 104 km (65 mi) NW earthquakes near Silver Bow County

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

Aftershocks so far

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

  1. 1.7 29 km WNW of Hebgen Lake Estates, Montana
  2. 1.9 31 km SSE of Virginia City, Montana
  3. 1.6 29 km SSE of Virginia City, Montana
  4. 2.4 8 km SSE of Pony, Montana
  5. 1.8 25 km WNW of Hebgen Lake Estates, Montana
  6. 2.1 29 km WNW of Hebgen Lake Estates, Montana
  7. 1.9 33 km S of Virginia City, Montana
  8. 1.5 28 km SE of Virginia City, Montana
  9. 1.5 28 km S of Ennis, Montana
  10. 2.6 43 km WNW of Hebgen Lake Estates, Montana
  11. 1.9 43 km W of Hebgen Lake Estates, Montana
  12. 1.7 18 km WNW of Hebgen Lake Estates, Montana
  13. 2.3 18 km NW of Hebgen Lake Estates, Montana
  14. 2.0 7 km SE of Pony, Montana
  15. 1.5 29 km SE of Virginia City, 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.