mining explosion · reviewed by a seismologist
M 3.1ml
Earthquake near Colstrip, MT
No earthquake was likely felt in Colstrip in the 24 hours to 2:49 pm MST (21:49 UTC). The last one was M 3.0, 19 km (12 mi) WSW, at 1:21 pm MDT on 2 June 2026, estimated intensity II (weak) in town. Every earthquake near Colstrip
No: USGS classifies this as a mining explosion, not an earthquake. A magnitude 3.1 mining explosion was recorded 9 km (5 mi) west of Colstrip, MT, at 10:37 am MDT on 23 July 2021 (16:37 UTC), less than 1 km deep.
USGS: 8 km W of Colstrip, Montana
- When
- 10:37 am MDT on 23 July 2021 ()
- Where
- 9 km (5 mi) west of Colstrip, MT · earthquakes near Colstrip
- Montana today
- every earthquake in Montana in the last 24 hours
- Magnitude
- M 3.1 (ml)
- Depth
- 0.0 km below the surface
- Felt
- no reports yet
- Nearest
- Rosebud County, 33 km N
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 1866 days ago
Earthquake alerts for Colstrip, MT
Get a notification in this browser when USGS records an earthquake near Colstrip, MT. No account or email needed.
Alerts are on for .
Not a warning. An alert comes after USGS publishes a quake, usually minutes after the shaking. For early warning use ShakeAlert, through your phone's Wireless Emergency Alerts or the MyShake app.
This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.
At this magnitude and depth, people at rest would likely notice it out to about 42 km (26 mi) from the epicentre. In Colstrip, 9 km away, the estimate is intensity III (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: Lame Deer 29 km, intensity II. Estimated for each town centre; each link is that town's own record.
USGS catalogues this as mining explosion, not an earthquake.
How big was it?
This earthquake released about 1,300 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.1 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 250,000× the energy of this one
- Mineral, Virginia 2011 M 5.8 11,000× the energy of this one
- Magna, Utah 2020 M 5.7 7,900× the energy of this one
- This earthquake M 3.1 about 1,300 lb of TNT
- Around the size people start to feel M 3.0 this one released 1.4× more
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 since 1900 lists no earthquake of M5 or more within 50 km.
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 45.8834, -106.7337. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Rosebud County, MT | 33 km (20 mi) | N | earthquakes near Rosebud County |
| Treasure County, MT | 57 km (35 mi) | NW | earthquakes near Treasure County |
| Big Horn County, MT | 81 km (50 mi) | SW | earthquakes near Big Horn County |
| Custer County, MT | 100 km (62 mi) | ENE | earthquakes near Custer County |
| Powder River County, MT | 106 km (66 mi) | ESE | earthquakes near Powder River County |
| Yellowstone County, MT | 120 km (74 mi) | W | earthquakes near Yellowstone County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
55 earthquakes have been recorded within 50 km since this one.
- 3.0 18 km WSW of Colstrip, Montana
- 3.0 9 km WSW of Colstrip, Montana
- 2.8 13 km W of Colstrip, Montana
- 3.2 12 km NW of Colstrip, Montana
- 3.0 14 km W of Colstrip, Montana
- 3.2 19 km N of Colstrip, Montana
- 3.0 16 km W of Colstrip, Montana
- 3.1 11 km SW of Colstrip, Montana
- 3.2 17 km SW of Colstrip, Montana
- 3.3 12 km SW of Colstrip, Montana
- 2.9 10 km SSE of Colstrip, Montana
- 3.3 15 km SE of Colstrip, Montana
- 2.9 13 km NNW of Muddy, Montana
- 2.9 10 km WSW of Colstrip, Montana
- 3.2 8 km NNE of Colstrip, 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
- The official USGS event page — the source of record for every value above
- Did you feel it? Report it to USGS — reports go to USGS, not to us
- ShakeMap for this event, when USGS has produced one
QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.