Earthquake · reviewed by a seismologist
M 1.5ml
Earthquake near Dillon, MT
No earthquake was likely felt in Dillon in the 24 hours to 1:21 pm MST (20:21 UTC). The last one was M 2.0, 14 km (9 mi) N, at 2:45 pm MDT on 7 May 2026, estimated intensity II (weak) in town. Every earthquake near Dillon
This page: a magnitude 1.5 earthquake was recorded 38 km (23 mi) south-southwest of Dillon, MT, at 8:52 am MDT on 28 August 2021 (14:52 UTC), 6.5 km deep.
USGS: 37 km SSW of Dillon, Montana
- When
- 8:52 am MDT on 28 August 2021 ()
- Where
- 38 km (23 mi) south-southwest of Dillon, MT · earthquakes near Dillon
- Montana today
- every earthquake in Montana in the last 24 hours
- Magnitude
- M 1.5 (ml)
- Depth
- 6.5 km below the surface
- Felt
- no reports yet
- Nearest
- Beaverhead County, 23 km N
- Nearest mapped fault
- Red Rock fault, 2 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 1899 days ago
Earthquake alerts for Dillon, MT
Get a notification in this browser when USGS records an earthquake near Dillon, 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 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 Dillon, 38 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.
How big was it?
This earthquake released about 5.9 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.5 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 2,500,000× the energy of this one
- Magna, Utah 2020 M 5.7 1,800,000× the energy of this one
- Around the size people start to feel M 3.0 160× the energy of this one
- This earthquake M 1.5 about 5.9 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
The largest earthquake within 50 km since 2016 was M 4.6 on 2019-04-09 — about 40,000 times the energy of this one.
Before 2016, the USGS record lists 2 earthquakes of M5 or more within 50 km:
- 5.1 19 km NW of Lima, Montana · 21 km SSE of this epicentre
- 5.1 22 km NW of Lima, Montana · 18 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 44.9293, -112.8905. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Beaverhead County, MT | 23 km (14 mi) | N | earthquakes near Beaverhead County |
| Lemhi County, ID | 78 km (49 mi) | W | earthquakes near Lemhi County |
| Clark County, ID | 83 km (51 mi) | SSE | earthquakes near Clark County |
| Madison County, MT | 88 km (55 mi) | ENE | earthquakes near Madison County |
| Silver Bow County, MT | 109 km (68 mi) | N | earthquakes near Silver Bow County |
| Custer County, ID | 130 km (81 mi) | WSW | earthquakes near Custer 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.
- 2.1 40 km SW of Dillon, Montana
- 1.8 39 km SW of Dillon, Montana
- 1.5 39 km SW of Dillon, Montana
- 1.6 40 km SW of Dillon, Montana
- 1.7 40 km SW of Dillon, Montana
- 2.0 40 km SW of Dillon, Montana
- 2.1 39 km SW of Dillon, Montana
- 1.5 40 km SW of Dillon, Montana
- 1.6 40 km SW of Dillon, Montana
- 1.7 39 km SW of Dillon, Montana
- 2.4 Idaho-Montana border region
- 1.9 38 km SW of Dillon, Montana
- 1.6 40 km SW of Dillon, Montana
- 1.9 40 km SW of Dillon, Montana
- 2.0 40 km SW of Dillon, 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.