Earthquake near Three Forks, MT

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 Three Forks, 6 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: Three Forks 6 km, intensity III · Manhattan 21 km, intensity II · Belgrade 36 km, intensity II · Whitehall 41 km, intensity II · Townsend 42 km, intensity II. Estimated for each town centre; each link is that town's own record.

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.

1. Northridge, California 1994 M 6.7 250,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 11,000× the energy of this one
3. Magna, Utah 2020 M 5.7 7,900× the energy of this one
4. This earthquake M 3.1 about 1,300 lb of TNT
5. 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

The largest earthquake within 50 km since 2016 was M 4.2 on 2019-08-16 — about 45 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 · 16 km NNE of this epicentre Jun 28, 1925
2. 6.4 Clarkston Valley, Montana (Aftershock) · 16 km NNE of this epicentre Jun 28, 1925
3. 5.5 Clarkston Valley, Montana (Aftershock) · 16 km NNE of this epicentre Jun 28, 1925
4. 5.5 Clarkston Valley, Montana (Aftershock) · 16 km NNE of this epicentre Jun 28, 1925
5. 5.5 Clarkston Valley, Montana (Aftershock) · 16 km NNE of this epicentre Jul 10, 1925

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 45.9472, -111.5731. Map © OpenStreetMap contributors.

Nearby places

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

Aftershocks so far

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

1. 1.9 9 km W of Townsend, Montana 19:00 UTC
2. 1.6 5 km SSW of Willow Creek, Montana 19:46 UTC
3. 2.1 3 km WNW of Pony, Montana 13:59 UTC
4. 1.8 5 km NNW of Logan, Montana 19:46 UTC
5. 1.5 Western Montana 16:12 UTC
6. 2.0 3 km WNW of Pony, Montana 05:17 UTC
7. 1.8 18 km N of Ennis, Montana 16:53 UTC
8. 2.5 3 km WNW of Pony, Montana 15:18 UTC
9. 1.6 Western Montana 16:48 UTC
10. 1.6 3 km WSW of Ponderosa Pines, Montana 06:51 UTC
11. 1.6 8 km W of Townsend, Montana 18:10 UTC
12. 1.7 6 km WSW of Townsend, Montana 19:31 UTC
13. 1.6 14 km ESE of Harrison, Montana 16:24 UTC
14. 1.5 10 km WNW of Four Corners, Montana 13:44 UTC
15. 1.6 5 km SE of Three Forks, Montana 10:08 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 14:45 UTC. 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.