Earthquake near Clancy, 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 74 km (46 mi) from the epicentre. In Clancy, 6 km away, the estimate is intensity IV (light). 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: Helena 10 km, intensity III · Boulder 30 km, intensity III · Townsend 44 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 4.8 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.7 would have released about 32 times as much.

1. Northridge, California 1994 M 6.7 35,000× the energy of this one
2. Mineral, Virginia 2011 M 5.8 1,600× the energy of this one
3. Magna, Utah 2020 M 5.7 1,100× the energy of this one
4. This earthquake M 3.7 about 4.8 tons of TNT
5. Around the size people start to feel M 3.0 this one released 10× 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 lists 4 earthquakes of M5 or more within 50 km:

1. 6.1 The 1935 Helena, Montana Earthquakes (Mainshock) · 31 km ENE of this epicentre Oct 19, 1935
2. 5.9 2 km ENE of Helena, Montana · 11 km NNE of this epicentre Oct 12, 1935
3. 5.9 The 1935 Helena, Montana Earthquakes (Largest Aftershock) · 15 km ENE of this epicentre Oct 31, 1935
4. 5.0 2 km ENE of Helena, Montana · 11 km NNE of this epicentre Nov 28, 1935

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 46.5037, -112.0352. Map © OpenStreetMap contributors.

Nearby places

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

Aftershocks so far

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

1. 3.8 4 km ESE of Avon, Montana 03:02 UTC
2. 3.4 9 km ENE of Marysville, Montana 02:26 UTC
3. 2.0 2 km NE of The Silos, Montana 22:47 UTC
4. 2.2 2 km NE of The Silos, Montana 22:12 UTC
5. 1.8 21 km SW of Craig, Montana 21:37 UTC
6. 1.6 22 km NE of Helena Valley Northeast, Montana 09:01 UTC
7. 1.6 3 km NNW of Helena Valley Northwest, Montana 05:06 UTC
8. 1.5 2 km NE of South Hills, Montana 17:17 UTC
9. 1.5 3 km NW of Helena Valley Northwest, Montana 06:06 UTC
10. 1.6 7 km WSW of Elliston, Montana 11:34 UTC
11. 1.7 2 km ENE of South Hills, Montana 22:54 UTC
12. 1.7 9 km NW of Radersburg, Montana 13:00 UTC
13. 2.7 8 km WSW of Elliston, MT 20:10 UTC
14. 1.8 7 km WSW of Elliston, Montana 07:10 UTC
15. 1.8 12 km N of Helena Valley Northeast, Montana 07:03 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 21:50 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.