quarry blast · reviewed by a seismologist
M 1.7ml
Earthquake near Townsend, MT
No earthquake was likely felt in Townsend in the 24 hours to 9:51 am MST (16:51 UTC). The last one was M 1.7, 9 km (5 mi) W, at 2:32 pm MDT on 15 October 2026, estimated intensity II (weak) in town. Every earthquake near Townsend
No: USGS classifies this as a quarry blast, not an earthquake. A magnitude 1.7 quarry blast was recorded 9 km (6 mi) west-southwest of Townsend, MT, at 12:04 pm MDT on 7 September 2021 (18:04 UTC), less than 1 km deep.
USGS: 9 km WSW of Townsend, Montana
- When
- 12:04 pm MDT on 7 September 2021 ()
- Where
- 9 km (6 mi) west-southwest of Townsend, MT · earthquakes near Townsend
- Montana today
- every earthquake in Montana in the last 24 hours
- Magnitude
- M 1.7 (ml)
- Depth
- -2.0 km below the surface
- Felt
- no reports yet
- Nearest
- Broadwater County, 12 km ENE
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 1891 days ago
Earthquake alerts for Townsend, MT
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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 12 km (7 mi) from the epicentre. In Townsend, 9 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.
Likely felt in: Townsend 9 km, intensity II. Estimated for each town centre; each link is that town's own record.
USGS catalogues this as quarry blast, not an earthquake.
How big was it?
This earthquake released about 11 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.7 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 1,400,000× the energy of this one
- Magna, Utah 2020 M 5.7 1,000,000× the energy of this one
- Around the size people start to feel M 3.0 89× the energy of this one
- This earthquake M 1.7 about 11 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 4.2 on 2019-08-16 — about 5,600 times the energy of this one.
Before 2016, the USGS record lists 10 earthquakes of M5 or more within 50 km; the five largest:
- 6.6 The 1925 Clarkston Valley, Montana Earthquake · 26 km SSE of this epicentre
- 6.4 Clarkston Valley, Montana (Aftershock) · 26 km SSE of this epicentre
- 6.1 The 1935 Helena, Montana Earthquakes (Mainshock) · 33 km N of this epicentre
- 5.9 2 km ENE of Helena, Montana · 44 km NW of this epicentre
- 5.9 The 1935 Helena, Montana Earthquakes (Largest Aftershock) · 32 km NNW 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 46.2920, -111.6380. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Broadwater County, MT | 12 km (7 mi) | ENE | earthquakes near Broadwater County |
| Jefferson County, MT | 37 km (23 mi) | WSW | earthquakes near Jefferson County |
| Meagher County, MT | 64 km (40 mi) | ENE | earthquakes near Meagher County |
| Silver Bow County, MT | 90 km (56 mi) | WSW | earthquakes near Silver Bow County |
| Gallatin County, MT | 94 km (58 mi) | SSE | earthquakes near Gallatin County |
| Lewis and Clark County, MT | 108 km (67 mi) | NNW | earthquakes near Lewis and Clark County |
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.
- 1.7 2 km NW of Montana City, Montana
- 1.5 18 km SSW of Radersburg, Montana
- 1.6 7 km WSW of Townsend, Montana
- 1.6 8 km WSW of Townsend, Montana
- 1.6 Western Montana
- 1.6 6 km NNW of Logan, Montana
- 1.7 5 km W of Ponderosa Pines, Montana
- 2.3 3 km WSW of Ponderosa Pines, Montana
- 2.1 3 km SW of Ponderosa Pines, Montana
- 2.0 11 km WSW of Radersburg, Montana
- 2.4 3 km WSW of Ponderosa Pines, Montana
- 1.8 5 km NW of Helena Valley Southeast, Montana
- 1.7 Western Montana
- 2.1 3 km NW of Elkhorn, Montana
- 1.6 4 km WNW of Elkhorn, 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.