M3.7 earthquake 9 km NNW of Great Falls, Montana, United States
A magnitude 3.7 earthquake struck 9 km NNW of Great Falls, Montana, United States at 07:40 local time (13:40 UTC) on 18 Sept 2026, at a depth of 10 km, according to USGS.
176 reports to USGS “Did You Feel It?”
Data: USGS · updated 2026-09-25 19:43 UTC · reviewed
- Magnitude
- 3.7minor
local magnitude (Richter) (ml) - Depth
- 10 km
- Status
- Reviewed
- Origin time
- 2026-09-18 13:40:41 UTC
- Local: 18 Sept 2026, 07:40:41 (America/Denver)
- Epicentre
- 47.581° N, 111.333° W
Circles show this event and others within 30 km from 7 days before to 30 days after. Lines: plate boundaries and GEM active faults. Open on the live map
Nearby places
| Place | Distance | Est. shaking |
|---|---|---|
| Great FallsMontana, United States · pop. 59,638 | 9 km | IVLight |
| Helena Valley SoutheastMontana, United States · pop. 8,227 | 116 km | INot felt |
| HelenaMontana, United States · pop. 32,091 | 123 km | INot felt |
Shaking is an estimate from the intensity prediction equation of Allen, Wald & Worden (2012), not an observation. Local ground and buildings can change it by a level or more. Likely felt out to about 31 km.
Every agency's solution
Agencies locate earthquakes with their own stations and methods, so their numbers differ. We match reports of the same event by time, distance and magnitude and show them side by side. The headline uses USGS, which has been reviewed by an analyst.
| Agency | Magnitude | Depth | Epicentre | Time offset | Status |
|---|---|---|---|---|---|
| USGSheadlineUSGS NEIC via U.S. Geological Survey | 3.7 ml | 10 km | 47.58° N, 111.33° W | – | Reviewed |
How big was it?
Often felt by people at rest close to the epicentre, rarely causes damage.
It released roughly the energy of 5.4 t of TNT. Magnitude is logarithmic: each whole step means about 32 times more energy and 10 times larger waves on a seismogram. Depth matters too: at 10 km this was a shallow earthquake, which is felt more strongly at the surface than a deeper one of the same size.
M3.7 releases about 32× the energy of M2.7, and its waves are about 10× taller on a seismogram. Energy: 5.4 t of TNT vs 169 kg of TNT.
Each square is the energy of one M2.7. Energy from log₁₀E = 1.5M + 4.8.
Aftershocks and nearby activity
No later earthquakes have been recorded within 30 km so far. Aftershock rates usually fall off roughly in proportion to 1/time.
Did you feel it?
Reports from people help show where shaking was strong. They are anonymous and shown here in aggregate.
Event id us7000tiax. First recorded here 28 Sept 2026, 17:32:11 UTC. Solutions: USGS (usgs:us7000tiax). Cite as: SeismoAtlas, “M3.7 earthquake 9 km NNW of Great Falls, Montana, United States”, https://seismoatlas.com/earthquake/us7000tiax-m3-7-earthquake-9-km-nnw-of-great-falls-montana-united-states, data from USGS.
JSON: /api/v1/events/us7000tiax. SeismoAtlas is not an official warning service.