Earthquake · reviewed by a seismologist
M 3.6mwr
22 km N of Spencer, Idaho
Yes. A magnitude 3.6 earthquake was recorded 22 km N of Spencer, Idaho, at 12:57 am MDT on 8 September 2025 (06:57 UTC), 10 km deep.
- When
- Idaho today
- every earthquake in Idaho in the last 24 hours
- Magnitude
- M 3.6 (mwr)
- Depth
- 10 km below the surface
- Felt
- no reports yet
- Measured shaking
- intensity IV (ShakeMap)
- Nearest
- Clark County, 32 km SSW
- Nearest mapped fault
- Centennial fault, 6 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 343 days ago
Earthquake alerts for Saint Anthony, ID
Get a notification in this browser when USGS records an earthquake near Saint Anthony, ID. 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 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 69 km (43 mi) from the epicentre. 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 3.8 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.6 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 45,000× the energy of this one
- Mineral, Virginia 2011 M 5.8 2,000× the energy of this one
- Magna, Utah 2020 M 5.7 1,400× the energy of this one
- This earthquake M 3.6 about 3.8 tons of TNT
- Around the size people start to feel M 3.0 this one released 7.9× 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 4.6 on 2019-04-09 — about 32 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 · 47 km WNW of this epicentre
- 5.0 39 km W of Hebgen Lake Estates, Montana · 46 km ENE 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 44.5629, -112.2270. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Clark County, ID | 32 km (20 mi) | SSW | earthquakes near Clark County |
| Fremont County, ID | 70 km (44 mi) | ESE | earthquakes near Fremont County |
| Beaverhead County, MT | 82 km (51 mi) | NW | earthquakes near Beaverhead County |
| Jefferson County, ID | 85 km (53 mi) | S | earthquakes near Jefferson County |
| Madison County, MT | 88 km (55 mi) | NNE | earthquakes near Madison County |
| Madison County, ID | 97 km (60 mi) | SSE | earthquakes near Madison County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
60 earthquakes have been recorded within 50 km since this one.
- 2.3 49 km NNE of Spencer, Idaho
- 1.8 20 km NE of Spencer, Idaho
- 2.8 19 km NE of Lima, Montana
- 1.8 26 km S of Lima, Montana
- 1.8 44 km NE of Spencer, Idaho
- 1.7 32 km S of Lima, Montana
- 2.6 24 km N of Spencer, Idaho
- 1.6 22 km N of Spencer, Idaho
- 1.8 47 km NE of Spencer, Idaho
- 2.1 2 km SSE of Lima, Montana
- 2.4 23 km N of Spencer, Idaho
- 1.6 23 km N of Spencer, Idaho
- 2.4 22 km N of Spencer, Idaho
- 2.4 23 km N of Spencer, Idaho
- 2.1 23 km N of Spencer, Idaho
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.