Earthquake · reviewed by a seismologist
M 3.5mwr
0 km WSW of Lima, Montana
Yes. A magnitude 3.5 earthquake was recorded 0 km WSW of Lima, Montana, at 1:30 pm MDT on 20 August 2023 (19:30 UTC), 12 km deep. 5 people have reported feeling it to USGS.
- When
- Montana today
- every earthquake in Montana in the last 24 hours
- Magnitude
- M 3.5 (mwr)
- Depth
- 12 km below the surface
- Felt
- 5 reports · strongest reported intensity III
- Measured shaking
- intensity III (ShakeMap)
- Nearest
- Clark County, 43 km SSE
- Nearest mapped fault
- Red Rock fault, 3 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 1110 days ago
Earthquake alerts for Dillon, MT
Get a notification in this browser when USGS records an earthquake near Dillon, MT. 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 62 km (39 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 2.7 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.5 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 63,000× the energy of this one
- Mineral, Virginia 2011 M 5.8 2,800× the energy of this one
- Magna, Utah 2020 M 5.7 2,000× the energy of this one
- This earthquake M 3.5 about 2.7 tons of TNT
- Around the size people start to feel M 3.0 this one released 5.6× 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 45 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 · 19 km NW of this epicentre
- 5.1 22 km NW of Lima, Montana · 23 km NW 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 44.6349, -112.5968. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Clark County, ID | 43 km (27 mi) | SSE | earthquakes near Clark County |
| Beaverhead County, MT | 60 km (37 mi) | NNW | earthquakes near Beaverhead County |
| Madison County, MT | 94 km (58 mi) | NE | earthquakes near Madison County |
| Jefferson County, ID | 96 km (60 mi) | SSE | earthquakes near Jefferson County |
| Fremont County, ID | 100 km (62 mi) | ESE | earthquakes near Fremont County |
| Lemhi County, ID | 107 km (66 mi) | WNW | earthquakes near Lemhi County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
57 earthquakes have been recorded within 50 km since this one.
- 1.6 11 km SE of Lima, Montana
- 1.9 11 km SE of Lima, Montana
- 1.8 11 km SE of Lima, Montana
- 1.7 10 km SE of Lima, Montana
- 2.6 9 km SE of Lima, Montana
- 1.7 25 km E of Leadore, Idaho
- 1.9 12 km NE of Lima, Montana
- 1.5 12 km NE of Lima, Montana
- 1.7 31 km NW of Lima, Montana
- 2.0 22 km NE of Lima, Montana
- 2.3 22 km NE of Lima, Montana
- 1.6 21 km NNW of Lima, Montana
- 1.8 35 km SSW of Lima, Montana
- 2.3 3 km NE of Lima, Montana
- 2.3 17 km NW of Lima, 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.