Earthquake · reviewed by a seismologist
M 3.3ml
Earthquake near Polson, MT
No earthquake was likely felt in Polson in the 24 hours to 4:21 pm MST (23:21 UTC). The last one was M 3.0, 32 km (20 mi) ENE, at 9:19 pm MDT on 14 March 2024, estimated intensity II (weak) in town; 1 felt report to USGS. Every earthquake near Polson
This page: a magnitude 3.3 earthquake was recorded 30 km (18 mi) east-northeast of Polson, MT, at 11:18 am MDT on 11 April 2020 (17:18 UTC), 16 km deep. 8 people have reported feeling it to USGS.
USGS: 16 km SSE of Swan Lake, Montana
- When
- 11:18 am MDT on 11 April 2020 ()
- Where
- 30 km (18 mi) east-northeast of Polson, MT · earthquakes near Polson
- Montana today
- every earthquake in Montana in the last 24 hours
- Magnitude
- M 3.3 (ml)
- Depth
- 16 km below the surface
- Felt
- 8 reports · strongest reported intensity IV
- Nearest
- Lake County, 27 km SW
- Nearest mapped fault
- Mission fault, 16 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 1456 days ago
Earthquake alerts for Polson, MT
Get a notification in this browser when USGS records an earthquake near Polson, 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 49 km (30 mi) from the epicentre. In Polson, 30 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: Polson 30 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 1.3 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.3 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 130,000× the energy of this one
- Mineral, Virginia 2011 M 5.8 5,600× the energy of this one
- Magna, Utah 2020 M 5.7 4,000× the energy of this one
- This earthquake M 3.3 about 1.3 tons of TNT
- Around the size people start to feel M 3.0 this one released 2.8× 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 one earthquake of M5 or more within 50 km:
- 5.5 Western Montana · 24 km N 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 47.7810, -113.7888. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Lake County, MT | 27 km (17 mi) | SW | earthquakes near Lake County |
| Flathead County, MT | 60 km (38 mi) | NNW | earthquakes near Flathead County |
| Missoula County, MT | 84 km (52 mi) | S | earthquakes near Missoula County |
| Sanders County, MT | 104 km (65 mi) | W | earthquakes near Sanders County |
| Teton County, MT | 113 km (70 mi) | E | earthquakes near Teton County |
| Glacier County, MT | 119 km (74 mi) | NNE | earthquakes near Glacier County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
56 earthquakes have been recorded within 50 km since this one.
- 2.1 20 km E of Finley Point, Montana
- 1.8 17 km E of Condon, Montana
- 1.7 19 km E of Finley Point, Montana
- 1.6 16 km NNE of Condon, Montana
- 1.6 6 km SW of Woods Bay, Montana
- 1.7 1 km S of Woods Bay, Montana
- 2.1 6 km SW of Woods Bay, Montana
- 1.6 6 km SW of Woods Bay, Montana
- 1.8 14 km WNW of Condon, Montana
- 2.1 27 km E of Swan Lake, Montana
- 2.5 24 km E of Swan Lake, Montana
- 2.4 27 km E of Swan Lake, Montana
- 2.3 10 km NNW of Swan Lake, Montana
- 1.7 15 km NNE of Bigfork, Montana
- 3.0 17 km SSE of Swan Lake, 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.