QuakeIndex

Earthquake · reviewed by a seismologist

M 1.5ml

Earthquake near Polson, MT

USGS: 10 km WNW of Condon, Montana

9:51 pm MST, Jan 27, 2020 · · 18 km deep · released about 5.6 lb of TNT

Every earthquake near Polson Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Lake County 21 kmMissoula County 60 kmFlathead County 83 kmSanders County 103 kmPowell County 105 kmMineral County 106 kmTeton County 119 kmLewis and Clark County 120 km
Distance rings around the epicentre, with the nearest towns at their true direction and later quakes as coloured dots. Not a shaking map — see the USGS ShakeMap for that.
When
9:51 pm MST on 27 January 2020 ()
Where
29 km (18 mi) ESE of Polson, MT · earthquakes near Polson
Magnitude
M 1.5 (ml)
Depth
18 km below the surface
Felt
no reports yet
Nearest
Lake County, 21 km WNW
Nearest mapped fault
Mission fault, 14 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 2439 days ago

A magnitude 1.5 earthquake was recorded 29 km (18 mi) ESE of Polson, MT, at 9:51 pm MST on 27 January 2020 (04:51 UTC). This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

Earthquakes near other towns within 30 km: Ronan, Pablo.

How big was it?

This earthquake released about 5.6 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.5 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 2,700,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 1,900,000× the energy of this one
  3. Around the size people start to feel M 3.0 170× the energy of this one
  4. This earthquake M 1.5 about 5.6 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

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:

  1. 5.5 Western Montana · 48 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 47.5680, -113.8307. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Lake County, MT 21 km (13 mi) WNW earthquakes near Lake County
Missoula County, MT 60 km (37 mi) S earthquakes near Missoula County
Flathead County, MT 83 km (51 mi) NNW earthquakes near Flathead County
Sanders County, MT 103 km (64 mi) WNW earthquakes near Sanders County
Powell County, MT 105 km (65 mi) SE earthquakes near Powell County
Mineral County, MT 106 km (66 mi) WSW earthquakes near Mineral 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. 1.8 14 km WNW of Condon, Montana
  2. 1.5 5 km NE of Saint Ignatius, Montana
  3. 2.1 27 km E of Swan Lake, Montana
  4. 2.5 24 km E of Swan Lake, Montana
  5. 2.4 27 km E of Swan Lake, Montana
  6. 1.8 17 km E of Arlee, Montana
  7. 3.0 17 km SSE of Swan Lake, Montana
  8. 1.6 9 km ENE of Ronan, Montana
  9. 1.5 6 km SW of Condon, Montana
  10. 1.6 15 km ESE of Condon, Montana
  11. 1.6 4 km W of Ravalli, Montana
  12. 1.5 8 km ESE of Woods Bay, Montana
  13. 2.1 18 km SSE of Swan Lake, Montana
  14. 1.8 17 km SSW of Condon, Montana
  15. 1.9 17 km SSW of Condon, 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

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.