Earthquake near Polson, MT

USGS: 8 km ESE of Camas, Montana

1:21 pm MDT, Mar 31, 2019 · 2019-03-31 19:21 UTC · 0.9 km deep · released about 6.6 lb of TNT

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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: 1:21 pm MDT on 31 March 2019 (2019-03-31 19:21 UTC)
Where: 33 km (20 mi) WSW of Polson, MT · earthquakes near Polson
Magnitude: M 1.6 (ml)
Depth: 0.9 km below the surface
Felt: no reports yet
Nearest: Lake County, 37 km ENE
Status: Reviewed by a seismologist

USGS · last changed by USGS 2742 days ago · we first saw it 2742 days ago

A magnitude 1.6 earthquake was recorded 33 km (20 mi) WSW of Polson, MT, at 1:21 pm MDT on 31 March 2019 (19:21 UTC). This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

Earthquakes near other towns within 30 km: Plains.

How big was it?

This earthquake released about 6.6 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.6 would have released about 32 times as much.

Mineral, Virginia 2011 M 5.8 2,300,000× the energy of this one
Magna, Utah 2020 M 5.7 1,600,000× the energy of this one
Around the size people start to feel M 3.0 140× the energy of this one
This earthquake M 1.6 about 6.6 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 since 1900 lists no earthquake of M5 or more within 50 km.

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

Map loads when it scrolls into view

Epicentre 47.5777, -114.5632. Map © OpenStreetMap contributors.

Nearby places

Place	Distance	Direction from the epicentre
Lake County, MT	37 km (23 mi)	ENE	earthquakes near Lake County
Sanders County, MT	50 km (31 mi)	WNW	earthquakes near Sanders County
Mineral County, MT	63 km (39 mi)	SW	earthquakes near Mineral County
Missoula County, MT	79 km (49 mi)	SE	earthquakes near Missoula County
Flathead County, MT	88 km (55 mi)	NNE	earthquakes near Flathead County
Shoshone County, ID	103 km (64 mi)	WSW	earthquakes near Shoshone County

Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.

Aftershocks so far

35 earthquakes have been recorded within 50 km since this one.

2.4 9 km SSW of Bear Dance, Montana 19:06 UTC
1.6 1 km SSW of Dayton, Montana 18:23 UTC
2.1 5 km WNW of Saint Ignatius, Montana 03:08 UTC
2.2 7 km WNW of Lake Mary Ronan, Montana 16:50 UTC
1.7 7 km WNW of Lake Mary Ronan, Montana 15:35 UTC
1.8 6 km WNW of Lake Mary Ronan, Montana 13:59 UTC
1.6 16 km WSW of Kerr, Montana 11:44 UTC
1.5 5 km NE of Saint Ignatius, Montana 08:42 UTC
2.0 17 km W of Niarada, Montana 20:28 UTC
1.6 4 km W of Ravalli, Montana 03:04 UTC
1.6 4 km NW of Niarada, Montana 17:27 UTC
1.8 17 km WNW of Niarada, Montana 22:41 UTC
1.8 6 km NNW of Plains, Montana 12:42 UTC
1.6 Western Montana 08:39 UTC
2.5 18 km WNW of Dixon, Montana 06:44 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 01:37 UTC. 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.