QuakeIndex

Earthquake · reviewed by a seismologist

M 1.8ml

Earthquake near Salmon, ID

USGS: 21 km N of Salmon, Idaho

5:43 am MDT, Aug 31, 2018 · · 3.9 km deep · released about 16 lb of TNT

Every earthquake near Salmon Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Lemhi County 49 kmBeaverhead County 81 kmRavalli County 81 kmDeer Lodge County 99 kmSilver Bow County 111 kmGranite 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
5:43 am MDT on 31 August 2018 ()
Where
21 km (13 mi) N of Salmon, ID · earthquakes near Salmon
Magnitude
M 1.8 (ml)
Depth
3.9 km below the surface
Felt
no reports yet
Nearest
Lemhi County, 49 km S
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2954 days ago

A magnitude 1.8 earthquake was recorded 21 km (13 mi) N of Salmon, ID, at 5:43 am MDT on 31 August 2018 (11:43 UTC). This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

How big was it?

This earthquake released about 16 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.8 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 930,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 660,000× the energy of this one
  3. Around the size people start to feel M 3.0 59× the energy of this one
  4. This earthquake M 1.8 about 16 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

Epicentre 45.3662, -113.8745. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Lemhi County, ID 49 km (30 mi) S earthquakes near Lemhi County
Beaverhead County, MT 81 km (50 mi) ESE earthquakes near Beaverhead County
Ravalli County, MT 81 km (50 mi) NNW earthquakes near Ravalli County
Deer Lodge County, MT 99 km (62 mi) NE earthquakes near Deer Lodge County
Silver Bow County, MT 111 km (69 mi) ENE earthquakes near Silver Bow County
Granite County, MT 120 km (74 mi) NNE earthquakes near Granite County

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

Aftershocks so far

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

  1. 2.7 10 km WNW of Wisdom, Montana
  2. 2.4 7 km W of Wisdom, Montana
  3. 1.9 6 km NW of Wisdom, Montana
  4. 1.6 4 km WSW of Wisdom, Montana
  5. 1.9 8 km WNW of Wisdom, Montana
  6. 3.4 12 km WNW of Wisdom, Montana
  7. 1.7 32 km WSW of Salmon, Idaho
  8. 1.5 32 km WSW of Salmon, Idaho
  9. 2.0 10 km WNW of Wisdom, Montana
  10. 1.6 12 km WNW of Wisdom, Montana
  11. 1.8 12 km WNW of Wisdom, Montana
  12. 1.5 6 km ESE of Salmon, Idaho
  13. 1.6 4 km NNE of Salmon, Idaho
  14. 1.7 12 km WNW of Wisdom, Montana
  15. 2.8 25 km NNW of Salmon, 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

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