QuakeIndex

Earthquake · reviewed by a seismologist

M 1.7md

Earthquake near Tremonton, UT

No earthquake was likely felt in Tremonton in the 24 hours to 9:40 pm MST (04:40 UTC). The last one was M 4.7, 140 km (87 mi) SE, at 7:49 am MST on 22 January 2026, estimated intensity II (weak) in town; 4,305 felt reports to USGS. Every earthquake near Tremonton

This page: a magnitude 1.7 earthquake was recorded 46 km (28 mi) west-northwest of Tremonton, UT, at 5:51 pm MDT on 28 September 2021 (23:51 UTC), 1.6 km deep. 4 people have reported feeling it to USGS.

USGS: 7 km SE of Snowville, Utah

5:51 pm MDT, Sep 28, 2021 · · 1.6 km deep · released about 9.3 lb of TNT

Every earthquake near Tremonton Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Oneida County 32 kmBox Elder County 47 kmFranklin County 74 kmCache County 77 kmPower County 88 kmCassia County 91 kmBannock County 93 kmWeber County 96 kmDavis County 104 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
5:51 pm MDT on 28 September 2021 ()
Where
46 km (28 mi) west-northwest of Tremonton, UT · earthquakes near Tremonton
Magnitude
M 1.7 (md)
Depth
1.6 km below the surface
Felt
4 reports · strongest reported intensity IV
Measured shaking
intensity IV (ShakeMap)
Nearest
Oneida County, 32 km NNE
Nearest mapped fault
North Promontory fault, 8 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 1775 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

At this magnitude and depth, people at rest would likely notice it out to about 12 km (7 mi) from the epicentre. In Tremonton, 46 km away, the estimate is intensity I (not felt). 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 9.3 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.7 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 1,600,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 1,100,000× the energy of this one
  3. Around the size people start to feel M 3.0 100× the energy of this one
  4. This earthquake M 1.7 about 9.3 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 7 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.6 The 1934 Hansel Valley, Utah Earthquake · 31 km SSW of this epicentre
  2. 6.1 17 km NE of Snowville, Utah · 18 km NNE of this epicentre
  3. 5.9 35 km SSW of Howell, Utah · 43 km S of this epicentre
  4. 5.6 Hansel Valley, Utah · 14 km SSW of this epicentre
  5. 5.2 27 km SW of Thatcher, Utah · 48 km SSE 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 41.9153, -112.6443. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Oneida County, ID 32 km (20 mi) NNE earthquakes near Oneida County
Box Elder County, UT 47 km (29 mi) SW earthquakes near Box Elder County
Franklin County, ID 74 km (46 mi) ENE earthquakes near Franklin County
Cache County, UT 77 km (48 mi) ESE earthquakes near Cache County
Power County, ID 88 km (55 mi) N earthquakes near Power County
Cassia County, ID 91 km (56 mi) WNW earthquakes near Cassia County

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

Aftershocks so far

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

  1. 1.7 10 km SSW of Malad City, Idaho
  2. 1.7 11 km SSW of Malad City, Idaho
  3. 1.5 9 km SSW of Malad City, Idaho
  4. 1.8 11 km SSW of Malad City, Idaho
  5. 2.4 17 km ENE of Snowville, Utah
  6. 1.6 11 km SSW of Malad City, Idaho
  7. 1.7 Utah
  8. 1.6 Utah
  9. 1.8 13 km NNE of Howell, Utah
  10. 2.1 12 km NNE of Howell, Utah
  11. 1.6 Utah
  12. 1.9 5 km W of Garland, Utah
  13. 1.5 10 km SSW of Malad City, Idaho
  14. 2.1 2 km SSW of Howell, Utah
  15. 1.7 9 km E of Snowville, Utah

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.