Earthquake · reviewed by a seismologist
M 3.9mwr
51 km S of Ten Sleep, Wyoming
Yes. A magnitude 3.9 earthquake was recorded 51 km S of Ten Sleep, Wyoming, at 6:22 am MDT on 13 April 2021 (12:22 UTC), 12 km deep. 25 people have reported feeling it to USGS.
- When
- Magnitude
- M 3.9 (mwr)
- Depth
- 12 km below the surface
- Felt
- 25 reports · strongest reported intensity III
- Measured shaking
- intensity IV (ShakeMap)
- Nearest
- Washakie County, 42 km NW
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 1971 days ago
Earthquake alerts for Worland, WY
Get a notification in this browser when USGS records an earthquake near Worland, WY. 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 89 km (55 mi) from the epicentre. 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 11 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.9 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 16,000× the energy of this one
- Mineral, Virginia 2011 M 5.8 710× the energy of this one
- Magna, Utah 2020 M 5.7 500× the energy of this one
- This earthquake M 3.9 about 11 tons of TNT
- Around the size people start to feel M 3.0 this one released 22× 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
The largest earthquake within 50 km since 2016 was M 4.0 on 2017-11-03 — about 1.4 times the energy of this one.
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 43.5729, -107.3683. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Washakie County, WY | 42 km (26 mi) | NW | earthquakes near Washakie County |
| Johnson County, WY | 82 km (51 mi) | NE | earthquakes near Johnson County |
| Natrona County, WY | 82 km (51 mi) | SE | earthquakes near Natrona County |
| Hot Springs County, WY | 87 km (54 mi) | W | earthquakes near Hot Springs County |
| Fremont County, WY | 116 km (72 mi) | WSW | earthquakes near Fremont County |
| Big Horn County, WY | 117 km (73 mi) | NNW | earthquakes near Big Horn County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
5 earthquakes have been recorded within 50 km since this one.
- 2.6 10 km SSE of Ten Sleep, Wyoming
- 3.7 Wyoming
- 2.3 56 km ESE of East Thermopolis, Wyoming
- 2.6 28 km SSE of Ten Sleep, Wyoming
- 3.6 43 km S of Ten Sleep, Wyoming
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.