mining explosion · reviewed by a seismologist
M 2.8ml
Earthquake near Sleepy Hollow, WY
No earthquake was likely felt in Sleepy Hollow in the 24 hours to 12:19 am MST (07:19 UTC). The last one was M 3.4, 38 km (23 mi) S, at 2:13 pm MDT on 6 July 2026, estimated intensity II (weak) in town. Every earthquake near Sleepy Hollow
No: USGS classifies this as a mining explosion, not an earthquake. A magnitude 2.8 mining explosion was recorded 21 km (13 mi) south-southeast of Sleepy Hollow, WY, at 9:25 am MDT on 23 July 2021 (15:25 UTC), less than 1 km deep.
USGS: 21 km SSE of Sleepy Hollow, Wyoming
- When
- 9:25 am MDT on 23 July 2021 ()
- Where
- 21 km (13 mi) south-southeast of Sleepy Hollow, WY · earthquakes near Sleepy Hollow
- Magnitude
- M 2.8 (ml)
- Depth
- 0.0 km below the surface
- Felt
- no reports yet
- Nearest
- Campbell County, 21 km NW
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 1866 days ago
Earthquake alerts for Sleepy Hollow, WY
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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 27 km (17 mi) from the epicentre. In Sleepy Hollow, 21 km away, the estimate is intensity II (weak). 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.
Earthquakes near other towns within 30 km: Antelope Valley-Crestview, Gillette.
USGS catalogues this as mining explosion, not an earthquake.
How big was it?
This earthquake released about 480 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.8 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 32,000× the energy of this one
- Magna, Utah 2020 M 5.7 22,000× the energy of this one
- Around the size people start to feel M 3.0 2× the energy of this one
- This earthquake M 2.8 about 480 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
The largest earthquake within 50 km since 2016 was M 4.0 on 2021-07-20 — about 63 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 44.0553, -105.3278. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Campbell County, WY | 21 km (13 mi) | NW | earthquakes near Campbell County |
| Weston County, WY | 65 km (40 mi) | ESE | earthquakes near Weston County |
| Crook County, WY | 85 km (53 mi) | NE | earthquakes near Crook County |
| Johnson County, WY | 101 km (63 mi) | W | earthquakes near Johnson County |
| Converse County, WY | 120 km (75 mi) | S | earthquakes near Converse County |
| Niobrara County, WY | 130 km (81 mi) | SSE | earthquakes near Niobrara County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
59 earthquakes have been recorded within 50 km since this one.
- 3.2 22 km SE of Wright, Wyoming
- 3.0 12 km E of Wright, Wyoming
- 3.1 15 km ESE of Wright, Wyoming
- 3.1 22 km ENE of Wright, Wyoming
- 3.2 19 km SE of Wright, Wyoming
- 3.2 Wyoming
- 3.0 19 km ENE of Wright, Wyoming
- 3.3 27 km NE of Wright, Wyoming
- 3.2 12 km SE of Wright, Wyoming
- 2.9 14 km SSE of Wright, Wyoming
- 3.3 24 km SE of Wright, Wyoming
- 3.0 26 km SSE of Antelope Valley-Crestview, Wyoming
- 3.0 Wyoming
- 3.1 11 km E of Wright, Wyoming
- 3.2 20 km SE of Wright, 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.