Earthquake · reviewed by a seismologist
M 3.9mwr
18 km SSW of Weston, CO
Yes. A magnitude 3.9 earthquake was recorded 18 km SSW of Weston, CO, at 10:56 am MDT on 23 August 2016 (16:56 UTC), 3.6 km deep. 10 people have reported feeling it to USGS.
- When
- Magnitude
- M 3.9 (mwr)
- Depth
- 3.6 km below the surface
- Felt
- 10 reports · strongest reported intensity III
- Measured shaking
- intensity IV (ShakeMap)
- USGS impact alert
- green
- Nearest
- Colfax County, 50 km SSE
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 3644 days ago
Earthquake alerts for Trinidad, CO
Get a notification in this browser when USGS records an earthquake near Trinidad, CO. 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 431 km (268 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.
Likely felt in: Trinidad 44 km, intensity III · Raton 46 km, intensity III. Estimated for each town centre; each link is that town's own record.
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 in our catalogue was M 4.0 on 2016-02-06 — about 1.4 times the energy of this one.
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 36.9863, -104.9449. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Colfax County, NM | 50 km (31 mi) | SSE | earthquakes near Colfax County |
| Costilla County, CO | 54 km (33 mi) | NW | earthquakes near Costilla County |
| Taos County, NM | 77 km (48 mi) | SW | earthquakes near Taos County |
| Huerfano County, CO | 78 km (48 mi) | N | earthquakes near Huerfano County |
| Las Animas County, CO | 88 km (55 mi) | ENE | earthquakes near Las Animas County |
| Alamosa County, CO | 99 km (61 mi) | NW | earthquakes near Alamosa County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
58 earthquakes have been recorded within 50 km since this one.
- 1.7 14 km SSE of Stonewall Gap, Colorado
- 2.1 16 km SSE of Stonewall Gap, Colorado
- 2.8 16 km SSE of Stonewall Gap, Colorado
- 1.6 15 km SSE of Stonewall Gap, Colorado
- 3.1 15 km SSE of Stonewall Gap, Colorado
- 1.5 13 km SSE of Stonewall Gap, Colorado
- 3.8 15 km SSE of Stonewall Gap, Colorado
- 1.7 6 km WNW of El Moro, Colorado
- 2.1 17 km SSE of Stonewall Gap, Colorado
- 1.5 5 km SSW of Weston, Colorado
- 2.0 12 km SW of Weston, Colorado
- 1.5 11 km SW of Weston, Colorado
- 2.7 31 km SSW of Weston, Colorado
- 1.8 14 km SSW of Aguilar, Colorado
- 1.5 15 km SW of Aguilar, Colorado
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.