Earthquake · reviewed by a seismologist
M 2.5ml
Earthquake near Alamosa, CO
No earthquake was likely felt in Alamosa in the 24 hours to 3:37 am MST (10:37 UTC). The last one was M 3.4, 89 km (55 mi) ESE, at 3:34 am MST on 8 November 2026, estimated intensity II (weak) in town; 2 felt reports to USGS. Every earthquake near Alamosa
This page: a magnitude 2.5 earthquake was recorded 41 km (25 mi) east-northeast of Alamosa, CO, at 10:41 pm MST on 21 November 2018 (05:41 UTC), 5.3 km deep.
USGS: 25 km N of Blanca, Colorado
- When
- 10:41 pm MST on 21 November 2018 ()
- Where
- 41 km (25 mi) east-northeast of Alamosa, CO · earthquakes near Alamosa
- Magnitude
- M 2.5 (ml)
- Depth
- 5.3 km below the surface
- Felt
- no reports yet
- Nearest
- Alamosa County, 29 km WSW
- Nearest mapped fault
- Northern Sangre de Cristo fault, 5 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 2839 days ago
Earthquake alerts for Alamosa, CO
Get a notification in this browser when USGS records an earthquake near Alamosa, 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 21 km (13 mi) from the epicentre. In Alamosa, 41 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.
How big was it?
This earthquake released about 170 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.5 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 89,000× the energy of this one
- Magna, Utah 2020 M 5.7 63,000× the energy of this one
- Around the size people start to feel M 3.0 5.6× the energy of this one
- This earthquake M 2.5 about 170 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 37.6644, -105.4787. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Alamosa County, CO | 29 km (18 mi) | WSW | earthquakes near Alamosa County |
| Costilla County, CO | 43 km (27 mi) | S | earthquakes near Costilla County |
| Huerfano County, CO | 46 km (28 mi) | E | earthquakes near Huerfano County |
| Custer County, CO | 50 km (31 mi) | N | earthquakes near Custer County |
| Saguache County, CO | 78 km (48 mi) | WNW | earthquakes near Saguache County |
| Conejos County, CO | 79 km (49 mi) | SW | earthquakes near Conejos 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.
- 1.6 22 km N of Blanca, Colorado
- 2.3 22 km N of Blanca, Colorado
- 1.6 Colorado
- 1.7 24 km N of Blanca, Colorado
- 2.0 25 km N of Blanca, Colorado
- 1.5 21 km N of Blanca, Colorado
- 1.7 25 km N of Blanca, Colorado
- 1.7 23 km N of Blanca, Colorado
- 1.5 24 km N of Blanca, Colorado
- 1.8 24 km N of Blanca, Colorado
- 1.6 24 km N of Blanca, Colorado
- 1.9 26 km N of Blanca, Colorado
- 1.6 23 km N of Blanca, Colorado
- 2.2 24 km N of Blanca, Colorado
- 1.8 24 km N of Blanca, 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.