Earthquake · reviewed by a seismologist
M 1.8md
Earthquake near Windsor, CA
No earthquake was likely felt in Windsor in the 24 hours to 8:16 am PST (16:16 UTC). The last one was M 3.0, 30 km (18 mi) N, at 11:06 pm PDT on 14 October 2026, estimated intensity II (weak) in town; 1 felt report to USGS. Every earthquake near Windsor
This page: a magnitude 1.8 earthquake was recorded 10 km (6 mi) north-northeast of Windsor, CA, at 12:22 am PDT on 31 August 2021 (07:22 UTC), 6.7 km deep.
USGS: 10km NNE of Windsor, CA
20 km (12 mi) NNW of Santa Rosa, CA
- When
- 12:22 am PDT on 31 August 2021 ()
- Where
- 10 km (6 mi) north-northeast of Windsor, CA · earthquakes near Windsor
- Magnitude
- M 1.8 (md)
- Depth
- 6.7 km below the surface
- Felt
- no reports yet
- Nearest
- Sonoma County, 18 km SW
- Nearest mapped fault
- Maacama fault, 2 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 1892 days ago
Earthquake alerts for Windsor, CA
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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 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 11 km (7 mi) from the epicentre. In Windsor, 10 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.
Likely felt in: Windsor 10 km, intensity II · Healdsburg 10 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 14 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.8 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 1,100,000× the energy of this one
- Magna, Utah 2020 M 5.7 760,000× the energy of this one
- Around the size people start to feel M 3.0 68× the energy of this one
- This earthquake M 1.8 about 14 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 5.0 on 2016-12-14 — about 70,000 times the energy of this one.
Before 2016, the USGS record lists 2 earthquakes of M5 or more within 50 km:
- 5.3 3 km E of Bloomfield, California · 34 km S of this epicentre
- 5.3 Northern California · 34 km S 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 38.6195, -122.7580. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Sonoma County, CA | 18 km (11 mi) | SW | earthquakes near Sonoma County |
| Napa County, CA | 40 km (25 mi) | ESE | earthquakes near Napa County |
| Lake County, CA | 54 km (34 mi) | N | earthquakes near Lake County |
| Marin County, CA | 63 km (39 mi) | S | earthquakes near Marin County |
| Yolo County, CA | 75 km (46 mi) | E | earthquakes near Yolo County |
| Colusa County, CA | 77 km (48 mi) | NE | earthquakes near Colusa 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.
- 1.8 4km NW of The Geysers, CA
- 2.2 8km NW of The Geysers, CA
- 1.5 8km NW of The Geysers, CA
- 1.8 10km WNW of The Geysers, CA
- 2.1 5km WNW of Cobb, CA
- 1.7 8km W of Cobb, CA
- 1.7 4km W of Cobb, CA
- 1.5 9km NE of Santa Rosa, CA
- 1.5 5km WNW of The Geysers, CA
- 1.9 10km NW of The Geysers, CA
- 1.6 2km N of The Geysers, CA
- 1.5 1km NNW of The Geysers, CA
- 1.9 3km SSW of Anderson Springs, CA
- 1.5 1km E of The Geysers, CA
- 1.8 2km SSW of Cobb, CA
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.