Earthquake · reviewed by a seismologist
M 1.9md
Earthquake near Vacaville, CA
No earthquake was likely felt in Vacaville in the 24 hours to 1:38 am PST (09:38 UTC). The last one was M 3.8, 68 km (42 mi) SSW, at 8:30 am PDT on 13 August 2026, estimated intensity II (weak) in town; 7,876 felt reports to USGS. Every earthquake near Vacaville
This page: a magnitude 1.9 earthquake was recorded 15 km (9 mi) southeast of Vacaville, CA, at 11:39 pm PDT on 21 April 2021 (06:39 UTC), 23 km deep.
USGS: 10km SSE of Elmira, CA
13 km (8 mi) SE of Vacaville, CA · 47 km (29 mi) SW of Sacramento, CA
- When
- 11:39 pm PDT on 21 April 2021 ()
- Where
- 15 km (9 mi) southeast of Vacaville, CA · earthquakes near Vacaville
- Magnitude
- M 1.9 (md)
- Depth
- 23 km below the surface
- Felt
- no reports yet
- Nearest
- Solano County, 7 km W
- Nearest mapped fault
- Great Valley thrust fault system, 8 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 2028 days ago
Earthquake alerts for Vacaville, 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 it was probably too small to be felt, even directly above it. In Vacaville, 15 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: Fairfield, Suisun, Hartley, Rio Vista, Dixon, Allendale.
How big was it?
This earthquake released about 20 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.9 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 760,000× the energy of this one
- Magna, Utah 2020 M 5.7 540,000× the energy of this one
- Around the size people start to feel M 3.0 48× the energy of this one
- This earthquake M 1.9 about 20 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 4.5 on 2019-10-15 — about 7,400 times the energy of this one.
Before 2016, the USGS record lists 3 earthquakes of M5 or more within 50 km:
- 6.0 The 2014 South Napa, California Earthquake · 40 km W of this epicentre
- 5.8 The 1980 Livermore, California Earthquake · 49 km S of this epicentre
- 5.4 South of Elmira, California · 5 km NW 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 38.2720, -121.8610. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Solano County, CA | 7 km (4 mi) | W | earthquakes near Solano County |
| Contra Costa County, CA | 40 km (25 mi) | SSW | earthquakes near Contra Costa County |
| Yolo County, CA | 45 km (28 mi) | N | earthquakes near Yolo County |
| Napa County, CA | 48 km (30 mi) | WNW | earthquakes near Napa County |
| Sacramento County, CA | 49 km (31 mi) | ENE | earthquakes near Sacramento County |
| San Joaquin County, CA | 64 km (40 mi) | SE | earthquakes near San Joaquin County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
33 earthquakes have been recorded within 50 km since this one.
- 1.8 5km ENE of Vallejo, CA
- 1.9 3km SW of Clayton, CA
- 1.6 11km NE of Napa, CA
- 2.5 12km ESE of Angwin, CA
- 1.5 13km E of Angwin, CA
- 1.8 1km ENE of Alamo, CA
- 2.4 13km NE of Yountville, CA
- 1.8 10km NE of Napa, CA
- 2.0 1km NNW of Pleasant Hill, CA
- 2.2 4km NNE of Blackhawk, CA
- 2.5 4km NNE of Blackhawk, CA
- 2.0 4km NE of Blackhawk, CA
- 2.3 2km WNW of Concord, CA
- 1.6 11km ENE of Yountville, CA
- 1.7 3km NNW of Byron, 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.