Earthquake · reviewed by a seismologist
M 1.8md
Earthquake near Allendale, CA
No earthquake was likely felt in Allendale in the 24 hours to 10:23 am PST (18:23 UTC). The last one was M 3.8, 79 km (49 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 Allendale
This page: a magnitude 1.8 earthquake was recorded 6 km (4 mi) west of Allendale, CA, at 10:42 pm PDT on 14 September 2021 (05:42 UTC), 21 km deep.
USGS: 6km W of Allendale, CA
11 km (7 mi) NNW of Vacaville, CA · 49 km (30 mi) WSW of Sacramento, CA
- When
- 10:42 pm PDT on 14 September 2021 ()
- Where
- 6 km (4 mi) west of Allendale, CA · earthquakes near Allendale
- Magnitude
- M 1.8 (md)
- Depth
- 21 km below the surface
- Felt
- no reports yet
- Nearest
- Solano County, 21 km SSE
- Nearest mapped fault
- Great Valley thrust fault system, 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 1877 days ago
Earthquake alerts for Allendale, 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 Allendale, 6 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: Hartley, Winters, Vacaville, Dixon, Fairfield, Suisun.
How big was it?
This earthquake released about 15 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 1,000,000× the energy of this one
- Magna, Utah 2020 M 5.7 710,000× the energy of this one
- Around the size people start to feel M 3.0 63× the energy of this one
- This earthquake M 1.8 about 15 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 lists 2 earthquakes of M5 or more within 50 km:
- 6.0 The 2014 South Napa, California Earthquake · 37 km SW of this epicentre
- 5.4 South of Elmira, California · 19 km SSE 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 38.4487, -122.0098. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Solano County, CA | 21 km (13 mi) | SSE | earthquakes near Solano County |
| Yolo County, CA | 27 km (17 mi) | NNE | earthquakes near Yolo County |
| Napa County, CA | 28 km (18 mi) | WNW | earthquakes near Napa County |
| Sacramento County, CA | 58 km (36 mi) | E | earthquakes near Sacramento County |
| Contra Costa County, CA | 59 km (37 mi) | S | earthquakes near Contra Costa County |
| Sutter County, CA | 71 km (44 mi) | NNE | earthquakes near Sutter County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
55 earthquakes have been recorded within 50 km since this one.
- 1.9 1km W of Martinez, CA
- 1.9 7km NW of Bay Point, CA
- 1.8 7km NW of Bay Point, CA
- 2.0 6km NW of Bay Point, CA
- 2.2 7km NW of Bay Point, CA
- 1.8 6km NNW of Bay Point, CA
- 1.9 5km NNW of Bay Point, CA
- 1.7 6km NNW of Bay Point, CA
- 4.1 7km NW of Bay Point, CA
- 2.3 14km ESE of Angwin, CA
- 1.6 13km ESE of Angwin, CA
- 1.9 10km WNW of Laguna West-Lakeside, CA
- 1.6 8km ENE of Vallejo, CA
- 1.9 6km ENE of Kenwood, CA
- 1.8 5km E of Vallejo, 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.