Earthquake · reviewed by a seismologist
M 4.2mw
Earthquake near Antioch, CA
No earthquake was likely felt in Antioch in the 24 hours to 2:54 am PST (10:54 UTC). The last one was M 3.0, 14 km (9 mi) S, at 6:47 am PDT on 14 September 2026, estimated intensity II (weak) in town; 52 felt reports to USGS. Every earthquake near Antioch
This page: a magnitude 4.2 earthquake was recorded 20 km (12 mi) northeast of Antioch, CA, at 9:29 am PDT on 18 October 2023 (16:29 UTC), 8.5 km deep. 7,899 people have reported feeling it to USGS.
USGS: 5 km SW of Isleton, CA
94 km (58 mi) N of San Jose, CA · 21 km (13 mi) NE of Antioch, CA
- When
- 9:29 am PDT on 18 October 2023 ()
- Where
- 20 km (12 mi) northeast of Antioch, CA · earthquakes near Antioch
- Magnitude
- M 4.2 (mw)
- Depth
- 8.5 km below the surface
- Felt
- 7,899 reports · strongest reported intensity V
- Measured shaking
- intensity VI (ShakeMap)
- USGS impact alert
- green
- Nearest
- Solano County, 30 km WNW
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 784 days ago
Earthquake alerts for Antioch, 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 light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon.
At this magnitude and depth, people at rest would likely notice it out to about 116 km (72 mi) from the epicentre. In Antioch, 20 km away, the estimate is intensity III (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: Rio Vista 6 km, intensity IV · Oakley 16 km, intensity IV · Antioch 20 km, intensity III · Brentwood 22 km, intensity III · Pittsburg 24 km, intensity III · Discovery Bay 25 km, intensity III · Suisun 37 km, intensity III · Fairfield 37 km, intensity III. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 35 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.2 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 4,900× the energy of this one
- Mineral, Virginia 2011 M 5.8 220× the energy of this one
- Magna, Utah 2020 M 5.7 150× the energy of this one
- This earthquake M 4.2 about 35 tons of TNT
- Around the size people start to feel M 3.0 this one released 72× 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 since 2016 was M 4.5 on 2019-10-15 — about 2.1 times the energy of this one.
Before 2016, the USGS record lists 4 earthquakes of M5 or more within 50 km:
- 5.8 The 1980 Livermore, California Earthquake · 34 km SSW of this epicentre
- 5.4 South of Elmira, California · 30 km NW of this epicentre
- 5.4 9 km NE of Livermore, California · 42 km S of this epicentre
- 5.1 11 km E of Blackhawk, California · 37 km SSW 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 38.1270, -121.6428. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Solano County, CA | 30 km (19 mi) | WNW | earthquakes near Solano County |
| Contra Costa County, CA | 36 km (22 mi) | SW | earthquakes near Contra Costa County |
| San Joaquin County, CA | 39 km (24 mi) | ESE | earthquakes near San Joaquin County |
| Sacramento County, CA | 44 km (28 mi) | NE | earthquakes near Sacramento County |
| Alameda County, CA | 58 km (36 mi) | SSW | earthquakes near Alameda County |
| Yolo County, CA | 65 km (41 mi) | NNW | earthquakes near Yolo County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
49 earthquakes have been recorded within 50 km since this one.
- 1.5 5 km E of Vallejo, CA
- 1.7 3 km E of Alamo, CA
- 1.7 5 km E of Vallejo, CA
- 1.6 2 km N of Livermore, CA
- 1.6 6 km ENE of Vallejo, CA
- 1.8 10 km ENE of Blackhawk, CA
- 1.8 10 km SSW of Brentwood, CA
- 1.5 6 km E of Walnut Creek, CA
- 1.7 1 km W of Pacheco, CA
- 2.0 10 km ESE of Clayton, CA
- 1.9 11 km E of Blackhawk, CA
- 2.6 3 km SE of Pleasant Hill, CA
- 1.9 2 km NW of Alamo, CA
- 1.8 2 km SE of Pacheco, CA
- 1.5 5 km 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.