QuakeIndex

Earthquake · reviewed by a seismologist

M 1.5md

Earthquake near Antioch, CA

No earthquake was likely felt in Antioch in the 24 hours to 3:30 pm PST (23:30 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 1.5 earthquake was recorded 8 km (5 mi) south-southwest of Antioch, CA, at 9:46 pm PDT on 9 May 2023 (04:46 UTC), 11 km deep. 1 person has reported feeling it to USGS.

USGS: 8km SSW of Antioch, CA

5 km (3 mi) SSW of Antioch, CA

9:46 pm PDT, May 9, 2023 · · 11 km deep · released about 5.7 lb of TNT

Every earthquake near Antioch Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Contra Costa County 11 kmAlameda County 33 kmSolano County 38 kmSan Joaquin County 48 kmSacramento County 71 kmSan Mateo County 76 kmNapa County 77 kmSanta Clara County 81 kmMarin County 82 km
Distance rings around the epicentre, with the nearest towns at their true direction and later quakes as coloured dots. Not a shaking map — see the USGS ShakeMap for that.
When
9:46 pm PDT on 9 May 2023 ()
Where
8 km (5 mi) south-southwest of Antioch, CA · earthquakes near Antioch
Magnitude
M 1.5 (md)
Depth
11 km below the surface
Felt
1 report · strongest reported intensity II
Nearest
Contra Costa County, 11 km W
Nearest mapped fault
Greenville fault, 6 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 1274 days ago

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 Antioch, 8 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: Clayton, Pittsburg, Brentwood, Oakley, Knightsen, Blackhawk.

How big was it?

This earthquake released about 5.7 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.5 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 2,600,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 1,900,000× the energy of this one
  3. Around the size people start to feel M 3.0 170× the energy of this one
  4. This earthquake M 1.5 about 5.7 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 26,000 times the energy of this one.

Before 2016, the USGS record lists 4 earthquakes of M5 or more within 50 km:

  1. 5.8 The 1980 Livermore, California Earthquake · 12 km SSE of this epicentre
  2. 5.4 South of Elmira, California · 41 km N of this epicentre
  3. 5.4 9 km NE of Livermore, California · 24 km SSE of this epicentre
  4. 5.1 11 km E of Blackhawk, California · 15 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 37.9387, -121.8243. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Contra Costa County, CA 11 km (7 mi) W earthquakes near Contra Costa County
Alameda County, CA 33 km (21 mi) SSW earthquakes near Alameda County
Solano County, CA 38 km (24 mi) NNW earthquakes near Solano County
San Joaquin County, CA 48 km (30 mi) E earthquakes near San Joaquin County
Sacramento County, CA 71 km (44 mi) NE earthquakes near Sacramento County
San Mateo County, CA 76 km (47 mi) SW earthquakes near San Mateo County

Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.

Aftershocks so far

54 earthquakes have been recorded within 50 km since this one.

  1. 2.0 2 km N of San Ramon, CA
  2. 1.8 1 km SSE of Pacheco, CA
  3. 2.0 2 km ENE of Berkeley, CA
  4. 1.8 3 km W of Orinda, CA
  5. 2.2 1 km NE of San Leandro, CA
  6. 1.6 0 km WSW of Diablo, CA
  7. 2.5 3 km NNW of Piedmont, CA
  8. 1.8 8 km S of Byron, CA
  9. 1.5 6 km NNE of Orinda, CA
  10. 2.0 10 km SW of Brentwood, CA
  11. 2.1 10 km WSW of San Lorenzo, CA
  12. 1.7 2 km ENE of San Leandro, CA
  13. 2.2 1 km NW of Green Valley, CA
  14. 2.1 4 km NNE of Fairview, CA
  15. 2.2 2 km NW of Concord, 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

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.