QuakeIndex

Earthquake · reviewed by a seismologist

M 2.6md

Earthquake near Brentwood, CA

No earthquake was likely felt in Brentwood in the 24 hours to 10:59 pm PST (06:59 UTC). The last one was M 3.0, 12 km (7 mi) WSW, at 6:47 am PDT on 14 September 2026, estimated intensity II (weak) in town; 52 felt reports to USGS. Every earthquake near Brentwood

This page: a magnitude 2.6 earthquake was recorded 11 km (7 mi) southwest of Brentwood, CA, at 6:19 pm PDT on 11 August 2023 (01:19 UTC), 14 km deep. 20 people have reported feeling it to USGS.

USGS: 8 km SW of Brentwood, CA

10 km (6 mi) SW of Brentwood, CA · 64 km (40 mi) N of San Jose, CA

6:19 pm PDT, Aug 11, 2023 · · 14 km deep · released about 280 lb of TNT

Every earthquake near Brentwood Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Contra Costa County 16 kmAlameda County 27 kmSan Joaquin County 46 kmSolano County 46 kmSan Mateo County 72 kmSanta Clara County 72 kmSacramento County 75 kmStanislaus County 77 kmNapa County 85 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
6:19 pm PDT on 11 August 2023 ()
Where
11 km (7 mi) southwest of Brentwood, CA · earthquakes near Brentwood
Magnitude
M 2.6 (md)
Depth
14 km below the surface
Felt
20 reports · strongest reported intensity IV
Nearest
Contra Costa County, 16 km WNW
Nearest mapped fault
Greenville fault, 4 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 987 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.

At this magnitude and depth, people at rest would likely notice it out to about 20 km (12 mi) from the epicentre. In Brentwood, 11 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: Brentwood 11 km, intensity II · Antioch 15 km, intensity II · Oakley 16 km, intensity II · Discovery Bay 17 km, intensity II · Danville 19 km, intensity II · San Ramon 19 km, intensity II · Pittsburg 20 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 280 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.6 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 55,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 39,000× the energy of this one
  3. Around the size people start to feel M 3.0 3.5× the energy of this one
  4. This earthquake M 2.6 about 280 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 540 times the energy of this one.

Before 2016, the USGS record lists 6 earthquakes of M5 or more within 50 km; the five largest:

  1. 5.8 The 1980 Livermore, California Earthquake · 4 km SSE of this epicentre
  2. 5.7 15 km NE of East Foothills, California · 44 km SSE of this epicentre
  3. 5.5 6 km NNE of East Foothills, California · 48 km S of this epicentre
  4. 5.4 South of Elmira, California · 49 km NNW of this epicentre
  5. 5.4 9 km NE of Livermore, 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 37.8677, -121.7873. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Contra Costa County, CA 16 km (10 mi) WNW earthquakes near Contra Costa County
Alameda County, CA 27 km (17 mi) SSW earthquakes near Alameda County
San Joaquin County, CA 46 km (28 mi) E earthquakes near San Joaquin County
Solano County, CA 46 km (29 mi) NNW earthquakes near Solano County
San Mateo County, CA 72 km (45 mi) SW earthquakes near San Mateo County
Santa Clara County, CA 72 km (45 mi) S earthquakes near Santa Clara County

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

Aftershocks so far

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

  1. 1.6 0 km WSW of Diablo, CA
  2. 2.2 9 km NE of Alum Rock, CA
  3. 2.5 3 km NNW of Piedmont, CA
  4. 2.0 9 km NE of Alum Rock, CA
  5. 1.8 8 km S of Byron, CA
  6. 1.5 6 km NNE of Orinda, CA
  7. 1.7 9 km NE of Milpitas, CA
  8. 2.0 10 km SW of Brentwood, CA
  9. 2.1 10 km WSW of San Lorenzo, CA
  10. 1.7 2 km ENE of San Leandro, CA
  11. 2.7 9 km NE of Alum Rock, CA
  12. 2.1 4 km NNE of Fairview, CA
  13. 2.2 2 km NW of Concord, CA
  14. 1.8 1 km ENE of Pittsburg, CA
  15. 1.8 3 km WNW 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.