QuakeIndex

Earthquake · reviewed by a seismologist

M 3.8mw

8 km E of Blackhawk, California

· 15 km deep · released about 7.1 tons of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Contra Costa County 17 kmAlameda County 22 kmSan Joaquin County 48 kmSolano County 51 kmSan Mateo County 68 kmSanta Clara County 68 kmStanislaus County 76 kmSacramento County 80 kmMarin County 86 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
Magnitude
M 3.8 (mw)
Depth
15 km below the surface
Felt
777 reports · strongest reported intensity III
Measured shaking
intensity III (ShakeMap)
Nearest
Contra Costa County, 17 km NW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2630 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage. 777 people have reported feeling it to USGS.

How big was it?

This earthquake released about 7.1 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.8 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 24,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 1,100× the energy of this one
  3. Magna, Utah 2020 M 5.7 760× the energy of this one
  4. This earthquake M 3.8 about 7.1 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 15× 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.

Where

Epicentre 37.8252, -121.8060. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Contra Costa County, CA 17 km (10 mi) SE of here earthquakes near Contra Costa County
Alameda County, CA 22 km (14 mi) NNE of here earthquakes near Alameda County
San Joaquin County, CA 48 km (30 mi) WSW of here earthquakes near San Joaquin County
Solano County, CA 51 km (31 mi) SSE of here earthquakes near Solano County
San Mateo County, CA 68 km (42 mi) NE of here earthquakes near San Mateo County
Santa Clara County, CA 68 km (42 mi) N of here earthquakes near Santa Clara County

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

Aftershocks so far

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

  1. 2.0 0 km W of Kensington, California
  2. 1.7 0 km W of Kensington, California
  3. 1.8 0 km E of Hayward, California
  4. 2.0 4 km NNW of Orinda, California
  5. 2.2 0 km ESE of North Gate, California
  6. 2.0 4 km NNW of Orinda, California
  7. 1.6 4 km SW of Danville, California
  8. 2.1 2 km SSW of San Ramon, California
  9. 2.2 1 km SSW of San Ramon, California
  10. 2.0 1 km W of Danville, California
  11. 1.5 2 km E of Berkeley, California
  12. 2.2 Northern California
  13. 1.6 11 km SE of Sunol, CA
  14. 2.2 5 km S of Livermore, California
  15. 1.7 3 km W of Byron, California

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.