QuakeIndex

Earthquake · reviewed by a seismologist

M 2.3md

9km NE of Blackhawk, CA

· 15 km deep · released about 85 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Contra Costa County 12 kmAlameda County 26 kmSolano County 45 kmSan Joaquin County 49 kmSan Mateo County 70 kmSanta Clara County 73 kmSacramento County 77 kmStanislaus County 80 kmNapa County 83 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 2.3 (md)
Depth
15 km below the surface
Felt
2 reports · strongest reported intensity I
Nearest
Contra Costa County, 12 km WNW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2251 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage. 2 people have reported feeling it to USGS.

How big was it?

This earthquake released about 85 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.3 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 180,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 130,000× the energy of this one
  3. Around the size people start to feel M 3.0 11× the energy of this one
  4. This earthquake M 2.3 about 85 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.

Where

Epicentre 37.8727, -121.8272. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Contra Costa County, CA 12 km (8 mi) ESE of here earthquakes near Contra Costa County
Alameda County, CA 26 km (16 mi) NNE of here earthquakes near Alameda County
Solano County, CA 45 km (28 mi) SSE of here earthquakes near Solano County
San Joaquin County, CA 49 km (31 mi) W of here earthquakes near San Joaquin County
San Mateo County, CA 70 km (43 mi) NE of here earthquakes near San Mateo County
Santa Clara County, CA 73 km (46 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

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

  1. 2.4 2km E of Berkeley, CA
  2. 2.6 4km ESE of Berkeley, CA
  3. 1.7 10km NE of Milpitas, CA
  4. 2.6 10km NNE of Milpitas, CA
  5. 2.0 7km S of Livermore, CA
  6. 1.9 7km S of Livermore, CA
  7. 3.3 10km NE of Milpitas, CA
  8. 2.9 10km NE of Milpitas, CA
  9. 2.7 10km NE of Milpitas, CA
  10. 2.1 4km ESE of Berkeley, CA
  11. 1.7 1km SW of Diablo, CA
  12. 1.9 10km NE of Milpitas, CA
  13. 1.6 10km NE of Milpitas, CA
  14. 1.8 10km NE of Milpitas, CA
  15. 2.1 10km NE of Milpitas, 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.

For this area

The largest earthquake within 50 km in our catalogue was M 4.5 on 2019-10-15 — it released about 1,700 times the energy of this one.

From the QuakeIndex catalogue, built from the USGS FDSN event service.

On USGS

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