QuakeIndex

Earthquake · reviewed by a seismologist

M 2.8md

3km NNW of Piedmont, CA

· 5.2 km deep · released about 420 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Contra Costa County 27 kmAlameda County 36 kmSan Mateo County 49 kmMarin County 50 kmSolano County 54 kmSan Francisco County 71 kmNapa County 74 kmSanta Clara County 85 kmSan Joaquin 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 2.8 (md)
Depth
5.2 km below the surface
Felt
1592 reports · strongest reported intensity III
Nearest
Contra Costa County, 27 km ENE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 370 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage. 1592 people have reported feeling it to USGS.

How big was it?

This earthquake released about 420 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.8 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 36,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 26,000× the energy of this one
  3. Around the size people start to feel M 3.0 2.3× the energy of this one
  4. This earthquake M 2.8 about 420 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 37.8467, -122.2403. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Contra Costa County, CA 27 km (17 mi) WSW of here earthquakes near Contra Costa County
Alameda County, CA 36 km (23 mi) NW of here earthquakes near Alameda County
San Mateo County, CA 49 km (31 mi) NNE of here earthquakes near San Mateo County
Marin County, CA 50 km (31 mi) ESE of here earthquakes near Marin County
Solano County, CA 54 km (33 mi) SSW of here earthquakes near Solano County
San Francisco County, CA 71 km (44 mi) E of here earthquakes near San Francisco County

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

Aftershocks so far

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

  1. 1.6 4km ENE of Oakland, CA
  2. 1.7 4km ESE of Union City, CA
  3. 1.5 4km NNW of Foster City, CA
  4. 2.2 3km ENE of Oakland, CA
  5. 2.1 2km ENE of San Ramon, CA
  6. 3.5 3km ENE of Oakland, CA
  7. 1.8 2km ENE of San Ramon, CA
  8. 1.6 2km ENE of San Ramon, CA
  9. 2.0 3km W of Pittsburg, CA
  10. 2.0 7km NW of San Francisco Zoo, CA
  11. 1.5 1km ENE of Diablo, CA
  12. 2.5 2km ENE of Danville, CA
  13. 2.2 3km ESE of Berkeley, CA
  14. 1.5 2km E of Danville, CA
  15. 2.6 5km NNW of Diablo, 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 4.4 on 2018-01-04 — it released about 270 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.