QuakeIndex

Earthquake · reviewed by a seismologist

M 2.1md

4 km E of Union City, CA

· 8.4 km deep · released about 38 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Alameda County 8 kmContra Costa County 35 kmSan Mateo County 41 kmSanta Clara County 50 kmSanta Cruz County 66 kmSan Joaquin County 72 kmSolano County 74 kmMarin County 84 kmStanislaus 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 2.1 (md)
Depth
8.4 km below the surface
Felt
1 report · strongest reported intensity III
Nearest
Alameda County, 8 km NE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 824 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage. 1 person has reported feeling it to USGS.

How big was it?

This earthquake released about 38 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.1 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 390,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 280,000× the energy of this one
  3. Around the size people start to feel M 3.0 25× the energy of this one
  4. This earthquake M 2.1 about 38 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 37.6048, -121.9790. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Alameda County, CA 8 km (5 mi) SW of here earthquakes near Alameda County
Contra Costa County, CA 35 km (22 mi) S of here earthquakes near Contra Costa County
San Mateo County, CA 41 km (25 mi) ENE of here earthquakes near San Mateo County
Santa Clara County, CA 50 km (31 mi) NNW of here earthquakes near Santa Clara County
Santa Cruz County, CA 66 km (41 mi) N of here earthquakes near Santa Cruz County
San Joaquin County, CA 72 km (45 mi) WSW of here earthquakes near San Joaquin County

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

Aftershocks so far

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

  1. 1.7 5 km E of El Granada, CA
  2. 1.7 4 km W of Daly City, CA
  3. 1.8 2 km SSW of Loyola, CA
  4. 1.8 4 km SSE of Rodeo, CA
  5. 2.0 6 km WSW of Antioch, CA
  6. 1.6 4 km WSW of Colma, CA
  7. 1.8 1 km ESE of El Cerrito, CA
  8. 1.6 5 km W of Colma, CA
  9. 1.7 1 km WSW of San Ramon, CA
  10. 2.0 1 km WSW of San Ramon, CA
  11. 2.0 1 km WSW of San Ramon, CA
  12. 1.9 5 km NNE of Castro Valley, CA
  13. 2.4 4 km ESE of El Sobrante, CA
  14. 1.6 4 km NNE of San Mateo, CA
  15. 1.7 2 km 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 5.1 on 2022-10-25 — it released about 31,000 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.