QuakeIndex

Earthquake · reviewed by a seismologist

M 2.1md

1 km ESE of Union City, CA

· 8.7 km deep · released about 38 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Alameda County 10 kmContra Costa County 36 kmSan Mateo County 38 kmSanta Clara County 50 kmSanta Cruz County 65 kmSan Joaquin County 75 kmSolano County 75 kmMarin County 83 kmStanislaus County 88 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
8.7 km below the surface
Felt
7 reports · strongest reported intensity IV
Nearest
Alameda County, 10 km NE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 500 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage. 7 people have 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 37.5955, -122.0033. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Alameda County, CA 10 km (6 mi) SW of here earthquakes near Alameda County
Contra Costa County, CA 36 km (23 mi) S of here earthquakes near Contra Costa County
San Mateo County, CA 38 km (24 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 65 km (40 mi) N of here earthquakes near Santa Cruz County
San Joaquin County, CA 75 km (46 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

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

  1. 1.9 14 km SE of Alum Rock, CA
  2. 1.6 5 km WSW of San Francisco Zoo, CA
  3. 2.4 2 km ESE of Berkeley, CA
  4. 1.7 1 km S of East Richmond Heights, CA
  5. 1.7 11 km ESE of Alum Rock, CA
  6. 1.6 4 km SW of Loyola, CA
  7. 1.9 11 km SSE of Livermore, CA
  8. 2.0 2 km SSE of Danville, CA
  9. 1.6 3 km SW of Clayton, CA
  10. 2.6 5 km WSW of Loyola, CA
  11. 3.0 5 km WSW of Loyola, CA
  12. 1.7 3 km SW of Clayton, CA
  13. 2.5 5 km SW of Loyola, CA
  14. 2.2 4 km S of Highlands-Baywood Park, CA
  15. 1.6 2 km NNW of Walnut Creek, 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.