QuakeIndex

Earthquake · reviewed by a seismologist

M 2.1md

3 km NW of Castro Valley, CA

· 5.8 km deep · released about 46 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Alameda County 19 kmContra Costa County 27 kmSan Mateo County 40 kmSolano County 64 kmSanta Clara County 66 kmMarin County 67 kmSan Joaquin County 78 kmSanta Cruz County 78 kmSan Francisco County 81 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
5.8 km below the surface
Felt
24 reports · strongest reported intensity II
Nearest
Alameda County, 19 km ESE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1159 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage. 24 people have reported feeling it to USGS.

How big was it?

This earthquake released about 46 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 5.8 330,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 230,000× the energy of this one
  3. Around the size people start to feel M 3.0 21× the energy of this one
  4. This earthquake M 2.1 about 46 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 37.7108, -122.1162. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Alameda County, CA 19 km (12 mi) WNW of here earthquakes near Alameda County
Contra Costa County, CA 27 km (17 mi) SSW of here earthquakes near Contra Costa County
San Mateo County, CA 40 km (25 mi) NE of here earthquakes near San Mateo County
Solano County, CA 64 km (40 mi) SSW of here earthquakes near Solano County
Santa Clara County, CA 66 km (41 mi) NW of here earthquakes near Santa Clara County
Marin County, CA 67 km (42 mi) SE of here earthquakes near Marin County

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

Aftershocks so far

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

  1. 1.5 6 km NNE of Orinda, CA
  2. 1.6 4 km WSW of Cupertino, CA
  3. 1.7 9 km NE of Milpitas, CA
  4. 2.0 10 km SW of Brentwood, CA
  5. 2.1 10 km WSW of San Lorenzo, CA
  6. 1.7 2 km ENE of San Leandro, CA
  7. 1.9 4 km WSW of Cupertino, CA
  8. 2.0 7 km NW of San Francisco Zoo, CA
  9. 2.7 9 km NE of Alum Rock, CA
  10. 1.9 3 km ESE of South San Francisco, CA
  11. 1.7 4 km WSW of Cupertino, CA
  12. 2.1 4 km WSW of Cupertino, CA
  13. 1.8 4 km WSW of Cupertino, CA
  14. 2.8 4 km WSW of Cupertino, CA
  15. 1.8 4 km WSW of Cupertino, 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 3,200 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.