QuakeIndex

Earthquake · automatic estimate, may change

M 2.1md

13 km NE of Alum Rock, CA

· 17 km deep · released about 40 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Santa Clara County 26 kmAlameda County 28 kmSanta Cruz County 55 kmContra Costa County 56 kmSan Mateo County 58 kmStanislaus County 64 kmSan Joaquin County 67 kmMerced County 92 kmSolano County 93 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
17 km below the surface
Felt
no reports yet
Nearest
Santa Clara County, 26 km S
Status
Automatic — a machine’s first estimate, which may change

USGS · last changed by USGS · we first saw it 355 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

How big was it?

This earthquake released about 40 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 5.8 380,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 270,000× the energy of this one
  3. Around the size people start to feel M 3.0 24× the energy of this one
  4. This earthquake M 2.1 about 40 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 37.4507, -121.7178. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Santa Clara County, CA 26 km (16 mi) N of here earthquakes near Santa Clara County
Alameda County, CA 28 km (17 mi) SE of here earthquakes near Alameda County
Santa Cruz County, CA 55 km (34 mi) NNE of here earthquakes near Santa Cruz County
Contra Costa County, CA 56 km (35 mi) SSE of here earthquakes near Contra Costa County
San Mateo County, CA 58 km (36 mi) E of here earthquakes near San Mateo County
Stanislaus County, CA 64 km (40 mi) W of here earthquakes near Stanislaus County

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

Aftershocks so far

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

  1. 1.8 4 km SE of San Ramon, CA
  2. 2.9 3 km SE of San Ramon, CA
  3. 1.9 4 km SE of San Ramon, CA
  4. 2.3 3 km SE of San Ramon, CA
  5. 1.7 4 km SE of San Ramon, CA
  6. 1.7 4 km SE of San Ramon, CA
  7. 2.9 3 km SE of San Ramon, CA
  8. 3.0 3 km SE of San Ramon, CA
  9. 2.4 4 km SE of San Ramon, CA
  10. 1.5 4 km SE of San Ramon, CA
  11. 1.6 4 km SE of San Ramon, CA
  12. 2.3 3 km SE of San Ramon, CA
  13. 1.7 4 km SE of San Ramon, CA
  14. 1.7 4 km SE of San Ramon, CA
  15. 1.6 4 km ESE of San Ramon, 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 30,000 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.