QuakeIndex

Earthquake · automatic estimate, may change

M 2.1md

4 km SE of San Ramon, CA

· 8.1 km deep · released about 38 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Alameda County 12 kmContra Costa County 19 kmSan Mateo County 53 kmSolano County 57 kmSan Joaquin County 62 kmSanta Clara County 63 kmMarin County 78 kmSanta Cruz County 83 kmStanislaus County 85 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
8.1 km below the surface
Felt
no reports yet
Nearest
Alameda County, 12 km SSE
Status
Automatic — a machine’s first estimate, which may change

USGS · last changed by USGS · we first saw it 293 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 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 37.7533, -121.9403. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Alameda County, CA 12 km (7 mi) NNW of here earthquakes near Alameda County
Contra Costa County, CA 19 km (11 mi) S of here earthquakes near Contra Costa County
San Mateo County, CA 53 km (33 mi) NE of here earthquakes near San Mateo County
Solano County, CA 57 km (36 mi) S of here earthquakes near Solano County
San Joaquin County, CA 62 km (39 mi) WSW of here earthquakes near San Joaquin County
Santa Clara County, CA 63 km (39 mi) NNW of here earthquakes near Santa Clara County

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

Aftershocks so far

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

  1. 1.7 5 km N of Dublin, CA
  2. 1.9 4 km WSW of Alamo, CA
  3. 1.8 4 km SE of San Ramon, CA
  4. 1.7 5 km SE of San Ramon, CA
  5. 2.3 2 km SE of Pacheco, CA
  6. 1.9 4 km SE of San Ramon, CA
  7. 2.4 4 km SE of San Ramon, CA
  8. 1.7 3 km SSW of Clayton, CA
  9. 2.0 5 km SE of San Ramon, CA
  10. 3.0 4 km SE of San Ramon, CA
  11. 1.6 5 km SE of San Ramon, CA
  12. 3.0 4 km SE of San Ramon, CA
  13. 1.7 5 km SW of San Lorenzo, CA
  14. 2.3 4 km SE of San Ramon, CA
  15. 1.6 4 km SE 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 4.5 on 2019-10-15 — it released about 3,800 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.