QuakeIndex

Earthquake · reviewed by a seismologist

M 2.8ml

3 km ESE of San Ramon, CA

· 8.5 km deep · released about 490 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Alameda County 13 kmContra Costa County 17 kmSan Mateo County 54 kmSolano County 56 kmSan Joaquin County 62 kmSanta Clara County 64 kmMarin County 77 kmSanta Cruz 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 2.8 (ml)
Depth
8.5 km below the surface
Felt
156 reports · strongest reported intensity III
Nearest
Alameda County, 13 km SSE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 115 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage. 156 people have reported feeling it to USGS.

How big was it?

This earthquake released about 490 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.8 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 31,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 22,000× the energy of this one
  3. Around the size people start to feel M 3.0 1.9× the energy of this one
  4. This earthquake M 2.8 about 490 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 37.7635, -121.9457. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Alameda County, CA 13 km (8 mi) NNW of here earthquakes near Alameda County
Contra Costa County, CA 17 km (11 mi) S of here earthquakes near Contra Costa County
San Mateo County, CA 54 km (34 mi) NE of here earthquakes near San Mateo County
Solano County, CA 56 km (35 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 64 km (40 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

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

  1. 1.7 3 km SW of Clayton, CA
  2. 1.6 4 km NE of San Leandro, CA
  3. 2.1 3 km SW of Alamo, CA
  4. 1.7 3 km WSW of Alamo, CA
  5. 1.5 3 km WSW of Alamo, CA
  6. 2.1 3 km WSW of Alamo, CA
  7. 2.0 3 km WSW of Alamo, CA
  8. 2.2 3 km SW of Alamo, CA
  9. 2.0 4 km NE of San Leandro, CA
  10. 1.5 4 km NNW of Pittsburg, CA
  11. 1.8 5 km S of Pittsburg, CA
  12. 1.6 2 km SE of East Richmond Heights, CA
  13. 1.6 3 km NW of Hercules, CA
  14. 1.7 3 km NW of Hercules, CA
  15. 1.6 5 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 4.5 on 2019-10-15 — it released about 300 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.