QuakeIndex

Earthquake · reviewed by a seismologist

M 2.9md

6 km SW of Alamo, CA

· 7.6 km deep · released about 680 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Contra Costa County 16 kmAlameda County 22 kmSan Mateo County 51 kmSolano County 53 kmMarin County 66 kmSan Joaquin County 71 kmSanta Clara County 73 kmNapa County 81 kmSan Francisco 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 2.9 (md)
Depth
7.6 km below the surface
Felt
197 reports · strongest reported intensity V
Nearest
Contra Costa County, 16 km NE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 429 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage. 197 people have reported feeling it to USGS.

How big was it?

This earthquake released about 680 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.9 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 22,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 16,000× the energy of this one
  3. Around the size people start to feel M 3.0 1.4× the energy of this one
  4. This earthquake M 2.9 about 680 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 37.8055, -122.0653. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Contra Costa County, CA 16 km (10 mi) SW of here earthquakes near Contra Costa County
Alameda County, CA 22 km (14 mi) NW of here earthquakes near Alameda County
San Mateo County, CA 51 km (32 mi) NNE of here earthquakes near San Mateo County
Solano County, CA 53 km (33 mi) SSW of here earthquakes near Solano County
Marin County, CA 66 km (41 mi) ESE of here earthquakes near Marin County
San Joaquin County, CA 71 km (44 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

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

  1. 2.0 2 km E of Hayward, CA
  2. 1.5 1 km SW of Vallejo, CA
  3. 1.7 5 km WSW of Antioch, CA
  4. 1.6 2 km E of Berkeley, CA
  5. 2.0 6 km SSE of Moraga, CA
  6. 1.6 6 km SW of Clayton, CA
  7. 1.6 1 km NNW of Pleasant Hill, CA
  8. 1.9 1 km E of Hayward, CA
  9. 2.0 9 km ENE of Milpitas, CA
  10. 1.6 5 km WSW of San Francisco Zoo, CA
  11. 2.4 2 km ESE of Berkeley, CA
  12. 1.7 1 km S of East Richmond Heights, CA
  13. 2.1 6 km ENE of Vallejo, CA
  14. 1.9 11 km SSE of Livermore, CA
  15. 2.0 2 km SSE of Danville, 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 220 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.