QuakeIndex

Earthquake · reviewed by a seismologist

M 3.3mw

5km NE of Alamo, CA

· 6.0 km deep · released about 1.3 tons of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Contra Costa County 6 kmAlameda County 26 kmSolano County 44 kmSan Mateo County 61 kmSan Joaquin County 63 kmMarin County 69 kmNapa County 76 kmSanta Clara County 77 kmSacramento 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 3.3 (mw)
Depth
6.0 km below the surface
Felt
706 reports · strongest reported intensity IV
Nearest
Contra Costa County, 6 km NNE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2984 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage. 706 people have reported feeling it to USGS.

How big was it?

This earthquake released about 1.3 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.3 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 130,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 5,600× the energy of this one
  3. Magna, Utah 2020 M 5.7 4,000× the energy of this one
  4. This earthquake M 3.3 about 1.3 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 2.8× more

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 37.8737, -121.9880. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Contra Costa County, CA 6 km (4 mi) SSW of here earthquakes near Contra Costa County
Alameda County, CA 26 km (16 mi) NNW of here earthquakes near Alameda County
Solano County, CA 44 km (27 mi) S of here earthquakes near Solano County
San Mateo County, CA 61 km (38 mi) NNE of here earthquakes near San Mateo County
San Joaquin County, CA 63 km (39 mi) W of here earthquakes near San Joaquin County
Marin County, CA 69 km (43 mi) ESE of here earthquakes near Marin 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. 2.9 15km ESE of Suisun City, CA
  2. 2.2 8km SE of Suisun City, CA
  3. 1.9 10km ESE of Black Point-Green Point, CA
  4. 3.7 10km ESE of Black Point-Green Point, CA
  5. 1.8 8km SE of Suisun City, CA
  6. 1.6 14km ENE of Milpitas, CA
  7. 1.5 5km NNE of Fremont, CA
  8. 1.8 3km E of Hayward, CA
  9. 1.9 3km NNE of Bay Point, CA
  10. 1.6 3km NW of Castro Valley, CA
  11. 2.9 2km NW of Castro Valley, CA
  12. 1.6 8km SSW of Brentwood, CA
  13. 1.9 7km SSW of Brentwood, CA
  14. 1.7 2km SE of Danville, CA
  15. 2.0 3km N of San Leandro, 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 4.4 on 2018-01-04 — it released about 42 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.