QuakeIndex

Earthquake · reviewed by a seismologist

M 1.8md

2 km WSW of Alamo, CA

· 13 km deep · released about 13 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Contra Costa County 12 kmAlameda County 25 kmSolano County 48 kmSan Mateo County 55 kmMarin County 65 kmSan Joaquin County 69 kmSanta Clara County 76 kmNapa County 78 kmSan Francisco County 87 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 1.8 (md)
Depth
13 km below the surface
Felt
no reports yet
Nearest
Contra Costa County, 12 km NE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 104 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 13 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.8 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 1,200,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 840,000× the energy of this one
  3. Around the size people start to feel M 3.0 75× the energy of this one
  4. This earthquake M 1.8 about 13 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 37.8403, -122.0512. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Contra Costa County, CA 12 km (8 mi) SW of here earthquakes near Contra Costa County
Alameda County, CA 25 km (15 mi) NNW of here earthquakes near Alameda County
Solano County, CA 48 km (30 mi) SSW of here earthquakes near Solano County
San Mateo County, CA 55 km (34 mi) NNE of here earthquakes near San Mateo County
Marin County, CA 65 km (41 mi) ESE of here earthquakes near Marin County
San Joaquin County, CA 69 km (43 mi) W 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. 1.6 11 km SE of Sunol, CA
  2. 2.1 2 km ESE of Pacifica, CA
  3. 1.9 1 km WNW of Lafayette, CA
  4. 1.6 1 km ESE of Pacifica, CA
  5. 1.7 5 km ENE of Vallejo, CA
  6. 2.3 5 km SSW of Alameda, CA
  7. 1.7 2 km SSW of Clayton, CA
  8. 1.5 3 km ESE of Woodside, CA
  9. 1.8 3 km NNE of Portola Valley, CA
  10. 2.5 2 km SE of Concord, CA
  11. 1.6 1 km ENE of Hayward, CA
  12. 1.6 2 km WNW of Concord, CA
  13. 2.2 3 km NNE of San Leandro, CA
  14. 1.6 4 km NNE of San Leandro, CA
  15. 2.8 4 km 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 4.5 on 2019-10-15 — it released about 12,000 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.