QuakeIndex

Earthquake · reviewed by a seismologist

M 1.9md

3km WSW of Portola Valley, CA

· 8.0 km deep · released about 18 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N San Mateo County 10 kmAlameda County 43 kmSanta Cruz County 47 kmSanta Clara County 54 kmContra Costa County 66 kmSan Francisco County 78 kmMarin County 86 kmSolano County 103 kmSan Joaquin County 107 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 1.9 (md)
Depth
8.0 km below the surface
Felt
no reports yet
Nearest
San Mateo County, 10 km WNW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 3062 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 18 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.9 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 840,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 600,000× the energy of this one
  3. Around the size people start to feel M 3.0 53× the energy of this one
  4. This earthquake M 1.9 about 18 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 37.3768, -122.2672. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
San Mateo County, CA 10 km (6 mi) ESE of here earthquakes near San Mateo County
Alameda County, CA 43 km (27 mi) SW of here earthquakes near Alameda County
Santa Cruz County, CA 47 km (29 mi) NNW of here earthquakes near Santa Cruz County
Santa Clara County, CA 54 km (34 mi) WNW of here earthquakes near Santa Clara County
Contra Costa County, CA 66 km (41 mi) SSW of here earthquakes near Contra Costa County
San Francisco County, CA 78 km (48 mi) ESE of here earthquakes near San Francisco County

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

Aftershocks so far

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

  1. 2.0 4km ESE of Union City, CA
  2. 1.7 8km NNE of Milpitas, CA
  3. 1.8 9km NNE of Alum Rock, CA
  4. 1.9 10km ESE of Sunol, CA
  5. 1.6 11km NE of Milpitas, CA
  6. 2.1 2km NE of Oakland, CA
  7. 2.8 2km NE of Oakland, CA
  8. 2.8 9km ENE of Milpitas, CA
  9. 1.5 2km WSW of San Lorenzo, CA
  10. 3.4 9km ENE of Milpitas, CA
  11. 2.1 5km E of Union City, CA
  12. 1.6 8km NE of Alum Rock, CA
  13. 1.6 0km E of Pacifica, CA
  14. 2.4 10km SW of Bonny Doon, CA
  15. 1.6 4km S of Loyola, 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.

On USGS

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.