QuakeIndex

quarry blast · reviewed by a seismologist

M 1.5md

5km S of Portola Valley, CA

· -0.3 km deep · released about 5.7 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N San Mateo County 15 kmSanta Cruz County 41 kmAlameda County 44 kmSanta Clara County 50 kmContra Costa County 69 kmSan Francisco County 83 kmMarin County 91 kmSolano County 106 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 1.5 (md)
Depth
-0.3 km below the surface
Felt
no reports yet
Nearest
San Mateo County, 15 km NW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 3076 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

USGS catalogues this as quarry blast, not an earthquake.

How big was it?

This earthquake released about 5.7 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.5 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 2,600,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 1,900,000× the energy of this one
  3. Around the size people start to feel M 3.0 170× the energy of this one
  4. This earthquake M 1.5 about 5.7 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 37.3395, -122.2307. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
San Mateo County, CA 15 km (9 mi) SE of here earthquakes near San Mateo County
Santa Cruz County, CA 41 km (26 mi) NNW of here earthquakes near Santa Cruz County
Alameda County, CA 44 km (27 mi) SW of here earthquakes near Alameda County
Santa Clara County, CA 50 km (31 mi) WNW of here earthquakes near Santa Clara County
Contra Costa County, CA 69 km (43 mi) SSW of here earthquakes near Contra Costa County
San Francisco County, CA 83 km (51 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

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

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

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