QuakeIndex

Earthquake · automatic estimate, may change

M 2.1md

6 km SSE of Portola Valley, CA

· 8.6 km deep · released about 51 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N San Mateo County 17 kmSanta Cruz County 40 kmAlameda County 44 kmSanta Clara County 48 kmContra Costa County 70 kmSan Francisco County 84 kmMarin County 93 kmSan Joaquin County 107 kmSolano 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 2.1 (md)
Depth
8.6 km below the surface
Felt
1 report · strongest reported intensity III
Nearest
San Mateo County, 17 km NW
Status
Automatic — a machine’s first estimate, which may change

USGS · last changed by USGS · we first saw it 359 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage. 1 person has reported feeling it to USGS.

How big was it?

This earthquake released about 51 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.1 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 300,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 210,000× the energy of this one
  3. Around the size people start to feel M 3.0 19× the energy of this one
  4. This earthquake M 2.1 about 51 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 37.3283, -122.2167. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
San Mateo County, CA 17 km (10 mi) SE of here earthquakes near San Mateo County
Santa Cruz County, CA 40 km (25 mi) NNW of here earthquakes near Santa Cruz County
Alameda County, CA 44 km (28 mi) SW of here earthquakes near Alameda County
Santa Clara County, CA 48 km (30 mi) WNW of here earthquakes near Santa Clara County
Contra Costa County, CA 70 km (43 mi) SSW of here earthquakes near Contra Costa County
San Francisco County, CA 84 km (53 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

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

  1. 2.2 3 km ESE of Union City, CA
  2. 1.7 11 km E of Alum Rock, CA
  3. 1.7 4 km SE of Pacifica, CA
  4. 1.8 3 km SE of Pacifica, CA
  5. 1.6 5 km SE of Oakland, CA
  6. 2.4 5 km SE of Oakland, CA
  7. 2.0 8 km E of Alum Rock, CA
  8. 2.0 3 km S of Sunol, CA
  9. 2.4 1 km E of Woodside, CA
  10. 1.6 1 km ESE of Woodside, CA
  11. 2.6 1 km ESE of Woodside, CA
  12. 2.2 1 km E of Woodside, CA
  13. 2.0 1 km ENE of Woodside, CA
  14. 2.5 1 km E of Woodside, CA
  15. 2.2 1 km E of Woodside, 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 5.1 on 2022-10-25 — it released about 23,000 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.