QuakeIndex

Earthquake · reviewed by a seismologist

M 1.9md

6km SSE of Portola Valley, CA

· 5.2 km deep · released about 22 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N San Mateo County 16 kmSanta Cruz County 40 kmAlameda County 44 kmSanta Clara County 49 kmContra Costa County 69 kmSan Francisco County 84 kmMarin County 92 kmSolano County 107 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
5.2 km below the surface
Felt
1 report · strongest reported intensity II
Nearest
San Mateo County, 16 km NW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1444 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 22 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 5.8 680,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 480,000× the energy of this one
  3. Around the size people start to feel M 3.0 43× the energy of this one
  4. This earthquake M 1.9 about 22 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 37.3327, -122.2212. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
San Mateo County, CA 16 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 49 km (30 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 84 km (52 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

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

  1. 1.8 4km SSW of Cupertino, CA
  2. 2.7 3km NE of San Leandro, CA
  3. 2.5 8km NNE of Alum Rock, CA
  4. 1.7 10km E of Alum Rock, CA
  5. 2.0 3km NNE of Fremont, CA
  6. 1.8 2km NE of Hayward, CA
  7. 1.6 2km NE of Hayward, CA
  8. 2.1 2km NNE of Hayward, CA
  9. 3.3 3km N of Union City, CA
  10. 2.9 2km NNE of San Leandro, CA
  11. 1.6 5km WSW of Cupertino, CA
  12. 2.1 12km ESE of Alum Rock, CA
  13. 3.6 13km ESE of Alum Rock, CA
  14. 1.8 3km WSW of Cupertino, CA
  15. 1.7 5km WNW of Dublin, 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 4.1 on 2017-10-10 — it released about 1,900 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.