QuakeIndex

Earthquake · reviewed by a seismologist

M 2.9md

5km NE of Alum Rock, CA

· 2.5 km deep · released about 590 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Santa Clara County 21 kmAlameda County 31 kmSanta Cruz County 47 kmSan Mateo County 52 kmContra Costa County 60 kmStanislaus County 71 kmSan Joaquin County 75 kmMerced County 96 kmSolano County 98 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 2.9 (md)
Depth
2.5 km below the surface
Felt
338 reports · strongest reported intensity VI
Nearest
Santa Clara County, 21 km SSE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2304 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage. 338 people have reported feeling it to USGS.

How big was it?

This earthquake released about 590 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.9 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 26,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 18,000× the energy of this one
  3. Around the size people start to feel M 3.0 1.6× the energy of this one
  4. This earthquake M 2.9 about 590 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 37.3932, -121.7810. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Santa Clara County, CA 21 km (13 mi) NNW of here earthquakes near Santa Clara County
Alameda County, CA 31 km (19 mi) SSE of here earthquakes near Alameda County
Santa Cruz County, CA 47 km (29 mi) NNE of here earthquakes near Santa Cruz County
San Mateo County, CA 52 km (32 mi) E of here earthquakes near San Mateo County
Contra Costa County, CA 60 km (38 mi) SSE of here earthquakes near Contra Costa County
Stanislaus County, CA 71 km (44 mi) WSW of here earthquakes near Stanislaus County

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

Aftershocks so far

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

  1. 1.5 9km N of Boulder Creek, CA
  2. 1.6 9km NE of San Martin, CA
  3. 1.7 3km W of Portola Valley, CA
  4. 1.8 3km W of Portola Valley, CA
  5. 1.8 2km SW of Los Altos Hills, CA
  6. 3.4 8km NE of Alum Rock, CA
  7. 1.8 4km E of Livermore, CA
  8. 2.1 8km ENE of Alum Rock, CA
  9. 1.6 15km E of Seven Trees, CA
  10. 1.6 1km SSE of San Ramon, CA
  11. 2.2 5km SSE of Newark, CA
  12. 1.8 12km WNW of Boulder Creek, CA
  13. 1.5 1km SSE of San Ramon, CA
  14. 2.2 13km ESE of Seven Trees, CA
  15. 1.9 1km S of San Ramon, 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 4.3 on 2019-07-16 — it released about 150 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.