QuakeIndex

Earthquake · reviewed by a seismologist

M 3.8mw

9km NNE of Alum Rock, CA

· 9.3 km deep · released about 8.1 tons of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Santa Clara County 25 kmAlameda County 27 kmSanta Cruz County 51 kmSan Mateo County 53 kmContra Costa County 56 kmStanislaus County 69 kmSan Joaquin County 71 kmSolano County 94 kmMerced County 97 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 3.8 (mw)
Depth
9.3 km below the surface
Felt
5757 reports · strongest reported intensity IV
Measured shaking
intensity IV (ShakeMap)
Nearest
Santa Clara County, 25 km SSE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2539 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage. 5757 people have reported feeling it to USGS.

How big was it?

This earthquake released about 8.1 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.8 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 21,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 930× the energy of this one
  3. Magna, Utah 2020 M 5.7 660× the energy of this one
  4. This earthquake M 3.8 about 8.1 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 17× more

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 37.4347, -121.7730. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Santa Clara County, CA 25 km (15 mi) NNW of here earthquakes near Santa Clara County
Alameda County, CA 27 km (17 mi) SSE of here earthquakes near Alameda County
Santa Cruz County, CA 51 km (32 mi) NNE of here earthquakes near Santa Cruz County
San Mateo County, CA 53 km (33 mi) E of here earthquakes near San Mateo County
Contra Costa County, CA 56 km (35 mi) SSE of here earthquakes near Contra Costa County
Stanislaus County, CA 69 km (43 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

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

  1. 1.7 2km NW of Diablo, CA
  2. 1.5 3km NW of Diablo, CA
  3. 1.7 4km ESE of Union City, CA
  4. 2.3 9km ENE of San Martin, CA
  5. 1.5 4km NNW of Foster City, CA
  6. 2.0 15km N of Morgan Hill, CA
  7. 3.1 14km N of Morgan Hill, CA
  8. 2.1 2km ENE of San Ramon, CA
  9. 1.9 13km SE of Livermore, CA
  10. 1.8 2km ENE of San Ramon, CA
  11. 1.6 2km ENE of San Ramon, CA
  12. 1.9 3km WSW of Portola Valley, CA
  13. 1.5 1km ENE of Diablo, CA
  14. 2.5 2km ENE of Danville, CA
  15. 1.6 8km E of Alum Rock, 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 2.5 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.