QuakeIndex

Earthquake · reviewed by a seismologist

M 2.8md

8km NNE of Alum Rock, CA

· 4.5 km deep · released about 510 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Santa Clara County 25 kmAlameda County 26 kmSanta Cruz County 50 kmSan Mateo County 51 kmContra Costa County 56 kmStanislaus County 72 kmSan Joaquin County 73 kmSolano County 94 kmMerced County 99 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 2.8 (md)
Depth
4.5 km below the surface
Felt
116 reports · strongest reported intensity III
Nearest
Santa Clara County, 25 km SSE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2507 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage. 116 people have reported feeling it to USGS.

How big was it?

This earthquake released about 510 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.8 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 30,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 21,000× the energy of this one
  3. Around the size people start to feel M 3.0 1.9× the energy of this one
  4. This earthquake M 2.8 about 510 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 37.4313, -121.7973. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Santa Clara County, CA 25 km (16 mi) NNW of here earthquakes near Santa Clara County
Alameda County, CA 26 km (16 mi) SSE of here earthquakes near Alameda County
Santa Cruz County, CA 50 km (31 mi) NNE of here earthquakes near Santa Cruz County
San Mateo County, CA 51 km (32 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 72 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

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

  1. 2.9 5km NE of Alum Rock, CA
  2. 1.6 3km WSW of Portola Valley, CA
  3. 2.0 3km WSW of Portola Valley, CA
  4. 1.7 5km NW of Sunol, CA
  5. 1.5 15km E of Seven Trees, CA
  6. 1.8 8km NE of Alum Rock, CA
  7. 2.3 16km N of Morgan Hill, CA
  8. 1.6 9km NE of Alum Rock, CA
  9. 1.9 2km NNE of San Ramon, CA
  10. 2.2 1km SW of Danville, CA
  11. 1.6 8km NE of Gilroy, CA
  12. 1.6 11km ESE of Sunol, CA
  13. 2.4 11km ESE of Sunol, CA
  14. 2.2 15km N of Morgan Hill, CA
  15. 1.5 10km E of Blackhawk, 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 170 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.