QuakeIndex

Earthquake · reviewed by a seismologist

M 2.1md

9km NNE of Alum Rock, CA

· 4.6 km deep · released about 41 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 51 kmSan Mateo County 52 kmContra Costa County 56 kmStanislaus County 70 kmSan Joaquin County 71 kmSolano County 93 kmMerced 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 2.1 (md)
Depth
4.6 km below the surface
Felt
no reports yet
Nearest
Santa Clara County, 25 km SSE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2736 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

How big was it?

This earthquake released about 41 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 5.8 370,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 260,000× the energy of this one
  3. Around the size people start to feel M 3.0 23× the energy of this one
  4. This earthquake M 2.1 about 41 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 37.4363, -121.7848. 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 51 km (32 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 56 km (35 mi) SSE of here earthquakes near Contra Costa County
Stanislaus County, CA 70 km (44 mi) W of here earthquakes near Stanislaus County

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

Aftershocks so far

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

  1. 1.5 2km SSW of Diablo, CA
  2. 2.1 13km WSW of Byron, CA
  3. 3.2 12km WSW of Byron, CA
  4. 4.3 12km WSW of Byron, CA
  5. 1.7 9km WSW of Mountain House, CA
  6. 3.3 16km N of Morgan Hill, CA
  7. 1.5 8km ENE of Alum Rock, CA
  8. 1.6 8km N of Day Valley, CA
  9. 2.1 8km WSW of Mountain House, CA
  10. 1.5 16km N of Morgan Hill, CA
  11. 2.4 8km NE of Alum Rock, CA
  12. 1.6 16km N of Morgan Hill, CA
  13. 1.5 13km NNE of Morgan Hill, CA
  14. 2.5 8km ENE of Alum Rock, CA
  15. 2.2 8km ENE 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 1,000 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.