QuakeIndex

Earthquake · reviewed by a seismologist

M 2.1md

15 km NE of Alum Rock, CA

· 8.6 km deep · released about 51 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Alameda County 25 kmSanta Clara County 28 kmContra Costa County 53 kmSan Mateo County 57 kmSanta Cruz County 57 kmStanislaus County 65 kmSan Joaquin County 65 kmSolano County 90 kmMerced County 94 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
8.6 km below the surface
Felt
no reports yet
Nearest
Alameda County, 25 km NW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 717 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 51 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 5.8 300,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 210,000× the energy of this one
  3. Around the size people start to feel M 3.0 19× the energy of this one
  4. This earthquake M 2.1 about 51 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 37.4757, -121.7292. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Alameda County, CA 25 km (16 mi) SE of here earthquakes near Alameda County
Santa Clara County, CA 28 km (18 mi) N of here earthquakes near Santa Clara County
Contra Costa County, CA 53 km (33 mi) SSE of here earthquakes near Contra Costa County
San Mateo County, CA 57 km (35 mi) E of here earthquakes near San Mateo County
Santa Cruz County, CA 57 km (35 mi) NNE of here earthquakes near Santa Cruz County
Stanislaus County, CA 65 km (40 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. 1.9 3 km S of Los Altos Hills, CA
  2. 2.8 10 km ESE of Alum Rock, CA
  3. 1.5 9 km NE of Alum Rock, CA
  4. 2.3 15 km NNE of Morgan Hill, CA
  5. 1.9 11 km ESE of Alum Rock, CA
  6. 2.1 9 km E of Milpitas, CA
  7. 2.0 16 km NNE of Morgan Hill, CA
  8. 2.1 2 km NW of Castro Valley, CA
  9. 1.5 10 km of Boulder Creek, CA
  10. 1.5 15 km ESE of Seven Trees, CA
  11. 1.5 13 km NNE of Morgan Hill, CA
  12. 2.8 2 km NW of Castro Valley, CA
  13. 1.5 11 km of Boulder Creek, CA
  14. 2.4 11 km of Boulder Creek, CA
  15. 2.2 2 km NNW 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 5.1 on 2022-10-25 — it released about 23,000 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.