QuakeIndex

Earthquake · reviewed by a seismologist

M 2.1md

15km ENE of Alum Rock, CA

· 4.5 km deep · released about 49 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Santa Clara County 23 kmAlameda County 32 kmSanta Cruz County 55 kmContra Costa County 60 kmStanislaus County 61 kmSan Mateo County 62 kmSan Joaquin County 67 kmMerced County 88 kmSolano County 96 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
4.5 km below the surface
Felt
3 reports · strongest reported intensity II
Nearest
Santa Clara County, 23 km S
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1511 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage. 3 people have reported feeling it to USGS.

How big was it?

This earthquake released about 49 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 5.8 310,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 220,000× 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 49 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 37.4258, -121.6723. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Santa Clara County, CA 23 km (14 mi) N of here earthquakes near Santa Clara County
Alameda County, CA 32 km (20 mi) SE of here earthquakes near Alameda County
Santa Cruz County, CA 55 km (34 mi) NNE of here earthquakes near Santa Cruz County
Contra Costa County, CA 60 km (37 mi) SSE of here earthquakes near Contra Costa County
Stanislaus County, CA 61 km (38 mi) WSW of here earthquakes near Stanislaus County
San Mateo County, CA 62 km (38 mi) E of here earthquakes near San Mateo County

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

Aftershocks so far

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

  1. 1.6 8km ENE of Gilroy, CA
  2. 1.8 10km ENE of Morgan Hill, CA
  3. 2.1 7km NE of San Martin, CA
  4. 1.5 11km SW of Mountain House, CA
  5. 1.6 1km SSE of San Ramon, CA
  6. 2.6 8km ENE of Alum Rock, CA
  7. 1.9 22km NE of Morgan Hill, CA
  8. 1.6 10km NE of Milpitas, CA
  9. 1.9 1km S of San Ramon, CA
  10. 1.6 9km SE of Sunol, CA
  11. 2.8 16km SSE of Livermore, CA
  12. 1.6 3km W of Fruitdale, CA
  13. 1.5 11km WSW of Saratoga, CA
  14. 1.6 11km WSW of Saratoga, CA
  15. 1.7 11km WSW of Saratoga, 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 1,800 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.