QuakeIndex

Earthquake · reviewed by a seismologist

M 2.1md

11km SSW of Loyola, CA

· 7.8 km deep · released about 40 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N San Mateo County 25 kmSanta Cruz County 31 kmSanta Clara County 42 kmAlameda County 48 kmContra Costa County 75 kmSan Francisco County 93 kmMarin County 102 kmStanislaus County 107 kmSan Joaquin County 108 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
7.8 km below the surface
Felt
no reports yet
Nearest
San Mateo County, 25 km NW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 3165 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 40 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 5.8 380,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 270,000× the energy of this one
  3. Around the size people start to feel M 3.0 24× the energy of this one
  4. This earthquake M 2.1 about 40 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 37.2628, -122.1572. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
San Mateo County, CA 25 km (16 mi) SE of here earthquakes near San Mateo County
Santa Cruz County, CA 31 km (19 mi) NNW of here earthquakes near Santa Cruz County
Santa Clara County, CA 42 km (26 mi) W of here earthquakes near Santa Clara County
Alameda County, CA 48 km (30 mi) SSW of here earthquakes near Alameda County
Contra Costa County, CA 75 km (47 mi) SSW of here earthquakes near Contra Costa County
San Francisco County, CA 93 km (58 mi) ESE of here earthquakes near San Francisco County

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

Aftershocks so far

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

  1. 1.6 8km E of Alum Rock, CA
  2. 1.5 9km ENE of Milpitas, CA
  3. 3.0 16km E of Seven Trees, CA
  4. 1.8 21km WNW of Bonny Doon, CA
  5. 1.7 4km ESE of Union City, CA
  6. 1.5 4km NNW of Foster City, CA
  7. 2.0 15km N of Morgan Hill, CA
  8. 3.1 14km N of Morgan Hill, CA
  9. 1.9 3km WSW of Portola Valley, CA
  10. 1.6 8km E of Alum Rock, CA
  11. 1.8 5km SSE of Portola Valley, CA
  12. 1.9 9km NNE of Alum Rock, CA
  13. 2.3 14km N of Morgan Hill, CA
  14. 1.7 9km NE of Milpitas, CA
  15. 1.5 5km S of Portola Valley, 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.