QuakeIndex

Earthquake · reviewed by a seismologist

M 2.1md

5km WSW of San Francisco Zoo, CA

· 8.1 km deep · released about 40 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N San Mateo County 37 kmMarin County 41 kmSan Francisco County 42 kmAlameda County 57 kmContra Costa County 58 kmSolano County 82 kmNapa County 90 kmSanta Cruz County 92 kmSanta Clara 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
8.1 km below the surface
Felt
no reports yet
Nearest
San Mateo County, 37 km SSE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2774 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 37.7147, -122.5575. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
San Mateo County, CA 37 km (23 mi) NNW of here earthquakes near San Mateo County
Marin County, CA 41 km (25 mi) SSE of here earthquakes near Marin County
San Francisco County, CA 42 km (26 mi) E of here earthquakes near San Francisco County
Alameda County, CA 57 km (36 mi) W of here earthquakes near Alameda County
Contra Costa County, CA 58 km (36 mi) WSW of here earthquakes near Contra Costa County
Solano County, CA 82 km (51 mi) SW of here earthquakes near Solano County

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

Aftershocks so far

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

  1. 1.5 3km ESE of Berkeley, CA
  2. 2.1 2km NNE of Pacifica, CA
  3. 1.9 2km SSE of Crockett, CA
  4. 1.6 4km NNW of Pacifica, CA
  5. 1.9 2km NNW of Crockett, CA
  6. 2.4 2km NNE of Pacifica, CA
  7. 2.1 4km ENE of Oakland, CA
  8. 1.5 8km S of Muir Beach, CA
  9. 1.8 3km WSW of Muir Beach, CA
  10. 1.9 2km NW of Crockett, CA
  11. 1.6 2km S of Alamo, CA
  12. 2.2 3km ESE of Berkeley, CA
  13. 1.9 4km SE of Rodeo, CA
  14. 1.7 1km N of East Richmond Heights, CA
  15. 2.0 5km N of San Leandro, 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 4.4 on 2018-01-04 — it released about 2,800 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.