QuakeIndex

Earthquake · automatic estimate, may change

M 2.1md

3 km ENE of Stinson Beach, CA

· 4.3 km deep · released about 40 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Marin County 19 kmSan Francisco County 42 kmContra Costa County 59 kmSan Mateo County 60 kmAlameda County 69 kmNapa County 71 kmSolano County 71 kmSonoma County 73 kmYolo County 106 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
4.3 km below the surface
Felt
1 report · strongest reported intensity I
Nearest
Marin County, 19 km NW
Status
Automatic — a machine’s first estimate, which may change

USGS · last changed by USGS · we first saw it 338 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage. 1 person has reported feeling it to USGS.

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 37.9128, -122.6195. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Marin County, CA 19 km (12 mi) SE of here earthquakes near Marin County
San Francisco County, CA 42 km (26 mi) ENE of here earthquakes near San Francisco County
Contra Costa County, CA 59 km (36 mi) W of here earthquakes near Contra Costa County
San Mateo County, CA 60 km (37 mi) NNW of here earthquakes near San Mateo County
Alameda County, CA 69 km (43 mi) WNW of here earthquakes near Alameda County
Napa County, CA 71 km (44 mi) SSW of here earthquakes near Napa County

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

Aftershocks so far

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

  1. 1.6 3 km SE of Pacifica, CA
  2. 2.4 11 km SSW of Bolinas, CA
  3. 1.5 3 km SE of Pacifica, CA
  4. 1.7 3 km NE of Oakland, CA
  5. 2.0 2 km SE of Pacifica, CA
  6. 1.5 3 km SE of Pacifica, CA
  7. 1.6 2 km ESE of Berkeley, CA
  8. 1.6 2 km SE of Pacifica, CA
  9. 1.6 4 km SE of Pacifica, CA
  10. 1.5 2 km E of Berkeley, CA
  11. 1.6 2 km SE of Pacifica, CA
  12. 2.5 3 km SE of Pacifica, CA
  13. 2.1 3 km SE of Pacifica, CA
  14. 1.5 3 km SE of Pacifica, CA
  15. 1.7 7 km ENE of Vallejo, 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.