QuakeIndex

Earthquake · reviewed by a seismologist

M 2.1md

5 km NW of San Francisco Zoo, CA

· 7.9 km deep · released about 49 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Marin County 37 kmSan Mateo County 41 kmSan Francisco County 42 kmContra Costa County 56 kmAlameda County 58 kmSolano County 79 kmNapa County 86 kmSonoma County 92 kmSanta Cruz County 95 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
7.9 km below the surface
Felt
72 reports · strongest reported intensity IV
Nearest
Marin County, 37 km NNW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 614 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage. 72 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 37.7513, -122.5560. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Marin County, CA 37 km (23 mi) SSE of here earthquakes near Marin County
San Mateo County, CA 41 km (25 mi) NNW of here earthquakes near San Mateo County
San Francisco County, CA 42 km (26 mi) E of here earthquakes near San Francisco County
Contra Costa County, CA 56 km (35 mi) WSW of here earthquakes near Contra Costa County
Alameda County, CA 58 km (36 mi) WNW of here earthquakes near Alameda County
Solano County, CA 79 km (49 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

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

  1. 1.7 4 km W of Alamo, CA
  2. 2.5 4 km W of Alamo, CA
  3. 2.5 4 km W of Alamo, CA
  4. 1.5 3 km WSW of San Francisco Zoo, CA
  5. 2.4 5 km WSW of San Francisco Zoo, CA
  6. 1.6 1 km S of Pacheco, CA
  7. 1.7 0 km NNE of East Richmond Heights, CA
  8. 1.7 3 km SSE of Pacifica, CA
  9. 2.0 3 km SSE of Pacifica, CA
  10. 1.7 4 km WSW of Millbrae, CA
  11. 1.5 4 km SE of Oakland, CA
  12. 1.6 4 km WSW of Millbrae, CA
  13. 2.3 2 km E of Hayward, CA
  14. 1.8 2 km E of Hayward, CA
  15. 2.5 5 km W of Pleasant Hill, 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 4.5 on 2019-10-15 — it released about 3,000 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.