QuakeIndex

Earthquake · reviewed by a seismologist

M 3.4ml

1km ENE of Pacifica, CA

· 9.1 km deep · released about 1.9 tons of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N San Mateo County 24 kmAlameda County 50 kmSan Francisco County 50 kmMarin County 54 kmContra Costa County 57 kmSanta Cruz County 79 kmSanta Clara County 82 kmSolano County 86 kmNapa County 100 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 3.4 (ml)
Depth
9.1 km below the surface
Felt
2675 reports · strongest reported intensity IV
Measured shaking
intensity IV (ShakeMap)
Nearest
San Mateo County, 24 km SSE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1065 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage. 2675 people have reported feeling it to USGS.

How big was it?

This earthquake released about 1.9 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.4 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 89,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 4,000× the energy of this one
  3. Magna, Utah 2020 M 5.7 2,800× the energy of this one
  4. This earthquake M 3.4 about 1.9 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 4× more

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 37.6173, -122.4773. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
San Mateo County, CA 24 km (15 mi) NNW of here earthquakes near San Mateo County
Alameda County, CA 50 km (31 mi) W of here earthquakes near Alameda County
San Francisco County, CA 50 km (31 mi) ESE of here earthquakes near San Francisco County
Marin County, CA 54 km (33 mi) SSE of here earthquakes near Marin County
Contra Costa County, CA 57 km (36 mi) SW of here earthquakes near Contra Costa County
Santa Cruz County, CA 79 km (49 mi) NNW of here earthquakes near Santa Cruz 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. 1.5 4 km ESE of Pacifica, CA
  2. 1.6 9 km SW of Loyola, CA
  3. 2.1 4 km NNE of Fairview, CA
  4. 1.5 10 km SSW of Half Moon Bay, CA
  5. 1.6 7 km SSE of Portola Valley, CA
  6. 2.1 3 km ESE of Pacifica, CA
  7. 3.0 2 km NW of Alamo, CA
  8. 1.7 4 km W of San Francisco Zoo, CA
  9. 2.3 2 km NNE of Millbrae, CA
  10. 1.6 7 km SSE of Portola Valley, CA
  11. 1.5 6 km ESE of Santa Venetia, CA
  12. 2.7 3 km N of Piedmont, CA
  13. 2.1 3 km NW of Castro Valley, CA
  14. 2.1 5 km ESE of Oakland, CA
  15. 1.5 1 km N of Pacifica, 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 30 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.