QuakeIndex

Earthquake · reviewed by a seismologist

M 2.4md

3 km WSW of Half Moon Bay, CA

· 9.0 km deep · released about 130 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N San Mateo County 9 kmAlameda County 53 kmSan Francisco County 58 kmSanta Cruz County 64 kmContra Costa County 69 kmMarin County 71 kmSanta Clara County 73 kmSolano County 101 kmNapa County 118 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 2.4 (md)
Depth
9.0 km below the surface
Felt
18 reports · strongest reported intensity III
Nearest
San Mateo County, 9 km ESE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1112 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage. 18 people have reported feeling it to USGS.

How big was it?

This earthquake released about 130 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.4 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 120,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 83,000× the energy of this one
  3. Around the size people start to feel M 3.0 7.4× the energy of this one
  4. This earthquake M 2.4 about 130 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 37.4558, -122.4648. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
San Mateo County, CA 9 km (6 mi) WNW of here earthquakes near San Mateo County
Alameda County, CA 53 km (33 mi) WSW of here earthquakes near Alameda County
San Francisco County, CA 58 km (36 mi) ESE of here earthquakes near San Francisco County
Santa Cruz County, CA 64 km (40 mi) NW of here earthquakes near Santa Cruz County
Contra Costa County, CA 69 km (43 mi) SW of here earthquakes near Contra Costa County
Marin County, CA 71 km (44 mi) SSE of here earthquakes near Marin County

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

Aftershocks so far

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

  1. 1.7 2 km ESE of Oakland, CA
  2. 2.1 1 km SSE of Los Altos Hills, CA
  3. 2.5 2 km SSE of Los Altos Hills, CA
  4. 1.6 4 km WSW of Colma, CA
  5. 1.5 1 km N of Millbrae, CA
  6. 1.9 2 km NNE of Millbrae, CA
  7. 2.2 4 km WSW of Cupertino, CA
  8. 2.2 6 km WNW of San Francisco Zoo, CA
  9. 1.5 6 km WNW of San Francisco Zoo, CA
  10. 2.1 3 km N of San Lorenzo, CA
  11. 1.5 2 km ESE of Pacifica, CA
  12. 1.7 2 km NNE of Saratoga, CA
  13. 1.6 4 km SW of Hillsborough, CA
  14. 1.6 4 km SW of Hillsborough, CA
  15. 1.5 2 km NNE of Millbrae, 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 870 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.