QuakeIndex

Earthquake · reviewed by a seismologist

M 2.2md

2 km NNE of Millbrae, CA

· 12 km deep · released about 56 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N San Mateo County 23 kmAlameda County 41 kmContra Costa County 50 kmMarin County 58 kmSan Francisco County 59 kmSanta Cruz County 75 kmSanta Clara County 75 kmSolano County 82 kmNapa County 99 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 2.2 (md)
Depth
12 km below the surface
Felt
17 reports · strongest reported intensity IV
Nearest
San Mateo County, 23 km S
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1064 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage. 17 people have reported feeling it to USGS.

How big was it?

This earthquake released about 56 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.2 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 270,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 190,000× the energy of this one
  3. Around the size people start to feel M 3.0 17× the energy of this one
  4. This earthquake M 2.2 about 56 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 37.6182, -122.3773. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
San Mateo County, CA 23 km (14 mi) N of here earthquakes near San Mateo County
Alameda County, CA 41 km (26 mi) W of here earthquakes near Alameda County
Contra Costa County, CA 50 km (31 mi) SW of here earthquakes near Contra Costa County
Marin County, CA 58 km (36 mi) SE of here earthquakes near Marin County
San Francisco County, CA 59 km (37 mi) ESE of here earthquakes near San Francisco County
Santa Cruz County, CA 75 km (47 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

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

  1. 1.7 5 km WSW of San Francisco Zoo, CA
  2. 3.2 5 km WSW of San Francisco Zoo, CA
  3. 2.2 3 km ESE of Woodside, CA
  4. 1.5 6 km S of Portola Valley, CA
  5. 2.1 3 km W of Woodside, CA
  6. 2.2 6 km S of Alameda, CA
  7. 1.6 6 km S of Alameda, CA
  8. 2.3 3 km ESE of Woodside, CA
  9. 1.6 4 km NE of Portola Valley, CA
  10. 1.5 6 km E of Santa Venetia, CA
  11. 1.6 1 km SSE of Pacheco, CA
  12. 1.5 2 km N of Pleasant Hill, CA
  13. 1.5 3 km W of Woodside, CA
  14. 1.8 7 km NW of San Francisco Zoo, CA
  15. 1.6 2 km ENE of Oakland, 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 2,600 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.