QuakeIndex

Earthquake · reviewed by a seismologist

M 1.6md

Earthquake near San Bruno, CA

No earthquake was likely felt in San Bruno in the 24 hours to 5:10 am PST (13:10 UTC). The last one was M 2.7, 5 km (3 mi) W, at 5:17 pm PDT on 28 October 2026, estimated intensity III (weak) in town; 526 felt reports to USGS. Every earthquake near San Bruno

This page: a magnitude 1.6 earthquake was recorded 4 km (3 mi) southwest of San Bruno, CA, at 3:36 pm PDT on 29 March 2023 (22:36 UTC), 6.7 km deep. 1 person has reported feeling it to USGS.

USGS: 4km SW of San Bruno, CA

20 km (12 mi) S of San Francisco, CA · 8 km (5 mi) SW of South San Francisco, CA

3:36 pm PDT, Mar 29, 2023 · · 6.7 km deep · released about 8.7 lb of TNT

Every earthquake near San Bruno Felt it? Tell USGS Check my area
10 km30 km60 km120 km N San Mateo County 21 kmAlameda County 47 kmSan Francisco County 54 kmContra Costa County 56 kmMarin County 57 kmSanta Cruz County 76 kmSanta Clara County 78 kmSolano County 86 kmNapa County 101 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
3:36 pm PDT on 29 March 2023 ()
Where
4 km (3 mi) southwest of San Bruno, CA · earthquakes near San Bruno
Magnitude
M 1.6 (md)
Depth
6.7 km below the surface
Felt
1 report
Nearest
San Mateo County, 21 km SSE
Nearest mapped fault
San Andreas fault, under 1 km from its surface trace — near is not the same as on
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1324 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

At this magnitude and depth, people at rest would likely notice it out to about 10 km (6 mi) from the epicentre. In San Bruno, 4 km away, the estimate is intensity II (weak). Estimated from magnitude, depth and distance with the intensity equation USGS Did You Feel It? uses; felt reports, where there are any, are the measurement.

Likely felt in: San Bruno 4 km, intensity II · Millbrae 5 km, intensity II · Pacifica 5 km, intensity II · Burlingame 7 km, intensity II · South San Francisco 7 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 8.7 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.6 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 1,700,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 1,200,000× the energy of this one
  3. Around the size people start to feel M 3.0 110× the energy of this one
  4. This earthquake M 1.6 about 8.7 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.

For this area

The largest earthquake within 50 km since 2016 was M 4.4 on 2018-01-04 — about 13,000 times the energy of this one.

Before 2016, the USGS record lists 2 earthquakes of M5 or more within 50 km:

  1. 7.9 The 1906 San Francisco, California Earthquake · 19 km NNW of this epicentre
  2. 5.3 The 1957 San Francisco, California Earthquake · 8 km NNW of this epicentre

Since 2016: the QuakeIndex catalogue (US, M1.5+), built from the USGS FDSN event service. Before 2016: USGS ComCat, M5+ from 1900. Distances are between epicentres. This is the record, not a forecast.

Where

Epicentre 37.5997, -122.4385. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
San Mateo County, CA 21 km (13 mi) SSE earthquakes near San Mateo County
Alameda County, CA 47 km (29 mi) E earthquakes near Alameda County
San Francisco County, CA 54 km (34 mi) WNW earthquakes near San Francisco County
Contra Costa County, CA 56 km (35 mi) NE earthquakes near Contra Costa County
Marin County, CA 57 km (35 mi) NNW earthquakes near Marin County
Santa Cruz County, CA 76 km (47 mi) SSE earthquakes near Santa Cruz County

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

Aftershocks so far

46 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. 1.6 4 km ENE of Dublin, CA
  7. 2.1 3 km ESE of Pacifica, CA
  8. 3.0 2 km NW of Alamo, CA
  9. 1.7 4 km W of San Francisco Zoo, CA
  10. 2.3 2 km NNE of Millbrae, CA
  11. 1.6 7 km SSE of Portola Valley, CA
  12. 1.5 6 km ESE of Santa Venetia, CA
  13. 2.7 3 km N of Piedmont, CA
  14. 2.1 3 km NW of Castro Valley, CA
  15. 2.1 5 km ESE 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.

On USGS

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.