QuakeIndex

Earthquake · reviewed by a seismologist

M 2.3md

Earthquake near Milpitas, CA

No earthquake was likely felt in Milpitas in the 24 hours to 3:44 pm PST (23:44 UTC). The last one was M 1.6, 9 km (5 mi) NNE, at 5:49 am PDT on 4 October 2026, estimated intensity II (weak) in town. Every earthquake near Milpitas

This page: a magnitude 2.3 earthquake was recorded 9 km (6 mi) northeast of Milpitas, CA, at 10:37 am PDT on 30 July 2023 (17:37 UTC), 7.8 km deep. 2 people have reported feeling it to USGS.

USGS: 9 km NE of Milpitas, CA

22 km (14 mi) N of San Jose, CA · 8 km (5 mi) NNE of Milpitas, CA

10:37 am PDT, Jul 30, 2023 · · 7.8 km deep · released about 85 lb of TNT

Every earthquake near Milpitas Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Alameda County 18 kmSanta Clara County 33 kmSan Mateo County 47 kmContra Costa County 49 kmSanta Cruz County 55 kmSan Joaquin County 70 kmStanislaus County 74 kmSolano County 87 kmMarin 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
10:37 am PDT on 30 July 2023 ()
Where
9 km (6 mi) northeast of Milpitas, CA · earthquakes near Milpitas
Magnitude
M 2.3 (md)
Depth
7.8 km below the surface
Felt
2 reports · strongest reported intensity II
Nearest
Alameda County, 18 km NNW
Nearest mapped fault
Hayward fault, 4 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 1199 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 18 km (11 mi) from the epicentre. In Milpitas, 9 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: Milpitas 9 km, intensity II · Fremont 14 km, intensity II · San Jose 17 km, intensity II · Newark 18 km, intensity II · Santa Clara 18 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 85 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.3 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 180,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 130,000× the energy of this one
  3. Around the size people start to feel M 3.0 11× the energy of this one
  4. This earthquake M 2.3 about 85 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 5.1 on 2022-10-25 — about 14,000 times the energy of this one.

Before 2016, the USGS record lists 16 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.5 Near Morgan Hill, California · 46 km SSE of this epicentre
  2. 6.2 Near San Jose, California · 22 km S of this epicentre
  3. 6.2 The 1984 Morgan Hill, California Earthquake · 25 km SE of this epicentre
  4. 6.1 Near San Jose, California · 33 km S of this epicentre
  5. 5.8 7 km NNW of Boulder Creek, California · 43 km SW 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 37.4912, -121.8427. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Alameda County, CA 18 km (11 mi) NNW earthquakes near Alameda County
Santa Clara County, CA 33 km (20 mi) SSE earthquakes near Santa Clara County
San Mateo County, CA 47 km (29 mi) W earthquakes near San Mateo County
Contra Costa County, CA 49 km (30 mi) NNW earthquakes near Contra Costa County
Santa Cruz County, CA 55 km (34 mi) SSW earthquakes near Santa Cruz County
San Joaquin County, CA 70 km (44 mi) NE earthquakes near San Joaquin County

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

Aftershocks so far

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

  1. 2.7 9 km NE of Alum Rock, CA
  2. 3.2 16 km WSW of Patterson, CA
  3. 1.9 3 km ESE of South San Francisco, CA
  4. 1.7 4 km WSW of Cupertino, CA
  5. 2.1 4 km WSW of Cupertino, CA
  6. 1.8 4 km WSW of Cupertino, CA
  7. 2.8 4 km WSW of Cupertino, CA
  8. 1.5 16 km SW of Westley, CA
  9. 1.8 4 km WSW of Cupertino, CA
  10. 1.6 5 km WSW of Cupertino, CA
  11. 1.9 4 km WSW of Cupertino, CA
  12. 2.9 4 km WSW of Cupertino, CA
  13. 1.6 18 km WSW of Patterson, CA
  14. 1.5 17 km WSW of Patterson, CA
  15. 1.5 18 km WSW of Patterson, 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.