QuakeIndex

Earthquake · reviewed by a seismologist

M 2.0md

Earthquake near Portola Valley, CA

No earthquake was likely felt in Portola Valley in the 24 hours to 2:08 pm PST (22:08 UTC). The last one was M 1.9, 6 km (4 mi) N, at 4:14 pm PDT on 11 October 2026, estimated intensity II (weak) in town; 1 felt report to USGS. Every earthquake near Portola Valley

This page: a magnitude 2.0 earthquake was recorded 7 km (4 mi) south-southeast of Portola Valley, CA, at 1:16 pm PDT on 26 June 2023 (20:16 UTC), 8.5 km deep.

USGS: 7km SSE of Portola Valley, CA

10 km (6 mi) SW of Palo Alto, CA · 35 km (22 mi) W of San Jose, CA

1:16 pm PDT, Jun 26, 2023 · · 8.5 km deep · released about 30 lb of TNT

Every earthquake near Portola Valley Felt it? Tell USGS Check my area
10 km30 km60 km120 km N San Mateo County 18 kmSanta Cruz County 39 kmAlameda County 44 kmSanta Clara County 47 kmContra Costa County 70 kmSan Francisco County 86 kmMarin County 94 kmSan Joaquin County 107 kmSolano County 107 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
1:16 pm PDT on 26 June 2023 ()
Where
7 km (4 mi) south-southeast of Portola Valley, CA · earthquakes near Portola Valley
Magnitude
M 2.0 (md)
Depth
8.5 km below the surface
Felt
no reports yet
Nearest
San Mateo County, 18 km NW
Nearest mapped fault
San Andreas fault, 2 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 1232 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 13 km (8 mi) from the epicentre. In Portola Valley, 7 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: Los Altos 11 km, intensity II · Mountain View 13 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 30 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.0 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 500,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 350,000× the energy of this one
  3. Around the size people start to feel M 3.0 32× the energy of this one
  4. This earthquake M 2.0 about 30 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 39,000 times the energy of this one.

Before 2016, the USGS record lists 18 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.9 The 1989 Loma Prieta, California Earthquake · 43 km SE of this epicentre
  2. 6.3 16 km SW of Davenport, California · 46 km SSW of this epicentre
  3. 6.2 Near San Jose, California · 36 km E of this epicentre
  4. 6.2 The 1984 Morgan Hill, California Earthquake · 47 km E of this epicentre
  5. 6.1 Near San Jose, California · 38 km ESE 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 37.3242, -122.2053. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
San Mateo County, CA 18 km (11 mi) NW earthquakes near San Mateo County
Santa Cruz County, CA 39 km (24 mi) SSE earthquakes near Santa Cruz County
Alameda County, CA 44 km (27 mi) NE earthquakes near Alameda County
Santa Clara County, CA 47 km (29 mi) ESE earthquakes near Santa Clara County
Contra Costa County, CA 70 km (43 mi) NNE earthquakes near Contra Costa County
San Francisco County, CA 86 km (53 mi) WNW earthquakes near San Francisco County

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

Aftershocks so far

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

  1. 2.4 8 km E of Fremont, CA
  2. 1.6 17 km WNW of Bonny Doon, CA
  3. 2.2 1 km NE of San Leandro, CA
  4. 2.7 8 km ENE of Alum Rock, CA
  5. 2.2 9 km NE of Alum Rock, CA
  6. 1.9 4 km WSW of Cupertino, CA
  7. 2.0 9 km NE of Alum Rock, CA
  8. 1.6 4 km WSW of Cupertino, CA
  9. 1.7 9 km NE of Milpitas, CA
  10. 2.1 10 km WSW of San Lorenzo, CA
  11. 1.7 2 km ENE of San Leandro, CA
  12. 1.9 4 km WSW of Cupertino, CA
  13. 2.7 9 km NE of Alum Rock, CA
  14. 1.9 3 km ESE of South San Francisco, CA
  15. 1.7 4 km WSW of Cupertino, 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.