Earthquake near Portola Valley, CA

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 Portola Valley, 2 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: Portola Valley 2 km, intensity II · Stanford 10 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 9.6 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.7 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 1,600,000× the energy of this one
2. Magna, Utah 2020 M 5.7 1,100,000× the energy of this one
3. Around the size people start to feel M 3.0 99× the energy of this one
4. This earthquake M 1.7 about 9.6 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

No earthquake of M4 or more has been recorded within 50 km since our catalogue begins in 2016.

Before 2016, the USGS record lists 15 earthquakes of M5 or more within 50 km; the five largest:

1. 7.9 The 1906 San Francisco, California Earthquake · 50 km NNW of this epicentre Apr 18, 1906
2. 6.9 The 1989 Loma Prieta, California Earthquake · 50 km SE of this epicentre Oct 18, 1989
3. 6.2 Near San Jose, California · 41 km E of this epicentre Aug 3, 1903
4. 6.1 Near San Jose, California · 44 km ESE of this epicentre Jun 11, 1903
5. 5.8 7 km NNW of Boulder Creek, California · 22 km SSE of this epicentre Sep 5, 1955

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 37.3702, -122.2532. Map © OpenStreetMap contributors.

Nearby places

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

Aftershocks so far

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

1. 1.5 5 km E of Alameda, California 01:54 UTC
2. 1.7 2 km S of Loyola, California 18:30 UTC
3. 1.6 2 km SSW of Loyola, California 18:28 UTC
4. 2.4 8 km NNE of East Foothills, California 05:09 UTC
5. 1.6 5 km ESE of Piedmont, California 14:30 UTC
6. 2.4 6 km WNW of Broadmoor, California 13:11 UTC
7. 1.6 1 km NW of Ashland, California 22:58 UTC
8. 2.0 2 km NNE of Pacifica, California 09:37 UTC
9. 1.5 2 km S of Loyola, California 18:23 UTC
10. 1.8 1 km NE of Pacifica, California 10:36 UTC
11. 1.7 1 km NNE of Pacifica, California 20:16 UTC
12. 2.0 2 km NE of Pacifica, California 13:59 UTC
13. 1.9 0 km WNW of Loyola, California 00:04 UTC
14. 1.7 5 km E of Alameda, California 15:35 UTC
15. 2.0 5 km E of Alameda, California 15:04 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 10:05 UTC. QuakeIndex does not forecast aftershocks. When USGS issues an operational aftershock forecast it appears on the USGS event page.

On USGS

• The official USGS event page — the source of record for every value above
• Did you feel it? Report it to USGS — reports go to USGS, not to us
• ShakeMap for this event, when USGS has produced one

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