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 11 km (7 mi) from the epicentre. In Portola Valley, 5 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. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 16 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.8 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 930,000× the energy of this one
2. Magna, Utah 2020 M 5.7 660,000× the energy of this one
3. Around the size people start to feel M 3.0 59× the energy of this one
4. This earthquake M 1.8 about 16 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 17 earthquakes of M5 or more within 50 km; the five largest:

1. 6.9 The 1989 Loma Prieta, California Earthquake · 45 km SE of this epicentre Oct 18, 1989
2. 6.3 16 km SW of Davenport, California · 47 km SSW of this epicentre Oct 22, 1926
3. 6.2 Near San Jose, California · 38 km E of this epicentre Aug 3, 1903
4. 6.2 The 1984 Morgan Hill, California Earthquake · 48 km E of this epicentre Apr 24, 1984
5. 6.1 Near San Jose, California · 40 km ESE of this epicentre Jun 11, 1903

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 37.3360, -122.2237. Map © OpenStreetMap contributors.

Nearby places

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. 1.9 14 km SE of Alum Rock, CA 14:56 UTC
2. 1.7 11 km ESE of Alum Rock, CA 18:36 UTC
3. 1.6 4 km SW of Loyola, CA 22:18 UTC
4. 2.6 5 km WSW of Loyola, CA 22:56 UTC
5. 3.0 5 km WSW of Loyola, CA 21:16 UTC
6. 2.5 5 km SW of Loyola, CA 11:58 UTC
7. 2.2 4 km S of Highlands-Baywood Park, CA 23:12 UTC
8. 1.9 3 km ESE of Hayward, CA 09:45 UTC
9. 1.7 14 km WSW of Portola Valley, CA 15:31 UTC
10. 2.9 5 km ENE of Fairview, CA 05:55 UTC
11. 1.9 5 km WNW of Dublin, CA 04:41 UTC
12. 1.6 11 km of Boulder Creek, CA 10:59 UTC
13. 1.8 6 km SSE of Portola Valley, CA 18:09 UTC
14. 1.7 6 km SW of Los Altos Hills, CA 01:24 UTC
15. 1.5 1 km E of Union City, CA 17:47 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 06:48 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.