Earthquake · reviewed by a seismologist
M 2.7md
Earthquake near Portola Valley, CA
No earthquake was likely felt in Portola Valley in the 24 hours to 2:24 am PST (10:24 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 2.7 earthquake was recorded 3 km (2 mi) west of Portola Valley, CA, at 8:09 pm PDT on 22 June 2020 (03:09 UTC), 10 km deep. 114 people have reported feeling it to USGS.
USGS: 3km W of Portola Valley, CA
11 km (7 mi) W of Palo Alto, CA · 41 km (26 mi) WNW of San Jose, CA
- When
- 8:09 pm PDT on 22 June 2020 ()
- Where
- 3 km (2 mi) west of Portola Valley, CA · earthquakes near Portola Valley
- Magnitude
- M 2.7 (md)
- Depth
- 10 km below the surface
- Felt
- 114 reports · strongest reported intensity V
- Nearest
- San Mateo County, 10 km WNW
- 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 2265 days ago
Earthquake alerts for Portola Valley, CA
Get a notification in this browser when USGS records an earthquake near Portola Valley, CA. No account or email needed.
Alerts are on for .
Not a warning. An alert comes after USGS publishes a quake, usually minutes after the shaking. For early warning use ShakeAlert, through your phone's Wireless Emergency Alerts or the MyShake app.
This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.
At this magnitude and depth, people at rest would likely notice it out to about 23 km (14 mi) from the epicentre. In Portola Valley, 3 km away, the estimate is intensity III (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: Menlo Park 11 km, intensity II · Redwood City 12 km, intensity II · Palo Alto 13 km, intensity II · Los Altos 14 km, intensity II · San Carlos 14 km, intensity II · East Palo Alto 15 km, intensity II · Belmont 15 km, intensity II · Mountain View 16 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 390 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.7 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 39,000× the energy of this one
- Magna, Utah 2020 M 5.7 28,000× the energy of this one
- Around the size people start to feel M 3.0 2.5× the energy of this one
- This earthquake M 2.7 about 390 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 14 earthquakes of M5 or more within 50 km; the five largest:
- 7.9 The 1906 San Francisco, California Earthquake · 48 km NNW of this epicentre
- 6.2 Near San Jose, California · 42 km ESE of this epicentre
- 6.1 Near San Jose, California · 46 km ESE of this epicentre
- 5.8 7 km NNW of Boulder Creek, California · 24 km SSE of this epicentre
- 5.5 Santa Cruz Mountains, California · 34 km SE 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 37.3842, -122.2670. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| San Mateo County, CA | 10 km (6 mi) | WNW | earthquakes near San Mateo County |
| Alameda County, CA | 43 km (27 mi) | NE | earthquakes near Alameda County |
| Santa Cruz County, CA | 47 km (29 mi) | SSE | earthquakes near Santa Cruz County |
| Santa Clara County, CA | 54 km (34 mi) | ESE | earthquakes near Santa Clara County |
| Contra Costa County, CA | 66 km (41 mi) | NNE | earthquakes near Contra Costa County |
| San Francisco County, CA | 77 km (48 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
54 earthquakes have been recorded within 50 km since this one.
- 2.0 11km NE of Milpitas, CA
- 2.9 10km NE of Milpitas, CA
- 1.7 10km NE of Milpitas, CA
- 2.6 10km NNE of Milpitas, CA
- 3.3 10km NE of Milpitas, CA
- 2.9 10km NE of Milpitas, CA
- 2.7 10km NE of Milpitas, CA
- 1.9 10km NE of Milpitas, CA
- 1.6 10km NE of Milpitas, CA
- 1.8 10km NE of Milpitas, CA
- 2.1 10km NE of Milpitas, CA
- 2.0 10km NE of Milpitas, CA
- 3.5 10km NE of Milpitas, CA
- 2.0 10km NE of Milpitas, CA
- 3.4 10km NE of Milpitas, 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
- 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.