Earthquake · reviewed by a seismologist
M 3.9mw
Earthquake near San Lorenzo, CA
No earthquake was likely felt in San Lorenzo in the 24 hours to 1:35 am PST (09:35 UTC). The last one was M 2.4, 19 km (12 mi) ENE, at 4:29 pm PDT on 19 October 2026, estimated intensity II (weak) in town; 5 felt reports to USGS. Every earthquake near San Lorenzo
This page: a magnitude 3.9 earthquake was recorded 4 km (2 mi) north-northeast of San Lorenzo, CA, at 6:29 pm PDT on 28 June 2021 (01:29 UTC), 9.2 km deep. 12,071 people have reported feeling it to USGS.
USGS: 3km N of San Lorenzo, CA
12 km (7 mi) SE of Oakland, CA · in San Leandro, CA
- When
- 6:29 pm PDT on 28 June 2021 ()
- Where
- 4 km (2 mi) north-northeast of San Lorenzo, CA · earthquakes near San Lorenzo
- Magnitude
- M 3.9 (mw)
- Depth
- 9.2 km below the surface
- Felt
- 12,071 reports · strongest reported intensity IV
- Measured shaking
- intensity IV (ShakeMap)
- Tsunami
- USGS flagged this event for tsunami evaluation. Follow tsunami.gov for official messages.
- Nearest
- Alameda County, 20 km ESE
- Nearest mapped fault
- Hayward fault, under 1 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 598 days ago
Earthquake alerts for San Lorenzo, CA
Get a notification in this browser when USGS records an earthquake near San Lorenzo, 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 89 km (55 mi) from the epicentre. In San Lorenzo, 4 km away, the estimate is intensity IV (light). 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: Castro Valley 3 km, intensity IV · San Leandro 4 km, intensity IV · San Lorenzo 4 km, intensity IV · Hayward 6 km, intensity IV · Alameda 14 km, intensity III · San Ramon 15 km, intensity III · Union City 15 km, intensity III · Dublin 16 km, intensity III. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 11 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.9 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 16,000× the energy of this one
- Mineral, Virginia 2011 M 5.8 710× the energy of this one
- Magna, Utah 2020 M 5.7 500× the energy of this one
- This earthquake M 3.9 about 11 tons of TNT
- Around the size people start to feel M 3.0 this one released 22× more
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 4.5 on 2019-10-15 — about 6.9 times the energy of this one.
Before 2016, the USGS record lists 8 earthquakes of M5 or more within 50 km; the five largest:
- 7.9 The 1906 San Francisco, California Earthquake · 38 km W of this epicentre
- 5.8 The 1980 Livermore, California Earthquake · 35 km ENE of this epicentre
- 5.7 15 km NE of East Foothills, California · 46 km ESE of this epicentre
- 5.5 6 km NNE of East Foothills, California · 43 km SE of this epicentre
- 5.4 9 km NE of Livermore, California · 37 km E 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 37.7062, -122.1223. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Alameda County, CA | 20 km (12 mi) | ESE | earthquakes near Alameda County |
| Contra Costa County, CA | 28 km (17 mi) | NNE | earthquakes near Contra Costa County |
| San Mateo County, CA | 39 km (24 mi) | SW | earthquakes near San Mateo County |
| Solano County, CA | 64 km (40 mi) | NNE | earthquakes near Solano County |
| Santa Clara County, CA | 66 km (41 mi) | SE | earthquakes near Santa Clara County |
| Marin County, CA | 67 km (42 mi) | NW | earthquakes near Marin 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.
- 3.1 6km WNW of Dublin, CA
- 1.5 5km E of Vallejo, CA
- 2.3 8km ESE of Fremont, CA
- 2.9 10km NE of Milpitas, CA
- 2.2 5km E of Vallejo, CA
- 1.8 1km NW of Diablo, CA
- 1.7 3km ESE of Pacheco, CA
- 1.7 6km WNW of Dublin, CA
- 1.6 5km E of Vallejo, CA
- 1.9 10km NE of Milpitas, CA
- 1.7 5km NW of Dublin, CA
- 2.6 6km S of Livermore, CA
- 2.4 11km NE of Milpitas, CA
- 1.8 5km ENE of Vallejo, CA
- 1.7 8km SSW of Livermore, 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.