Earthquake · reviewed by a seismologist
M 2.7md
Earthquake near San Ramon, CA
No earthquake was likely felt in San Ramon in the 24 hours to 2:45 am PST (10:45 UTC). The last one was M 2.1, 6 km (4 mi) NNE, at 7:18 am PDT on 31 October 2026, estimated intensity II (weak) in town; 1 felt report to USGS. Every earthquake near San Ramon
This page: a magnitude 2.7 earthquake was recorded 6 km (3 mi) south-southwest of San Ramon, CA, at 1:49 am PDT on 30 June 2021 (08:49 UTC), 7.8 km deep. 117 people have reported feeling it to USGS.
USGS: 6km SSW of San Ramon, CA
7 km (4 mi) SW of San Ramon, CA · 38 km (24 mi) E of San Francisco, CA
- When
- 1:49 am PDT on 30 June 2021 ()
- Where
- 6 km (3 mi) south-southwest of San Ramon, CA · earthquakes near San Ramon
- Magnitude
- M 2.7 (md)
- Depth
- 7.8 km below the surface
- Felt
- 117 reports · strongest reported intensity III
- Nearest
- Alameda County, 12 km SE
- Nearest mapped fault
- Calaveras fault, 4 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 1821 days ago
Earthquake alerts for San Ramon, CA
Get a notification in this browser when USGS records an earthquake near San Ramon, 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 24 km (15 mi) from the epicentre. In San Ramon, 6 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: San Ramon 6 km, intensity III · Dublin 6 km, intensity III · Castro Valley 9 km, intensity III · Danville 10 km, intensity III · Hayward 10 km, intensity III · Pleasanton 13 km, intensity II · Alamo 14 km, intensity II · San Lorenzo 14 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 350 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 43,000× the energy of this one
- Magna, Utah 2020 M 5.7 31,000× the energy of this one
- Around the size people start to feel M 3.0 2.7× the energy of this one
- This earthquake M 2.7 about 350 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 4.5 on 2019-10-15 — about 420 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 · 49 km W of this epicentre
- 5.8 The 1980 Livermore, California Earthquake · 23 km ENE of this epicentre
- 5.7 15 km NE of East Foothills, California · 39 km SE of this epicentre
- 5.5 6 km NNE of East Foothills, California · 38 km SSE of this epicentre
- 5.4 9 km NE of Livermore, California · 25 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 37.7307, -121.9923. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Alameda County, CA | 12 km (7 mi) | SE | earthquakes near Alameda County |
| Contra Costa County, CA | 21 km (13 mi) | N | earthquakes near Contra Costa County |
| San Mateo County, CA | 48 km (30 mi) | SW | earthquakes near San Mateo County |
| Solano County, CA | 60 km (37 mi) | N | earthquakes near Solano County |
| Santa Clara County, CA | 63 km (39 mi) | SSE | earthquakes near Santa Clara County |
| San Joaquin County, CA | 67 km (42 mi) | ENE | earthquakes near San Joaquin 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.
- 1.5 3km NNW of Union City, CA
- 1.6 5km NW of Dublin, CA
- 2.4 9km ESE of Fremont, CA
- 1.5 6km WNW of Dublin, CA
- 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
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.