Earthquake · reviewed by a seismologist
M 1.6md
Earthquake near San Ramon, CA
No earthquake was likely felt in San Ramon in the 24 hours to 12:52 am PST (08:52 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 1.6 earthquake was recorded 2 km (1 mi) northeast of San Ramon, CA, at 4:30 am PST on 23 December 2021 (12:30 UTC), 9.8 km deep. 2 people have reported feeling it to USGS.
USGS: 2km NE of San Ramon, CA
in San Ramon, CA · 40 km (25 mi) E of San Francisco, CA
- When
- 4:30 am PST on 23 December 2021 ()
- Where
- 2 km (1 mi) northeast of San Ramon, CA · earthquakes near San Ramon
- Magnitude
- M 1.6 (md)
- Depth
- 9.8 km below the surface
- Felt
- 2 reports · strongest reported intensity II
- Nearest
- Contra Costa County, 14 km N
- Nearest mapped fault
- Pleasanton 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 1778 days ago
Earthquake alerts for San Ramon, CA
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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 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 6 km (4 mi) from the epicentre. In San Ramon, 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: San Ramon 2 km, intensity II · Danville 4 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 8.1 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.6 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 1,900,000× the energy of this one
- Magna, Utah 2020 M 5.7 1,300,000× the energy of this one
- Around the size people start to feel M 3.0 120× the energy of this one
- This earthquake M 1.6 about 8.1 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 18,000 times the energy of this one.
Before 2016, the USGS record lists 7 earthquakes of M5 or more within 50 km; the five largest:
- 5.8 The 1980 Livermore, California Earthquake · 18 km ENE of this epicentre
- 5.7 15 km NE of East Foothills, California · 43 km SE of this epicentre
- 5.5 6 km NNE of East Foothills, California · 43 km SSE of this epicentre
- 5.4 9 km NE of Livermore, California · 23 km ESE of this epicentre
- 5.3 The 1957 San Francisco, California Earthquake · 48 km WSW 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 37.7947, -121.9630. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Contra Costa County, CA | 14 km (9 mi) | N | earthquakes near Contra Costa County |
| Alameda County, CA | 17 km (11 mi) | SSE | earthquakes near Alameda County |
| Solano County, CA | 53 km (33 mi) | N | earthquakes near Solano County |
| San Mateo County, CA | 56 km (34 mi) | SW | earthquakes near San Mateo County |
| San Joaquin County, CA | 63 km (39 mi) | ENE | earthquakes near San Joaquin County |
| Santa Clara County, CA | 68 km (42 mi) | SSE | earthquakes near Santa Clara County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
57 earthquakes have been recorded within 50 km since this one.
- 2.0 2km E of Hayward, CA
- 1.6 2km E of Hayward, CA
- 1.6 2km ESE of Hayward, CA
- 2.0 8km ENE of Milpitas, CA
- 1.7 16km SSE of Livermore, CA
- 1.9 4km NNW of Crockett, CA
- 1.5 8km WSW of Brentwood, CA
- 2.3 4km SSE of Vallejo, CA
- 2.8 1km ENE of El Cerrito, CA
- 1.7 9km ENE of Alum Rock, CA
- 1.8 5km ESE of Blackhawk, CA
- 1.8 14km SE of Livermore, CA
- 1.6 10km NNE of Alum Rock, CA
- 1.6 5km E of Vallejo, CA
- 1.6 8km NNE 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.