quarry blast · reviewed by a seismologist
M 1.5md
Earthquake near Clayton, CA
No earthquake was likely felt in Clayton in the 24 hours to 2:44 am PST (10:44 UTC). The last one was M 2.1, 11 km (7 mi) W, at 4:05 am PST on 8 November 2026, estimated intensity II (weak) in town; 3 felt reports to USGS. Every earthquake near Clayton
No: USGS classifies this as a quarry blast, not an earthquake. A magnitude 1.5 quarry blast was recorded 3 km (2 mi) southwest of Clayton, CA, at 12:27 pm PDT on 17 July 2026 (19:27 UTC), less than 1 km deep.
USGS: 3 km SW of Clayton, CA
7 km (4 mi) SE of Concord, CA · 44 km (27 mi) ENE of San Francisco, CA
- When
- 12:27 pm PDT on 17 July 2026 ()
- Where
- 3 km (2 mi) southwest of Clayton, CA · earthquakes near Clayton
- Magnitude
- M 1.5 (md)
- Depth
- -0.2 km below the surface
- Felt
- no reports yet
- Nearest
- Contra Costa County, 0 km SE
- Nearest mapped fault
- Greenville fault, 3 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 107 days ago
Earthquake alerts for Clayton, CA
Get a notification in this browser when USGS records an earthquake near Clayton, 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 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 10 km (6 mi) from the epicentre. In Clayton, 3 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: Concord 9 km, intensity II · Pleasant Hill 10 km, intensity II · Walnut Creek 10 km, intensity II. Estimated for each town centre; each link is that town's own record.
USGS catalogues this as quarry blast, not an earthquake.
How big was it?
This earthquake released about 5.4 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.5 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 2,800,000× the energy of this one
- Magna, Utah 2020 M 5.7 2,000,000× the energy of this one
- Around the size people start to feel M 3.0 180× the energy of this one
- This earthquake M 1.5 about 5.4 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 28,000 times the energy of this one.
Before 2016, the USGS record lists 5 earthquakes of M5 or more within 50 km:
- 6.0 The 2014 South Napa, California Earthquake · 45 km NW of this epicentre
- 5.8 The 1980 Livermore, California Earthquake · 19 km ESE of this epicentre
- 5.4 South of Elmira, California · 42 km N of this epicentre
- 5.4 9 km NE of Livermore, California · 29 km SE of this epicentre
- 5.1 11 km E of Blackhawk, California · 20 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 37.9223, -121.9550. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Contra Costa County, CA | 0 km (0 mi) | SE | earthquakes near Contra Costa County |
| Alameda County, CA | 31 km (19 mi) | S | earthquakes near Alameda County |
| Solano County, CA | 38 km (24 mi) | N | earthquakes near Solano County |
| San Joaquin County, CA | 60 km (37 mi) | E | earthquakes near San Joaquin County |
| San Mateo County, CA | 67 km (42 mi) | SSW | earthquakes near San Mateo County |
| Marin County, CA | 71 km (44 mi) | WNW | earthquakes near Marin County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
49 earthquakes have been recorded within 50 km since this one.
- 1.1 2 km NE of Danville, CA
- 1.4 12 km SE of Livermore, CA
- 1.1 13 km SE of Livermore, CA
- 1.4 4 km NNW of San Leandro, CA
- 1.4 3 km SW of American Canyon, CA
- 1.7 3 km ENE of San Rafael, CA
- 2.0 9 km ESE of Livermore, CA
- 1.7 2 km NNE of Pleasant Hill, CA
- 2.0 3 km W of Dublin, CA
- 2.2 3 km W of Dublin, CA
- 1.6 3 km W of Dublin, CA
- 1.9 6 km SW of Antioch, CA
- 2.4 3 km WNW of Dublin, CA
- 3.0 9 km SW of Brentwood, CA
- 2.5 9 km SW of Brentwood, 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.