Earthquake · automatic estimate, may change
M 1.7md
Earthquake near Blackhawk, CA
No earthquake was likely felt in Blackhawk in the 24 hours to 2:25 am PST (10:25 UTC). The last one was M 2.1, 5 km (3 mi) WNW, at 7:18 am PDT on 31 October 2026, estimated intensity II (weak) in town; 1 felt report to USGS. Every earthquake near Blackhawk
This page: a magnitude 1.7 earthquake was recorded 11 km (7 mi) east of Blackhawk, CA, at 6:55 pm PDT on 27 September 2025 (01:55 UTC), 14 km deep. The magnitude and location are an automatic first estimate and may change.
USGS: 11 km E of Blackhawk, CA
13 km (8 mi) SSW of Brentwood, CA · 60 km (37 mi) N of San Jose, CA
- When
- 6:55 pm PDT on 27 September 2025 ()
- Where
- 11 km (7 mi) east of Blackhawk, CA · earthquakes near Blackhawk
- Magnitude
- M 1.7 (md)
- Depth
- 14 km below the surface
- Felt
- no reports yet
- Nearest
- Contra Costa County, 18 km WNW
- Nearest mapped fault
- Greenville fault, 3 km from its surface trace — near is not the same as on
- Status
- Automatic — a machine’s first estimate, which may change
USGS · last changed by USGS · we first saw it 410 days ago
Earthquake alerts for Blackhawk, CA
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This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.
At this magnitude and depth it was probably too small to be felt, even directly above it. In Blackhawk, 11 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.
Earthquakes near other towns within 30 km: Byron, Brentwood, Diablo, Livermore, Clayton, Discovery Bay.
How big was it?
This earthquake released about 9.3 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.7 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 1,600,000× the energy of this one
- Magna, Utah 2020 M 5.7 1,100,000× the energy of this one
- Around the size people start to feel M 3.0 100× the energy of this one
- This earthquake M 1.7 about 9.3 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 16,000 times the energy of this one.
Before 2016, the USGS record lists 6 earthquakes of M5 or more within 50 km; the five largest:
- 5.8 The 1980 Livermore, California Earthquake · 2 km ENE of this epicentre
- 5.7 15 km NE of East Foothills, California · 40 km SSE of this epicentre
- 5.5 6 km NNE of East Foothills, California · 44 km S of this epicentre
- 5.4 9 km NE of Livermore, California · 12 km SE of this epicentre
- 5.3 6 km E of East Foothills, California · 49 km S 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 37.8338, -121.7835. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Contra Costa County, CA | 18 km (11 mi) | WNW | earthquakes near Contra Costa County |
| Alameda County, CA | 24 km (15 mi) | SSW | earthquakes near Alameda County |
| San Joaquin County, CA | 46 km (29 mi) | ENE | earthquakes near San Joaquin County |
| Solano County, CA | 50 km (31 mi) | NNW | earthquakes near Solano County |
| Santa Clara County, CA | 69 km (43 mi) | S | earthquakes near Santa Clara County |
| San Mateo County, CA | 70 km (43 mi) | SW | earthquakes near San Mateo County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
47 earthquakes have been recorded within 50 km since this one.
- 2.1 4 km SE of San Ramon, CA
- 1.6 4 km SE of San Ramon, CA
- 1.9 4 km SE of San Ramon, CA
- 1.6 3 km SE of San Ramon, CA
- 2.3 3 km SE of San Ramon, CA
- 3.0 4 km SE of San Ramon, CA
- 2.9 4 km SE of San Ramon, CA
- 2.3 4 km SE of San Ramon, CA
- 3.0 4 km SE of San Ramon, CA
- 3.8 3 km SE of San Ramon, CA
- 1.7 6 km ENE of Vallejo, CA
- 1.6 5 km SE of Oakland, CA
- 1.7 4 km E of Brentwood, CA
- 2.4 5 km SE of Oakland, CA
- 2.6 2 km WNW of Concord, 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.