QuakeIndex

Earthquake · reviewed by a seismologist

M 3.1ml

Earthquake near Blackhawk, CA

No earthquake was likely felt in Blackhawk in the 24 hours to 2:56 am PST (10:56 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 3.1 earthquake was recorded 9 km (6 mi) east-northeast of Blackhawk, CA, at 12:25 am PDT on 12 September 2026 (07:25 UTC), 16 km deep. 257 people have reported feeling it to USGS.

USGS: 9 km ENE of Blackhawk, CA

12 km (7 mi) SW of Brentwood, CA · 63 km (39 mi) N of San Jose, CA

12:25 am PDT, Sep 12, 2026 · · 16 km deep · released about 1,400 lb of TNT

Every earthquake near Blackhawk Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Contra Costa County 13 kmAlameda County 25 kmSolano County 46 kmSan Joaquin County 49 kmSan Mateo County 70 kmSanta Clara County 72 kmSacramento County 77 kmStanislaus County 79 kmMarin County 84 km
Distance rings around the epicentre, with the nearest towns at their true direction and later quakes as coloured dots. Not a shaking map — see the USGS ShakeMap for that.
When
12:25 am PDT on 12 September 2026 ()
Where
9 km (6 mi) east-northeast of Blackhawk, CA · earthquakes near Blackhawk
Magnitude
M 3.1 (ml)
Depth
16 km below the surface
Felt
257 reports · strongest reported intensity III
Nearest
Contra Costa County, 13 km WNW
Nearest mapped fault
Greenville fault, 2 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 51 days ago

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 40 km (25 mi) from the epicentre. In Blackhawk, 9 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: Brentwood 13 km, intensity II · Antioch 16 km, intensity II · Danville 16 km, intensity II · San Ramon 17 km, intensity II · Oakley 18 km, intensity II · Alamo 19 km, intensity II · Pittsburg 19 km, intensity II · Discovery Bay 20 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 1,400 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.1 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 230,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 10,000× the energy of this one
  3. Magna, Utah 2020 M 5.7 7,400× the energy of this one
  4. This earthquake M 3.1 about 1,400 lb of TNT
  5. Around the size people start to feel M 3.0 this one released 1.5× 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 100 times the energy of this one.

Before 2016, the USGS record lists 6 earthquakes of M5 or more within 50 km; the five largest:

  1. 5.8 The 1980 Livermore, California Earthquake · 5 km ESE of this epicentre
  2. 5.7 15 km NE of East Foothills, California · 44 km SSE of this epicentre
  3. 5.5 6 km NNE of East Foothills, California · 48 km S of this epicentre
  4. 5.4 South of Elmira, California · 49 km N of this epicentre
  5. 5.4 9 km NE of Livermore, California · 16 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 37.8628, -121.8208. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Contra Costa County, CA 13 km (8 mi) WNW earthquakes near Contra Costa County
Alameda County, CA 25 km (16 mi) SSW earthquakes near Alameda County
Solano County, CA 46 km (29 mi) NNW earthquakes near Solano County
San Joaquin County, CA 49 km (30 mi) E earthquakes near San Joaquin County
San Mateo County, CA 70 km (43 mi) SW earthquakes near San Mateo County
Santa Clara County, CA 72 km (45 mi) S earthquakes near Santa Clara County

Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.

Aftershocks so far

43 earthquakes have been recorded within 50 km since this one.

  1. 1.6 1 km WSW of San Ramon, CA
  2. 1.4 2 km W of San Ramon, CA
  3. 1.1 2 km SSW of San Ramon, CA
  4. 1.8 1 km SW of San Ramon, CA
  5. 1.6 2 km WSW of Alamo, CA
  6. 0.8 12 km SE of Livermore, CA
  7. 1.5 13 km SE of Livermore, CA
  8. 1.0 13 km SE of Livermore, CA
  9. 1.7 2 km N of Pleasant Hill, CA
  10. 1.2 1 km WNW of Alamo, CA
  11. 1.4 3 km NNE of San Leandro, CA
  12. 0.9 14 km SSE of Livermore, CA
  13. 1.6 6 km SW of Clayton, CA
  14. 1.7 4 km NW of Orinda, CA
  15. 0.9 3 km ESE of Berkeley, 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

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.