QuakeIndex

Earthquake · reviewed by a seismologist

M 3.8mw

Earthquake near Blackhawk, CA

No earthquake was likely felt in Blackhawk in the 24 hours to 4:41 am PST (12:41 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 3.8 earthquake was recorded 9 km (6 mi) east of Blackhawk, CA, at 6:29 pm PDT on 29 April 2017 (01:29 UTC), 15 km deep. 777 people have reported feeling it to USGS.

USGS: 8 km E of Blackhawk, California

13 km (8 mi) ENE of San Ramon, CA · 59 km (37 mi) N of San Jose, CA

6:29 pm PDT, Apr 29, 2017 · · 15 km deep · released about 7.1 tons of TNT

Every earthquake near Blackhawk Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Contra Costa County 17 kmAlameda County 22 kmSan Joaquin County 48 kmSolano County 51 kmSan Mateo County 68 kmSanta Clara County 68 kmStanislaus County 76 kmSacramento County 80 kmMarin County 86 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
6:29 pm PDT on 29 April 2017 ()
Where
9 km (6 mi) east of Blackhawk, CA · earthquakes near Blackhawk
Magnitude
M 3.8 (mw)
Depth
15 km below the surface
Felt
777 reports · strongest reported intensity III
Measured shaking
intensity III (ShakeMap)
Nearest
Contra Costa County, 17 km NW
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 2676 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 80 km (50 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 15 km, intensity III · San Ramon 16 km, intensity III · Livermore 16 km, intensity III · Danville 17 km, intensity III · Dublin 18 km, intensity III · Pleasanton 19 km, intensity III · Antioch 20 km, intensity III · Alamo 20 km, intensity III. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 7.1 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.8 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 24,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 1,100× the energy of this one
  3. Magna, Utah 2020 M 5.7 760× the energy of this one
  4. This earthquake M 3.8 about 7.1 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 15× 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

No earthquake of M4 or more has been recorded within 50 km since our catalogue begins in 2016.

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 · 4 km ENE of this epicentre
  2. 5.7 15 km NE of East Foothills, California · 40 km SSE of this epicentre
  3. 5.5 6 km NNE of East Foothills, California · 44 km S of this epicentre
  4. 5.4 9 km NE of Livermore, California · 12 km SE of this epicentre
  5. 5.3 6 km E of East Foothills, California · 48 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 37.8252, -121.8060. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Contra Costa County, CA 17 km (10 mi) NW earthquakes near Contra Costa County
Alameda County, CA 22 km (14 mi) SSW earthquakes near Alameda County
San Joaquin County, CA 48 km (30 mi) ENE earthquakes near San Joaquin County
Solano County, CA 51 km (31 mi) NNW earthquakes near Solano County
San Mateo County, CA 68 km (42 mi) SW earthquakes near San Mateo County
Santa Clara County, CA 68 km (42 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

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

  1. 2.0 0 km W of Kensington, California
  2. 1.7 0 km W of Kensington, California
  3. 1.8 0 km E of Hayward, California
  4. 2.0 4 km NNW of Orinda, California
  5. 2.2 0 km ESE of North Gate, California
  6. 2.0 4 km NNW of Orinda, California
  7. 1.6 4 km SW of Danville, California
  8. 2.1 2 km SSW of San Ramon, California
  9. 2.2 1 km SSW of San Ramon, California
  10. 2.0 1 km W of Danville, California
  11. 1.5 2 km E of Berkeley, California
  12. 2.2 Northern California
  13. 1.6 11 km SE of Sunol, CA
  14. 2.2 5 km S of Livermore, California
  15. 1.7 3 km W of Byron, California

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.