Earthquake · reviewed by a seismologist
M 2.0md
Earthquake near Blackhawk, CA
No earthquake was likely felt in Blackhawk in the 24 hours to 2:40 am PST (10:40 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 2.0 earthquake was recorded 4 km (3 mi) northeast of Blackhawk, CA, at 6:48 pm PDT on 31 July 2021 (01:48 UTC), 7.8 km deep.
USGS: 4km NE of Blackhawk, CA
11 km (7 mi) NNE of San Ramon, CA · 48 km (30 mi) E of San Francisco, CA
- When
- 6:48 pm PDT on 31 July 2021 ()
- Where
- 4 km (3 mi) northeast of Blackhawk, CA · earthquakes near Blackhawk
- Magnitude
- M 2.0 (md)
- Depth
- 7.8 km below the surface
- Felt
- no reports yet
- Nearest
- Contra Costa County, 10 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 1921 days ago
Earthquake alerts for Blackhawk, CA
Get a notification in this browser when USGS records an earthquake near Blackhawk, 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 14 km (9 mi) from the epicentre. In Blackhawk, 4 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: Danville 11 km, intensity II · San Ramon 12 km, intensity II · Alamo 13 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 32 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.0 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 470,000× the energy of this one
- Magna, Utah 2020 M 5.7 330,000× the energy of this one
- Around the size people start to feel M 3.0 30× the energy of this one
- This earthquake M 2.0 about 32 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 4,600 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 · 10 km E of this epicentre
- 5.7 15 km NE of East Foothills, California · 45 km SSE of this epicentre
- 5.5 6 km NNE of East Foothills, California · 47 km SSE of this epicentre
- 5.4 South of Elmira, California · 50 km N of this epicentre
- 5.4 9 km NE of Livermore, California · 19 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 37.8518, -121.8810. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Contra Costa County, CA | 10 km (6 mi) | NW | earthquakes near Contra Costa County |
| Alameda County, CA | 23 km (14 mi) | S | earthquakes near Alameda County |
| Solano County, CA | 46 km (29 mi) | N | earthquakes near Solano County |
| San Joaquin County, CA | 54 km (34 mi) | E | earthquakes near San Joaquin County |
| San Mateo County, CA | 65 km (40 mi) | SW | earthquakes near San Mateo County |
| Santa Clara County, CA | 72 km (45 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
59 earthquakes have been recorded within 50 km since this one.
- 2.1 4km ENE of El Sobrante, CA
- 1.6 10km NE of Milpitas, CA
- 1.5 3km SSW of Clayton, CA
- 1.9 1km S of San Ramon, CA
- 1.6 9km SE of Sunol, CA
- 1.6 5km SW of Clayton, CA
- 2.8 16km SSE of Livermore, CA
- 1.6 6km E of Vallejo, CA
- 2.1 3km WNW of Crockett, CA
- 2.1 4km WSW of Alamo, CA
- 2.1 6km SSW of Moraga, CA
- 1.9 5km SW of Pacheco, CA
- 1.8 2km SE of Pacheco, CA
- 1.6 1km S of Blackhawk, CA
- 2.7 0km N of Byron, 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.