Earthquake · reviewed by a seismologist
M 1.7md
Earthquake near Blackhawk, CA
No earthquake was likely felt in Blackhawk in the 24 hours to 4:25 am PST (12:25 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 5 km (3 mi) south of Blackhawk, CA, at 11:53 am PST on 7 December 2020 (19:53 UTC), 16 km deep.
USGS: 5km S of Blackhawk, CA
in San Ramon, CA · 45 km (28 mi) E of San Francisco, CA
- When
- 11:53 am PST on 7 December 2020 ()
- Where
- 5 km (3 mi) south of Blackhawk, CA · earthquakes near Blackhawk
- Magnitude
- M 1.7 (md)
- Depth
- 16 km below the surface
- Felt
- no reports yet
- Nearest
- Alameda County, 14 km S
- Nearest mapped fault
- Pleasanton 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 2164 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 it was probably too small to be felt, even directly above it. In Blackhawk, 5 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: San Ramon, Diablo, Dublin, Danville, Pleasanton, Alamo.
How big was it?
This earthquake released about 10 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 1,500,000× the energy of this one
- Magna, Utah 2020 M 5.7 1,000,000× the energy of this one
- Around the size people start to feel M 3.0 92× the energy of this one
- This earthquake M 1.7 about 10 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 14,000 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 · 15 km ENE of this epicentre
- 5.7 15 km NE of East Foothills, California · 38 km SSE of this epicentre
- 5.5 6 km NNE of East Foothills, California · 40 km SSE of this epicentre
- 5.4 9 km NE of Livermore, California · 18 km E of this epicentre
- 5.3 6 km E of East Foothills, California · 45 km SSE 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 37.7745, -121.9118. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Alameda County, CA | 14 km (9 mi) | S | earthquakes near Alameda County |
| Contra Costa County, CA | 16 km (10 mi) | NNW | earthquakes near Contra Costa County |
| Solano County, CA | 55 km (34 mi) | N | earthquakes near Solano County |
| San Mateo County, CA | 57 km (35 mi) | SW | earthquakes near San Mateo County |
| San Joaquin County, CA | 59 km (37 mi) | ENE | earthquakes near San Joaquin County |
| Santa Clara County, CA | 65 km (40 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
54 earthquakes have been recorded within 50 km since this one.
- 1.8 4km NE of Pleasanton, CA
- 2.7 8km ESE of Fremont, CA
- 1.9 6km N of Alum Rock, CA
- 2.0 0km SE of Pleasant Hill, CA
- 2.1 8km ESE of Fremont, CA
- 2.0 11km NE of Milpitas, CA
- 1.6 11km NE of Milpitas, CA
- 1.6 10km NE of Milpitas, CA
- 1.5 10km NE of Milpitas, CA
- 1.8 10km NE of Milpitas, CA
- 3.2 10km NE of Milpitas, CA
- 2.0 9km E of Alum Rock, CA
- 1.5 3km ESE of Berkeley, CA
- 2.6 3km ESE of Berkeley, CA
- 2.1 2km WNW of Castro Valley, 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.