Earthquake · reviewed by a seismologist
M 1.7md
Earthquake near Diablo, CA
No earthquake was likely felt in Diablo in the 24 hours to 11:03 pm PST (07:03 UTC). The last one was M 2.5, 18 km (11 mi) NNW, at 1:23 am PST on 2 November 2026, estimated intensity II (weak) in town; 39 felt reports to USGS. Every earthquake near Diablo
This page: a magnitude 1.7 earthquake was recorded in Diablo, CA, at 4:25 am PDT on 28 September 2020 (11:25 UTC), 8.7 km deep.
USGS: 1km SW of Diablo, CA
8 km (5 mi) NNW of San Ramon, CA · 40 km (25 mi) E of San Francisco, CA
- When
- 4:25 am PDT on 28 September 2020 ()
- Where
- in Diablo, CA · earthquakes near Diablo
- Magnitude
- M 1.7 (md)
- Depth
- 8.7 km below the surface
- Felt
- no reports yet
- Nearest
- Contra Costa County, 10 km N
- 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 2228 days ago
Earthquake alerts for Diablo, CA
Get a notification in this browser when USGS records an earthquake near Diablo, 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 8 km (5 mi) from the epicentre. 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 3 km, intensity II · San Ramon 6 km, intensity II · Alamo 6 km, intensity II. Estimated for each town centre; each link is that town's own record.
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 · 17 km E of this epicentre
- 5.7 15 km NE of East Foothills, California · 46 km SSE of this epicentre
- 5.5 6 km NNE of East Foothills, California · 47 km SSE of this epicentre
- 5.4 9 km NE of Livermore, California · 25 km ESE of this epicentre
- 5.3 The 1957 San Francisco, California Earthquake · 49 km WSW 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 37.8308, -121.9652. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Contra Costa County, CA | 10 km (6 mi) | N | earthquakes near Contra Costa County |
| Alameda County, CA | 21 km (13 mi) | SSE | earthquakes near Alameda County |
| Solano County, CA | 49 km (30 mi) | N | earthquakes near Solano County |
| San Mateo County, CA | 59 km (36 mi) | SW | earthquakes near San Mateo County |
| San Joaquin County, CA | 62 km (38 mi) | E | earthquakes near San Joaquin 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
56 earthquakes have been recorded within 50 km since this one.
- 2.6 1km WNW of Bay Point, CA
- 1.9 2km NNE of San Leandro, CA
- 1.6 2km NW of Bay Point, CA
- 1.7 2km E of Berkeley, CA
- 1.8 2km SE of Pacheco, CA
- 1.6 3km ESE of Pacheco, CA
- 1.6 9km NE of Milpitas, CA
- 2.5 0km SE of Rollingwood, CA
- 1.6 0km SE of Rollingwood, CA
- 2.1 4km ESE of Hayward, CA
- 2.1 4km WNW of Dublin, CA
- 1.7 4km WNW of Dublin, CA
- 1.7 4km WNW of Dublin, CA
- 2.3 4km WNW of Dublin, CA
- 2.0 2km E of Pacheco, 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.