Earthquake · reviewed by a seismologist
M 2.3md
Earthquake near Discovery Bay, CA
No earthquake was likely felt in Discovery Bay in the 24 hours to 4:47 am PST (12:47 UTC). The last one was M 3.5, 56 km (35 mi) SSE, at 7:21 am PDT on 27 September 2026, estimated intensity II (weak) in town; 8 felt reports to USGS. Every earthquake near Discovery Bay
This page: a magnitude 2.3 earthquake was recorded in Discovery Bay, CA, at 4:01 pm PST on 13 December 2021 (00:01 UTC), 18 km deep.
USGS: 2km SW of Discovery Bay, CA
10 km (6 mi) ESE of Brentwood, CA · 69 km (43 mi) NNE of San Jose, CA
- When
- 4:01 pm PST on 13 December 2021 ()
- Where
- in Discovery Bay, CA · earthquakes near Discovery Bay
- Magnitude
- M 2.3 (md)
- Depth
- 18 km below the surface
- Felt
- no reports yet
- Nearest
- Contra Costa County, 30 km W
- Nearest mapped fault
- Greenville fault, 19 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 1791 days ago
Earthquake alerts for Discovery Bay, CA
Get a notification in this browser when USGS records an earthquake near Discovery Bay, 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 9 km (6 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: Discovery Bay in town, intensity II · Brentwood 8 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 85 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.3 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 180,000× the energy of this one
- Magna, Utah 2020 M 5.7 130,000× the energy of this one
- Around the size people start to feel M 3.0 11× the energy of this one
- This earthquake M 2.3 about 85 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 1,700 times the energy of this one.
Before 2016, the USGS record lists 4 earthquakes of M5 or more within 50 km:
- 5.8 The 1980 Livermore, California Earthquake · 15 km WSW of this epicentre
- 5.7 15 km NE of East Foothills, California · 47 km S of this epicentre
- 5.4 9 km NE of Livermore, California · 18 km SSW of this epicentre
- 5.1 11 km E of Blackhawk, California · 17 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 37.8973, -121.6112. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Contra Costa County, CA | 30 km (19 mi) | W | earthquakes near Contra Costa County |
| San Joaquin County, CA | 30 km (19 mi) | E | earthquakes near San Joaquin County |
| Alameda County, CA | 38 km (24 mi) | SW | earthquakes near Alameda County |
| Solano County, CA | 50 km (31 mi) | NW | earthquakes near Solano County |
| Stanislaus County, CA | 65 km (41 mi) | SE | earthquakes near Stanislaus County |
| Sacramento County, CA | 66 km (41 mi) | NNE | earthquakes near Sacramento County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
55 earthquakes have been recorded within 50 km since this one.
- 1.6 10km ENE of Blackhawk, CA
- 1.8 3km S of Pittsburg, CA
- 1.9 5km ESE of Moraga, CA
- 2.7 4km S of Pittsburg, CA
- 1.9 6km SW of Clayton, CA
- 1.6 4km SW of San Ramon, CA
- 1.6 4km SW of San Ramon, CA
- 1.6 2km E of Pleasant Hill, CA
- 1.6 5km E of Fremont, CA
- 1.7 10km ESE of Clayton, CA
- 2.0 9km NE of Blackhawk, CA
- 2.0 2km E of Pacheco, CA
- 2.2 2km NW of Diablo, CA
- 2.0 2km E of Hayward, CA
- 1.6 2km E of Hayward, 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.