Earthquake · reviewed by a seismologist
M 2.8md
Earthquake near Piedmont, CA
No earthquake was likely felt in Piedmont in the 24 hours to 12:53 am PST (08:53 UTC). The last one was M 2.6, 5 km (3 mi) NNW, at 6:23 pm PST on 1 November 2026, estimated intensity III (weak) in town; 114 felt reports to USGS. Every earthquake near Piedmont
This page: a magnitude 2.8 earthquake was recorded 2 km (1 mi) north of Piedmont, CA, at 12:18 am PDT on 28 April 2021 (07:18 UTC), 5.5 km deep. 2,614 people have reported feeling it to USGS.
USGS: 2km N of Piedmont, CA
8 km (5 mi) N of Oakland, CA · 6 km (4 mi) ESE of Berkeley, CA
- When
- 12:18 am PDT on 28 April 2021 ()
- Where
- 2 km (1 mi) north of Piedmont, CA · earthquakes near Piedmont
- Magnitude
- M 2.8 (md)
- Depth
- 5.5 km below the surface
- Felt
- 2,614 reports · strongest reported intensity V
- Nearest
- Contra Costa County, 26 km ENE
- Nearest mapped fault
- Hayward fault, under 1 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 1479 days ago
Earthquake alerts for Piedmont, CA
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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 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 25 km (16 mi) from the epicentre. In Piedmont, 2 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: Berkeley 4 km, intensity III · Oakland 6 km, intensity III · Orinda 6 km, intensity III · Alameda 9 km, intensity III · El Cerrito 10 km, intensity III · Lafayette 11 km, intensity III · Richmond 14 km, intensity II · San Leandro 15 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 420 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.8 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 36,000× the energy of this one
- Magna, Utah 2020 M 5.7 26,000× the energy of this one
- Around the size people start to feel M 3.0 2.3× the energy of this one
- This earthquake M 2.8 about 420 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 350 times the energy of this one.
Before 2016, the USGS record lists 6 earthquakes of M5 or more within 50 km; the five largest:
- 7.9 The 1906 San Francisco, California Earthquake · 30 km WSW of this epicentre
- 6.0 The 2014 South Napa, California Earthquake · 42 km N of this epicentre
- 5.8 The 1980 Livermore, California Earthquake · 41 km E of this epicentre
- 5.4 9 km NE of Livermore, California · 48 km ESE of this epicentre
- 5.3 The 1957 San Francisco, California Earthquake · 29 km SW 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 37.8457, -122.2350. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Contra Costa County, CA | 26 km (16 mi) | ENE | earthquakes near Contra Costa County |
| Alameda County, CA | 36 km (22 mi) | SE | earthquakes near Alameda County |
| San Mateo County, CA | 49 km (31 mi) | SSW | earthquakes near San Mateo County |
| Marin County, CA | 50 km (31 mi) | WNW | earthquakes near Marin County |
| Solano County, CA | 54 km (33 mi) | NNE | earthquakes near Solano County |
| San Francisco County, CA | 71 km (44 mi) | W | earthquakes near San Francisco County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
52 earthquakes have been recorded within 50 km since this one.
- 1.5 2km ESE of Berkeley, CA
- 1.5 4km E of Moraga, CA
- 1.8 7km S of Muir Beach, CA
- 2.2 4km NNE of Blackhawk, CA
- 2.5 4km NNE of Blackhawk, CA
- 2.0 4km NE of Blackhawk, CA
- 1.9 4km SSW of Colma, CA
- 2.3 2km WNW of Concord, CA
- 1.7 2km E of Berkeley, CA
- 1.8 5km E of Fremont, CA
- 2.1 8km S of Muir Beach, CA
- 1.6 8km S of Muir Beach, CA
- 1.6 3km NNW of Piedmont, CA
- 2.1 2km ENE of Berkeley, CA
- 1.7 3km 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.