Earthquake · reviewed by a seismologist
M 3.5mw
Earthquake near Byron, CA
No earthquake was likely felt in Byron in the 24 hours to 7:15 am PST (15:15 UTC). The last one was M 3.5, 53 km (33 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 Byron
This page: a magnitude 3.5 earthquake was recorded 2 km (2 mi) north-northeast of Byron, CA, at 6:21 pm PST on 28 February 2024 (02:21 UTC), 8.2 km deep. 589 people have reported feeling it to USGS.
USGS: 2 km NNE of Byron, CA
9 km (6 mi) SE of Brentwood, CA · 68 km (42 mi) NNE of San Jose, CA
- When
- 6:21 pm PST on 28 February 2024 ()
- Where
- 2 km (2 mi) north-northeast of Byron, CA · earthquakes near Byron
- Magnitude
- M 3.5 (mw)
- Depth
- 8.2 km below the surface
- Felt
- 589 reports · strongest reported intensity IV
- Measured shaking
- intensity IV (ShakeMap)
- Nearest
- Contra Costa County, 28 km W
- Nearest mapped fault
- Greenville fault, 17 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 840 days ago
Earthquake alerts for Byron, 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 62 km (39 mi) from the epicentre. In Byron, 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: Discovery Bay 3 km, intensity III · Brentwood 7 km, intensity III · Oakley 14 km, intensity III · Antioch 20 km, intensity III · Tracy 24 km, intensity III · Livermore 26 km, intensity II · Pittsburg 27 km, intensity II · Rio Vista 31 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 2.6 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.5 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 65,000× the energy of this one
- Mineral, Virginia 2011 M 5.8 2,900× the energy of this one
- Magna, Utah 2020 M 5.7 2,100× the energy of this one
- This earthquake M 3.5 about 2.6 tons of TNT
- Around the size people start to feel M 3.0 this one released 5.4× more
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 29 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 · 13 km WSW of this epicentre
- 5.7 15 km NE of East Foothills, California · 46 km S of this epicentre
- 5.4 9 km NE of Livermore, California · 17 km SSW of this epicentre
- 5.1 11 km E of Blackhawk, California · 15 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 37.8887, -121.6303. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Contra Costa County, CA | 28 km (18 mi) | W | earthquakes near Contra Costa County |
| San Joaquin County, CA | 32 km (20 mi) | E | earthquakes near San Joaquin County |
| Alameda County, CA | 37 km (23 mi) | SW | earthquakes near Alameda County |
| Solano County, CA | 50 km (31 mi) | NNW | earthquakes near Solano County |
| Stanislaus County, CA | 66 km (41 mi) | ESE | earthquakes near Stanislaus County |
| Sacramento County, CA | 67 km (42 mi) | NNE | earthquakes near Sacramento County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
51 earthquakes have been recorded within 50 km since this one.
- 1.6 13 km SSE of Livermore, CA
- 2.5 13 km SSE of Livermore, CA
- 1.6 5 km NNE of Fairview, CA
- 1.7 7 km SW of Brentwood, CA
- 1.5 2 km SSE of Pacheco, CA
- 3.0 10 km E of Blackhawk, CA
- 1.8 2 km WNW of Concord, CA
- 1.6 8 km NNE of Bay Point, CA
- 2.0 2 km NNE of Pleasant Hill, CA
- 1.7 10 km WSW of Mountain House, CA
- 2.8 2 km SSE of Pacheco, CA
- 2.3 7 km SSE of Elmira, CA
- 1.8 7 km SE of Fremont, CA
- 2.1 4 km E of Union City, CA
- 1.8 7 km SSE of Sunol, 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.