Earthquake · reviewed by a seismologist
M 1.5md
Earthquake near Byron, CA
No earthquake was likely felt in Byron in the 24 hours to 7:28 am PST (15:28 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 1.5 earthquake was recorded 6 km (4 mi) south-southeast of Byron, CA, at 3:31 pm PDT on 18 October 2019 (22:31 UTC), 14 km deep.
USGS: 6km SSE of Byron, CA
60 km (37 mi) NNE of San Jose, CA · 16 km (10 mi) SSE of Brentwood, CA
- When
- 3:31 pm PDT on 18 October 2019 ()
- Where
- 6 km (4 mi) south-southeast of Byron, CA · earthquakes near Byron
- Magnitude
- M 1.5 (md)
- Depth
- 14 km below the surface
- Felt
- no reports yet
- Nearest
- Contra Costa County, 31 km WNW
- Nearest mapped fault
- Corral Hollow-Carnegie fault, 14 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 2575 days ago
Earthquake alerts for Byron, CA
Get a notification in this browser when USGS records an earthquake near Byron, 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 Byron, 6 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: Mountain House, Discovery Bay, Brentwood, Knightsen, Tracy, Livermore.
How big was it?
This earthquake released about 5.7 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.5 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 2,600,000× the energy of this one
- Magna, Utah 2020 M 5.7 1,900,000× the energy of this one
- Around the size people start to feel M 3.0 170× the energy of this one
- This earthquake M 1.5 about 5.7 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 26,000 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 · 13 km WNW of this epicentre
- 5.7 15 km NE of East Foothills, California · 38 km S of this epicentre
- 5.5 6 km NNE of East Foothills, California · 44 km SSW of this epicentre
- 5.4 9 km NE of Livermore, California · 11 km SW of this epicentre
- 5.3 6 km E of East Foothills, California · 48 km SSW 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 37.8145, -121.6192. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Contra Costa County, CA | 31 km (20 mi) | WNW | earthquakes near Contra Costa County |
| Alameda County, CA | 32 km (20 mi) | SW | earthquakes near Alameda County |
| San Joaquin County, CA | 33 km (21 mi) | ENE | earthquakes near San Joaquin County |
| Solano County, CA | 58 km (36 mi) | NNW | earthquakes near Solano County |
| Stanislaus County, CA | 61 km (38 mi) | ESE | earthquakes near Stanislaus County |
| Santa Clara County, CA | 66 km (41 mi) | S | earthquakes near Santa Clara County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
59 earthquakes have been recorded within 50 km since this one.
- 2.9 5km NE of Alum Rock, CA
- 1.9 2km SE of Pacheco, CA
- 1.7 5km NW of Sunol, CA
- 2.1 2km NW of Concord, CA
- 1.8 8km NE of Alum Rock, CA
- 1.8 1km ESE of Pacheco, CA
- 1.6 9km NE of Alum Rock, CA
- 1.9 2km NNE of San Ramon, CA
- 2.2 1km SW of Danville, CA
- 1.9 4km N of Diablo, CA
- 1.6 11km ESE of Sunol, CA
- 2.4 11km ESE of Sunol, CA
- 1.5 10km E of Blackhawk, CA
- 2.1 18km W of Westley, CA
- 1.5 3km NE of Union City, 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.