Earthquake · reviewed by a seismologist
M 4.1mw
Earthquake near Chester, CA
No earthquake was likely felt in Chester in the 24 hours to 4:13 am PST (12:13 UTC). The last one was M 2.1, 17 km (11 mi) SE, at 8:09 am PDT on 29 October 2026, estimated intensity II (weak) in town. Every earthquake near Chester
This page: a magnitude 4.1 earthquake was recorded 11 km (7 mi) southeast of Chester, CA, at 4:26 am PDT on 26 May 2023 (11:26 UTC), 6.7 km deep. 89 people have reported feeling it to USGS.
USGS: 2km NNE of Prattville, CA
- When
- 4:26 am PDT on 26 May 2023 ()
- Where
- 11 km (7 mi) southeast of Chester, CA · earthquakes near Chester
- Magnitude
- M 4.1 (mw)
- Depth
- 6.7 km below the surface
- Felt
- 89 reports · strongest reported intensity IV
- Measured shaking
- intensity IV (ShakeMap)
- USGS impact alert
- green
- Nearest
- Plumas County, 38 km SE
- Nearest mapped fault
- Almanor fault, 2 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 1202 days ago
Earthquake alerts for Chester, CA
Get a notification in this browser when USGS records an earthquake near Chester, 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 light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon.
At this magnitude and depth, people at rest would likely notice it out to about 106 km (66 mi) from the epicentre. In Chester, 11 km away, the estimate is intensity IV (light). 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: Chester 11 km, intensity IV · Westwood 15 km, intensity IV · Greenville 19 km, intensity III · East Quincy 39 km, intensity III · Susanville 47 km, intensity III. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 24 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.1 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 7,200× the energy of this one
- Mineral, Virginia 2011 M 5.8 320× the energy of this one
- Magna, Utah 2020 M 5.7 230× the energy of this one
- This earthquake M 4.1 about 24 tons of TNT
- Around the size people start to feel M 3.0 this one released 50× 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 5.5 on 2023-05-11 — about 110 times the energy of this one.
Before 2016, the USGS record lists 2 earthquakes of M5 or more within 50 km:
- 5.7 2 km NNE of Canyondam, California · 8 km ESE of this epicentre
- 5.5 15 km NE of Mineral, California · 37 km NW 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 40.2267, -121.1478. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Plumas County, CA | 38 km (24 mi) | SE | earthquakes near Plumas County |
| Lassen County, CA | 70 km (44 mi) | NE | earthquakes near Lassen County |
| Butte County, CA | 74 km (46 mi) | SSW | earthquakes near Butte County |
| Sierra County, CA | 90 km (56 mi) | SE | earthquakes near Sierra County |
| Tehama County, CA | 93 km (58 mi) | W | earthquakes near Tehama County |
| Shasta County, CA | 96 km (60 mi) | NW | earthquakes near Shasta 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.
- 2.1 4 km NNE of Canyondam, CA
- 2.1 0 km E of Almanor, CA
- 1.8 4 km NW of Spring Garden, California
- 1.6 1 km E of Almanor, CA
- 1.7 4 km NNE of Canyondam, CA
- 1.8 37 km N of Chester, CA
- 1.8 1 km ENE of Almanor, CA
- 2.4 4 km WSW of Hamilton Branch, CA
- 2.1 10 km SW of Almanor, CA
- 2.5 2 km NNE of Canyondam, CA
- 1.9 4 km NW of Almanor, CA
- 2.9 1 km ESE of Almanor, CA
- 2.2 1 km N of Almanor, CA
- 2.1 1 km NNE of Almanor, CA
- 1.9 1 km N of Prattville, 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.