Earthquake · reviewed by a seismologist
M 2.8md
Earthquake near Ferndale, CA
No earthquake was likely felt in Ferndale in the 24 hours to 9:56 pm PST (05:56 UTC). The last one was M 5.0, 113 km (70 mi) W, at 8:56 pm PST on 4 November 2026, estimated intensity III (weak) in town; 145 felt reports to USGS. Every earthquake near Ferndale
This page: a magnitude 2.8 earthquake was recorded 42 km (26 mi) west-southwest of Ferndale, CA, at 7:30 pm PDT on 2 August 2023 (02:30 UTC), 25 km deep. 1 person has reported feeling it to USGS.
USGS: 38 km WNW of Petrolia, CA
- When
- 7:30 pm PDT on 2 August 2023 ()
- Where
- 42 km (26 mi) west-southwest of Ferndale, CA · earthquakes near Ferndale
- Magnitude
- M 2.8 (md)
- Depth
- 25 km below the surface
- Felt
- 1 report · strongest reported intensity III
- Nearest
- Humboldt County, 73 km ENE
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 1131 days ago
Earthquake alerts for Ferndale, 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 9 km (6 mi) from the epicentre. In Ferndale, 42 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.
How big was it?
This earthquake released about 430 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 35,000× the energy of this one
- Magna, Utah 2020 M 5.7 25,000× the energy of this one
- Around the size people start to feel M 3.0 2.2× the energy of this one
- This earthquake M 2.8 about 430 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 6.4 on 2022-12-20 — about 280,000 times the energy of this one.
Before 2016, the USGS record lists 43 earthquakes of M5 or more within 50 km; the five largest:
- 7.2 The 1992 Petrolia, California Earthquake · 43 km ESE of this epicentre
- 6.6 32 km SW of Ferndale, California · 15 km ESE of this epicentre
- 6.5 The 1932 Eureka, California Earthquake · 49 km NE of this epicentre
- 6.5 30 km WSW of Ferndale, California · 13 km E of this epicentre
- 6.5 The 2010 Eureka, California Earthquake · 25 km N 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 40.4298, -124.7160. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Humboldt County, CA | 73 km (46 mi) | ENE | earthquakes near Humboldt County |
| Mendocino County, CA | 155 km (96 mi) | SE | earthquakes near Mendocino 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.
- 2.6 49 km W of Ferndale, CA
- 2.7 83 km W of Petrolia, CA
- 2.2 15 km WSW of Ferndale, CA
- 1.6 3 km SSW of Petrolia, CA
- 3.6 4 km S of Petrolia, CA
- 4.1 3 km S of Petrolia, CA
- 2.5 19 km WSW of Ferndale, CA
- 2.1 17 km SW of Ferndale, CA
- 2.6 17 km WSW of Ferndale, CA
- 4.2 17 km WSW of Ferndale, CA
- 4.7 3 km SW of Ferndale, CA
- 2.1 16 km WSW of Ferndale, CA
- 1.5 7 km NW of Ferndale, CA
- 2.3 40 km WNW of Petrolia, CA
- 2.1 23 km WNW of Petrolia, 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.