Earthquake · reviewed by a seismologist
M 2.8md
Earthquake near Fortuna, CA
No earthquake was likely felt in Fortuna in the 24 hours to 11:26 am PST (19:26 UTC). The last one was M 5.0, 123 km (76 mi) W, at 8:56 pm PST on 4 November 2026, estimated intensity II (weak) in town; 145 felt reports to USGS. Every earthquake near Fortuna
This page: a magnitude 2.8 earthquake was recorded 24 km (15 mi) southwest of Fortuna, CA, at 12:29 pm PST on 20 December 2021 (20:29 UTC), 26 km deep. 1 person has reported feeling it to USGS.
USGS: 12km NNW of Petrolia, CA
- When
- 12:29 pm PST on 20 December 2021 ()
- Where
- 24 km (15 mi) southwest of Fortuna, CA · earthquakes near Fortuna
- Magnitude
- M 2.8 (md)
- Depth
- 26 km below the surface
- Felt
- 1 report
- Nearest
- Humboldt County, 46 km NE
- Nearest mapped fault
- Mattole Canyon fault, 21 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 1717 days ago
Earthquake alerts for Fortuna, CA
Get a notification in this browser when USGS records an earthquake near Fortuna, 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 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 4 km (2 mi) from the epicentre. In Fortuna, 24 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: Ferndale, Rio Dell, Hydesville.
How big was it?
This earthquake released about 450 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 34,000× the energy of this one
- Magna, Utah 2020 M 5.7 24,000× the energy of this one
- Around the size people start to feel M 3.0 2.1× the energy of this one
- This earthquake M 2.8 about 450 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 6.2 on 2021-12-20 — about 130,000 times the energy of this one.
Before 2016, the USGS record lists 40 earthquakes of M5 or more within 50 km; the five largest:
- 7.2 The 1992 Petrolia, California Earthquake · 13 km SE of this epicentre
- 6.6 32 km SW of Ferndale, California · 21 km WSW of this epicentre
- 6.5 The 1932 Eureka, California Earthquake · 34 km N of this epicentre
- 6.5 30 km WSW of Ferndale, California · 21 km W of this epicentre
- 6.5 The 2010 Eureka, California Earthquake · 40 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 40.4258, -124.3193. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Humboldt County, CA | 46 km (28 mi) | NE | earthquakes near Humboldt County |
| Trinity County, CA | 105 km (65 mi) | ENE | earthquakes near Trinity County |
| Mendocino County, CA | 133 km (83 mi) | SE | earthquakes near Mendocino County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
60 earthquakes have been recorded within 50 km since this one.
- 3.0 8km SSW of Ferndale, CA
- 1.7 9km SSW of Ferndale, CA
- 1.8 14km N of Petrolia, CA
- 1.9 7km N of Petrolia, CA
- 2.8 14km N of Petrolia, CA
- 2.3 11km SSW of Ferndale, CA
- 2.2 8km N of Petrolia, CA
- 2.7 29km W of Petrolia, CA
- 1.9 20km SSE of Rio Dell, CA
- 2.6 21km W of Petrolia, CA
- 2.4 7km NNW of Petrolia, CA
- 2.5 12km SW of Rio Dell, CA
- 2.0 11km NNE of Petrolia, CA
- 2.6 22km SW of Ferndale, CA
- 2.8 29km W 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.