QuakeIndex

Earthquake · reviewed by a seismologist

M 6.2mw

Earthquake near Fortuna, CA

No earthquake was likely felt in Fortuna in the 24 hours to 1:55 pm PST (21:55 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 6.2 earthquake was recorded 26 km (16 mi) south-southwest of Fortuna, CA, at 12:10 pm PST on 20 December 2021 (20:10 UTC), 27 km deep. 4,378 people have reported feeling it to USGS.

USGS: 7km N of Petrolia, CA

12:10 pm PST, Dec 20, 2021 · · 27 km deep · released about 30 kilotons of TNT

Every earthquake near Fortuna Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Humboldt County 47 kmTrinity County 104 km
Distance rings around the epicentre, with the nearest towns at their true direction and later quakes as coloured dots. Not a shaking map — see the USGS ShakeMap for that.
When
12:10 pm PST on 20 December 2021 ()
Where
26 km (16 mi) south-southwest of Fortuna, CA · earthquakes near Fortuna
Magnitude
M 6.2 (mw)
Depth
27 km below the surface
Felt
4,378 reports · strongest reported intensity VIII
Measured shaking
intensity VII (ShakeMap)
USGS impact alert
yellow
Tsunami
USGS flagged this event for tsunami evaluation. Follow tsunami.gov for official messages.
Nearest
Humboldt County, 47 km NE
Nearest mapped fault
Mattole Canyon fault, 18 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 326 days ago

This was a strong earthquake. Damage is likely near the epicentre and it is felt over a wide area.

At this magnitude and depth, people at rest would likely notice it out to about 386 km (240 mi) from the epicentre. In Fortuna, 26 km away, the estimate is intensity V (moderate). 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: Rio Dell 20 km, intensity V · Ferndale 21 km, intensity V · Fortuna 26 km, intensity V · Humboldt Hill 38 km, intensity V · Eureka 47 km, intensity V. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 30 kilotons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 7.2 would have released about 32 times as much.

  1. Ridgecrest, California 2019 M 7.1 22× the energy of this one
  2. Loma Prieta, California 1989 M 6.9 11× the energy of this one
  3. Northridge, California 1994 M 6.7 5.6× the energy of this one
  4. This earthquake M 6.2 about 30 kilotons of TNT
  5. Mineral, Virginia 2011 M 5.8 this one released 4× more
  6. Magna, Utah 2020 M 5.7 this one released 5.6× 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 (31 mi) since our catalogue begins in 2016. The previous largest was M 5.7 on 2021-12-20.

Before 2016, the USGS record lists 35 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.2 The 1992 Petrolia, California Earthquake · 8 km SE of this epicentre
  2. 6.6 32 km SW of Ferndale, California · 22 km W of this epicentre
  3. 6.5 The 1932 Eureka, California Earthquake · 38 km N of this epicentre
  4. 6.5 30 km WSW of Ferndale, California · 23 km WNW of this epicentre
  5. 6.5 The 2010 Eureka, California Earthquake · 44 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 40.3902, -124.2980. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Humboldt County, CA 47 km (29 mi) NE earthquakes near Humboldt County
Trinity County, CA 104 km (65 mi) ENE earthquakes near Trinity County
Mendocino County, CA 129 km (80 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.

  1. 2.6 8km W of Petrolia, CA
  2. 1.9 4km NNE of Petrolia, CA
  3. 3.9 6km NE of Petrolia, CA
  4. 3.3 18km SW of Ferndale, CA
  5. 2.2 12km SSW of Ferndale, CA
  6. 2.3 12km SW of Rio Dell, CA
  7. 2.4 11km SSW of Ferndale, CA
  8. 2.4 11km NNE of Petrolia, CA
  9. 2.4 14km NNW of Petrolia, CA
  10. 3.2 11km NNE of Petrolia, CA
  11. 2.0 4km ENE of Petrolia, CA
  12. 2.6 12km SSW of Ferndale, CA
  13. 2.7 15km SW of Ferndale, CA
  14. 2.6 14km N of Petrolia, CA
  15. 3.3 13km SSW of Ferndale, 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

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.