QuakeIndex

Earthquake · reviewed by a seismologist

M 4.9mw

Earthquake near Rio Dell, CA

No earthquake was likely felt in Rio Dell in the 24 hours to 1:36 am PST (09:36 UTC). The last one was M 5.0, 126 km (78 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 Rio Dell

This page: a magnitude 4.9 earthquake was recorded 7 km (5 mi) west-northwest of Rio Dell, CA, at 2:39 am PST on 20 December 2022 (10:39 UTC), 27 km deep. 133 people have reported feeling it to USGS.

USGS: 7km WNW of Rio Dell, CA

2:39 am PST, Dec 20, 2022 · · 27 km deep · released about 360 tons of TNT

Every earthquake near Rio Dell Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Humboldt County 30 kmTrinity County 92 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
2:39 am PST on 20 December 2022 ()
Where
7 km (5 mi) west-northwest of Rio Dell, CA · earthquakes near Rio Dell
Magnitude
M 4.9 (mw)
Depth
27 km below the surface
Felt
133 reports · strongest reported intensity VI
Measured shaking
intensity V (ShakeMap)
USGS impact alert
green
Nearest
Humboldt County, 30 km NE
Nearest mapped fault
Little Salmon fault, 10 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 1352 days ago

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 182 km (113 mi) from the epicentre. In Rio Dell, 7 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: Rio Dell 7 km, intensity IV · Ferndale 9 km, intensity IV · Fortuna 9 km, intensity IV · Humboldt Hill 23 km, intensity IV · Eureka 31 km, intensity III · Bayside 37 km, intensity III · McKinleyville 48 km, intensity III. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 360 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.9 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 470× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 21× the energy of this one
  3. Magna, Utah 2020 M 5.7 15× the energy of this one
  4. This earthquake M 4.9 about 360 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 760× 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 6.4 on 2022-12-20 — about 170 times the energy of this one.

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 · 21 km S of this epicentre
  2. 6.6 32 km SW of Ferndale, California · 35 km WSW of this epicentre
  3. 6.5 The 1932 Eureka, California Earthquake · 24 km NNW of this epicentre
  4. 6.5 30 km WSW of Ferndale, California · 34 km WSW of this epicentre
  5. 6.5 The 2010 Eureka, California Earthquake · 45 km WNW 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 40.5228, -124.1882. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Humboldt County, CA 30 km (19 mi) NE earthquakes near Humboldt County
Trinity County, CA 92 km (57 mi) E earthquakes near Trinity 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. 2.1 12km WSW of Ferndale, CA
  2. 1.8 16km WSW of Ferndale, CA
  3. 2.1 13km WSW of Ferndale, CA
  4. 2.1 16km WSW of Ferndale, CA
  5. 2.4 4km SE of Fortuna, CA
  6. 2.5 21km WSW of Ferndale, CA
  7. 2.0 5km SSW of Ferndale, CA
  8. 3.0 5km E of Fortuna, CA
  9. 2.6 6km SW of Ferndale, CA
  10. 2.1 5km ESE of Ferndale, CA
  11. 2.2 5km SE of Ferndale, CA
  12. 2.5 7km SW of Ferndale, CA
  13. 2.2 21km SW of Ferndale, CA
  14. 1.7 2km SW of Fortuna, CA
  15. 2.4 5km N of Hydesville, 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.