QuakeIndex

Earthquake · reviewed by a seismologist

M 4.5mw

Earthquake near Ferndale, CA

No earthquake was likely felt in Ferndale in the 24 hours to 2:23 am PST (10:23 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 4.5 earthquake was recorded 10 km (6 mi) west-southwest of Ferndale, CA, at 4:18 pm PDT on 21 March 2023 (23:18 UTC), 18 km deep. 738 people have reported feeling it to USGS.

USGS: 10km WSW of Ferndale, CA

4:18 pm PDT, Mar 21, 2023 · · 18 km deep · released about 97 tons of TNT

Every earthquake near Ferndale Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Humboldt County 42 kmTrinity County 107 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
4:18 pm PDT on 21 March 2023 ()
Where
10 km (6 mi) west-southwest of Ferndale, CA · earthquakes near Ferndale
Magnitude
M 4.5 (mw)
Depth
18 km below the surface
Felt
738 reports · strongest reported intensity IV
Measured shaking
intensity IV (ShakeMap)
USGS impact alert
green
Tsunami
USGS flagged this event for tsunami evaluation. Follow tsunami.gov for official messages.
Nearest
Humboldt County, 42 km ENE
Nearest mapped fault
Little Salmon fault, 20 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 1266 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 142 km (88 mi) from the epicentre. In Ferndale, 10 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: Ferndale 10 km, intensity IV · Fortuna 19 km, intensity III · Rio Dell 23 km, intensity III · Humboldt Hill 26 km, intensity III · Eureka 34 km, intensity III · Bayside 42 km, intensity III. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 97 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.5 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 1,700× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 78× the energy of this one
  3. Magna, Utah 2020 M 5.7 55× the energy of this one
  4. This earthquake M 4.5 about 97 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 200× 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 620 times the energy of this one.

Before 2016, the USGS record lists 41 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.2 The 1992 Petrolia, California Earthquake · 26 km SSE of this epicentre
  2. 6.6 32 km SW of Ferndale, California · 23 km SW of this epicentre
  3. 6.5 The 1932 Eureka, California Earthquake · 22 km NNE of this epicentre
  4. 6.5 30 km WSW of Ferndale, California · 20 km SW of this epicentre
  5. 6.5 The 2010 Eureka, California Earthquake · 30 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 40.5415, -124.3725. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Humboldt County, CA 42 km (26 mi) ENE earthquakes near Humboldt County
Trinity County, CA 107 km (66 mi) E earthquakes near Trinity County

Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.

Aftershocks so far

56 earthquakes have been recorded within 50 km since this one.

  1. 1.8 18km WNW of Ferndale, CA
  2. 2.1 14km NNW of Petrolia, CA
  3. 1.8 19km E of Hydesville, CA
  4. 3.5 44km WSW of Ferndale, CA
  5. 2.2 14km WSW of Ferndale, CA
  6. 2.0 14km WSW of Ferndale, CA
  7. 2.3 16km WSW of Ferndale, CA
  8. 3.0 16km WSW of Ferndale, CA
  9. 2.6 44km WNW of Petrolia, CA
  10. 2.0 5km SW of Ferndale, CA
  11. 2.9 24km WNW of Petrolia, CA
  12. 1.5 14km SE of Petrolia, CA
  13. 2.3 5km SE of Ferndale, CA
  14. 2.0 6km NNE of Hydesville, CA
  15. 2.2 6km N 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

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