QuakeIndex

Earthquake · reviewed by a seismologist

M 4.4mw

Earthquake near Fortuna, CA

No earthquake was likely felt in Fortuna in the 24 hours to 4:05 am PST (12:05 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 4.4 earthquake was recorded 50 km (31 mi) southwest of Fortuna, CA, at 1:21 am PDT on 2 April 2021 (08:21 UTC), 19 km deep. 46 people have reported feeling it to USGS.

USGS: 27km W of Petrolia, CA

1:21 am PDT, Apr 2, 2021 · · 19 km deep · released about 52 tons of TNT

Every earthquake near Fortuna Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Humboldt County 73 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
1:21 am PDT on 2 April 2021 ()
Where
50 km (31 mi) southwest of Fortuna, CA · earthquakes near Fortuna
Magnitude
M 4.4 (mw)
Depth
19 km below the surface
Felt
46 reports · strongest reported intensity IV
Measured shaking
intensity III (ShakeMap)
USGS impact alert
green
Nearest
Humboldt County, 73 km NE
Nearest mapped fault
Mattole Canyon fault, 14 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 1899 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 125 km (78 mi) from the epicentre. In Fortuna, 50 km away, the estimate is intensity III (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.

Likely felt in: Ferndale 42 km, intensity III · Rio Dell 47 km, intensity III · Fortuna 50 km, intensity III. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 52 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.4 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 3,200× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 140× the energy of this one
  3. Magna, Utah 2020 M 5.7 100× the energy of this one
  4. This earthquake M 4.4 about 52 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 110× 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 5.8 on 2020-03-09 — about 130 times the energy of this one.

Before 2016, the USGS record lists 43 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.2 The 1992 Petrolia, California Earthquake · 32 km E of this epicentre
  2. 6.6 32 km SW of Ferndale, California · 10 km NNE of this epicentre
  3. 6.5 30 km WSW of Ferndale, California · 15 km NNE of this epicentre
  4. 6.5 The 2010 Eureka, California Earthquake · 40 km N of this epicentre
  5. 6.0 Near Rio Dell, California · 40 km ENE 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 40.3035, -124.6010. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Humboldt County, CA 73 km (45 mi) NE earthquakes near Humboldt County
Mendocino County, CA 138 km (86 mi) SE earthquakes near Mendocino County

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

Aftershocks so far

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

  1. 2.4 17km NW of Petrolia, CA
  2. 1.5 16km WNW of Petrolia, CA
  3. 2.4 45km W of Ferndale, CA
  4. 1.8 4km NW of Petrolia, CA
  5. 1.6 23km W of Petrolia, CA
  6. 2.5 13km N of Petrolia, CA
  7. 1.8 22km NW of Petrolia, CA
  8. 2.1 12km WNW of Petrolia, CA
  9. 2.1 21km W of Petrolia, CA
  10. 2.2 16km W of Petrolia, CA
  11. 2.8 36km WNW of Petrolia, CA
  12. 2.5 22km W of Petrolia, CA
  13. 1.7 17km E of Petrolia, CA
  14. 2.5 44km W of Ferndale, CA
  15. 2.9 31km 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

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