QuakeIndex

Earthquake · reviewed by a seismologist

M 3.3ml

Earthquake near Fortuna, CA

No earthquake was likely felt in Fortuna in the 24 hours to 5:50 am PST (13:50 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 3.3 earthquake was recorded 47 km (29 mi) west-southwest of Fortuna, CA, at 9:50 pm PST on 13 November 2020 (05:50 UTC), 23 km deep. 4 people have reported feeling it to USGS.

USGS: 35km WNW of Petrolia, CA

9:50 pm PST, Nov 13, 2020 · · 23 km deep · released about 1.4 tons of TNT

Every earthquake near Fortuna Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Humboldt County 70 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
9:50 pm PST on 13 November 2020 ()
Where
47 km (29 mi) west-southwest of Fortuna, CA · earthquakes near Fortuna
Magnitude
M 3.3 (ml)
Depth
23 km below the surface
Felt
4 reports · strongest reported intensity I
Measured shaking
intensity II (ShakeMap)
Nearest
Humboldt County, 70 km ENE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2115 days ago

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 47 km (29 mi) from the epicentre. In Fortuna, 47 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.

Likely felt in: Ferndale 38 km, intensity II · Fortuna 47 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 1.4 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.3 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 120,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 5,200× the energy of this one
  3. Magna, Utah 2020 M 5.7 3,700× the energy of this one
  4. This earthquake M 3.3 about 1.4 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 3× 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 4,700 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 · 39 km ESE of this epicentre
  2. 6.6 32 km SW of Ferndale, California · 11 km ESE of this epicentre
  3. 6.5 The 1932 Eureka, California Earthquake · 46 km NE of this epicentre
  4. 6.5 30 km WSW of Ferndale, California · 9 km E of this epicentre
  5. 6.5 The 2010 Eureka, California Earthquake · 24 km N 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 40.4362, -124.6682. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Humboldt County, CA 70 km (43 mi) ENE earthquakes near Humboldt County
Mendocino County, CA 153 km (95 mi) SE earthquakes near Mendocino County

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

Aftershocks so far

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

  1. 3.0 58km W of Ferndale, CA
  2. 1.8 7km N of Petrolia, CA
  3. 1.8 13km SE of Petrolia, CA
  4. 2.4 13km SE of Petrolia, CA
  5. 2.9 27km W of Petrolia, CA
  6. 2.3 25km WNW of Ferndale, CA
  7. 2.6 61km W of Petrolia, CA
  8. 2.5 14km WNW of Petrolia, CA
  9. 2.6 15km WSW of Petrolia, CA
  10. 2.5 18km WNW of Petrolia, CA
  11. 2.8 24km W of Petrolia, CA
  12. 2.2 8km WSW of Petrolia, CA
  13. 1.8 19km W of Petrolia, CA
  14. 2.4 16km SW of Ferndale, CA
  15. 2.6 9km WSW 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.