QuakeIndex

Earthquake · reviewed by a seismologist

M 4.2mw

Earthquake near Fortuna, CA

No earthquake was likely felt in Fortuna in the 24 hours to 1:31 pm PST (21:31 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 4.2 earthquake was recorded 32 km (20 mi) southwest of Fortuna, CA, at 9:55 pm PDT on 28 March 2019 (04:55 UTC), 28 km deep. 713 people have reported feeling it to USGS.

USGS: 19km NW of Petrolia, CA

9:55 pm PDT, Mar 28, 2019 · · 28 km deep · released about 29 tons of TNT

Every earthquake near Fortuna Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Humboldt County 55 kmTrinity County 117 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
9:55 pm PDT on 28 March 2019 ()
Where
32 km (20 mi) southwest of Fortuna, CA · earthquakes near Fortuna
Magnitude
M 4.2 (mw)
Depth
28 km below the surface
Felt
713 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, 55 km NE
Nearest mapped fault
Mattole Canyon fault, 19 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 2700 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 108 km (67 mi) from the epicentre. In Fortuna, 32 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 24 km, intensity III · Rio Dell 31 km, intensity III · Fortuna 32 km, intensity III · Humboldt Hill 40 km, intensity III · Eureka 49 km, intensity III. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 29 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.2 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 5,800× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 260× the energy of this one
  3. Magna, Utah 2020 M 5.7 180× the energy of this one
  4. This earthquake M 4.2 about 29 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 61× 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 4.7 on 2018-03-23 — about 5.1 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 · 23 km ESE of this epicentre
  2. 6.6 32 km SW of Ferndale, California · 9 km SW of this epicentre
  3. 6.5 The 1932 Eureka, California Earthquake · 37 km NNE of this epicentre
  4. 6.5 30 km WSW of Ferndale, California · 9 km W of this epicentre
  5. 6.5 The 2010 Eureka, California Earthquake · 31 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 40.4288, -124.4655. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Humboldt County, CA 55 km (34 mi) NE earthquakes near Humboldt County
Trinity County, CA 117 km (73 mi) ENE earthquakes near Trinity County
Mendocino County, CA 141 km (88 mi) SE earthquakes near Mendocino County

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

Aftershocks so far

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

  1. 2.3 14km WSW of Petrolia, CA
  2. 1.5 22km NW of Petrolia, CA
  3. 2.6 13km WSW of Petrolia, CA
  4. 2.3 12km W of Petrolia, CA
  5. 2.6 37km WNW of Petrolia, CA
  6. 1.7 23km WNW of Petrolia, CA
  7. 2.5 7km SW of Rio Dell, CA
  8. 2.4 9km SSE of Ferndale, CA
  9. 2.0 12km NW of Petrolia, CA
  10. 1.7 17km W of Petrolia, CA
  11. 1.7 16km WNW of Petrolia, CA
  12. 1.7 16km W of Petrolia, CA
  13. 2.2 8km NNE of Hydesville, CA
  14. 1.8 12km SW of Ferndale, CA
  15. 1.7 18km N of Shelter Cove, 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.