QuakeIndex

Earthquake · reviewed by a seismologist

M 4.5mw

Earthquake near Fortuna, CA

No earthquake was likely felt in Fortuna in the 24 hours to 10:41 pm PST (06:41 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 4.5 earthquake was recorded 47 km (29 mi) southwest of Fortuna, CA, at 10:01 pm PST on 8 March 2018 (06:01 UTC), 15 km deep. 196 people have reported feeling it to USGS.

USGS: 22km W of Petrolia, CA

10:01 pm PST, Mar 8, 2018 · · 15 km deep · released about 79 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
10:01 pm PST on 8 March 2018 ()
Where
47 km (29 mi) southwest of Fortuna, CA · earthquakes near Fortuna
Magnitude
M 4.5 (mw)
Depth
15 km below the surface
Felt
196 reports · strongest reported intensity IV
Measured shaking
intensity III (ShakeMap)
USGS impact alert
green
Tsunami
USGS flagged this event for tsunami evaluation. Follow tsunami.gov for official messages.
Nearest
Humboldt County, 70 km NE
Nearest mapped fault
Mattole Canyon fault, 9 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 3079 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 137 km (85 mi) from the epicentre. In Fortuna, 47 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 39 km, intensity III · Rio Dell 44 km, intensity III · Fortuna 47 km, intensity III. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 79 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 2,100× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 95× the energy of this one
  3. Magna, Utah 2020 M 5.7 68× the energy of this one
  4. This earthquake M 4.5 about 79 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 170× 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 (31 mi) since our catalogue begins in 2016. The previous largest was M 4.4 on 2016-01-02.

Before 2016, the USGS record lists 40 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.2 The 1992 Petrolia, California Earthquake · 27 km E of this epicentre
  2. 6.6 32 km SW of Ferndale, California · 10 km N of this epicentre
  3. 6.5 30 km WSW of Ferndale, California · 16 km N of this epicentre
  4. 6.5 The 2010 Eureka, California Earthquake · 42 km NNW of this epicentre
  5. 6.0 Near Rio Dell, California · 37 km NE 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 40.2918, -124.5423. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Humboldt County, CA 70 km (43 mi) NE earthquakes near Humboldt County
Mendocino County, CA 134 km (83 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. 1.7 10km WSW of Petrolia, CA
  2. 2.8 35km W of Petrolia, CA
  3. 2.1 6km SW of Petrolia, CA
  4. 2.4 9km SW of Petrolia, CA
  5. 2.2 20km W of Petrolia, CA
  6. 2.5 34km WNW of Petrolia, CA
  7. 2.8 59km WNW of Petrolia, CA
  8. 2.4 21km W of Petrolia, CA
  9. 1.7 21km NW of Petrolia, CA
  10. 2.6 65km W of Ferndale, CA
  11. 2.7 35km WNW of Ferndale, CA
  12. 2.6 35km WNW of Ferndale, CA
  13. 1.9 12km NW of Petrolia, CA
  14. 2.5 8km NNW of Petrolia, CA
  15. 2.5 9km NNW 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.