QuakeIndex

Earthquake · reviewed by a seismologist

M 1.7md

Earthquake near Fortuna, CA

No earthquake was likely felt in Fortuna in the 24 hours to 10:08 pm PST (06:08 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 1.7 earthquake was recorded 36 km (22 mi) southwest of Fortuna, CA, at 6:41 pm PDT on 6 July 2018 (01:41 UTC), 21 km deep.

USGS: 14km WNW of Petrolia, CA

6:41 pm PDT, Jul 6, 2018 · · 21 km deep · released about 10 lb of TNT

Every earthquake near Fortuna Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Humboldt County 58 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
6:41 pm PDT on 6 July 2018 ()
Where
36 km (22 mi) southwest of Fortuna, CA · earthquakes near Fortuna
Magnitude
M 1.7 (md)
Depth
21 km below the surface
Felt
no reports yet
Nearest
Humboldt County, 58 km NE
Nearest mapped fault
Mattole Canyon fault, 12 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 3050 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

At this magnitude and depth it was probably too small to be felt, even directly above it. In Fortuna, 36 km away, the estimate is intensity I (not felt). 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.

Earthquakes near other towns within 30 km: Ferndale.

How big was it?

This earthquake released about 10 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.7 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 1,500,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 1,100,000× the energy of this one
  3. Around the size people start to feel M 3.0 95× the energy of this one
  4. This earthquake M 1.7 about 10 lb of TNT

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 30,000 times the energy of this one.

Before 2016, the USGS record lists 42 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.2 The 1992 Petrolia, California Earthquake · 18 km E of this epicentre
  2. 6.6 32 km SW of Ferndale, California · 10 km WNW of this epicentre
  3. 6.5 The 1932 Eureka, California Earthquake · 43 km NNE of this epicentre
  4. 6.5 30 km WSW of Ferndale, California · 13 km NW of this epicentre
  5. 6.5 The 2010 Eureka, California Earthquake · 38 km NNW 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 40.3645, -124.4433. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Humboldt County, CA 58 km (36 mi) NE earthquakes near Humboldt County
Trinity County, CA 117 km (72 mi) ENE earthquakes near Trinity 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. 2.3 8km WSW of Petrolia, CA
  2. 2.4 28km WNW of Petrolia, CA
  3. 2.2 6km NNE of Hydesville, CA
  4. 2.1 17km WNW of Petrolia, CA
  5. 2.1 6km NNE of Hydesville, CA
  6. 2.7 6km NNE of Hydesville, CA
  7. 2.6 34km W of Petrolia, CA
  8. 2.6 51km W of Ferndale, CA
  9. 2.6 25km NW of Petrolia, CA
  10. 1.9 15km NW of Petrolia, CA
  11. 2.1 21km W of Petrolia, CA
  12. 2.3 22km WSW of Ferndale, CA
  13. 2.2 20km WSW of Ferndale, CA
  14. 2.5 55km W of Petrolia, CA
  15. 2.0 11km W 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.