QuakeIndex

Earthquake · reviewed by a seismologist

M 1.8md

Earthquake near Fort Bragg, CA

No earthquake was likely felt in Fort Bragg in the 24 hours to 5:55 pm PST (01:55 UTC). The last one was M 5.0, 186 km (115 mi) NW, at 8:56 pm PST on 4 November 2026, estimated intensity II (weak) in town; 145 felt reports to USGS. Every earthquake near Fort Bragg

This page: a magnitude 1.8 earthquake was recorded 39 km (24 mi) north-northwest of Fort Bragg, CA, at 9:31 pm PDT on 6 May 2018 (04:31 UTC), 3.1 km deep.

USGS: 14km WNW of Cape Vizcaino, CA

9:31 pm PDT, May 6, 2018 · · 3.1 km deep · released about 16 lb of TNT

Every earthquake near Fort Bragg Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Mendocino County 59 kmHumboldt County 105 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
9:31 pm PDT on 6 May 2018 ()
Where
39 km (24 mi) north-northwest of Fort Bragg, CA · earthquakes near Fort Bragg
Magnitude
M 1.8 (md)
Depth
3.1 km below the surface
Felt
no reports yet
Nearest
Mendocino County, 59 km SE
Nearest mapped fault
San Andreas fault, under 1 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 3110 days ago

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

At this magnitude and depth, people at rest would likely notice it out to about 13 km (8 mi) from the epicentre. In Fort Bragg, 39 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.

How big was it?

This earthquake released about 16 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.8 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 930,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 660,000× the energy of this one
  3. Around the size people start to feel M 3.0 59× the energy of this one
  4. This earthquake M 1.8 about 16 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 4.3 on 2017-12-14 — about 4,600 times the energy of this one.

Before 2016, the USGS record lists 4 earthquakes of M5 or more within 50 km:

  1. 6.0 44 km SW of Shelter Cove, California · 36 km W of this epicentre
  2. 5.9 9 km S of Leggett, California · 22 km E of this epicentre
  3. 5.9 29 km W of Shelter Cove, California · 50 km NW of this epicentre
  4. 5.5 7 km ESE of Shelter Cove, California · 27 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 39.7613, -123.9902. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Mendocino County, CA 59 km (37 mi) SE earthquakes near Mendocino County
Humboldt County, CA 105 km (65 mi) N earthquakes near Humboldt County
Trinity County, CA 123 km (77 mi) NE earthquakes near Trinity County
Lake County, CA 129 km (80 mi) SE earthquakes near Lake 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. 2.1 4km NW of Redway, CA
  2. 3.1 3km NW of Redway, CA
  3. 2.3 17km N of Rockport, CA
  4. 2.0 3km NNW of Redway, CA
  5. 1.5 4km N of Redway, CA
  6. 3.2 3km NNW of Redway, CA
  7. 2.1 13km SSW of Laytonville, CA
  8. 1.6 13km SSW of Laytonville, CA
  9. 1.9 9km ESE of Redway, CA
  10. 2.3 14km SW of Laytonville, CA
  11. 3.5 20km WNW of Fort Bragg, CA
  12. 1.8 12km NW of Laytonville, CA
  13. 1.6 2km SW of Laytonville, CA
  14. 2.1 3km ESE of Rockport, CA
  15. 1.8 15km SE of Rockport, 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.