QuakeIndex

Earthquake · reviewed by a seismologist

M 3.5mw

Earthquake near Fort Bragg, CA

No earthquake was likely felt in Fort Bragg in the 24 hours to 7:20 pm PST (03:20 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 3.5 earthquake was recorded 20 km (12 mi) west-northwest of Fort Bragg, CA, at 5:09 pm PDT on 30 September 2019 (00:09 UTC), 10 km deep. 141 people have reported feeling it to USGS.

USGS: 20km WNW of Fort Bragg, CA

5:09 pm PDT, Sep 30, 2019 · · 10 km deep · released about 2.6 tons of TNT

Every earthquake near Fort Bragg Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Mendocino County 49 kmLake County 118 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
5:09 pm PDT on 30 September 2019 ()
Where
20 km (12 mi) west-northwest of Fort Bragg, CA · earthquakes near Fort Bragg
Magnitude
M 3.5 (mw)
Depth
10 km below the surface
Felt
141 reports · strongest reported intensity III
Measured shaking
intensity III (ShakeMap)
Nearest
Mendocino County, 49 km ESE
Nearest mapped fault
San Andreas fault, 4 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 2297 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 62 km (39 mi) from the epicentre. In Fort Bragg, 20 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: Fort Bragg 20 km, intensity III · Laytonville 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 2.6 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.5 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 65,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 2,900× the energy of this one
  3. Magna, Utah 2020 M 5.7 2,100× the energy of this one
  4. This earthquake M 3.5 about 2.6 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 5.4× 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 4.3 on 2017-12-14 — about 14 times the energy of this one.

Before 2016, the USGS record lists 2 earthquakes of M5 or more within 50 km:

  1. 6.0 44 km SW of Shelter Cove, California · 42 km WNW of this epicentre
  2. 5.9 9 km S of Leggett, California · 35 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 39.5390, -123.9980. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Mendocino County, CA 49 km (31 mi) ESE earthquakes near Mendocino County
Lake County, CA 118 km (73 mi) ESE earthquakes near Lake County
Sonoma County, CA 146 km (91 mi) SE earthquakes near Sonoma County

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

Aftershocks so far

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

  1. 1.6 10km NE of Navarro Head, CA
  2. 2.3 17km NNW of Laytonville, CA
  3. 2.5 14km NNW of Brooktrails, CA
  4. 3.0 20km NNE of Rockport, CA
  5. 2.1 20km NNE of Rockport, CA
  6. 2.3 17km S of Shelter Cove, CA
  7. 1.8 4km N of Laytonville, CA
  8. 2.1 11km WSW of Cape Vizcaino, CA
  9. 1.6 20km NNE of Rockport, CA
  10. 1.8 21km NNE of Rockport, CA
  11. 1.8 20km NNE of Rockport, CA
  12. 2.0 20km NNE of Rockport, CA
  13. 2.2 21km NNE of Rockport, CA
  14. 2.3 20km NNE of Rockport, CA
  15. 2.8 21km NNE 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.