QuakeIndex

Earthquake · reviewed by a seismologist

M 3.5mw

20km WNW of Fort Bragg, CA

· 10 km deep · released about 2.6 tons of TNT

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
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
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2252 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage. 141 people have reported feeling it to USGS.

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.

Where

Epicentre 39.5390, -123.9980. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Mendocino County, CA 49 km (31 mi) WNW of here earthquakes near Mendocino County
Lake County, CA 118 km (73 mi) WNW of here earthquakes near Lake County
Sonoma County, CA 146 km (91 mi) NW of here 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.

For this area

The largest earthquake within 50 km in our catalogue was M 4.3 on 2017-12-14 — it released about 14 times the energy of this one.

From the QuakeIndex catalogue, built from the USGS FDSN event service.

On USGS

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.