QuakeIndex

Earthquake · reviewed by a seismologist

M 1.7md

Earthquake near Fort Bragg, CA

No earthquake was likely felt in Fort Bragg in the 24 hours to 4:58 am PST (12:58 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 1.7 earthquake was recorded 35 km (22 mi) north-northeast of Fort Bragg, CA, at 5:50 pm PDT on 25 April 2020 (00:50 UTC), less than 1 km deep.

USGS: 11km E of Rockport, CA

5:50 pm PDT, Apr 25, 2020 · · -0.1 km deep · released about 9.3 lb of TNT

Every earthquake near Fort Bragg Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Mendocino County 40 kmLake County 107 kmHumboldt County 109 kmGlenn County 111 kmTrinity County 112 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
5:50 pm PDT on 25 April 2020 ()
Where
35 km (22 mi) north-northeast of Fort Bragg, CA · earthquakes near Fort Bragg
Magnitude
M 1.7 (md)
Depth
-0.1 km below the surface
Felt
no reports yet
Nearest
Mendocino County, 40 km SSE
Nearest mapped fault
Maacama fault, 10 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 2389 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 12 km (7 mi) from the epicentre. In Fort Bragg, 35 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: Laytonville.

How big was it?

This earthquake released about 9.3 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 1,600,000× 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 3.0 100× the energy of this one
  4. This earthquake M 1.7 about 9.3 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 7,900 times the energy of this one.

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

  1. 5.9 9 km S of Leggett, California · 6 km NW of this epicentre
  2. 5.5 7 km ESE of Shelter Cove, California · 40 km NW 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 39.7420, -123.6817. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Mendocino County, CA 40 km (25 mi) SSE earthquakes near Mendocino County
Lake County, CA 107 km (66 mi) SE earthquakes near Lake County
Humboldt County, CA 109 km (68 mi) N earthquakes near Humboldt County
Glenn County, CA 111 km (69 mi) E earthquakes near Glenn County
Trinity County, CA 112 km (69 mi) NNE earthquakes near Trinity County

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

Aftershocks so far

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

  1. 1.9 9km NNE of Brooktrails, CA
  2. 1.5 14km NNE of Brooktrails, CA
  3. 2.0 20km NE of Brooktrails, CA
  4. 1.9 21km NNE of Rockport, CA
  5. 2.2 21km NNE of Rockport, CA
  6. 1.7 13km ESE of Redway, CA
  7. 2.5 6km NNE of Fort Bragg, CA
  8. 1.7 11km SE of Laytonville, CA
  9. 1.7 4km NNW of Redway, CA
  10. 1.9 4km NNW of Redway, CA
  11. 2.6 3km NNW of Redway, CA
  12. 2.6 3km NNW of Redway, CA
  13. 1.9 14km N of Rockport, CA
  14. 2.4 9km W of Covelo, CA
  15. 1.8 7km NE of Brooktrails, 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.