QuakeIndex

Earthquake · reviewed by a seismologist

M 2.8md

Earthquake near Humboldt Hill, CA

No earthquake was likely felt in Humboldt Hill in the 24 hours to 11:45 pm PST (07:45 UTC). The last one was M 5.0, 123 km (76 mi) WSW, at 8:56 pm PST on 4 November 2026, estimated intensity II (weak) in town; 145 felt reports to USGS. Every earthquake near Humboldt Hill

This page: a magnitude 2.8 earthquake was recorded 4 km (3 mi) south-southwest of Humboldt Hill, CA, at 5:27 am PST on 6 December 2017 (13:27 UTC), 1.9 km deep. 92 people have reported feeling it to USGS.

USGS: 4km SSW of Humboldt Hill, CA

5:27 am PST, Dec 6, 2017 · · 1.9 km deep · released about 480 lb of TNT

Every earthquake near Humboldt Hill Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Humboldt County 24 kmTrinity County 93 kmDel Norte County 120 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
5:27 am PST on 6 December 2017 ()
Where
4 km (3 mi) south-southwest of Humboldt Hill, CA · earthquakes near Humboldt Hill
Magnitude
M 2.8 (md)
Depth
1.9 km below the surface
Felt
92 reports · strongest reported intensity IV
Nearest
Humboldt County, 24 km E
Nearest mapped fault
Little Salmon fault, 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 3157 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 27 km (17 mi) from the epicentre. In Humboldt Hill, 4 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: Humboldt Hill 4 km, intensity III · Fortuna 11 km, intensity III · Eureka 13 km, intensity III · Ferndale 13 km, intensity III · Bayside 21 km, intensity II · Rio Dell 23 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 480 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.8 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 32,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 22,000× the energy of this one
  3. Around the size people start to feel M 3.0 2× the energy of this one
  4. This earthquake M 2.8 about 480 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 4.8 on 2016-07-21 — about 1,000 times the energy of this one.

Before 2016, the USGS record lists 34 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.2 The 1980 Eureka, California Earthquake · 48 km N of this epicentre
  2. 7.2 The 1992 Petrolia, California Earthquake · 39 km S of this epicentre
  3. 6.6 32 km SW of Ferndale, California · 45 km SW of this epicentre
  4. 6.5 The 1932 Eureka, California Earthquake · 8 km NW of this epicentre
  5. 6.5 30 km WSW of Ferndale, California · 41 km SW 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 40.6892, -124.2112. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Humboldt County, CA 24 km (15 mi) E earthquakes near Humboldt County
Trinity County, CA 93 km (58 mi) E earthquakes near Trinity County
Del Norte County, CA 120 km (74 mi) N earthquakes near Del Norte County

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

Aftershocks so far

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

  1. 2.4 11km WSW of Rio Dell, CA
  2. 2.5 17km ESE of Hydesville, CA
  3. 1.8 12km SSE of Rio Dell, CA
  4. 2.5 20km WNW of Petrolia, CA
  5. 1.9 11km S of Rio Dell, CA
  6. 2.3 25km WNW of Petrolia, CA
  7. 1.7 19km NW of Petrolia, CA
  8. 2.9 18km NW of Petrolia, CA
  9. 2.2 10km S of Ferndale, CA
  10. 2.5 18km WNW of Petrolia, CA
  11. 4.7 22km WNW of Petrolia, CA
  12. 4.4 17km W of Humboldt Hill, CA
  13. 2.5 17km WSW of Petrolia, CA
  14. 2.5 30km W of Bayview, CA
  15. 2.5 27km WNW 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.