QuakeIndex

Earthquake · reviewed by a seismologist

M 1.8md

Earthquake near Blue Lake, CA

No earthquake was likely felt in Blue Lake in the 24 hours to 7:29 pm PST (03:29 UTC). The last one was M 5.0, 145 km (90 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 Blue Lake

This page: a magnitude 1.8 earthquake was recorded 27 km (17 mi) south-southeast of Blue Lake, CA, at 1:06 pm PDT on 4 April 2021 (20:06 UTC), 26 km deep.

USGS: 27km SSE of Blue Lake, CA

1:06 pm PDT, Apr 4, 2021 · · 26 km deep · released about 16 lb of TNT

Every earthquake near Blue Lake Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Humboldt County 9 kmTrinity County 60 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
1:06 pm PDT on 4 April 2021 ()
Where
27 km (17 mi) south-southeast of Blue Lake, CA · earthquakes near Blue Lake
Magnitude
M 1.8 (md)
Depth
26 km below the surface
Felt
no reports yet
Nearest
Humboldt County, 9 km WNW
Nearest mapped fault
Mad River fault, 8 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 2043 days ago

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

At this magnitude and depth it was probably too small to be felt, even directly above it. In Blue Lake, 27 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.

Earthquakes near other towns within 30 km: Hydesville, Bayside, Pine Hills, Myrtletown, Cutten, Fortuna.

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 5.8 970,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 680,000× the energy of this one
  3. Around the size people start to feel M 3.0 61× 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 4.8 on 2016-07-21 — about 32,000 times the energy of this one.

Before 2016, the USGS record lists 16 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.5 The 1932 Eureka, California Earthquake · 39 km W of this epicentre
  2. 6.4 The 1954 Eureka-Arcata, California Earthquake · 20 km NNW of this epicentre
  3. 6.0 Near Rio Dell, California · 37 km WSW of this epicentre
  4. 5.8 Near Eureka, California · 20 km NW of this epicentre
  5. 5.6 15 km SW of Burnt Ranch, California · 18 km ENE 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 40.6765, -123.8245. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Humboldt County, CA 9 km (6 mi) WNW earthquakes near Humboldt County
Trinity County, CA 60 km (37 mi) E earthquakes near Trinity County
Del Norte County, CA 120 km (75 mi) N earthquakes near Del Norte County
Siskiyou County, CA 148 km (92 mi) NE earthquakes near Siskiyou County

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

Aftershocks so far

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

  1. 1.7 12km SSW of Ferndale, CA
  2. 1.7 12km SSW of Ferndale, CA
  3. 2.6 6km ENE of Petrolia, CA
  4. 2.3 8km E of Willow Creek, CA
  5. 1.7 33km ENE of Hydesville, CA
  6. 2.5 19km SE of Bayside, CA
  7. 1.8 9km SSW of Ferndale, CA
  8. 1.6 9km SSW of Ferndale, CA
  9. 1.7 9km SSW of Ferndale, CA
  10. 2.0 11km SSW of Ferndale, CA
  11. 2.3 11km SSW of Ferndale, CA
  12. 1.8 9km W of Willow Creek, CA
  13. 2.4 36km NNE of Redway, CA
  14. 2.2 20km SE of Willow Creek, CA
  15. 2.1 16km ESE of Willow Creek, 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.