QuakeIndex

Earthquake · reviewed by a seismologist

M 2.2md

Earthquake near Rio Dell, CA

No earthquake was likely felt in Rio Dell in the 24 hours to 5:01 am PST (13:01 UTC). The last one was M 5.0, 126 km (78 mi) W, at 8:56 pm PST on 4 November 2026, estimated intensity II (weak) in town; 145 felt reports to USGS. Every earthquake near Rio Dell

This page: a magnitude 2.2 earthquake was recorded 27 km (17 mi) east of Rio Dell, CA, at 11:20 pm PDT on 23 September 2018 (06:20 UTC), 24 km deep.

USGS: 27km E of Rio Dell, CA

11:20 pm PDT, Sep 23, 2018 · · 24 km deep · released about 56 lb of TNT

Every earthquake near Rio Dell Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Humboldt County 27 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
11:20 pm PDT on 23 September 2018 ()
Where
27 km (17 mi) east of Rio Dell, CA · earthquakes near Rio Dell
Magnitude
M 2.2 (md)
Depth
24 km below the surface
Felt
no reports yet
Nearest
Humboldt County, 27 km NNW
Nearest mapped fault
Little Salmon 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 2970 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 Rio Dell, 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.

How big was it?

This earthquake released about 56 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.2 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 270,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 190,000× the energy of this one
  3. Around the size people start to feel M 3.0 17× the energy of this one
  4. This earthquake M 2.2 about 56 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 8,800 times the energy of this one.

Before 2016, the USGS record lists 15 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.2 The 1992 Petrolia, California Earthquake · 41 km WSW of this epicentre
  2. 6.5 The 1932 Eureka, California Earthquake · 50 km WNW of this epicentre
  3. 6.4 The 1954 Eureka-Arcata, California Earthquake · 41 km NNW of this epicentre
  4. 6.0 Near Rio Dell, California · 35 km W of this epicentre
  5. 6.0 30 km SSW of Scotia, California · 50 km WSW 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 40.4878, -123.7900. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Humboldt County, CA 27 km (17 mi) NNW earthquakes near Humboldt County
Trinity County, CA 60 km (37 mi) ENE earthquakes near Trinity County
Mendocino County, CA 121 km (75 mi) SSE earthquakes near Mendocino County
Glenn County, CA 154 km (96 mi) SE earthquakes near Glenn County

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

Aftershocks so far

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

  1. 1.8 4km E of Redway, CA
  2. 2.1 5km E of Redway, CA
  3. 2.3 7km SSE of Ferndale, CA
  4. 1.9 30km W of Hayfork, CA
  5. 2.2 10km NNE of Petrolia, CA
  6. 2.7 33km SW of Hayfork, CA
  7. 2.5 14km E of Petrolia, CA
  8. 2.4 9km WSW of Rio Dell, CA
  9. 2.5 3km WNW of Petrolia, CA
  10. 2.1 14km SE of Petrolia, CA
  11. 2.6 19km NNW of Hayfork, CA
  12. 2.6 11km E of Blue Lake, CA
  13. 1.9 29km W of Hayfork, CA
  14. 1.9 31km W of Hayfork, CA
  15. 2.1 13km ESE of Blue Lake, 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.