QuakeIndex

Earthquake · reviewed by a seismologist

M 2.1md

Earthquake near Bayside, CA

No earthquake was likely felt in Bayside in the 24 hours to 4:21 am PST (12:21 UTC). The last one was M 5.0, 137 km (85 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 Bayside

This page: a magnitude 2.1 earthquake was recorded 46 km (29 mi) east-southeast of Bayside, CA, at 9:51 pm PDT on 9 August 2025 (04:51 UTC), 25 km deep. 2 people have reported feeling it to USGS.

USGS: 36 km S of Willow Creek, CA

9:51 pm PDT, Aug 9, 2025 · · 25 km deep · released about 40 lb of TNT

Every earthquake near Bayside Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Humboldt County 29 kmTrinity County 42 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
9:51 pm PDT on 9 August 2025 ()
Where
46 km (29 mi) east-southeast of Bayside, CA · earthquakes near Bayside
Magnitude
M 2.1 (md)
Depth
25 km below the surface
Felt
2 reports · strongest reported intensity III
Nearest
Humboldt County, 29 km WNW
Nearest mapped fault
Bald Mountain-Big Lagoon fault, 24 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 450 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 Bayside, 46 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.

How big was it?

This earthquake released about 40 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.1 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 380,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 270,000× the energy of this one
  3. Around the size people start to feel M 3.0 24× the energy of this one
  4. This earthquake M 2.1 about 40 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 5.3 on 2023-01-01 — about 80,000 times the energy of this one.

Before 2016, the USGS record lists 5 earthquakes of M5 or more within 50 km:

  1. 6.4 The 1954 Eureka-Arcata, California Earthquake · 35 km NW of this epicentre
  2. 5.8 Near Eureka, California · 39 km WNW of this epicentre
  3. 5.6 15 km SW of Burnt Ranch, California · 11 km N of this epicentre
  4. 5.4 3 km NNW of Burnt Ranch, California · 26 km NNE of this epicentre
  5. 5.0 2 km E of Rio Dell, California · 42 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 40.6148, -123.6058. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Humboldt County, CA 29 km (18 mi) WNW earthquakes near Humboldt County
Trinity County, CA 42 km (26 mi) E earthquakes near Trinity County
Tehama County, CA 128 km (80 mi) ESE earthquakes near Tehama County
Siskiyou County, CA 141 km (87 mi) NE earthquakes near Siskiyou County
Glenn County, CA 152 km (95 mi) SE earthquakes near Glenn County

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

Aftershocks so far

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

  1. 2.1 7 km E of Fortuna, CA
  2. 2.1 19 km E of Hydesville, CA
  3. 2.3 4 km NNE of Hayfork, CA
  4. 1.8 33 km SW of Hayfork, CA
  5. 3.0 16 km ENE of Hydesville, CA
  6. 2.4 20 km ENE of Willow Creek, CA
  7. 1.9 8 km E of Hydesville, CA
  8. 1.9 35 km NE of Redway, CA
  9. 1.8 20 km NE of Hydesville, CA
  10. 2.0 10 km S of Rio Dell, CA
  11. 1.7 35 km E of Hydesville, CA
  12. 2.3 22 km NNE of Redway, CA
  13. 1.6 13 km NE of Hydesville, CA
  14. 1.5 18 km SSE of Rio Dell, CA
  15. 2.4 28 km ESE of Rio Dell, 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.