Earthquake · reviewed by a seismologist
M 2.4md
Earthquake near Arcata, CA
No earthquake was likely felt in Arcata in the 24 hours to 9:10 pm PST (05:10 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 Arcata
This page: a magnitude 2.4 earthquake was recorded 50 km (31 mi) northeast of Arcata, CA, at 1:54 am PDT on 25 September 2021 (08:54 UTC), 37 km deep.
USGS: 12km SE of Weitchpec, CA
- When
- 1:54 am PDT on 25 September 2021 ()
- Where
- 50 km (31 mi) northeast of Arcata, CA · earthquakes near Arcata
- Magnitude
- M 2.4 (md)
- Depth
- 37 km below the surface
- Felt
- no reports yet
- Nearest
- Humboldt County, 54 km SSW
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 1870 days ago
Earthquake alerts for Arcata, CA
Get a notification in this browser when USGS records an earthquake near Arcata, CA. No account or email needed.
Alerts are on for .
Not a warning. An alert comes after USGS publishes a quake, usually minutes after the shaking. For early warning use ShakeAlert, through your phone's Wireless Emergency Alerts or the MyShake app.
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 Arcata, 50 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: Willow Creek.
How big was it?
This earthquake released about 130 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.4 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 110,000× the energy of this one
- Magna, Utah 2020 M 5.7 80,000× the energy of this one
- Around the size people start to feel M 3.0 7.2× the energy of this one
- This earthquake M 2.4 about 130 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 4.4 on 2019-02-06 — about 870 times the energy of this one.
Before 2016, the USGS record lists 8 earthquakes of M5 or more within 50 km; the five largest:
- 6.4 The 1954 Eureka-Arcata, California Earthquake · 39 km SW of this epicentre
- 5.8 Near Eureka, California · 49 km SW of this epicentre
- 5.6 15 km SW of Burnt Ranch, California · 45 km S of this epicentre
- 5.6 26 km NNW of Willow Creek, California · 17 km W of this epicentre
- 5.4 3 km NNW of Burnt Ranch, California · 32 km SSE 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 41.1178, -123.5932. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Humboldt County, CA | 54 km (33 mi) | SSW | earthquakes near Humboldt County |
| Trinity County, CA | 66 km (41 mi) | SE | earthquakes near Trinity County |
| Del Norte County, CA | 77 km (48 mi) | NNW | earthquakes near Del Norte County |
| Siskiyou County, CA | 103 km (64 mi) | ENE | earthquakes near Siskiyou County |
| Tehama County, CA | 159 km (99 mi) | SE | earthquakes near Tehama County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
52 earthquakes have been recorded within 50 km since this one.
- 2.9 3km SSE of Somes Bar, CA
- 2.0 16km SE of Blue Lake, CA
- 2.4 17km E of Willow Creek, CA
- 2.9 5km N of Willow Creek, CA
- 2.1 29km E of Willow Creek, CA
- 4.3 16km WSW of Weitchpec, CA
- 3.7 16km WSW of Weitchpec, CA
- 2.7 21km ESE of Weitchpec, CA
- 3.6 6km E of McKinleyville, CA
- 2.7 21km SE of Blue Lake, CA
- 2.8 20km SE of Blue Lake, CA
- 2.5 24km SE of Blue Lake, CA
- 2.3 15km E of Willow Creek, CA
- 2.4 17km ENE of Willow Creek, CA
- 1.8 20km SSE 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
- The official USGS event page — the source of record for every value above
- Did you feel it? Report it to USGS — reports go to USGS, not to us
- ShakeMap for this event, when USGS has produced one
QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.