Earthquake · reviewed by a seismologist
M 1.8md
Earthquake near Hayfork, CA
No earthquake was likely felt in Hayfork in the 24 hours to 6:02 am PST (14:02 UTC). The last one was M 3.7, 42 km (26 mi) W, at 2:44 pm PDT on 7 September 2026, estimated intensity II (weak) in town; 15 felt reports to USGS. Every earthquake near Hayfork
This page: a magnitude 1.8 earthquake was recorded 26 km (16 mi) south-southwest of Hayfork, CA, at 5:33 am PDT on 4 August 2023 (12:33 UTC), 30 km deep.
USGS: 26 km SSW of Hayfork, CA
- When
- 5:33 am PDT on 4 August 2023 ()
- Where
- 26 km (16 mi) south-southwest of Hayfork, CA · earthquakes near Hayfork
- Magnitude
- M 1.8 (md)
- Depth
- 30 km below the surface
- Felt
- no reports yet
- Nearest
- Trinity County, 38 km NNE
- Nearest mapped fault
- Bartlett Springs fault system, 17 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 1195 days ago
Earthquake alerts for Hayfork, CA
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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 Hayfork, 26 km away, the estimate is intensity I (not felt). 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 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.
- Mineral, Virginia 2011 M 5.8 970,000× the energy of this one
- Magna, Utah 2020 M 5.7 680,000× the energy of this one
- Around the size people start to feel M 3.0 61× the energy of this one
- 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 4.5 on 2016-08-28 — about 10,000 times the energy of this one.
Before 2016, the USGS record lists one earthquake of M5 or more within 50 km:
- 5.5 33 km NW of Rancho Tehama Reserve, California · 49 km ESE 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 40.3272, -123.2650. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Trinity County, CA | 38 km (24 mi) | NNE | earthquakes near Trinity County |
| Humboldt County, CA | 70 km (44 mi) | NW | earthquakes near Humboldt County |
| Tehama County, CA | 90 km (56 mi) | ESE | earthquakes near Tehama County |
| Mendocino County, CA | 101 km (63 mi) | S | earthquakes near Mendocino County |
| Glenn County, CA | 109 km (68 mi) | SE | earthquakes near Glenn County |
| Shasta County, CA | 114 km (71 mi) | ENE | earthquakes near Shasta County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
53 earthquakes have been recorded within 50 km since this one.
- 2.5 41 km ENE of Covelo, CA
- 2.4 41 km NNE of Covelo, CA
- 1.5 10 km SE of Redway, CA
- 2.2 35 km WSW of Hayfork, CA
- 2.4 13 km ESE of Redway, CA
- 1.5 21 km NE of Redway, CA
- 2.5 26 km WSW of Hayfork, CA
- 2.1 12 km ESE of Redway, CA
- 1.6 12 km ESE of Redway, CA
- 2.4 12 km ESE of Redway, CA
- 3.9 36 km E of Hydesville, CA
- 2.3 12 km ESE of Redway, CA
- 2.0 12 km ESE of Redway, CA
- 1.9 27 km WSW of Hayfork, CA
- 1.7 30 km NNE of Redway, 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.