Earthquake · reviewed by a seismologist
M 2.5md
Earthquake near Hayfork, CA
No earthquake was likely felt in Hayfork in the 24 hours to 10:18 pm PST (06:18 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 2.5 earthquake was recorded 40 km (25 mi) south-southeast of Hayfork, CA, at 1:44 am PDT on 8 August 2018 (08:44 UTC), 44 km deep. 2 people have reported feeling it to USGS.
USGS: 40km SSE of Hayfork, CA
- When
- 1:44 am PDT on 8 August 2018 ()
- Where
- 40 km (25 mi) south-southeast of Hayfork, CA · earthquakes near Hayfork
- Magnitude
- M 2.5 (md)
- Depth
- 44 km below the surface
- Felt
- 2 reports · strongest reported intensity II
- Nearest
- Trinity County, 49 km N
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 3017 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 small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.
At this magnitude and depth it was probably too small to be felt, even directly above it. In Hayfork, 40 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 180 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.5 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 86,000× the energy of this one
- Magna, Utah 2020 M 5.7 61,000× the energy of this one
- Around the size people start to feel M 3.0 5.4× the energy of this one
- This earthquake M 2.5 about 180 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 930 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 · 28 km E 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 40.2102, -123.0410. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Trinity County, CA | 49 km (30 mi) | N | earthquakes near Trinity County |
| Tehama County, CA | 69 km (43 mi) | E | earthquakes near Tehama County |
| Glenn County, CA | 87 km (54 mi) | SE | earthquakes near Glenn County |
| Humboldt County, CA | 93 km (58 mi) | NW | earthquakes near Humboldt County |
| Mendocino County, CA | 93 km (58 mi) | SSW | earthquakes near Mendocino County |
| Shasta County, CA | 104 km (65 mi) | NE | earthquakes near Shasta County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
40 earthquakes have been recorded within 50 km since this one.
- 2.7 37km SSE of Hayfork, CA
- 1.5 41km NE of Covelo, CA
- 1.9 21km W of Rancho Tehama Reserve, CA
- 1.7 8km ENE of Covelo, CA
- 1.9 19km NNW of Alder Springs, CA
- 1.8 20km NNW of Alder Springs, CA
- 2.0 11km WNW of Hayfork, CA
- 2.0 11km WNW of Hayfork, CA
- 1.6 24km W of Rancho Tehama Reserve, CA
- 2.6 17km SSE of Hayfork, CA
- 2.0 42km N of Covelo, CA
- 1.6 30km NE of Covelo, CA
- 1.7 30km NE of Covelo, CA
- 1.7 36km NNW of Alder Springs, CA
- 1.6 34km WNW of Rancho Tehama Reserve, 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.