Earthquake · reviewed by a seismologist
M 2.7md
Earthquake near Hayfork, CA
No earthquake was likely felt in Hayfork in the 24 hours to 8:56 am PST (16:56 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 2.7 earthquake was recorded in Hayfork, CA, at 3:48 pm PST on 20 December 2017 (23:48 UTC), 29 km deep. 4 people have reported feeling it to USGS.
USGS: 1km ENE of Hayfork, CA
- When
- 3:48 pm PST on 20 December 2017 ()
- Where
- in Hayfork, CA · earthquakes near Hayfork
- Magnitude
- M 2.7 (md)
- Depth
- 29 km below the surface
- Felt
- 4 reports · strongest reported intensity III
- Nearest
- Trinity County, 11 km NNE
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 3248 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. 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: Weaverville.
How big was it?
This earthquake released about 340 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.7 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 45,000× the energy of this one
- Magna, Utah 2020 M 5.7 32,000× the energy of this one
- Around the size people start to feel M 3.0 2.8× the energy of this one
- This earthquake M 2.7 about 340 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 480 times the energy of this one.
Before 2016, the USGS record lists 2 earthquakes of M5 or more within 50 km:
- 5.6 15 km SW of Burnt Ranch, California · 41 km WNW of this epicentre
- 5.4 3 km NNW of Burnt Ranch, California · 42 km NW 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 40.5562, -123.1710. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Trinity County, CA | 11 km (7 mi) | NNE | earthquakes near Trinity County |
| Humboldt County, CA | 66 km (41 mi) | WNW | earthquakes near Humboldt County |
| Tehama County, CA | 93 km (58 mi) | ESE | earthquakes near Tehama County |
| Shasta County, CA | 98 km (61 mi) | ENE | earthquakes near Shasta County |
| Glenn County, CA | 125 km (77 mi) | SSE | earthquakes near Glenn County |
| Siskiyou County, CA | 127 km (79 mi) | NNE | earthquakes near Siskiyou 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.
- 2.6 19km NNW of Hayfork, CA
- 1.9 29km W of Hayfork, CA
- 1.9 31km W of Hayfork, CA
- 1.7 30km W of Hayfork, CA
- 2.0 38km E of Hydesville, CA
- 1.9 29km NNE of Redway, CA
- 2.0 34km SW of Hayfork, CA
- 3.3 14km ESE of Willow Creek, CA
- 2.0 14km WNW of Hayfork, CA
- 1.9 30km SW of Hayfork, CA
- 1.9 23km NNW of Hayfork, CA
- 1.6 29km NNW of Hayfork, CA
- 1.8 19km SSE of Hayfork, CA
- 1.9 36km SSE of Hayfork, CA
- 1.9 28km W of Hayfork, 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.