Earthquake · reviewed by a seismologist
M 4.5mw
Earthquake near Hayfork, CA
No earthquake was likely felt in Hayfork in the 24 hours to 4:32 pm PST (00:32 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 4.5 earthquake was recorded 23 km (14 mi) southwest of Hayfork, CA, at 2:20 pm PDT on 28 August 2016 (21:20 UTC), 36 km deep. 136 people have reported feeling it to USGS.
USGS: 8 km ESE of Mad River, California
- When
- 2:20 pm PDT on 28 August 2016 ()
- Where
- 23 km (14 mi) southwest of Hayfork, CA · earthquakes near Hayfork
- Magnitude
- M 4.5 (mw)
- Depth
- 36 km below the surface
- Felt
- 136 reports · strongest reported intensity IV
- Measured shaking
- intensity III (ShakeMap)
- USGS impact alert
- green
- Nearest
- Trinity County, 34 km NE
- Nearest mapped fault
- Bartlett Springs fault system, 23 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 3526 days ago
Earthquake alerts for Hayfork, CA
Get a notification in this browser when USGS records an earthquake near Hayfork, 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 light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon.
At this magnitude and depth, people at rest would likely notice it out to about 134 km (83 mi) from the epicentre. In Hayfork, 23 km away, the estimate is intensity III (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.
Likely felt in: Hayfork 23 km, intensity III · Redway 50 km, intensity III. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 82 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.5 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 2,100× the energy of this one
- Mineral, Virginia 2011 M 5.8 92× the energy of this one
- Magna, Utah 2020 M 5.7 65× the energy of this one
- This earthquake M 4.5 about 82 tons of TNT
- Around the size people start to feel M 3.0 this one released 170× more
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 (31 mi) since our catalogue begins in 2016. No other earthquake of M4 or more has been recorded this close in that time.
Before 2016, the USGS record lists 2 earthquakes of M5 or more within 50 km:
- 5.6 15 km SW of Burnt Ranch, California · 36 km NNW of this epicentre
- 5.4 3 km NNW of Burnt Ranch, California · 45 km N 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 40.4365, -123.4078. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Trinity County, CA | 34 km (21 mi) | NE | earthquakes near Trinity County |
| Humboldt County, CA | 53 km (33 mi) | NW | earthquakes near Humboldt County |
| Tehama County, CA | 106 km (66 mi) | ESE | earthquakes near Tehama County |
| Mendocino County, CA | 112 km (69 mi) | S | earthquakes near Mendocino County |
| Shasta County, CA | 121 km (75 mi) | ENE | earthquakes near Shasta County |
| Glenn County, CA | 126 km (78 mi) | SE | earthquakes near Glenn County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
49 earthquakes have been recorded within 50 km since this one.
- 1.7 19 km NNE of Redcrest, California
- 2.0 32 km ESE of Ruth, California
- 1.8 15 km E of Hydesville, California
- 2.5 1 km W of Trinity Village, California
- 1.7 24 km SE of Alderpoint, California
- 1.7 17 km ENE of Hydesville, California
- 1.6 15 km WNW of Mad River, California
- 2.1 15 km ENE of Hydesville, California
- 1.9 19 km E of Hydesville, California
- 2.1 13 km SSW of Douglas City, California
- 2.0 9 km WSW of Burnt Ranch, California
- 2.9 12 km WSW of Mad River, California
- 1.9 13 km N of Alderpoint, California
- 2.2 14 km WSW of Mad River, California
- 1.7 26 km SE of Alderpoint, California
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.