Earthquake · reviewed by a seismologist
M 4.0mw
Earthquake near Willits, CA
No earthquake was likely felt in Willits in the 24 hours to 1:08 am PST (09:08 UTC). The last one was M 1.5, 9 km (5 mi) ESE, at 10:30 pm PST on 2 November 2026, estimated intensity II (weak) in town. Every earthquake near Willits
This page: a magnitude 4.0 earthquake was recorded 21 km (13 mi) south-southwest of Willits, CA, at 8:41 am PDT on 24 March 2021 (15:41 UTC), 8.2 km deep. 126 people have reported feeling it to USGS.
USGS: 21km SSW of Willits, CA
- When
- 8:41 am PDT on 24 March 2021 ()
- Where
- 21 km (13 mi) south-southwest of Willits, CA · earthquakes near Willits
- Magnitude
- M 4.0 (mw)
- Depth
- 8.2 km below the surface
- Felt
- 126 reports · strongest reported intensity IV
- Measured shaking
- intensity IV (ShakeMap)
- Nearest
- Mendocino County, 21 km N
- Nearest mapped fault
- Maacama fault, 20 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 1827 days ago
Earthquake alerts for Willits, CA
Get a notification in this browser when USGS records an earthquake near Willits, 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 small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.
At this magnitude and depth, people at rest would likely notice it out to about 95 km (59 mi) from the epicentre. In Willits, 21 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: Willits 21 km, intensity III · Brooktrails 23 km, intensity III · Ukiah 25 km, intensity III · Boonville 28 km, intensity III · Fort Bragg 36 km, intensity III · Laytonville 49 km, intensity II · Upper Lake 49 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 14 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.0 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 12,000× the energy of this one
- Mineral, Virginia 2011 M 5.8 540× the energy of this one
- Magna, Utah 2020 M 5.7 380× the energy of this one
- This earthquake M 4.0 about 14 tons of TNT
- Around the size people start to feel M 3.0 this one released 30× 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 since 2016 was M 4.4 on 2020-12-06 — about 4.1 times the energy of this one.
Before 2016, the USGS record lists one earthquake of M5 or more within 50 km:
- 5.2 6 km ESE of Talmage, California · 36 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 39.2448, -123.4743. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Mendocino County, CA | 21 km (13 mi) | N | earthquakes near Mendocino County |
| Lake County, CA | 65 km (40 mi) | ESE | earthquakes near Lake County |
| Sonoma County, CA | 93 km (58 mi) | SSE | earthquakes near Sonoma County |
| Glenn County, CA | 100 km (62 mi) | ENE | earthquakes near Glenn County |
| Colusa County, CA | 107 km (66 mi) | E | earthquakes near Colusa County |
| Napa County, CA | 129 km (80 mi) | SE | earthquakes near Napa County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
60 earthquakes have been recorded within 50 km since this one.
- 1.9 8km NNW of Redwood Valley, CA
- 2.0 12km WNW of Lake Pillsbury, CA
- 1.9 4km NNW of Lake Pillsbury, CA
- 1.8 6km E of Willits, CA
- 1.8 9km NNW of Redwood Valley, CA
- 2.2 7km E of Willits, CA
- 1.7 10km SW of Ukiah, CA
- 1.6 7km E of Willits, CA
- 1.6 9km NNW of Redwood Valley, CA
- 1.7 8km NNW of Redwood Valley, CA
- 1.7 19km SW of Laytonville, CA
- 1.9 15km N of Brooktrails, CA
- 2.9 4km SSE of Redwood Valley, CA
- 2.0 12km WNW of Redwood Valley, CA
- 1.8 10km NNW of Redwood Valley, 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.