Earthquake · reviewed by a seismologist
M 4.0mw
21km SSW of Willits, CA
- When
- 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
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 1781 days ago
This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage. 126 people have reported feeling it to USGS.
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.
Where
Epicentre 39.2448, -123.4743. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction | |
|---|---|---|---|
| Mendocino County, CA | 21 km (13 mi) | S of here | earthquakes near Mendocino County |
| Lake County, CA | 65 km (40 mi) | WNW of here | earthquakes near Lake County |
| Sonoma County, CA | 93 km (58 mi) | NNW of here | earthquakes near Sonoma County |
| Glenn County, CA | 100 km (62 mi) | WSW of here | earthquakes near Glenn County |
| Colusa County, CA | 107 km (66 mi) | W of here | earthquakes near Colusa County |
| Napa County, CA | 129 km (80 mi) | NW of here | 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.
For this area
The largest earthquake within 50 km in our catalogue was M 4.4 on 2020-12-06 — it released about 4.1 times the energy of this one.
From the QuakeIndex catalogue, built from the USGS FDSN event service.
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.