Earthquake · reviewed by a seismologist
M 3.5mw
Earthquake near Redwood Valley, CA
No earthquake was likely felt in Redwood Valley in the 24 hours to 9:12 pm PST (05:12 UTC). The last one was M 1.5, 7 km (5 mi) SE, at 12:31 pm PST on 11 November 2026, estimated intensity II (weak) in town. Every earthquake near Redwood Valley
This page: a magnitude 3.5 earthquake was recorded 10 km (6 mi) north-northwest of Redwood Valley, CA, at 1:48 am PDT on 27 August 2020 (08:48 UTC), 8.3 km deep. 81 people have reported feeling it to USGS.
USGS: 10km NNW of Redwood Valley, CA
- When
- 1:48 am PDT on 27 August 2020 ()
- Where
- 10 km (6 mi) north-northwest of Redwood Valley, CA · earthquakes near Redwood Valley
- Magnitude
- M 3.5 (mw)
- Depth
- 8.3 km below the surface
- Felt
- 81 reports · strongest reported intensity IV
- Measured shaking
- intensity V (ShakeMap)
- Nearest
- Mendocino County, 19 km WNW
- Nearest mapped fault
- Maacama fault, 7 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 2168 days ago
Earthquake alerts for Redwood Valley, CA
Get a notification in this browser when USGS records an earthquake near Redwood Valley, 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 64 km (40 mi) from the epicentre. In Redwood Valley, 10 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 11 km, intensity III · Brooktrails 16 km, intensity III · Ukiah 23 km, intensity III · Upper Lake 36 km, intensity II · Boonville 40 km, intensity II · Laytonville 43 km, intensity II · Lakeport 45 km, intensity II · Covelo 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 2.9 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.5 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 59,000× the energy of this one
- Mineral, Virginia 2011 M 5.8 2,600× the energy of this one
- Magna, Utah 2020 M 5.7 1,900× the energy of this one
- This earthquake M 3.5 about 2.9 tons of TNT
- Around the size people start to feel M 3.0 this one released 6× 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 5.1 on 2016-08-10 — about 230 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 · 29 km SSE 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 39.3533, -123.2433. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Mendocino County, CA | 19 km (12 mi) | WNW | earthquakes near Mendocino County |
| Lake County, CA | 51 km (32 mi) | ESE | earthquakes near Lake County |
| Glenn County, CA | 77 km (48 mi) | ENE | earthquakes near Glenn County |
| Colusa County, CA | 89 km (55 mi) | ESE | earthquakes near Colusa County |
| Sonoma County, CA | 96 km (60 mi) | SSE | earthquakes near Sonoma County |
| Tehama County, CA | 122 km (76 mi) | NE | earthquakes near Tehama 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 N of Lake Pillsbury, CA
- 2.9 10km ESE of Willits, CA
- 2.2 10km ESE of Willits, CA
- 1.9 10km ESE of Willits, CA
- 1.9 10km ESE of Willits, CA
- 1.8 10km ESE of Willits, CA
- 2.7 10km ESE of Willits, CA
- 1.6 10km ESE of Willits, CA
- 1.7 11km ESE of Willits, CA
- 1.6 2km W of Redwood Valley, CA
- 1.9 10km SE of Willits, CA
- 1.6 11km ESE of Willits, CA
- 1.7 10km SE of Willits, CA
- 1.6 11km NNW of Redwood Valley, CA
- 2.0 10km ESE of Willits, 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.