Earthquake · reviewed by a seismologist
M 3.9mw
Earthquake near Ukiah, CA
Yes: an earthquake was likely felt in Ukiah in the last 24 hours. M 1.5, 5 km (3 mi) E of Ukiah, at 3:26 am PST on 12 November 2026 (11:26 UTC); the estimated shaking in Ukiah was intensity II (weak). Every earthquake near Ukiah
This page: a magnitude 3.9 earthquake was recorded 44 km (28 mi) north-northeast of Ukiah, CA, at 4:18 am PDT on 23 April 2021 (11:18 UTC), 7.4 km deep. 14 people have reported feeling it to USGS.
USGS: 15km NNW of Lake Pillsbury, CA
- When
- 4:18 am PDT on 23 April 2021 ()
- Where
- 44 km (28 mi) north-northeast of Ukiah, CA · earthquakes near Ukiah
- Magnitude
- M 3.9 (mw)
- Depth
- 7.4 km below the surface
- Felt
- 14 reports · strongest reported intensity IV
- Measured shaking
- intensity III (ShakeMap)
- USGS impact alert
- green
- Nearest
- Mendocino County, 36 km WSW
- Nearest mapped fault
- Bartlett Springs fault system, 1 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 1955 days ago
Earthquake alerts for Ukiah, CA
Get a notification in this browser when USGS records an earthquake near Ukiah, 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 90 km (56 mi) from the epicentre. In Ukiah, 44 km away, the estimate is intensity II (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 30 km, intensity III · Brooktrails 31 km, intensity III · Covelo 35 km, intensity III · Upper Lake 42 km, intensity III · Laytonville 42 km, intensity III · Ukiah 44 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 11 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.9 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 15,000× the energy of this one
- Mineral, Virginia 2011 M 5.8 680× the energy of this one
- Magna, Utah 2020 M 5.7 480× the energy of this one
- This earthquake M 3.9 about 11 tons of TNT
- Around the size people start to feel M 3.0 this one released 23× 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 59 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 · 46 km S 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 39.5257, -123.0365. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Mendocino County, CA | 36 km (23 mi) | WSW | earthquakes near Mendocino County |
| Lake County, CA | 53 km (33 mi) | SSE | earthquakes near Lake County |
| Glenn County, CA | 55 km (34 mi) | E | earthquakes near Glenn County |
| Colusa County, CA | 79 km (49 mi) | ESE | earthquakes near Colusa County |
| Tehama County, CA | 96 km (60 mi) | NE | earthquakes near Tehama County |
| Sonoma County, CA | 112 km (69 mi) | S | earthquakes near Sonoma County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
54 earthquakes have been recorded within 50 km since this one.
- 1.6 7km ESE of Willits, CA
- 2.8 7km ESE of Willits, CA
- 2.5 7km ESE of Willits, CA
- 1.8 4km NNE of Lake Pillsbury, CA
- 2.7 15km ESE of Lake Pillsbury, CA
- 1.9 4km NNW of Laytonville, CA
- 1.8 10km SE of Willits, CA
- 1.6 8km ENE of Willits, CA
- 1.8 6km N of Lake Pillsbury, CA
- 1.8 16km NE of Upper Lake, CA
- 2.0 11km W of Alder Springs, CA
- 1.9 14km SE of Lake Pillsbury, CA
- 1.5 10km SE of Willits, CA
- 1.9 10km SE of Willits, CA
- 1.9 5km SSE 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.