Earthquake · reviewed by a seismologist
M 1.8md
Earthquake near Ukiah, CA
No earthquake was likely felt in Ukiah in the 24 hours to 5:47 am PST (13:47 UTC). The last one was M 1.5, 5 km (3 mi) E, at 3:26 am PST on 12 November 2026, estimated intensity II (weak) in town. Every earthquake near Ukiah
This page: a magnitude 1.8 earthquake was recorded 34 km (21 mi) northeast of Ukiah, CA, at 9:40 am PDT on 21 April 2020 (16:40 UTC), 8.1 km deep.
USGS: 11km SSE of Lake Pillsbury, CA
- When
- 9:40 am PDT on 21 April 2020 ()
- Where
- 34 km (21 mi) northeast of Ukiah, CA · earthquakes near Ukiah
- Magnitude
- M 1.8 (md)
- Depth
- 8.1 km below the surface
- Felt
- no reports yet
- Nearest
- Lake County, 27 km SSE
- Nearest mapped fault
- Bartlett Springs fault system, under 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 2313 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 minor earthquake. Quakes this small are rarely felt and do not cause damage.
At this magnitude and depth, people at rest would likely notice it out to about 10 km (6 mi) from the epicentre. In Ukiah, 34 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.
Earthquakes near other towns within 30 km: Upper Lake, Nice, North Lakeport, Redwood Valley.
How big was it?
This earthquake released about 13 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.8 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 1,200,000× the energy of this one
- Magna, Utah 2020 M 5.7 840,000× the energy of this one
- Around the size people start to feel M 3.0 75× the energy of this one
- This earthquake M 1.8 about 13 lb of TNT
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 100,000 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 SW 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 39.3255, -122.8888. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Lake County, CA | 27 km (17 mi) | SSE | earthquakes near Lake County |
| Mendocino County, CA | 49 km (30 mi) | WNW | earthquakes near Mendocino County |
| Glenn County, CA | 52 km (32 mi) | NE | earthquakes near Glenn County |
| Colusa County, CA | 58 km (36 mi) | ESE | earthquakes near Colusa County |
| Sonoma County, CA | 89 km (55 mi) | S | earthquakes near Sonoma County |
| Napa County, CA | 103 km (64 mi) | SSE | earthquakes near Napa County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
57 earthquakes have been recorded within 50 km since this one.
- 3.9 11km ESE of Willits, CA
- 2.1 10km ESE of Willits, CA
- 1.8 10km ESE of Willits, CA
- 3.3 11km NNW of Redwood Valley, CA
- 4.2 11km ESE of Willits, CA
- 2.9 10km ESE of Willits, CA
- 1.9 9km NNE of Brooktrails, CA
- 1.5 14km NNE of Brooktrails, CA
- 1.7 21km SE of Covelo, CA
- 2.1 20km NNW of Lake Pillsbury, CA
- 1.6 9km NNW of Redwood Valley, CA
- 1.8 9km E of Redwood Valley, CA
- 2.0 20km NE of Brooktrails, CA
- 1.6 8km NNE of Redwood Valley, CA
- 1.9 20km NNW of Lake Pillsbury, 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.