M4.0 earthquake 45 km NNE of Ukiah, California, United States
A magnitude 4.0 earthquake struck 45 km NNE of Ukiah, California, United States at 05:01 local time (12:01 UTC) on 28 Oct 2026, at a depth of 12 km, according to USGS.
revised from M3.9 · 7 reports to USGS “Did You Feel It?”
Data: USGS · updated 2026-10-28 16:23 UTC · reviewed
- Magnitude
- 4.0light
moment magnitude (mw)
revised from 3.9 - Depth
- 11.6 km
- Status
- Reviewed
- Origin time
- 2026-10-28 12:01:11 UTC
- Local: 28 Oct 2026, 05:01:11 (America/Los Angeles)
- Epicentre
- 39.501° N, 122.952° W
Circles show this event and others within 30 km from 7 days before to 30 days after. Lines: plate boundaries and GEM active faults. Open on the live map
Nearby places
| Place | Distance | Est. shaking |
|---|---|---|
| UkiahCalifornia, United States · pop. 15,917 | 45 km | IIWeak |
| WillowsCalifornia, United States · pop. 6,069 | 65 km | IIWeak |
| ChicoCalifornia, United States · pop. 121,345 | 99 km | INot felt |
| WindsorCalifornia, United States · pop. 27,464 | 106 km | INot felt |
| ParadiseCalifornia, United States · pop. 26,476 | 118 km | INot felt |
| Santa RosaCalifornia, United States · pop. 178,127 | 120 km | INot felt |
| SacramentoCalifornia, United States · pop. 524,943 | 163 km | INot felt |
| San FranciscoCalifornia, United States · pop. 827,526 | 198 km | INot felt |
Shaking is an estimate from the intensity prediction equation of Allen, Wald & Worden (2012), not an observation. Local ground and buildings can change it by a level or more. Likely felt out to about 43 km.
Every agency's solution
Agencies locate earthquakes with their own stations and methods, so their numbers differ. We match reports of the same event by time, distance and magnitude and show them side by side. The headline uses USGS · NC, which has been reviewed by an analyst.
| Agency | Magnitude | Depth | Epicentre | Time offset | Status |
|---|---|---|---|---|---|
| USGS · NCheadlineNorthern California Seismic System via U.S. Geological Survey | 4.0 mwwas 3.9 | 11.6 km | 39.50° N, 122.95° W | – | Reviewed · 3 revisions |
How big was it?
Widely felt near the epicentre: rattling windows and objects. Significant damage is unlikely.
It released roughly the energy of 16 t of TNT. Magnitude is logarithmic: each whole step means about 32 times more energy and 10 times larger waves on a seismogram. Depth matters too: at 12 km this was a shallow earthquake, which is felt more strongly at the surface than a deeper one of the same size.
M4.0 releases about 33× the energy of M3.0, and its waves are about 10× taller on a seismogram. Energy: 16 t of TNT vs 477 kg of TNT.
Each square is the energy of one M3.0. Energy from log₁₀E = 1.5M + 4.8.
Aftershocks and nearby activity
12 later earthquakes within 30 km; the largest was M2.5 7 days ago. 7 in the 7 days before. Aftershock rates usually fall off roughly in proportion to 1/time.
Mainshock M4.0
12 later earthquakes nearby. Aftershock rates typically fall off roughly as 1/time (Omori's law).
| Time after mainshock (hours) | Magnitude | Depth (km) |
|---|---|---|
| 0.18 | 1.8 | 6 |
| 0.19 | 2.2 | 9 |
| 0.80 | 1.7 | 11 |
| 4.20 | 1.8 | 11 |
| 48.56 | 2.4 | 10 |
| 49.11 | 1.6 | 7 |
| 57.30 | 1.6 | 7 |
| 109.57 | 1.8 | 8 |
| 138.49 | 1.5 | 2 |
| 189.01 | 2.5 | 10 |
| 318.71 | 1.4 | 9 |
| 330.38 | 1.8 | 8 |
- 2.544 km NNE of Ukiah, California, United States11-05 09:01
- 2.445 km NNE of Ukiah, California, United States10-30 12:34
- 2.244 km NNE of Ukiah, California, United States10-28 12:12
- 1.822 km N of Ukiah, California, United States11-11 06:23
- 1.824 km N of Ukiah, California, United States11-02 01:35
- 1.844 km NNE of Ukiah, California, United States10-28 16:13
- 1.842 km NNE of Ukiah, California, United States10-28 12:11
- 1.745 km NNE of Ukiah, California, United States10-28 12:49
- 1.648 km NE of Ukiah, California, United States10-30 13:07
- 1.646 km NNE of Ukiah, California, United States10-30 21:18
- 1.526 km N of Ukiah, California, United States11-03 06:30
- 1.424 km N of Ukiah, California, United States11-10 18:44
Did you feel it?
Reports from people help show where shaking was strong. They are anonymous and shown here in aggregate.
Reports close 14 days after an earthquake.
Event id nc75458907. First recorded here 28 Oct 2026, 12:05:55 UTC. Solutions: USGS · NC (usgs:nc75458907). Cite as: SeismoAtlas, “M4.0 earthquake 45 km NNE of Ukiah, California, United States”, https://seismoatlas.com/earthquake/nc75458907-m4-0-earthquake-45-km-nne-of-ukiah-california-united-states, data from USGS.
JSON: /api/v1/events/nc75458907. SeismoAtlas is not an official warning service.