M1.8 earthquake 4 km S of Larkfield-Wikiup, California, United States
A magnitude 1.8 earthquake struck 4 km S of Larkfield-Wikiup, California, United States at 23:13 local time (06:13 UTC) on 30 Sept 2026, at a depth of 7 km, according to USGS. The solution is preliminary and may be revised.
Data: USGS · updated 2026-10-01 06:14 UTC · automatic solution
- Magnitude
- 1.8micro
duration magnitude (md) - Depth
- 7.3 km
- Status
- Automatic
- Origin time
- 2026-10-01 06:13:18 UTC
- Local: 30 Sept 2026, 23:13:18 (America/Los Angeles)
- Epicentre
- 38.472° N, 122.743° W
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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 |
|---|---|---|
| Larkfield-WikiupCalifornia, United States · pop. 8,884 | 4 km | IIWeak |
| Santa RosaCalifornia, United States · pop. 178,127 | 5 km | IIWeak |
| WindsorCalifornia, United States · pop. 27,464 | 11 km | INot felt |
| Rohnert ParkCalifornia, United States · pop. 42,407 | 15 km | INot felt |
| Agua CalienteCalifornia, United States · pop. 27,090 | 28 km | INot felt |
| San FranciscoCalifornia, United States · pop. 827,526 | 83 km | INot felt |
| OaklandCalifornia, United States · pop. 419,267 | 85 km | INot felt |
| SacramentoCalifornia, United States · pop. 524,943 | 110 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.
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.
| Agency | Magnitude | Depth | Epicentre | Time offset | Status |
|---|---|---|---|---|---|
| USGS · NCheadlineNorthern California Seismic System via U.S. Geological Survey | 1.8 md | 7.3 km | 38.47° N, 122.74° W | – | Automatic |
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How big was it?
Usually not felt. Recorded by nearby seismometers; thousands occur worldwide every day.
It released roughly the energy of 7 kg 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 7 km this was a shallow earthquake, which is felt more strongly at the surface than a deeper one of the same size.
M1.8 releases about 14× the energy of M1.0, and its waves are about 5.9× taller on a seismogram. Energy: 7 kg of TNT vs 477 g of TNT.
Each square is the energy of one M1.0. Energy from log₁₀E = 1.5M + 4.8.
Aftershocks and nearby activity
5 later earthquakes within 30 km; the largest was M2.4 10 days ago. 4 in the 7 days before. Aftershock rates usually fall off roughly in proportion to 1/time.
Mainshock M1.8
5 later earthquakes nearby. Aftershock rates typically fall off roughly as 1/time (Omori's law).
| Time after mainshock (hours) | Magnitude | Depth (km) |
|---|---|---|
| 39.83 | 2.4 | -1 |
| 93.89 | 1.4 | 7 |
| 230.80 | 2.1 | 0 |
| 240.74 | 1.6 | 0 |
| 244.31 | 1.9 | 0 |
- 2.46 km WNW of Petaluma, California, United States10-02 22:02
- 2.17 km N of Saint Helena, California, United States10-10 21:01
- 1.912 km NW of Agua Caliente, California, United States10-11 10:31
- 1.68 km NNE of Saint Helena, California, United States10-11 06:57
- 1.411 km SSE of Saint Helena, California, United States10-05 04:06
Did you feel it?
Reports from people help show where shaking was strong. They are anonymous and shown here in aggregate.
Reports on SeismoAtlas
No reports yet.
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Event id nc75442181. First recorded here 1 Oct 2026, 06:16:27 UTC. Solutions: USGS · NC (usgs:nc75442181). Cite as: SeismoAtlas, “M1.8 earthquake 4 km S of Larkfield-Wikiup, California, United States”, https://seismoatlas.com/earthquake/nc75442181-m1-8-earthquake-4-km-s-of-larkfield-wikiup-california-united-states, data from USGS.
JSON: /api/v1/events/nc75442181. SeismoAtlas is not an official warning service.