M0.9 earthquake near Charter Oak, California, United States
A magnitude 0.9 earthquake struck near Charter Oak, California, United States at 02:41 local time (09:41 UTC) on 4 Oct 2026, at a depth of 3 km, according to USGS.
revised from M1.0
Data: USGS · updated 2026-10-04 19:23 UTC · reviewed
- Magnitude
- 0.9micro
local magnitude (Richter) (ml)
revised from 1.0 - Depth
- 2.8 km
- Status
- Reviewed
- Origin time
- 2026-10-04 09:41:23 UTC
- Local: 4 Oct 2026, 02:41:23 (America/Los Angeles)
- Epicentre
- 34.101° N, 117.850° 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 |
|---|---|---|
| Charter OakCalifornia, United States · pop. 9,310 | 0 km | IIWeak |
| San DimasCalifornia, United States · pop. 34,630 | 4 km | INot felt |
| CovinaCalifornia, United States · pop. 48,984 | 4 km | INot felt |
| GlendoraCalifornia, United States · pop. 52,009 | 5 km | INot felt |
| AzusaCalifornia, United States · pop. 49,690 | 6 km | INot felt |
| AnaheimCalifornia, United States · pop. 350,742 | 30 km | INot felt |
| Los AngelesCalifornia, United States · pop. 3,820,914 | 36 km | INot felt |
| Santa AnaCalifornia, United States · pop. 310,227 | 39 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 · CI, which has been reviewed by an analyst.
| Agency | Magnitude | Depth | Epicentre | Time offset | Status |
|---|---|---|---|---|---|
| USGS · CIheadlineSouthern California Seismic Network via U.S. Geological Survey | 0.9 mlwas 1.0 | 2.8 km | 34.10° N, 117.85° W | – | Reviewed · 2 revisions |
How big was it?
Usually not felt. Recorded by nearby seismometers; thousands occur worldwide every day.
It released roughly the energy of 326 g 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 3 km this was a shallow earthquake, which is felt more strongly at the surface than a deeper one of the same size.
M1.0 releases about 1.5× the energy of M0.9, and its waves are about 1.3× taller on a seismogram. Energy: 477 g of TNT vs 326 g of TNT.
Each square is the energy of one M0.9. Energy from log₁₀E = 1.5M + 4.8.
Aftershocks and nearby activity
25 later earthquakes within 30 km; the largest was M1.7 34 days ago. 9 in the 7 days before. Aftershock rates usually fall off roughly in proportion to 1/time.
Mainshock M0.9
25 later earthquakes nearby. Aftershock rates typically fall off roughly as 1/time (Omori's law).
| Time after mainshock (hours) | Magnitude | Depth (km) |
|---|---|---|
| 23.39 | 1.2 | 21 |
| 23.39 | 0.9 | 9 |
| 32.72 | 0.7 | 13 |
| 74.96 | 0.6 | 9 |
| 98.11 | 1.5 | 11 |
| 98.73 | 0.6 | 7 |
| 118.69 | 0.7 | 5 |
| 132.12 | 1.7 | 5 |
| 245.62 | 1.2 | 10 |
| 329.10 | 1.0 | 4 |
| 354.45 | 0.6 | 13 |
| 370.17 | 1.2 | -1 |
| 372.34 | 0.9 | 7 |
| 446.79 | 0.8 | 11 |
| 510.59 | 1.4 | 8 |
| 539.58 | 1.0 | -1 |
| 558.59 | 0.9 | 8 |
| 616.75 | 1.3 | 7 |
| 624.67 | 1.1 | 11 |
| 640.08 | 0.9 | 4 |
| 640.29 | 1.1 | 4 |
| 645.05 | 0.9 | 13 |
| 650.24 | 0.5 | 7 |
| 660.39 | 1.1 | 11 |
| 685.41 | 1.2 | 12 |
- 1.77 km WNW of Jurupa Valley, California, United States10-09 21:48
- 1.5Near Mayflower Village, California, United States10-08 11:47
- 1.46 km NW of Jurupa Valley, California, United States10-25 16:16
- 1.37 km NNW of Eastvale, California, United States10-30 02:26
- 1.26 km NNW of Glendora, California, United States11-01 23:06
- 1.2Near Pico Rivera, California, United States10-05 09:04
- 1.24 km SSW of Yorba Linda, California, United States10-14 15:18
- 1.26 km NNW of Azusa, California, United States10-19 19:51
- 1.1Near Rancho Cucamonga, California, United States10-31 22:04
- 1.1Near South El Monte, California, United States10-30 10:21
- 1.110 km N of Rancho Cucamonga, California, United States10-31 01:58
- 1.05 km NNW of Azusa, California, United States10-26 21:16
- 1.010 km N of Rancho Cucamonga, California, United States10-18 02:47
- 0.9Near Alhambra, California, United States10-19 22:01
- 0.94 km S of San Dimas, California, United States10-31 06:44
- 0.94 km SE of Yorba Linda, California, United States10-05 09:05
- 0.99 km N of Rancho Cucamonga, California, United States10-31 01:46
- 0.99 km S of Los Serranos, California, United States10-27 16:16
- 0.83 km NNW of Sierra Madre, California, United States10-23 00:28
- 0.7Near South Pasadena, California, United States10-05 18:24
- 0.77 km WNW of Jurupa Valley, California, United States10-09 08:22
- 0.69 km N of Rancho Cucamonga, California, United States10-08 12:24
- 0.6Near Covina, California, United States10-19 04:08
- 0.610 km NNW of Rancho Cucamonga, California, United States10-07 12:38
- 0.56 km N of Altadena, California, United States10-31 11:55
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Reports on SeismoAtlas
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Event id ci41342927. First recorded here 4 Oct 2026, 09:44:01 UTC. Solutions: USGS · CI (usgs:ci41342927). Cite as: SeismoAtlas, “M0.9 earthquake near Charter Oak, California, United States”, https://seismoatlas.com/earthquake/ci41342927-m0-9-earthquake-near-charter-oak-california-united-states, data from USGS.
JSON: /api/v1/events/ci41342927. SeismoAtlas is not an official warning service.