M1.2 earthquake near Muscoy, California, United States
A magnitude 1.2 earthquake struck near Muscoy, California, United States at 15:50 local time (22:50 UTC) on 21 Sept 2026, at a depth of 10 km, according to USGS.
Data: USGS · updated 2026-09-22 17:30 UTC · reviewed
- Magnitude
- 1.2micro
local magnitude (Richter) (ml) - Depth
- 9.9 km
- Status
- Reviewed
- Origin time
- 2026-09-21 22:50:40 UTC
- Local: 21 Sept 2026, 15:50:40 (America/Los Angeles)
- Epicentre
- 34.145° N, 117.342° 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 |
|---|---|---|
| MuscoyCalifornia, United States · pop. 10,644 | 1 km | INot felt |
| RialtoCalifornia, United States · pop. 103,132 | 5 km | INot felt |
| San BernardinoCalifornia, United States · pop. 216,108 | 6 km | INot felt |
| ColtonCalifornia, United States · pop. 54,621 | 9 km | INot felt |
| BloomingtonCalifornia, United States · pop. 23,851 | 10 km | INot felt |
| RiversideCalifornia, United States · pop. 317,261 | 22 km | INot felt |
| AnaheimCalifornia, United States · pop. 350,742 | 62 km | INot felt |
| Santa AnaCalifornia, United States · pop. 310,227 | 66 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 | 1.2 ml | 9.9 km | 34.14° N, 117.34° W | – | Reviewed |
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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 1 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 10 km this was a shallow earthquake, which is felt more strongly at the surface than a deeper one of the same size.
M1.2 releases about 2.2× the energy of M1.0, and its waves are about 1.7× taller on a seismogram. Energy: 1 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
20 later earthquakes within 30 km; the largest was M2.0 6 days ago. 1 in the 7 days before. Aftershock rates usually fall off roughly in proportion to 1/time.
Mainshock M1.2
20 later earthquakes nearby. Aftershock rates typically fall off roughly as 1/time (Omori's law).
| Time after mainshock (hours) | Magnitude | Depth (km) |
|---|---|---|
| 23.83 | 2.0 | 3 |
| 36.39 | 0.6 | 13 |
| 56.38 | 0.9 | 7 |
| 59.56 | 0.9 | 11 |
| 60.97 | 0.9 | 15 |
| 65.67 | 1.1 | 16 |
| 66.67 | 1.1 | 15 |
| 84.80 | 0.9 | 14 |
| 84.83 | 0.7 | 14 |
| 95.01 | 0.7 | 11 |
| 96.82 | 0.8 | 13 |
| 102.93 | 1.3 | 6 |
| 109.50 | 1.0 | 13 |
| 114.64 | 1.1 | 16 |
| 134.55 | 0.3 | 17 |
| 136.13 | 0.8 | 11 |
| 136.92 | 1.0 | 11 |
| 144.88 | 0.8 | 16 |
| 157.29 | 1.5 | 14 |
| 165.48 | 1.1 | 15 |
- 2.05 km NW of Highland, California, United States09-22 22:40
- 1.5Near Loma Linda, California, United States09-28 12:07
- 1.3Near Fontana, California, United States09-26 05:46
- 1.14 km N of Jurupa Valley, California, United States09-26 17:29
- 1.16 km S of Redlands, California, United States09-28 20:19
- 1.1Near Calimesa, California, United States09-24 16:30
- 1.16 km S of Redlands, California, United States09-24 17:30
- 1.05 km WNW of Calimesa, California, United States09-26 12:20
- 1.06 km S of Loma Linda, California, United States09-27 15:45
- 0.9Near Muscoy, California, United States09-24 10:24
- 0.97 km S of Redlands, California, United States09-25 11:38
- 0.95 km WNW of Calimesa, California, United States09-24 11:49
- 0.96 km NNW of Jurupa Valley, California, United States09-24 07:13
- 0.8Near Loma Linda, California, United States09-25 23:39
- 0.8Near Loma Linda, California, United States09-27 23:43
- 0.86 km S of Loma Linda, California, United States09-27 14:58
- 0.76 km NE of Moreno Valley, California, United States09-25 21:51
- 0.77 km S of Redlands, California, United States09-25 11:40
- 0.64 km ESE of Moreno Valley, California, United States09-23 11:14
- 0.310 km NE of Rancho Cucamonga, California, United States09-27 13:23
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.
Event id ci41336415. First recorded here 28 Sept 2026, 17:32:12 UTC. Solutions: USGS · CI (usgs:ci41336415). Cite as: SeismoAtlas, “M1.2 earthquake near Muscoy, California, United States”, https://seismoatlas.com/earthquake/ci41336415-m1-2-earthquake-near-muscoy-california-united-states, data from USGS.
JSON: /api/v1/events/ci41336415. SeismoAtlas is not an official warning service.