Earthquake · reviewed by a seismologist
M 1.6ml
Earthquake near Muscoy, CA
No earthquake was likely felt in Muscoy in the 24 hours to 5:33 am PST (13:33 UTC). The last one was M 2.2, 17 km (10 mi) SE, at 8:15 pm PDT on 29 October 2026, estimated intensity II (weak) in town; 1 felt report to USGS. Every earthquake near Muscoy
This page: a magnitude 1.6 earthquake was recorded 6 km (3 mi) northeast of Muscoy, CA, at 2:32 am PDT on 4 September 2023 (09:32 UTC), 9.0 km deep.
USGS: 6 km NE of Muscoy, CA
5 km (3 mi) N of San Bernardino, CA
- When
- 2:32 am PDT on 4 September 2023 ()
- Where
- 6 km (3 mi) northeast of Muscoy, CA · earthquakes near Muscoy
- Magnitude
- M 1.6 (ml)
- Depth
- 9.0 km below the surface
- Felt
- no reports yet
- Nearest
- Orange County, 72 km SW
- Nearest mapped fault
- San Andreas fault, 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 1164 days ago
Earthquake alerts for Muscoy, CA
Get a notification in this browser when USGS records an earthquake near Muscoy, 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 6 km (4 mi) from the epicentre. In Muscoy, 6 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.
Likely felt in: Muscoy 6 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 6.4 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.5 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 2,400,000× the energy of this one
- Magna, Utah 2020 M 5.7 1,700,000× the energy of this one
- Around the size people start to feel M 3.0 150× the energy of this one
- This earthquake M 1.6 about 6.4 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 4.4 on 2016-01-06 — about 18,000 times the energy of this one.
Before 2016, the USGS record lists 14 earthquakes of M5 or more within 50 km; the five largest:
- 6.3 The 1992 Big Bear, California Earthquake · 44 km E of this epicentre
- 6.2 3 km SE of San Bernardino, California · 12 km SSE of this epicentre
- 5.6 7km ENE of Running Springs, CA · 25 km ENE of this epicentre
- 5.5 The 1990 Upland, California Earthquake · 37 km W of this epicentre
- 5.5 11km SSE of Big Bear Lake, California · 41 km E 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 34.1877, -117.2997. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Orange County, CA | 72 km (45 mi) | SW | earthquakes near Orange County |
| Los Angeles County, CA | 89 km (55 mi) | W | earthquakes near Los Angeles County |
| San Bernardino County, CA | 127 km (79 mi) | NE | earthquakes near San Bernardino County |
| Riverside County, CA | 130 km (81 mi) | ESE | earthquakes near Riverside County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
47 earthquakes have been recorded within 50 km since this one.
- 2.2 4 km S of Big Bear City, CA
- 1.5 4 km ENE of Calimesa, CA
- 2.3 10 km NNW of Big Bear City, CA
- 2.3 9 km NNW of Big Bear City, CA
- 2.1 8 km NE of Yucaipa, CA
- 1.8 4 km NNE of Fontana, CA
- 1.6 4 km SSE of Ontario, CA
- 1.6 7 km SSE of Home Gardens, CA
- 1.8 4 km SSE of Home Gardens, CA
- 1.6 6 km S of Loma Linda, CA
- 2.7 7 km ENE of Rancho Cucamonga, CA
- 1.9 5 km ESE of Beaumont, CA
- 2.5 3 km E of Devore, CA
- 1.9 3 km S of Loma Linda, CA
- 2.1 6 km NNE of Fontana, 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.