Earthquake · reviewed by a seismologist
M 2.0ml
Earthquake near Muscoy, CA
No earthquake was likely felt in Muscoy in the 24 hours to 7:41 am PST (15:41 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 2.0 earthquake was recorded in Muscoy, CA, at 10:48 pm PDT on 7 April 2021 (05:48 UTC), 6.1 km deep. 8 people have reported feeling it to USGS.
USGS: 2km N of Muscoy, CA
6 km (4 mi) WNW of San Bernardino, CA · 99 km (62 mi) E of Los Angeles, CA
- When
- 10:48 pm PDT on 7 April 2021 ()
- Where
- in Muscoy, CA · earthquakes near Muscoy
- Magnitude
- M 2.0 (ml)
- Depth
- 6.1 km below the surface
- Felt
- 8 reports · strongest reported intensity III
- Nearest
- Orange County, 68 km SW
- Nearest mapped fault
- San Jacinto fault, 2 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 2043 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 15 km (9 mi) from the epicentre. 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 in town, intensity II · Rialto 7 km, intensity II · San Bernardino 9 km, intensity II · Colton 11 km, intensity II · Fontana 12 km, intensity II · Highland 14 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 30 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.0 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 500,000× the energy of this one
- Magna, Utah 2020 M 5.7 350,000× the energy of this one
- Around the size people start to feel M 3.0 32× the energy of this one
- This earthquake M 2.0 about 30 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 3,800 times the energy of this one.
Before 2016, the USGS record lists 15 earthquakes of M5 or more within 50 km; the five largest:
- 6.3 The 1992 Big Bear, California Earthquake · 48 km E of this epicentre
- 6.2 3 km SE of San Bernardino, California · 12 km SE of this epicentre
- 5.6 7km ENE of Running Springs, CA · 29 km ENE of this epicentre
- 5.5 The 1990 Upland, California Earthquake · 32 km W of this epicentre
- 5.5 11km SSE of Big Bear Lake, California · 46 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 34.1692, -117.3475. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Orange County, CA | 68 km (42 mi) | SW | earthquakes near Orange County |
| Los Angeles County, CA | 84 km (52 mi) | W | earthquakes near Los Angeles County |
| San Bernardino County, CA | 131 km (82 mi) | NE | earthquakes near San Bernardino County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
44 earthquakes have been recorded within 50 km since this one.
- 1.7 11km E of Yorba Linda, CA
- 1.5 4km ENE of Running Springs, CA
- 1.8 4km SE of Loma Linda, CA
- 1.6 4km SE of Loma Linda, CA
- 1.6 12km NW of Big Bear Lake, CA
- 1.6 7km E of Calimesa, CA
- 2.1 11km E of Yorba Linda, CA
- 1.8 5km SSE of Home Gardens, CA
- 1.5 1km NNE of Loma Linda, CA
- 1.8 7km SSE of Home Gardens, CA
- 1.5 6km N of Banning, CA
- 1.6 4km SW of Rancho Cucamonga, CA
- 1.5 11km E of Yorba Linda, CA
- 1.6 7km NNW of Mira Loma, CA
- 1.9 5km SE of Home Gardens, 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.