This Thursday, July 31, 2025 at 9:32 a.m. local time, the USGS recorded a preliminary magnitude 4.3 earthquake with an epicenter near Muscoy (San Bernardino County), about 60 km east of Los Angeles, and an estimated depth of 3.3 miles (~5.3 km).
This event was widely felt, including in areas such as Riverside, San Diego and Santa Clarita, with nearly 5,000 people reporting the shaking through public awareness systems.
Aftershocks reported after the tremor
This event was widely felt
QuéOnnda.com
Within an hour, at least three USGS-confirmed aftershocks of the quake occurred in the area northwest of Rialto:
One of magnitude 3.0 at 8:34 a.m., one of 2.8 at 8:42 a.m., and one of 3.1 at 9:36 a.m., with an approximate depth of 3.8 miles (~6 km).
No damage or injuries reported
So far, no structural damage or injuries have been reported.
Inhabitants of the region reported on social networks that they were frightened when they felt the tremor, but no major adverse events were confirmed.
Geological context: why did it happen here?
Buzzy
The Rialto and Muscoy area is close to the San Andreas Fault, part of the well-known active geologic system in southern California, which causes moderate frequency of earthquakes.
Although no earthquakes greater than magnitude 3 were recorded near Rialto in the last month, historically the region has experienced tremors of up to magnitude 7.1 in 2019, located between 100 and 200 km to the north.
What should U.S. Hispanic residents do?
1. Stay informed through the USGS and Cal OES ShakeAlert system, which issues alerts for earthquakes greater than 4.5 magnitude.
2. Follow basic safety precautions: duck, cover and stay away from windows.
3. Prepare an emergency kit with water, non-perishable food, flashlight, documents and medical kit.
For more information, visit QuéOnnda.com.
