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Muscoy Quake Rattles Southern California, Aftershocks Persist
31 Jul
Summary
- 4.3-magnitude quake hits near Muscoy, felt widely
- Series of smaller quakes and aftershocks in Rialto area
- Seismologist calls quakes "foreshocks" in active fault zone
On the morning of July 31, 2025, a swarm of small earthquakes rattled residents across San Bernardino and Riverside counties in Southern California. The shaking began just after 8:30 a.m. with a 3.0-magnitude quake near Rialto, followed by a 2.8-magnitude quake and a series of light aftershocks.
The strongest of the quakes came at 9:32 a.m., when a 4.3-magnitude earthquake struck near the community of Muscoy, just north of San Bernardino. The tremors were felt widely across the region, with reports of shaking as far north as Bakersfield and as far south as Santa Ysabel.
Seismologist Dr. Lucy Jones called the quakes "foreshocks" and explained they occurred in an area known as the "Fontana trend," which tends to experience clusters of seismic activity. Just a few minutes after the 4.3-magnitude quake, another 3.1-magnitude tremor hit the Rialto area, with residents in parts of Riverside County also feeling the shaking.
As of now, there are no immediate reports of injuries or significant damage from the earthquake swarm. However, experts warn that the region remains seismically active and prone to such earthquake clusters, advising residents to stay prepared and vigilant.
