Southern California experienced a magnitude 4.0 earthquake near Ontario early Sunday morning, followed by numerous aftershocks, with no reports of injuries or significant damage. The quake was felt widely across the region, including San Bernardino, Riverside, Orange County, and parts of Los Angeles. This seismic event is part of a larger pattern of increased earthquake activity in California, which saw three minor quakes earlier in the week, raising concerns about the state's seismic volatility. The US Geological Survey continues to monitor these developments and encourages public participation in reporting tremors for improved data accuracy.