A strong earthquake with a preliminary magnitude of 5.4 struck Southern California early Monday, alarming residents and emphasizing the region’s “seismic vulnerability,” according to the U.S. Geological Survey (USGS). The quake occurred where the Pacific and North American tectonic plates meet, a highly active zone known for powerful tremors.

Witnesses described the experience as intense but brief. One resident wrote, “It felt really bad,” while others said the ground “shook suddenly, accompanied by a deep rumble.” Social media quickly filled with videos showing shaking lights and rattling windows.

Authorities confirmed that no casualties or major damage were reported, though several schools suspended classes as a safety measure. Emergency crews are inspecting bridges, hospitals, and key infrastructure to ensure stability.

Experts noted that the quake’s epicenter lay within the San Andreas Fault system, one of the world’s most monitored seismic zones. Its movement serves as a reminder that California remains at constant risk of larger earthquakes in the future.