The quake, according to the US Geological Survey, struck at 10.08 am local time, and was centred in San Diego County only 4 kilometres from Julian, a mountain town of about 1,500 people that is known for its apple pie shops

It was felt as far north as Los Angeles County, about 193 kilometres away. The quake was followed by several aftershocks

Transportation officials warned motorists to watch out for rocks that tumbled down hillsides and onto roads and highways, including State Route 76 northwest of Julian. Crews were assessing roadways for potential damage, the California Department of Transportation in San Diego County said

Schoolchildren were escorted outside of buildings as a precaution when the ground started moving, said Capt. Thomas Shoots of the California Department of Forestry and Fire Protection for San Diego County. He got a shake alert and then started feeling things rolling and banging

"There was a lot of shaking and rattling around," he said. "But thankfully everything seems to be back to normal"

The San Diego County Sheriff's Department also said they had received no immediate reports of damage or injuries

Riley Ozuna, owner of the Julian Cafe & Bakery, said some cups fell onto the ground at her business. "But everything is OK," she said

The quake struck 13.4 kilometres deep near the Elsinore fault zone, one of the busiest seismic areas in California and part of the famous San Andreas fault system that usually sees at least one magnitude 4.0 quake every year, according to Lucy Jones, a veteran seismologist in Southern California

Jones said the Sunday quake felt in Julian was a 3.5 magnitude temblor that was a foreshock to Monday's larger earthquake