SAN DIEGO — A 5.2-magnitude earthquake shook Southern California on Monday morning, sending boulders tumbling onto rural roadways outside San Diego, items rattling off shelves and elephants at the San Diego Zoo Safari Park scrambling to encircle their young. Officials reported no injuries or major damage.

The quake, according to the U.S. Geological Survey, struck at 10:08 a.m. local time, and was centered in San Diego County only a couple miles 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 120 miles away. The quake was followed by several aftershocks.

“I thought the single-pane windows were going to crack because they were shaking pretty good, but they didn't,” said Paul Nelson, owner of a former gold mine that operated in the 1870s in Julian.

He said some picture frames on the counter at the gift shop fell over at the Eagle Mining Co., but the tunnels that tourists can explore suffered no damage. On Sunday, Nelson said a smaller quake hit when about two dozen visitors were touring the defunct mine but everyone stayed calm. No one was inside the old mine when Monday's temblor rocked the ground for a longer time.

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.

At the San Diego Zoo Safari Park, a herd of African elephants was caught on video running over to protect their young by encircling them during the quake. Elephants have the ability to feel sound through their feet, and the behavior is known as an “alert circle.” The herd consisting of Ndlula, Umngani, Khosi, and youngsters Zuli and Mkhaya, appeared to relax after several minutes, the park said.

North County Transit District trains were delayed so crews could inspect the tracks for any potential damage, spokesperson Mary Dover said in an email to The Associated Press.

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 8.3 miles 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.

Some San Diego County residents who subscribe to the early warning system by the USGS called ShakeAlert were notified a second or two before it was felt Monday.

Others got the notification after the rocking stopped.

Meanwhile, in Michigan, more than 2,000 miles away, residents still recovering from a major ice storm also got a “shake alert” on their wireless devices from the USGS: “Earthquake Detected! Drop, cover, hold on.”

It was a mistaken reference to the California earthquake. Portable cell towers from California are being temporarily used in Vanderbilt, Michigan, while the region tries to rebound from the ice storm that knocked out power to thousands of people, state police said.

“It is an odd alert to get in Michigan,” Lt. Ashley Miller said. “It was just poor timing. We just experienced this ice storm. I'm sure there were some people on edge.”