The 9:56 a.m. temblor, initially reported to be a 5.2-magnitude shaker before being downgraded by the U.S. Geological Survey, was centered 12 miles east-southeast of Anza in Riverside County and occurred at a depth of about 7 miles.
The Los Angeles Times reported the quake was felt across a wide region, from downtown Los Angeles to Mexico.
USGS seismologist Susan Hough said it was the biggest to strike the greater Los Angeles area since a 5.4-magnitude quake in 2010, the newspaper said.
No injuries or major damage were reported, the Times said.
KTLA-TV, Los Angeles, reported a few products fell from the shelves at the Sunshine Market in Anza.
Shannon Haber, who was in the Los Angeles Unified District building in Westlake, told the Times she was frightened a bit because she hasn't had much experience with quakes, having moved to California from Minnesota in 1996.
"There was small shaking, and it made me nervous because I'm 23 floors up," she said.
"It was a slow, swaying motion. It sort of felt like I was on a boat, a sort of wavy feeling that lasted 10 to 20 seconds. ... No one else reacted around me. They're all veterans of earthquakes."
Holly Lawson said the brief quake rattled the windows of her campground kiosk at Anza-Borrego Desert State Park about 60 miles south of the epicenter and caused a truck outside to sway back and forth.
"The truck was actually physically moving," Lawson said.
"I'm always concerned about these windows when we feel a quake. We're surrounded by them."
She said campers in nearby recreational vehicles came by to ask if it was an earthquake "or if they were just going crazy."