A small earthquake with a preliminary magnitude of 3.5 shook parts of southern California late on Friday, the U.S. Geological Survey said.
The earthquake was reported 3 miles (5 km) southeast of Tijuana, just south of the United States border with Mexico, the agency said.
There were no initial reports of injuries or damage.
The quake was felt briefly in the San Diego metro area, according to postings on social media.
"Nothing like an earthquake to wake you up, small but nearby," wrote San Diego graphic designer Shawna Chalmers on Twitter.
(Reporting by Brendan O'Brien; Editing by Alexander Smith)